Tag Archives: vapor barrier

Tear Down to Rebuild? Bay Spacing, and Condensation Problems

DEAR POLE BARN GURU: Hello, I am going to tear down a 30x40x10 pole building to rebuild on my property. I noticed that the trusses are spaced 10 feet apart and are set on the 6×6 pole that has been notched. With no header board. This is an all metal building. Was wondering if this is an acceptable method of notching the post to put trusses on. Thanks. SHAWN in INDUSTRY

DEAR SHAWN: The most typical engineered post frame design provided by Hansen Pole Buildings utilizes a double (two ply) prefabricated wood truss notched into the columns (most usually spaced every 12 feet). This, in my humble opinion, is a combination which provides the best possible truss to column connection for post frame buildings, along with the reliability of the double truss system.

I would have concerns about the reassembly of a tear down, due to possible materials damage, as well as the building possibly having been designed to a no longer valid building code. My recommendation would be to contact the original engineer of record for advice as to how to proceed. If you are unable to contact him or her, then a local RDP (Registered Design Professional – architect or engineer) should be engaged to determine the structural integrity of the building as well as its adequacy to support the given climactic loads under the current building code.

DEAR POLE BARN GURU: Hello again! I reread the instructions and it said for immediate response to leave email. So I posted it above. Hello Pole Barn Guru! Wishing you a blessed day. My question is about a studded wall with double trusses. What I am trying to do is avoid having to build a 14 ft wall to accommodate a car lift. I am building a 30×50 shop. The garage doors will be on the 50 side. My thinking is build stud walls and frame in laminated posts to resemble a 6×6. They would be set at 10 widths to accommodate a 10×10 garage door. This way I could set the trusses and have open overhead bays between the trusses to accommodate the car lift and not have to build 14 ft walls. Would the idea of double trusses work in this type of build? TONY in ATHENS

DEAR TONY: If you are starting from scratch, why not just construct an engineered post frame building and columns and double trusses approximately every ten feet? I say approximately as a 10 foot width residential overhead door requires roughly 10’1″ of width between the columns. We can design a building for you, which would not have bottom chord bracing between the trusses in the bay where the overhead door would fall – thus allowing for extra headroom for your car lift. You will certainly get the most for your building investment by using post frame design.

In the event you are already constructing some other sort of building, you should consult with the Registered Design Professional (RDP – registered architect or engineer) who designed your building, as he or she would need to make the appropriate alterations to ensure the structural adequacy of what you have in mind.

In any case, for the sake of safety, do not attempt to do design work on your own – entrust it to a RDP.

 

DEAR POLE BARN GURU: I have a pole barn in Colo Springs.   I have pretty bad ceiling condensation in the winter.  The prior owner just stuck R-36 up there.  I am thinking of removing each roof panel and putting Rufco Vapor Barrier and putting the metal roof panels back down. 

I would prefer to do it inside with a radiant barrier but that will probably not work.  Any suggestions?  Something better than Rufco?  Thank you. FRANK in COLORADO SPRINGS

Reflective InsulationDEAR FRANK: On your existing building – while Rufco is an excellent vapor barrier, it will not stop condensation issues, as it does not provide a thermal break. If the prior owner installed the batt insulation in the plane of the ceiling, I would recommend the use of closed cell spray foam on the underside of the roof steel. This would eliminate having to remove and reinstall the roof panels. If this is your only option, Hansen Pole Buildings does provide a reflective radiant barrier in six foot net coverage widths with a tab on one side with an adhesive pull strip for easy sealing of laps. You might give this a consideration.

 

A Stone Base Floor? Trusses vs Rafters, and Entry Door Install

DEAR POLE BARN GURU: I have a 40 x 24 pole barn with a 4 inch stone base floor. Can I place 2×4 grid framing 24 in on center with 3/4 inch T&G 4 x 8 sheets for light weight shop usage? No vehicles. JEFF in SYCAMORE

DEAR JEFF: Some ifs – if your site is drained so as to not have excess moisture beneath the building, if the subgrade is thoroughly compacted and if you have a well-sealed vapor barrier underneath, then it might work. Be prepared for the possibility of frost heaving. Both the framing and the sheathing should be pressure preservative treated to a minimum UC-4B level to prevent possible deterioration.

 

craigslist pole barnDEAR POLE BARN GURU: You compare scissor trusses to conventional trusses, but I see nothing about using beams instead. I’m aware of only one post frame supplier that provides beam systems in lieu of trusses. Are there any down sides to using beams and avoiding trusses all together? RACHEL in ST. LOUIS

DEAR RACHEL: My only guess would be you mean rafters, not beams. Or it could be your intent is a ridge beam supporting rafters. In any case, the answer is going to come down to time, money and reliability. If an alternate system to prefabricated wood roof trusses is to be used, it should most certainly be a design which has been thoroughly reviewed and sealed by a Registered Professional Engineer. Obviously prefabricated wood roof trusses are most highly prevalent because they offer the advantages without the expense of time and labor.

DEAR POLE BARN GURU: Can I install a 36″ steel entrance door before the exterior girts are applied? DONAVON in EAGLE GROVE

DEAR DONAVON: In most cases, the columns on one or both sides of the entry door are trimmed off above the door and supported by a wall girt which runs between two roof supporting columns. If your particular application has framing on both sides of the door which is attached to the roof system, then it would probably be possible to install the entry door prior to the wall girts. I am not seeing any apparent advantage to doing so and it would add to the possibility of inadvertent damage to the door.

 

Condensation Solutions, A Ceiling the Right Way, and Timing

Advice about condensation, ceilings done right, and the timing of questions

DEAR POLE BARN GURU: My deck roof is metal panels on 2×4 purlins, rafters are 2×6, like a pole barn. I am enclosing it, and need to stop the condensation. I spray foamed it with closed cell, but there is some condensation on the foam in a few places. It will be covered with drywall. Would a 6 mil plastic vapor barrier on the conditioned side work? MICHAEL in FRAZIER’S BOTTOM

DEAR MICHAEL: Provided you are able to reduce the moisture content within the building so as no vapor is being trapped between the vapor barrier and the foam, it should take care of the problem. In all reality, as long as you have no holes in the gypsum drywall, once it is painted you should have eliminated the problem of condensation against the insulation.

Now getting to the real problem – you have too much moisture in your building. If you did not place a well sealed vapor barrier under your concrete slab floor, you need to seal it. Walls also need a vapor barrier (without holes) on the conditioned side to prevent moisture from passing through.

 

DEAR POLE BARN GURU: I have a 40 x 80 pole barn with 8 foot truss spacing. I will be installing faced rolled insulation between each truss. What is the recommended ceiling product to install on the inside? Wood, metal, that will be lightweight and easy to install?? Thanks JEFF in SYCAMORE

DEAR JEFF: I see problems in your future….

Faced insulation is the absolute wrong product to use for insulating your ceiling. Any insulation placed at the truss bottom chord level should be unfaced. The best bet would be to blow insulation in above the finished ceiling.

In any case, you must adequately vent the attic space.

Now, on to the ceiling.

 

I am hopeful you have trusses designed with a minimum of a five psf (pounds per square foot) ceiling load, with 10 psf being even better. Confirm with your RDP (Registered Design Professional – architect or engineer) who designed your building, however 2×4 #2 ceiling joists at 24 inches on center between the bottom chords with joist hangers should adequately support a ceiling.

My choice of ceiling product?

5/8” Type X gypsum wallboard. It is affordable, weighs under three psf and provides fire resistance.

 

DEAR POLE BARN GURU: I’m putting up a building with a 3/12 pitch single sloped roof. radiant reflective polyethylene, vapor barrier insulation between the purlins and the metal roof sheathing. Probably rock wool batts under the 1-3″ draped barrier. Do you think the roof has to be vented, and how would this work? CHRIS in BROOKLINE

DEAR CHRIS: Yes, it would need to be vented and it is my feeling you are going about this entirely in the wrong direction. Your question is well timed, as I have just written an article on how to properly insulate between purlins, which will be posted soon. The basic gist is your best solution is to use closed cell spray foam applied directly to the underside of the roof steel.

 

Post Frame Insulation in the South

Post Frame Insulation in the Hot and Humid South

Reader RICK in LUCEDALE writes: Dear Pole Barn Guru, I am in the planning stage for designing a post frame house. I live in a “Hot and Humid” climate in the southern US. Joseph Lstiburek, a building science guru, suggests having an unvented roof for my climate zone with the HVAC in the conditioned air space. The metal roof would have a layer of single bubble vapor barrier under it with BIBS insulation installed in the roof purlins. The walls would have a building wrap behind the metal siding and BIBS insulation. The walls would have a vapor barrier between the drywall interior and the insulation. Does the roof assembly need another vapor barrier on the inside? What happens at the intersections between the single layer bubble vapor barrier, the building wrap, and the sub slab vapor barrier? I assume I can use non venting closure strips at the ridge and closed non venting soffits? What size should the purlin be to get an R value of 30+ ? What would be your recommendations? Thanks.”

Mike the Pole Barn Guru writes:

Unless your post frame house will have extremely large purlins, you will not be able to get sufficient depth of insulation using BIBs. Energystar.gov recommends roof insulation values of R-30 to R-60 for your part of the country. BIBs provides an R value of 4.23 per inch, so to achieve a minimal value of R-30 would require at least a 2×8 purlin and would realistically not provide the insulation value I would personally be looking for.

I’d be looking at the use of closed cell spray foam insulation, which would give you R-7 or better per inch of depth. It also completely seals everything, eliminating the need for a reflective barrier below the roof steel. With 2×6 purlins, one could spray eight inches of foam completely filling the space between the purlins as well as covering the underside of them (and the underside of the roof truss top chords).

The goal here is to achieve a complete envelope seal of your building’s perimeter. You will not want a vapor barrier between the living space and the attic. The building wrap is not a vapor barrier, it is a weather barrier. The vapor barrier on the inside of the walls should be installed so as to be sealed into the roof plane spray foam and sealed tightly to the slab on grade (although I prefer living over a crawl space).

Soffits should be non-ventilated and closed cell foam closure strips should be used at the top and bottom of all steel panels.

Post Frame Antiperspirant- Ventilation Frustration

This is a sad story I hear all too often from pole (post frame) building owners who have buildings which were not properly designed for future uses, especially when it comes to insulation and ventilation.

Reader JASON in TENINO writes:

Hi Pole Barn Guru,

I recently purchased a new house and it came with a 40×60 shop. This past year I’ve experienced terrible slab sweating every time there is a change in humidity. Now that it’s summer I would like to prevent the sweating from occurring again. What are my best options on a limited budget? I’ve looked into using a penetrating concrete sealer, but I don’t think that addresses the underlying condensation problem.

As far as I can tell the shop has no ventilation of any kind (ridge/gable/soffit). And I’m noticing black mold starting to develop in the insulation below the roof. And I’m not sure if any sort of vapor barrier was placed before the slab was poured.

In the future I would like to insulate and heat the shop, but for now, I’d be happy if I can stop my condensation problems.

Thank you for your help!!!

DEAR JASON:

Yep – you have a problem on your hands. I can pretty much guarantee there is no vapor barrier under your concrete floor, which is a shame someone cheaped out. Vapor barriers are so inexpensive.

Taking care of first things first, let’s get the floor sealed. Here is the information you will need: http://www.hansenpolebuildings.com/2012/07/concrete-sealer/.

Secondly – get rid of the mold. Mix in the ratio of one cup bleach per gallon of water and use a hand pump sprayer to saturate all moldy surfaces. You can also use a scrub brush to remove the existing mold.

Third – I am going to leap ahead to your future plans, as they will impact your solutions now. I am not a gambling man, but I would put money on your shop’s trusses not having been designed to support the weight of a ceiling. This means if you want to eventually insulate and heat the building, you will have to insulate above the bottom chord of the trusses and up the roof line. On the walls, you can frame in either with a stud wall or with bookshelf girts to create a method to support insulation, with either batts or BIBs (Blow in Blanket) insulation being the most cost efficient and effective for your investment dollars.

Insulating the roof, not so easy, as the only really practical solution will be to use closed cell spray foam between the roof purlins. You will want to consult with an installer to get their opinion as to whether the metal building insulation under the roof steel will have to be removed prior to spraying.

If you are going to spray foam, then you do not want to use a ridge vent, as the foam would cover it.

Here is my best advice (provided you have the space on your property) – use your existing building only for cold storage. Since you do not have vented sidewall overhangs to create an air intake, the only solution for ventilation is to use large vents in each endwall. At a bare minimum, you should have at least 576 square inches on net free flowing vent in each end – located in the top half of the gables. You may need to add power vents, in order to adequately move the moisture out of the building.

When your budget allows for some climate controlled space, construct a new building which is properly designed to be able to be energy efficient.

Here is a short list of features which you should include:

Underslab vapor barrier
Pex tubing in slab for in floor heat
Perimeter slab insulation (rigid foam)
Bookshelf wall girts to create an insulation cavity
Housewrap between wall girts and siding
Vented sidewall overhangs
Ceiling loaded trusses with ceiling joists
Raised heel trusses to allow full insulation depth from wall to wall
Blow in R-45 to 60 of ceiling insulation
Reflective radiant barrier between purlins and roof steel

Good luck and let me know how things turn out!

Mike the Pole Barn Guru

Converting a Pole Barn to a Residence

One trend I have seen over the past ten years is folks purposefully designing post frame buildings to homes – they are recognizing the advantages, among them savings in foundation costs, speed of construction, flexibility of design and ability to insulate. Along with this, more and more post frame buildings are being re-purposed from pole barns to living spaces. This becomes a challenge when advance thought was not put into the original building design as to what future uses might bring.

Reader MARK from FOSTER is in the midst of wanting to do one of these conversions and he writes:

“DEAR POLE BARN GURU: I have a pole barn that has foil bubble wrap on both roof and wide walls. I’m wanting to convert this into living space. I have 7″ of space in the walls to put insulation. So to insulate this can I add un-faced batt insulation and then drywall. I know that the foil-bubble wrap is waterproof so I don’t think I need a vapor barrier before the drywall because if any moisture was able to get in, it would not be able to get out. For the ceiling do I add Faced Batts with the facing point towards the heated space and then Drywall. You are the Guru and I want to see what your experience has to say. Thanks for your time.”

DEAR MARK: As a living space, your pole barn (post frame building) will generate a significant amount of moisture which you do not want to have get into the walls. This means putting a vapor barrier on the inside face of the wall insulation. You will want to make sure the un-faced batts completely fill the insulation cavity, so you will need material with a greater thickness than the R-19 six inch batts sold at your nearby big box store.

Now the challenge – you need to poke holes in the reflective wall insulation to allow any chance moisture from within the wall to escape. Trapping water vapor between the two vapor barriers will only lead to eventual grief in the form of mold, mildew and/or rot.

For the ceiling, it is essential to ventilate the dead air attic space you will be creating. Ideally your building was constructed with vented eaves and ridge and life will be good. You will want to use either un-faced batts, or ideally blow in insulation above your ceiling. Do not place a vapor barrier in the attic – as you want moisture to be able to rise into the attic space and be exhausted through the ridge vents.

 

Planning a new post frame building? If your building will have dimensions which could ever lend themselves to some or all of the building being used as conditioned space (heated and/or cooled), it would be prudent to design for it now, rather than having to face doing more work (as well as spending more money) at a future date.

An Apartment Addition?

DEAR POLE BARN GURU: Can you supply me with a copy of the sparrow barn in Texas plans It is a wedding venue I would like to copy. JAMES in HAMPTON

DEAR JAMES: Certainly we can, stamped by a registered professional engineer, and custom designed for your climactic loads – and for free. They come along with your investment in a new Hansen Pole Building complete kit package.

Pole Barn Prices

DEAR POLE BARN GURU: I built a 40x60x14 pole barn, trusses 4’oc, cement floor with seal, foil bubble wrap outside all girts and purlins, vented soffits and continuous ridgevent. Trusses have 5psf bottom cord rating. I have read all the posts of yours I could. Would like to put in 24×40 apartment and was looking to put in BIBS insulation with horizontal bookcase framing but ran into a few questions. I’m concerned about drywall cracking/nail popping if I strap bottom truss cords and apply drywall to that. If I drop the ceiling, however, I’ll have to do vertical studs for the ceiling joists to sit on. I see a problem with fireblocking too. How best do you fireblock behind posts (between girts) with bookcased studs? Vertical studs would be even more difficult to fireblock, with 1.5 inch gaps everywhere. Last question is insulation…..With the impermeable foil bubble wrap up against the steel siding, I was going to use the mesh fabric and BIBS only before drywall. I’m concerned about a vapor barrier against drywall as this will primarily be used in summer with a/c on the interior and an outside humid climate. I appreciate any help and advice. MARCUS in ROANOKE

DEAR MARCUS: I appreciate you being a loyal reader!

You will want to place 2×4 ceiling joists on edge (two inch face towards the floor and sky) every 24 inches between the truss bottom chords, using Simpson 2×4 joist hangers on each end. With 5/8″ gypsum wallboard, screwed on per the manufacturer’s installation instructions, it is unlikely you will experience unusual drywall cracking or nail popping. Properly done, your bookcase studs (wall girts) should be supporting the siding on the outside and drywall on the inside. Installed this way, they effectively serve as fire blocking. In the event your building has “barn” style wall girts (flat on the outside face of the columns), use bookshelf girts of a large enough dimension to reach the siding, as well as extend to at least the inside face of the columns (e.g. 2×8 on a 6×6 column).

Commercial-Wall-Girts_EditedThere is going to be a challenge on the walls….your building should actually have building wrap on the outside of the framing to allow any water vapor in the wall cavity to escape to the outside world. The wall vapor barrier should be on the inside face of the wall girts to prevent moist air from inside of your apartment from entering the wall cavity. The reflective insulation in your walls should be either removed or at the very least punctured frequently, prior to wall insulation being installed.

 

DEAR POLE BARN GURU: I am installing shutters on my home, which is a barn style home with metal siding.  My husband is very concerned about which type of screws to use to prevent leaking or rusting.  What do you suggest? AMELIA in HONEA PATH

DEAR AMELIA: Builders Edge Shutter-Lok patented fastening system makes installation fast and easy. Shutter-Lok holds in any material. Shutter-Lok features a durable copolymer construction with molded-through color so that there is no paint to ever scratch, flake, or fade. Installation requires drill with 1/4″ masonry bit.

Spray Foam Insulation with Dupont Tyvek House Wrap

Hansen Pole Buildings Designer Rachel asked me about this today:

“I have more and more builders say they put Tyvek® on the walls and roof and then spray foam.  This is so they can replace the siding/roofing in the future.  Do you find any downfalls with this?  I thought this was a pretty good idea.”

Having just written an article about spray foam insulation (http://www.hansenpolebuildings.com/2016/07/advantages-spray-foam-over-batt-insulation/), this is a well timed question.

Tyvek and all house wraps are NOT (I repeat NOT) vapor barriers. They are weather barriers: http://www.hansenpolebuildings.com/2016/01/determining-the-most-effective-building-weather-resistant-barrier-part-1/.

Spray-Foam-Insulation-150x150In doing my research on the whys and why-nots I found apparently there are some spray foam insulation contractors who will not spray foam against house wraps, apparently from not being able to guarantee their product would properly adhere to the house wrap.

In one particular case – the spray foam insulation contractor tried to persuade the client to use BIBS® insulation (read about BIBS® here: http://www.hansenpolebuildings.com/2011/11/bibs/) due to the potential adhesion issues.

There apparently is an adhesive additive for spray foam, which will assist in the foam being able to stick to house wraps or other slick surfaces.

As spray foam is a vapor barrier, and is resistant to moisture passing through it in either direction, adding a weather barrier to the outside becomes redundant.

If the idea is to use a product to allow for easy residing or reroofing, then a product such as clear visqueen (http://www.hansenpolebuildings.com/2013/07/moisture-barrier/) might prove to be as effective, as well as less costly than a weather barrier. This is, of course, providing the spray foam installer is willing to spray over it.

As a good, high quality steel roofing and siding should last the life of the building – installing any product between it and the siding, under the premise of making future replacement easier, it sounds much more like someone trying to make a feature into a benefit, than it does something which will add value to the client as a benefit!

Concrete & Rain in My New Pole Building

This is a story which is heard all too frequently. And it always revolves around clients having just poured the concrete slabs in their new buildings. Even more so when the building has a low perm rated vapor retarder under the concrete.

Vapor retarders do exactly as their name implies, they retard the movement of water vapor through a system. They are not barriers which completely block the movement of moisture vapor. The amount of water vapor which passes through a vapor retarder is a function of perm rating, vapor pressure differential and penetrations.

The lower the perm rating of a vapor retarded, the better. A 1.0 perm rating will allow approximately 10 times more water vapor to pass through than a product rated 0.09, under the same conditions.

Moisture will flow from areas of high humidity or temperature to areas where these conditions are low. The force which drives the moisture through a vapor retarder is the vapor pressure differential.

wet concrete floorFreshly poured concrete contains a tremendous amount of moisture. In a typical two car garage (24 feet square) with a nominal four inch thick slab – the concrete contains approximately 138 gallons of water! As the concrete cures, much of this water is liberated into the air, increasing the relative humidity and vapor pressure within the building.

Ventilation is the simplest way to reduce humidity and vapor pressure and also lower the probability of condensation related problems. Failure to adequately ventilate a building during and after a concrete pour can result in condensation on the surface of the vapor retarder and potentially within any insulation. This is particularly critical in colder temperatures.

The easiest solution to “rain” after a new pour? Open up all of the doors and windows until the “rain” quits! And don’t panic – this will resolve the problem. My lovely bride came up with the idea of putting several fans on the concrete –but the concrete should NOT be forced to dry any “faster” as this lessens the overall strength of the finished concrete. You are best to retard the rate at which the concrete dries.

The whole point is – as the concrete dries, at its own natural rate, to ventilate out the moisture it releases into the air

Condenstop

Eric’s storage building has 5040 square feet of enclosed area. This made for a big roof. A big insulated roof which had a reflective radiant barrier applied between the roof purlins and the steel roofing.

Whatever type of insulation is chosen for this type of installation, if it is windy – it isn’t going to be fun.

So why even worry about roof insulation or vapor barriers?

Single skin metal roofs (typically found in pole building construction) are prone to condensation due to changing outdoor or indoor conditions. Condensation, sweating and dripping can have severe adverse effects on the condition of the building and its valuable contents.

CondenstopCondenStop fleece is factory applied to the underside or inside of steel roofing and siding panels. It effectively reduces or eliminates the problems caused by condensation.

The Condenstop fleece absorbs, stores and releases significant quantities of moisture when condensation would normally occur. When the temperature of a steel roof drops below the dew point, the CondenStop fleece will absorb and store the condensing water vapor. The absorbed water will evaporate again into the ambient air under appropriate temperature and ventilation conditions.

Condenstop has been commercially available for 15 years and is the industry leader. It is made from durable polyester materials designed to last the lifetime of the steel panels. A wide variety of testing and in-place projects confirm the product’s durability. Once factory applied, the adhesion is quite strong and comes with a 20-year delamination warranty.

The product’s R-value is minimal, only 0.3691, however the product’s value is from its ability to store and release moisture where other materials cannot.

Moisture held in the CondenStop will not harm the steel. Full length panels should be used from eave to ridge to eliminate panel end laps and panel areas which are not enclosed. The bottom edge of the steel overhanging a fascia board, or areas in unenclosed overhangs – should be painted, or the Condenstop burned off to prevent microfibers from absorbing moisture from the outside.

The use of Condenstop does not take away the need for proper ventilation practices, either in performance, or under the Building Code.

CondenStop is Class I flame retardant per ASTM E84-04. It will hold 21 pounds of moisture per 100 square feet (equal to over 10 quarts of water). The microfibers do not support mold growth. It also reduces noise from outside such as rain as well as absorbing sound from inside the building.

On Eric’s building, we easily lost an entire day for the crew due to having to fight the winds installing a reflective radiant barrier. In wind prone areas – CondenStop is an option I would recommend, for the savings in labor costs and time alone. Next time – CondenStop for our building!

Dear Pole Barn Guru: How Much is Truss Weight??

New!  The Pole Barn Guru’s mailbox is overflowing with questions.  Due to high demand, he is answering questions on Saturdays as well as Mondays.

Welcome to Ask the Pole Barn Guru – where you can ask questions about building topics, with answers posted on Mondays.  With many questions to answer, please be patient to watch for yours to come up on a future Monday or Saturday segment.  If you want a quick answer, please be sure to answer with a “reply-able” email address.

Email all questions to: PoleBarnGuru@HansenPoleBuildings.com

                                             

DEAR POLE BARN GURU: Hello, I’m an engineering student doing a research about sustainable buildings, can you tell me the approximate 20′ metal truss weight and 24′ wood truss weight?

Please I need the answer urgently. CALCULATING IN KALAMAZOO

 

DEAR CALCULATING: Nice to have engineering students reading this column!

Having been given no parameters for load carrying capacity, truss spacing or roof slope, leaves me just winging out an answer.

For wood trusses with a total load of around 180 pounds per lineal foot (30 pounds per square foot spaced one at six foot or two at 12 feet), a single 24 foot span 4/12 slope truss weight should be about 125 pounds.

I’ve never dealt with steel trusses, however I was able to find several formulas, as well as a table for calculating the steel truss weight, W being weight per horizontal square foot, S = span in feet, P = capacity of truss in pounds per horizontal square foot, and A the distance center to center of trusses in feet:

Charles Evan Fowler, P. E., for Fink trusses:

W = .06S + .6 for heavy loads; W= .04S + .4 for light loads.

H. G. Tyrrell, P. E.:

W = .05S+ distance center to center.

C. W. Bryan, P. E.:

W = .04S + 4.

M. S. Ketchum. P. E.:

+ For scissors trusses increase one-third.

Weight Per Square Foot Of Roof Surface For Steel Trusses

6/12 Slope 4/12 Slope 3/12 Slope
Up to 40 ft. 5.25 6.3 6.8 7.6
50 ft. 5.75 6.6 7.2 8.0
60 ft. 6.75 8.0 8.6 9.6
70 ft. 7.25 8.5 9.2 10.2
80 ft. 7.75 9.0 9.7 10.8
100 ft. 8.5 10.0 10.8 12.0
120 ft. 9.5 11.0 12.0 13.2
140 ft. 10.0 11.6 12.6 14.0

As you can see – lots of opinions on the steel truss (as are probably huge variants in their configuration).

DEAR POLE BARN GURU:We’ve just had a 40’x60′ steel pole barn constructed (in the woods) for storing classic cars. We had the builder install and frame fiberglass insulation in. We’re installing OSB wall panels ourselves. Wondering if we should cover the fiberglass with ‘Visqueen’ for vapor barrier or would we be better served by installing foil faced OSB panels?

Thanks CONCERNED IN KOKOMO

DEAR CONCERNED: Most often fiberglass batt insulation which is used in walls has a paper (or “kraft”) facing on the inside, which when properly installed serves as the vapor barrier. If unfaced batts were used, then a clear plastic vapor barrier should be installed on the inside face. Foil faced OSB panels are designed to be placed below roofing to assist in keeping attics cooler in warm climates, it is not designed to be or replace vapor barriers in walls.

 

 

Dear Guru: Can I Add to My Pole Barn in the Future?

DEAR POLE BARN GURU: I’m very interested in doing business with you, I just have a few questions. I originally asked for a quote of a pole barn of 200×50 I believe it was, my question is, can your buildings be added on to? Would we be able to start with something much smaller and then add on to the barn as we go? NOW IN NEW JERSEY

DEAR NOW: Yes, our buildings can be added on to. I would recommend the initial design be done with the idea of what the ultimate finished goal will be for size. Oftentimes, original structures are not structurally set up for the eventual expansion, which keeps the initial price low, but results in headaches and costs later, which could have been avoided with proper planning. A gabled roof will be the easiest roof style to work with when it comes to future expansion.

We have several customers who have done just as you suggest, adding on to one or both ends as they expand. Get the width you ultimately want, then adding length is much easier You can remove endwall siding, add on additional bays, and put the endwall siding back on. You may have to purchase more trims, but if steel siding, is easily reused for the addition.

And I always recommend – build as much building as you have space for and can afford economically, as whatever size you pick, it will never be large enough.

DEAR POLE BARN GURU: I’ve read ALL of your blogs!  Back to 2010. And love them. I write similar stuff in my business.

The question is do you have, or can you get, closures similar to ridge vent, but as a bottom closure to be used at the eave of a building without overhangs? BREEZY

DEAR BREEZY: Thank you for your dedicated readership and …good question! There is not such a beast, and even if there was, the net ventilation would be tiny – not enough to yield any positive results, as the only area which could have a vent would be just at the high ribs. The correct way to vent would really be with enclosed vented overhangs.

DEAR POLE BARN GURU:I have an existing pole building with badly deteriorating insulation and vapor barrier for the roof.

I plan to pull all of the old insulation and vapor barrier out to replace it.  I’d like to use the reflective radiant barrier / vapor barrier you recommend for new construction.  I’m considering pulling the metal roofing off to do it right so I don’t have to do it again later.

Do you recommend installing the reflective radiant barrier / vapor barrier between the metal roofing and purlins or between the purlins and roof trusses? DETERIORATING IN DELAWARE

DEAR DETERIORATING:
Place the reflective radiant barrier over the purlins and directly under the roof steel. You will need to use larger diameter, longer screws to reattach the roof steel.

DEAR POLE BARN GURU:Where can I buy Owens Corning Foamular Fanfold foam 1/4″ thick? A lot of my fellow RC plane hobbyists are having a hard time finding this stuff. Thanks in advance. FLYING IN FREMONT                          DEAR FLYING: Visit the Contractor Desk of any The Home Depot®. If it is not in stock, it can be ordered in within a matter of just a few days.

Dear Guru: What Steps Should I Take to Add Insulation To My Pole Barn?

Welcome to Ask the Pole Barn Guru – where you can ask questions about building topics, with answers posted on Mondays.  With many questions to answer, please be patient to watch for yours to come up on a future Monday segment.  If you want a quick answer, please be sure to answer with a “reply-able” email address.

Email all questions to: PoleBarnGuru@HansenPoleBuildings.com

DEAR POLE BARN GURU: My question concerns insulation and ventilation. I have an existing 30 x 50 pole barn. It is split in half lengthwise, with one half enclosed and the other half open on one side. I am wanting to frame and enclose the open wall and make the building into a woodworking shop. I would primarily use this shop during the warmer months, but would like to be able to work in there in the wintertime on occasion. I am planning to re-tin the entire building including the roof. The current enclosed portion has trusses that span roughly 15 feet from wall to wall with a 12/3 pitch. The area that I am wanting to enclose is “lean to” construction with 2 x 10 rafters that span from the truss beams of the already enclosed area to a double 2 x 12 beam (approximately 15 feet). My building does not have soffit ventilation or ridge ventilation. From what I have learned from your blog, I am planning to add reflective barrier between the purlins and metal roof when it is replaced. I also know that my trusses are most likely not designed to bear the weight of a ceiling and insulation. I would like to either insulate the entire building or at least the newly enclosed area and keep the other as cold storage. I would like to know what options I have to make either of these a reality and what steps to take as far as insulation and vapor barrier is concerned? I have included my e-mail and I tried to include photos but could not attach them. Please respond with your e-mail and I will send the photos right away and any additional information you might need. Thanks so much! NO CRISIS IN KANSAS

 DEAR KANSAS: We did figure out how to get photos from your hands to our eyes, thank you very much for your efforts.

After seeing the photos, my response was, Rather than throwing a lot of dollars into your existing building, have you considered just leaving it as is for cold storage, and putting up a new woodworking shop?”

 I’ve written in the past about renovation and remodel work on pole buildings:

http://www.hansenpolebuildings.com/blog/2013/01/pole-barn-remodel/

http://www.hansenpolebuildings.com/blog/2013/05/renovating-a-pole-barn/

A little more input from this very kind gentlemen helped: “I was trying to use my existing building because it already has concrete floors and 200 amp electrical service.”

And back from me: “Trying to re-purpose and existing building is rarely the most economical or practical solution. Especially if it involves the cost of residing and reroofing (since these two items typically represent about 50% of the cost of the building). In looking at the photos, the way the concrete is poured leads me to believe you are going to have water coming in under the outside building wall.”

What clinched me having to help this guy out was: “The existing barn may be my only option due to the wife wanting its appearance improved regardless!”

If mama ain’t happy, ain’t no body happy!

As I do not know the version of the Building Code (if any) your building was constructed under, nor the applicable wind and snow loads, I can only make broad structural recommendations. In most permit issuing jurisdictions, they work you propose to do does require a building permit to be acquired. I’d recommend you confirm yes or no.

In the end, it would be an excellent idea to contract with a registered design professional RDP (engineer or architect) to confirm structural integrity of the existing building, as well as to appropriately size new members being added, as well as their connections.

Starting with the basics, remove all of the siding and roofing. Where an exterior wall will have a climate controlled area opposite, remove all girts. Install new wall girts at 24 inches on center, of a size large enough to be flush on the outside of the walls with existing pressure treated splash planks, etc. With 6×6 columns, it will take 2×8 girts placed like bookshelves. In order to keep wall screw lines even, you may want to opt to swap out the girts universally (it also allows the future ability to insulate other portions of the building at a later date).

As you will be down to bare framing, I would highly recommend adding enclosed vented overhangs on all four sides of the building. This will allow for an air intake, which is going to be essential to the overall system performance during steps outlined below.

Before installing new roof steel, install the reflective radiant barrier on top of the roof purlins. I recommend the A1V product from www.buyreflectiveinsulation.com, as it has tabs with adhesive pull strips to seal each piece to the prior one. Use high quality vented ridge closures under the ridge cap, to provide an air exhaust.

Wrap the building walls with a high quality building wrap.

Read more here: http://www.hansenpolebuildings.com/blog/2012/11/house-wrap/

In areas you want to climate control, install a 2x beam (or header) to the inside face of the columns. From beam to beam ceiling joists can be placed every two feet to support gypsum wallboard.

With the newly created wall cavities, you can use batt insulation or BIBs. For the ceiling, I’d suggest blowing in insulation, once the ceiling has been drywalled.

Assuming you move forward with this, I am hoping you won’t mind sharing progress photos.

When it is all done, it should look and function just like a new building.

Dear Guru: Do I Need Vapor Barrier Under Insulation?

Welcome to Ask the Pole Barn Guru – where you can ask questions about building topics, with answers posted on Mondays.  With many questions to answer, please be patient to watch for yours to come up on a future Monday segment.  If you want a quick answer, please be sure to answer with a “reply-able” email address.

Email all questions to: PoleBarnGuru@HansenPoleBuildings.com

DEAR POLE BARN GURU: Is it a huge mistake to go without a vapor barrier on the walls?  How about Tyvek on the walls during construction?  I was thinking of doing Tyvek between the metal siding and the purlins to at least get that vapor barrier in there, just in case I decide to put insulation in my walls later when the budget allows.  Thoughts? CONTEMPLATING IN KANSAS CITY

DEAR CONTEMPLATING: If you EVER think you or the person(s) who own your pole building after you, will ever apply insulation to the walls of a building – then placing a quality house wrap between the wall girts and the siding (whether it be steel or any other material) is an excellent idea for a vapor barrier. At time of construction is the one single time in which it will be extremely easy to add.

To learn more about house wrap: http://www.hansenpolebuildings.com/blog/2012/11/house-wrap/

 

DEAR POLE BARN GURU Insulation – I read your warning about the steel skin acting like “unibody” construction, so it should be applied directly to framing. What is a good way to use foil-faced foam board for putting insulation on a roof? I want to avoid using the large rolls of insulation that will sag in 6-8 years? LEARY IN LOUISIANA

DEAR LEARY: I am glad you have been reading and paying attention.  Your new building will be well planned, with pleasing results. I just am seeing no way for foil-faced foam board to be a practical and economical solution for roof insulation. Here is a link to an article I wrote which might give you some further food for thought:

http://www.hansenpolebuildings.com/blog/2013/07/insulation-6/

Moisture Barrier: A Bad Place for Plastic

Eric, one of the owners of Hansen Buildings, was chattering with me today about the number of interesting telephone calls he fields. Many of these are probably due to this blog, as well as “Ask the Pole Barn Guru” – the weekly advice column for those with pole building questions, concerns, or who just are looking for free therapy.

A gentleman had recently erected a pole building, and placed six ml (0.15 millimeter thick) clear plastic visqueen as a vapor barrier between his sidewall girts and wall steel.

clear-plastic-wrapVisqueen is a brand of polyethylene plastic sheeting produced by British Polythene Industries Limited, and has become a generic description for any plastic sheeting (think Kleenex). Because I know lots of near worthless trivial information, it is important to know Visqueen was first produced about 1950 by the Visking Corporation, a company founded in the 1920s by Erwin O. Freund for the purpose of making casings for meat products. Visking investigated the post-World War II emerging technology of polyethylene, and developed manufacturing techniques to make pure virgin polyethylene film. Originally spelled VisQueen, the film is an excellent moisture barrier and was marketed to many industrial, architectural, and consumer applications, such as moisture barriers, plant seedbed protection films, building fumigation barriers, drop cloths, case liners, and tarpaulins.

Anyhow, in the application above, there isn’t any problem….until the building owner wants to insulate the building walls, then place another vapor barrier on the inside of the walls.

Every Fall, when I was a youngster, my grandmother would make massive quantities of apple sauce, at their lake cabin. All of the wonderful smelling boiling concoction put lots of water vapor into the air of the kitchen. When this warm moist air met the nice cool window glass, it became condensation. The same happens with any surface or material which stops vapor. For example, the painted surface of the drywall will also prevent most moisture from passing through …. which is why higher gloss paint is used in kitchens and bathrooms. If the drywall were not painted, the moisture / vapor would simply absorb into the drywall material. So think of the paint as a type of moisture barrier to protect the drywall.

But vapor can occur even without obvious introduction of moisture into the air. Wherever warm air meets cold air there will be a high concentration of vapor in the area. So wherever the vapor barrier is placed in a wall is where the condensation will occur.
Think of it as a cold and warm weather front meeting inside a wall …. and the forecast is rain.

The condensation held by the vapor barrier will eventually go back into the air once the volume of vapor decreases. This is allowed to happen only if there is good ventilation on both sides of the barrier.

Vapor will penetrate any material in its way until it hits a barrier, this is why it is important to position vapor barriers on the warm (inside) side of walls. When warmer air meets colder air condensation will develop. Imagine the damage to insulation if the barrier was on the outer side of the insulation? Warm air (and/or moisture) would create condensation on the vapor barrier which would eventually absorb into the insulation causing all kinds of water damage and possible mold growth.

Our friend would have been so much further ahead by having used a house wrap between the wall girts and the steel siding, as house wrap is permeable (it allows excess moisture to pass through).

My expert advice would be to slice holes in the visqueen to allow any accumulated moisture to pass through.

 

What House Wrap is Good For

Over the past three decades, house wrap has become a staple feature on millions of buildings. Wrapping a wood framed building in a protective envelope is a good building practice which helps combat a building’s worst enemies: water, moisture and air infiltration. House wrap behind a building’s siding is an excellent secondary defense against the weather.

House wrap is a weatherization membrane which provides a protective layer under a building’s siding and over the wall girts or sheathing. It is literally wrapped around a building, cut out around windows and doors and taped at the seams.

The unique, nonwoven-fiber structure of house wrap resists air infiltration and water intrusion, yet is engineered to readily allow moisture vapor to diffuse through the sheet, helping prevent mold and mildew buildup and wood rot. The fibrous structure is engineered with microscopic pores which readily allow moisture vapor to evaporate but are so small bulk water and air cannot penetrate. Siding, whether vinyl, wood, stucco, brick, or composite, does not completely prevent air and water penetration. House wrap is designed as a secondary defense to help manage a building’s wall systems.

R-Value ratings for insulation are only maintained as long as the air within the insulation stays still and dry. The Department of Energy estimates nearly 40% of a building’s energy loss is the result of air infiltration caused by wind driven pressures from the outside. The opposing forces of pressure between inside and outside walls cause heat and air conditioning to be virtually sucked from a building– through walls, ceilings, sill plates, sheathing joints, top plates, electrical outlets and every inch of the estimated half-mile of cracks in newly constructed buildings. As air infiltrates, it causes changes in temperature which require heaters or air conditioners to work harder. Constant temperature fluctuations also reduce comfort levels. Occupants feel too cold or too warm. Reducing air infiltration increases a building’s comfort factor.

Insulation can help increase the R-value, but it is only marginally effective in reducing air infiltration. When air infiltrates, the R-value itself can be reduced up to 60%. Adding thicker insulation won’t solve the problem. Stopping air from getting in, will.

Properly applied, house wrap helps reduce air infiltration, preserving R-values, conserving energy, reducing heating costs and creating a more comfortable interior.

The tighter the building, the more comfortable and efficient. Unfortunately, the tighter a home, the more susceptible to moisture problems which can cause mold, mildew and rot. So all systems need to be in balance–designed to manage water and moisture effectively.

There are two main ways water and moisture get into wall systems:

Bulk water intrusion from the exterior (rain and snow) can enter the wall and, if not allowed to dry in a reasonable amount of time, can raise the moisture content of the wood above 30% and cause rotting or mold and mildew.

Air transported moisture occurs when air leaks from the warm side of the wall to the cool side. Warm air will hold higher amounts of moisture than cold air. As warm air travels through a wall heading to the cold side, it will begin to cool and be forced to release moisture. This is called the dew point where condensation will occur. When there is a significant temperature drop across the wall, the dew point will occur somewhere within the wall. In the winter months the point of condensation is usually on the inside surface of the exterior sheathing. Moisture carried by air flow through the wall is deposited at the back side of the sheathing and accumulates. In hot and humid climates where air flow is traveling from the outside to the inside, warm moist air from the outside will be cooled on the way to the air conditioned inside, releasing moisture within the wall cavity. House wrap is a breathable membrane with microscopic pores which allow the moisture vapor to dissipate, helping to dry out a wall system to avoid damage.

Moisture Vapor Transmission Rate or perm rate of a material determines the ability for water vapor to diffuse or evaporate through the wall. The higher the perm rate, the more “breathable” the material is and the easier it is for water vapor to pass through. Materials with Perms below 1 are considered vapor retarders since the rate of moisture vapor flow through a 1 Perm material is so low there is essentially no flow. House wraps have Perm rates in the area of at least 58 Perms which is very open to allow moisture vapor to flow through.

What house wrap is not, is a vapor barrier or an insulation. I’ve seen instances where people have applied house wrap directly between roof purlins and roof steel, in an effort to control condensation. House wrap is quite permeable; any warm moist air which would rise to it will pass through to the underside of the roof steel and condense.

House wrap is great…if used for what it was intended for…a secondary defense against the weather.

And Now…Insulation Crime!

If you didn’t read yesterday’s blog – is good to catch up as a lead-in for today – well worth the time.  In it I discussed a problem a reader had asked for tech support about an insulation issue.

So today – yet another reader has written….

“I am in the process of finishing a pole building. The building will be used as my workshop and it will be heated, I live in Washington State. The contractor that put up the exterior placed R-23 Kraft Faced fiberglass insulation between the 2 X 6 rafters with the facing against the metal corrugated roof. This means that the vapor barrier is facing the roof, not the inside of my building. I plan to install sheetrock on the ceiling. It is not uncommon for the temperature to dip below zero here, and in the summer reach 100 for a month or more. My question is can I place a 4 mil poly vapor barrier on the interior side of the roof thereby wrapping the fiberglass insulation in two vapor barriers?”

What this building owner has is a pole building with 2×6 roof purlins on edge. Condensation on the inside of steel roofing applied directly on top of purlins can be an issue. This particular builder errantly installed batt insulation with the vapor barrier towards the steel, in efforts to reduce or eliminate the condensation problem.

If the builder would have properly installed the insulation between the purlins, with the Kraft facing towards the climate controlled area, making sure all seams were sealed, it would have been both effective as insulation and the vapor barrier would have kept the warm moist air inside the building, from condensing on the underside of the roof steel.

Why do I call this scenario “insulation crime”?  Because the builder took his client’s hard earned money and in return, gave him nothing but a problem to be solved.

Nearly every jurisdiction in the state of Washington requires both a Building Permit as well as the inspection of new buildings under construction. If this was a permitted building, the Building Inspector should have noticed the improper insulation installation and issued a correction notice – rather than signing off on a final inspection.

Insulation Dilemma

A reader writes (spelling, grammar errors included):

“When I built my barn I had 2″ insulation bats put between the outside framing and the tin. The side toward the tin is just open insulation. The inside is that heavy with plastic or whatever it is. I built with books shelve perlins on 2′ centers. Thinking it would make it an easy job to just fill those cavities with insulation. 

Where I’m confused is on the vapor barrier. We have a local business that makes insulation. Actually my insulation came from them. They guy there told me to just slice open the white vapor barrier and add insulation then use plastic over the added insulation prior to finishing my walls. So I’m just looking for affirmation that this is the correct way to go. Or other ideas and opinions.

Thanks.”

From the description, I will assume the two inch insulation batts are what is known as Metal Building Insulation. This type of insulation is actually designed to reduce condensation issues in building which have steel roofing and/or siding applied directly over roof purlins or wall girts.

Metal Building Insulation is not an effective insulator, as the fiberglass insulation gets crushed down to nothing every time it crosses a framing member.

This particular building is designed with sidewall framing (girts actually, not purlins which are on a roof) placed bookshelf style to create an insulation cavity. The builder did not do his customer any favors and actually spent his customer’s money unwisely.

Moisture within the walls of a pole building can cause serious problems.  In the colder months, moisture tends to move from the inside to the outside of buildings.  As it passes through the walls, it may condense within them, causing the potential for rot and mildew.  In walls with insulation, the water may condense within the insulation decreasing its R-value.  In the worst case, moisture can actually freeze within the walls, accumulating until a thaw melts it and causes visible damage such as wall or ceiling staining!

A vapor barrier is designed to keep moisture in pole barns from getting inside exterior walls.  Batt and roll insulations usually come with a vapor barrier attached.  However, leakage can occur where the facings meet.  This is especially true if the facings are not stapled to the inside of the wall girts, but instead the insulation is just pressed into place or stapled on the inside of the girt (all too common of a practice with foil faced insulation).  For the best possible vapor barrier, supplement the facing by installing a 4mil or thicker clear plastic sheet over the inside of the entire framed wall before installing any interior finishes (like gypsum wallboard).

Never sandwich the insulation between two vapor barriers. For example, do not install insulation with the vapor barrier facing the climate controlled space and then put plastic sheeting, or some type of vapor barrier, across the outside of the framing. Since some leakage of moisture into the insulation in inevitable, it needs to be able to freely escape from the insulation to the outside world ….. not be trapped inside!

 

Thermodynamics and Reflective Radiant Barriers Part II: Application

As I said yesterday, the reflective radiant barrier inhibits heat transfer by thermal radiation. It does not necessarily protect against heat transfer by conduction or convection.  Why do you need to know about reflective radiant barriers?  It could mean thousands of dollars saved over the years for heating/cooling, in what you choose for roofing materials, and what lies beneath them. It might help for you to read yesterday’s blog for background on how I got to this point.

Continuing on….

For installing a reflective radiant barrier under a pole building steel roof, the reflective radiant barrier may be applied directly by draping the reflective radiant barrier over the roof purlins. Even more effective is to install the reflective radiant barrier over the purlins, install 2×4 furring strips on top of the insulation, and then the roof steel. The furring strips ensure the reflective radiant barrier faces into a sufficient air space to be effective. If an air space is not present or is too small, heat may be able to conduct through the reflective radiant barrier. Since the metal in the reflective radiant barrier is highly conductive, the heat transfer would all be through conduction and the heat would not be blocked.

I did this on my huge 3 story gambrel style accessory building I built in South Dakota about 7 years ago.  I put 2×4’s over the reflective radiant barrier, and then applied the roof steel.  My wife chose black steel, and so I added in the 2×4’s both to counteract her color choice and get the most out of the insulating value of the reflective radiant barrier.  Our heating/cooling bills are phenomenally small.  In fact, this 84’ x 60’ x 20’ building is easily a third less expensive to heat/cool than our 30’ x 60’ single story home across the road from it!

For shingled roofs, the reflective radiant barrier may be applied over the rafters or trusses and under the roof decking (usually osb or plywood). This application method has the reflective radiant barrier sheets draped over the trusses of rafters, creating a small air space above with the reflective radiant barrier facing into the entire interior attic space below.

I even used this method in re-roofing our house two summers ago.  The shingles had seen their better use, so we applied 2×4’s right over the shingles, put down the reflective radiant barrier and then applied white roof steel for a “cool roof” solution.  It’s noticeably cooler in summer and much warmer in winter, along with lower energy bills.

Another method of applying a reflective radiant barrier to the roof in new construction would be to use a reflective radiant barrier which is pre-laminated to OSB or roof sheathing. While manufacturers of this installation method often tout the savings in labor costs in using a product which serves as roof decking and a reflective radiant barrier in one, these products are generally considered by most to be “pricey”.

One common misconception regarding reflective radiant barriers is the heat reflecting off the reflective radiant barrier back out the roof has the potential to increase the roof temperature and possibly damage shingles. This is simply not the case. Performance testing by Florida Solar Energy Center conclusively proved the increase in temperature at the hottest part of the day was no more than about 5 degrees F. In fact, this study showed the reflective radiant barrier had the potential to decrease the roof temperature once the sun went down because it was preventing the heat loss through the roof. RIMA (Roofing Insulation Manufacturers Association) International wrote a technical paper on the subject, where they collected statements from the largest roofing manufacturers, and none said a reflective radiant barrier would in any way affect the warranty of the shingles

Wrapping a building’s walls with a reflective radiant barrier can result in a 10% to 20% reduction in the tonnage air conditioning system requirement, and save both energy and construction costs.

Reflective radiant barriers are also quite effective in floor systems above unheated basements and crawl spaces. The reflective radiant barrier may be either stapled below the floor joists, creating a single reflective air space, or between the joists, followed by some type of sheathing. Reflective radiant barriers work extremely well in this application for two reasons. First, a reflective radiant barrier which is not perforated for breathability acts as an excellent vapor barrier. This means ground moisture will not be able to pass through the reflective radiant barrier and enter the living space. Secondly, the floor is the only part of the building where the heat flow is always down, unlike a roof where the heat would be coming down during the summer and rising to escape in the winter. When the heat flow is down, 93% of the heat is radiant heat, which is exactly what the reflective radiant barrier is designed to block.

A reflective radiant barrier actually IS insulation and it DOES have actual R values in tested systems. It IS highly directional, meaning it is better against heat gain, than heat loss. In tests, it rates as high as R-14, depending upon the installation.

However reflective radiant barrier are not the “end all” of insulation. My preference is to use it for what it is great as – an insulated vapor barrier.

There are many commercially available vapor barriers. These include Tyvek® (a registered trademark of the DuPont Corporation) and other similar housewraps. Even polyethylene plastic sheeting (think of British Polythene Industries Limited’s product Visqueen) is a vapor barrier.

While fine vapor barriers, none of these products have insulation bonded to them, so are not an effective method of condensation control. In order to control condensation, a thermal break must be created. It is the layer of air cells sandwiched between the facings of the reflective radiant barrier (most commonly a white inner facing and an aluminum exterior facing) which creates the necessary thermal break.

If the only intention for heating a pole building is to take the chill off for a few hours with light heat (like throwing a space heater on), then the reflective radiant barrier can be an affordable option. For buildings which are to be climate controlled, other options are more practical.

For more information on reflective radiant barriers, I’d recommend visiting http://www.buyreflectiveinsulation.com, which also features a handy calculator to determine the required amounts of insulation for gable roofed buildings.

Reflective radiant barrier in Pole Buildings

As I mentioned yesterday, once you decide what your “needs” are when it comes to insulation, you can begin to narrow down your choices.  Just knowing the “R” value is not enough.  Sometimes insulation is used in other ways – like a reflective radiant barrier.

We use a product which “just is what it is”.  Meaning, it’s not high on the R value, but the “use” is of far greater importance than true insulating value.

Our standard insulation is what is known as “A1V”.  This is a layer of closed air cells sandwiched between a reflective aluminum (A= Aluminum) facing on the exterior and a white vinyl (V= vinyl) facing on the interior. This product is “directional” when installed on a roof – it is better at preventing heat gain, than heat loss. Laboratory test results have given it values as great as R-14 against heat gain. Under no circumstances should you necessarily expect numbers close to this, or rely upon a reflective radiant barrier as the sole method of preventing heat loss or heat gain. The way I think of reflective radiant barrier is this: If you have a steel roof – it is a condensation barrier so it doesn’t rain on whatever I have in my building.

I have folks who tell me, “but I live in Arizona so I don’t need vapor barrier”.  Or they think because their “roof only” building where they are stacking hay underneath is totally open to the air underneath – it’s going to stay dry.  Think again.  No matter where you are, at some point in time the warm air rises from the ground after being bathed in sun all day. And when it hits the cooler temperature of the steel roof, the moisture condenses and yes, it will rain on you!

Another thing – because my newest building has a black roof which loves those sun rays, the aluminum facing reflects the heat and keeps my cooling costs down in the summertime.

There is also A2V – which is just what it sounds like: A=Aluminum, then 2 layers of air cells – and then V=Vinyl backing.  This is the insulation I have underneath my concrete floor to aid in keeping the heat – in the concrete and not end up trying to heat “halfway to China” as my Mother used to say.  The 2 layers of air cells are necessary from the standpoint of the bearing the weight of the concrete floor.  This time the aluminum side is “face down”, as the aluminum will react with the chemicals in the concrete. A2V is also pretty handy (easy to apply) around foundations, around water heaters and insulating garage doors.

One more product I want to mention is A2A – which as the name implies, has two layers of air cells between a layer of aluminum on both outer surfaces.  Once again, the layers of air cells are giving you two layers of tiny pockets of air to resist the transfer of heat through materials.  More layers of air cells means more layers of insulating value.  Back to the purpose of why you are using it – if indeed you are looking for some heavy duty insulation – A1V or even A2V alone is not the answer.  In combination with other products – you get the best of both worlds.

And this is why I wrapped my entire building in A1V, but then filled the attic and exterior wall cavities with BIBS® insulation.  My heating and cooling bills for this 7200 square accessory building are less than the costs for heating/cooling my double wide 2100 square foot 1994 home across the street.  Now that’s scary!  Back tomorrow with more on insulation – the itchy kind!

Building Insulation: Vapor Barrier

Insulation is one of the topics, once brought into conversation, seems to make most folks’ eyes glaze over.  Many know enough to ask about R Value, and understand “the higher the better”.  Or so they think.  Sometimes you need to stop a minute and go back to the source of what I call “the need”.  This is the way I teach our Building Designers, and clients as well, to think about any feature or addition to their pole building kit when they design their new building.  What are you going to need for your building?  Don’t just throw a bunch of stuff in and on there because it “my neighbor put it on his building”.  What are your needs?  Obviously we all choose features we want on our building, “just because”.  Just because it looks nice, gives the building a classier look, a lower profile, or we think the eagle on the weathervane hovering over the cupola is “pretty cool”.  This is all well and good, but insulation is not one of those “pretty parts” of a building.  Necessary yes, but what type and where do you put it?

When I designed my most recent pole building for my own use, I researched several types of insulation, and ended up using not one or two, but three different types of insulation, and each of them for their own specific purpose in relation to cost.  In other words, “what is the cost value” for each of them?

The types of insulation I looked at ranged from what most folks think of when you say “insulation”: fiberglass insulation, to foam board, spray on foam and B.I.B.’s (Blow in Blanket) along with the reflective type vapor barrier insulation in various configurations and applications.  I ended up putting reflective radiant barrier under my roof steel, wrapped my entire outside of the building in a reflective radiant barrier, put reflective radiant barrier under the heated concrete floor, fiberglass insulation in the interior walls, and then B.I.B.’s in the exterior walls.  Wow, I hear clients saying, “How do you know what to put where?”  Easy – once again it goes back to the “need”.  Over the next couple of days I will cover a few of the insulation choices out there, so get out a sheet of paper, make yourself a grid, and next time you need insulation, ask yourself these easy questions to decide “which insulation you are going to put where” in your new pole building.

First question, what is R value? For those of you who are not familiar with R values, it is simply the measure of resistance to heat flow. R-1 is equal to the resistance of a 1” thickness of wood. Insulation materials have tiny pockets of trapped air. These pockets resist the transfer of heat through material.  The ability of insulation to slow the transfer of heat is measured in R-values.  The higher the R-value, the better insulation’s ability to resist the flow of heat through it. Before you consider these products, read the test reports carefully.  In order to achieve the full promised values, the products must be installed in the center of an appropriate dead air space.

Second question, what are you going to be using your building for?  This will help you to determine what type of insulation you are going to need.  Of course, your “need” for insulation also depends on where you live.  If you are in Minnesota where I have my newest building, and want to change the oil in your car in January, putting reflective radiant barrier in the roof and even on the walls is probably not going to keep me warm.  No heating system is going to keep up with the heat pumping out of my building!

And, if you live in Knoxville, Tennessee and are OK working in your shop with coveralls on a few hours a week, your insulation answer will be greatly different than if you want to sit in your new shop in your shirtsleeves with your buddies watching the Super Bowl come January!

So your first project is this: take a sheet of paper and write down all the things you want to “do” within the confines your new building, including keeping pets, horses, or other animals at the right temperature.  Also make a list of other reasons we put insulation in spaces – noise for one.  Do you need good sound abatement for the “practice garage” for your son’s rock and roll band?  Is the loft bedroom right above where you work on motors or have a workshop with noisy machinery?

Once you decide on what your needs are for insulation, you can just match it to the Insulation Grid we’ll be making over the next several days.  I’ll be back tomorrow to start with the simplest of all insulation: reflective radiant barrier which includes a vapor barrier.  Winter is coming, so stay warm!

Lying or Just Plain Stupid?

Yesterday afternoon, one of our senior building designers sent me this instant message:Kid ready to make a bad decision

“So what do you do with a customer who is being sold a bill of goods by his contractor? Starting from, client was told he needed to pour footings and build with 2×6 studs because pole buildings ‘move too much’. All the way to – ‘you need to sheet your walls and roof with plywood before you put steel on’. This is because of security and dust coming through the walls. Not to mention on the roof for a vapor barrier.”

It amazes me the ignorance about pole buildings after over 80 years of solid pole building construction.

A bit more about this particular client’s building. It is 40’ x 80’ with a 14’ eave height. The client initially contacted the builder to get a labor quote only –  to construct a Hansen Building kit.  The client specifically asked for one of our pole buildings.  The builder told this client a pole building would be way too complicated to construct and the stick frame building would be less expensive.

Let’s look at the realities of the situation. To construct a stick frame building will take excavating a trench around the perimeter of the building to below the frost line (and it DOES freeze deep in Maine). A footing must be formed and poured. With a wall this tall, I’d imagine at the least it would have to be eight inches thick and 16 inches wide with rebar in it. On top of the footing will need to be formed up a foundation wall. This foundation is going to be a minimum of four feet tall, due to the frost depth. The wall should probably be an eight inch wall, but assuming six inch thick, three truckloads of concrete will be used for the footings and foundation! With the pole building, holes are augered in the ground and around five yards of concrete are required for the backfill. Pretty low tech and saves a bunch of money in equipment, materials and labor.

A kicker the contractor may not have considered, or has ignored….the maximum stud wall height allowed (according to code) without engineering is 10’. His building is going to need to be designed by a registered professional engineer in order to meet code requirements.

As far as “movement”, steel roofing and siding has shear values nearly equal to those of 7/16” osb or ½” plywood. Imagine the steel as being very thin, very strong plywood. It is the sheathing of a building which holds the frame stable, not the framework. With steel and plywood virtually equal for strength, it takes away the “movement” issue. Our Hansen pole building office is 44 feet high from ground to roof peak and has no noticeable movement in even the extreme wind loads of South Dakota.

Moving on, let’s address the issue of “eliminating dust”.  Each steel panel overlaps the adjacent panel which prevents dust infiltration. Base trim (aka “rat guard”) keeps dust from entering around the base of the building. All other steel edges have trims which cover possible infiltration areas. The eave edge of the roof steel and under the ridge cap are sealed by form fitting closure strips, which seal those areas.

The only place for dust to enter either style of building is going to be via an open door! Same goes for security – your building is only going to be as secure  as the quality of the doors. Chances are the builder is going to provide entry doors with wood jambs, which is an invitation to enter via a good swift kick. The commercial steel doors we provide have steel jambs as well.  No one is going to break those jambs with a kick.

As for a vapor barrier, our buildings come standard with a reflective radiant barrier for under the roof steel. With our exclusive PSA (pull strip attached) adhesive strips, proper installation assures the elimination of condensation. A side benefit being the increased insulation value and the reflective radiant barrier is superior against heat gain. Using plywood on a roof proves to be expensive, adds weight to the roof system and requires the use of asphalt felt paper or other similar and materials to create a water tight seal.

If ignorance is bliss, this particular contractor is either very happy, or he is feeding a line to the client. If the first, he is doing no justice to the client, if the second, he’s worse yet.  My guess is… stick framed is all he knows.  He is just too lazy to try something “new”, easier….and cheaper for the customer, while being just as solid, air tight and long lasting.

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