Tag Archives: radiant reflective barrier

Decisions, Decisions – Vapor Barrier for a Post Frame Steel Reroof

Decisions, Decisions – Vapor Barrier for a Post Frame Steel Reroof

There are few reasons to replace an existing post frame building’s steel roof, as properly installed it should last a lifetime. Among these reasons could be:

Tired of Existing Color
Old roofing was nailed on
Tree fell through roof

This last one actually occurred to our shouse (shop/house) when I lived in Northeast Washington!

Loyal reader and Hansen Pole Buildings’ client MIKE in COUPEVILLE writes:

Reflective Insulation“I am currently re-siding/re-roofing an existing pole building in order to match the exterior of the building I recently purchased from you.  This building is roughly 32 x34 and the roof purlins are 2×6 on end roughly every 2 feet.  I’m using Fabral’s grand rib 3 29ga for the roof and it will have fully vented soffit overhangs and a vented ridge cap.  I am trying to figure out what I’m going to do for at least a vapor barrier under the roof steel, I see you seem to recommend foil faced bubble insulation but that is not very common in my area.  I am seeing a lot of people using lamtec wmp-vrr (fiberglass insulation with a poly backing)  3″ thick and I believe they lay these wide rolls on top of the purlins and then place the metal roofing on top of that then screw down the roofing compressing the fiberglass insulation between the metal roofing and the purlins.  Have you seen this style of insulating before?  Do you think it is an acceptable way of doing it?  I see as killing two birds with one stone.  I may be insulating this shop in the future so if I do then the roof is already insulated plus I believe it acts as a vapor barrier which is the main reason to do it as I don’t want any condensation dripping down on the inside of the shop.  I live in the Seattle area if that helps to know what my climate is like.  Thanks in advance for your input.” 


Mike the Pole Barn Guru responds:

Our recommendation would be to order your roof steel with factory applied I.C.C. (https://www.hansenpolebuildings.com/2020/09/integral-condensation-control-2/).

Metal Building Insulation (fiberglass with a vinyl facing) is a decent condensation control, provided all of the seams are tightly sealed. It is a pain to work with, provides very little effective insulation value and makes your roofing pucker outwards between purlins https://www.hansenpolebuildings.com/2011/11/metal-building-insulation-in-pole-buildings-part-i/.

If it is too late for an I.C.C. then the radiant reflective barrier (https://www.hansenpolebuildings.com/2017/05/effective-reflective-insulation/)

 is probably your best option.  Order in six foot width rolls to minimize seams and make sure to get a product including a tab along one edge with an adhesive pull strip attached.

Installing Steel Liner Panels in an Existing Pole Barn

Installing Steel Liner Panels in an Existing Pole Barn

Reader JASON in WHITEHOUSE STATION writes:

“ Hello! I have a post frame 30X40 Pole Barn that was built prior to me owning the house. Currently, the shop is not insulated. I would really like to insulate it, as it’s quite unbearable in the summer and winter. The building has soffit vents, a ridge vent, and two gable vents. With the way the building is set up with all that ventilation (possibly too much?), is putting in a ceiling with insulation on top my best bet? I know there are many options when it comes to insulation, but I am trying to determine what is best for my application. I am leaning towards 6 mil poly on the bottom side of the truss, ceiling liner panel over that with blown in insulation on top. My truss is 8′ on center. Is there a recommended length of panel I should use? Thank you for your help with this. I’m sorry if I asked too many questions.”

Mike the Pole Barn Guru responds:

Provided your building has roof trusses designed to adequately support a ceiling load, your best bet will be to blow in insulation above a flat level ceiling. If you do not have original truss drawings available to determine if they have a bottom chord dead load (BCDL) of three or more, then you will need to find the manufacturer’s stamp placed on truss bottom chords and contact them with your site address. With this information they should be able to pull up records and give you a yes or no. If you are yet unable to make this determination, a Registered Professional Engineer should be retained to evaluate your trusses and advise as to if they are appropriate to carry a ceiling and if not, what upgrades will be required.

If your building does not have some sort of thermal break between roof framing and roof steel (a radiant reflective barrier, sheathing, etc.) you should have two inches of closed cell spray foam applied to the underside of roof steel, or else you will have condensation issues (even with the ventilation). With trusses every eight feet (again provided trusses can carry ceiling weight), I would add ceiling joists between truss bottom chords every four feet and run 30 foot long (verify from actual field measurements) steel panels from wall to wall.

You do not have too much ventilation – and be careful not to block off airflow at eaves. You can omit poly between liner panels and ceiling framing.

A Real Life Climate Controlled Post Frame Wall

Reader BRANDON in WICHITA writes:

“Hello Mike!  I am in the engineering field and we are just about to put up a personal climate controlled post frame building.  I have followed many of the teachings of Dr. Lstiburek on wall and roof assemblies.  I also enjoy your very detailed write ups.  I am conflicted in our assembly a bit.  Most builders here install a thin (1/8″) foam product with Aluminum foil towards the outside to act as a vapor and radiant barrier between the metal sheathing and wood frame.  That seems well and good if no additional layers are added to the wall/roof assemblies.  However, many quickly learn about the false and ridiculous R value claims of these products and add more insulation later.  Usually glass batts.  This largely concerns me because there is always another air/vapor barrier faced on the batts that would be in the interior, which creates a double vapor barrier.  

Due to this, and realizing it is nearly impossible to totally eliminate ‘some’ condensate from forming on the underside of the sheathing, we were going to use Typar house wrap on the walls AND roof between the sheathing and purlins/girts.  The product has a perm rating of about 11.  What we are targeting is an ‘air’ barrier, that is liquid proof, but still has ‘some’ permeability since some vapor would eventually get in the cavity and we need a way for it to escape.  Our assembly would follow up this building wrap with unfaced glass batts to roof/walls, then covered with the same reinforced white facing they typically use that is a vapor/air barrier and has an aluminum facing towards the outside.  

One issue faced here is the big question about climate!  Our state, as with many, have both hot/humid summers AND cold dry winters.  

I am not an advocate of Typar but selected it due to it’s toughness during install, and very low perm rating.  Not to be confused with big box store ‘generic’ wraps which are just perforated plastic! 

I have a test piece sitting with water on it right now on a paper towel and after hours, it still has not penetrated the product.  Our intention with its use is to create an air barrier on the outside as all the metal seams and corrugations can create wind washing through the glass batts, and to shed water droplets.

Your thoughts would be greatly appreciated!  We have the columns currently up so a timely response would great!”

Thank you for being a loyal reader. Your views on usage of Radiant Reflective Barriers for wall applications are spot on. Other than if people are 100% certain they will never, ever add insulation to their walls (and who can be certain about future building users/owners?) it is just an incorrect product to be used. A good, well-sealed Weather Resistant Barrier would be appropriate to use, followed by filling your insulation cavity with unfaced batts. For interior face, there is really no benefit to going to the expense of an aluminum faced product. A well-sealed 6mil clear visqueen will do everything you need it to do.

For more information on this subject, please read my Ultimate Guide to Post Frame Building Insulation https://www.hansenpolebuildings.com/2019/11/post-frame-building-insulation/.

Plans Only? Moisture Barriers? and Two Story Houses?

This week the Pole Barn Guru answers questions about “plans only” purchases, proper use of moisture barriers when adding insulation to an existing building, as well as the possibility or building a two story post frame house.

DEAR POLE BARN GURU: Do you offer just the plans? I own a sawmill and would like to mill my own lumber for my project. With the exception of the trusses. I can also source the metal roofing locally. THERON in WALDEN

Engineer sealed pole barnDEAR THERON: Thank you for your inquiry.

We are unable to provide just plans as it becomes a liability issue for our engineers – it takes away insuring materials specified actually end up being delivered to your building site.

 

There are also issues with attempting to use home milled lumber: https://www.hansenpolebuildings.com/2020/01/free-home-milled-lumber/

As an example, in sourcing your own metal roofing locally, even if steel quality was equivalent, they will not be able to provide powder coated diaphragm screws to attach it.

DEAR POLE BARN GURU: Purchased property with existing fairly new pole barn. Question is regarding wall insulation. Some installers say use double backed 6 inch glass rolls insulation under my drywall. Then I spoke with another & he says mandatory to spray closed cell foam or condition will ruin insulation…..there is no vapor barrier wrap on outside. Any help would be appreciated. Thanks, DAN in GRANBURY

DEAR DAN: You should have some sort of barrier between wall framing and wall steel to prevent condensation within the wall cavity. Wall cavity moisture can lead to a plethora of challenges – premature rusting of steel siding, rot, mold and mildew on wood framing and lack of performance of fiberglass insulation.

 

You could remove wall steel and add a Weather Resistant Barrier (highly labor intensive and things never go back together as well as they were originally assembled), or do a two inch coating of closed cell spray foam, then use fiberglass inside of it.

Here is my Ultimate Guide to Post Frame Building Insulation: https://www.hansenpolebuildings.com/2019/11/post-frame-building-insulation/

DEAR POLE BARN GURU: Hi there! I was wondering if y’all do two story residential pole houses? Second question, if I sent you guys a rough sketch of a blue print would you guys be able to give me an estimate off of that? (with included trim choices and such)

Thank you! MAX

Gambrel roof pole barnDEAR MAX: I happen to live in a two story post frame shouse (shop/house) with a partial third story. Back in the great state of Washington, I also have a three story post frame building with roof top deck! We can provide any low rise building with up to 40 foot tall walls and three floors (or 50 feet and four floors with sprinklers).

 

Send us what you have and chances are very good we can get you an estimate from it (we might want to ask you a few questions about what you intend to build).

 

Overhead Door Header Problems

Overhead Door Header Problems (and More)


Reader MITCH in NASHVILLE writes:

“I recently purchased a property that the previous owner had just built a 30×50 pole barn on. It has foil faced double bubble on the roof and walls. I need to heat and possibly cool the space. What are the options for insulating the ceiling? The ridge is vented. There is no soffit and thus no vent there. The trusses are 5ft apart. Your all-seeing wisdom is appreciated.”

There are times I wish I was not what Mitch feels is “all-seeing”, because I find lots of problems in photos building owners are unaware of. 

Back in my post frame building contractor days I would go visit some of our newly constructed buildings, as time and logistics allowed. I generally had very, very good crews and we had an extremely high satisfaction rate from our clients. I would find things wrong (in my eyes anyhow) and send crews out to make repairs. More than once I would field phone calls from clients asking what was going on. They were perfectly happy with their buildings. I would explain to them they might be satisfied, but I was not!

Mitch’s photo shows a frequent challenge posed with post frame buildings where headers (in this case more appropriately known as truss carriers), support trusses between columns. I am not a gambler, but would place money on this not having been an engineered building. Just guessing, this builder used the same size truss carrier for all locations. Usually these truss carriers would be sized to support a single truss centered between two columns. Here, due to door location and width, this carrier supports two trusses, or double what it should have been carrying. 

Look back at this photo – there is a noticeable sag across overhead door top! This same sag will be evident along sidewall eave line outside.

Before any thoughts of insulating are considered, a competent professional engineer should be engaged to design an appropriate repair for this header. Engineer should be advised this header will also need to be capable of handling the weight of a ceiling without undue deflection occurring.

Moving forward, contact the roof truss manufacturer to get a truss repair to upgrade trusses to support at least a five psf (pounds per square foot) bottom chord dead load, with 10 psf being even better. Each truss should be stamped with information of who fabricated them.

Once header and truss repairs have been completed, use white duct tape to seal all gaps present in your roof’s radiant reflective barrier. Without these being sealed, there is a potential for warm moist air to get between barrier and roof steel and condensing.

Place ceiling joists on hangers between roof truss bottom chords every two feet. Your previously engaged engineer can verify if 2×4 Standard ceiling joists will be adequate.

Install vents in each gable end. Placed in the top half of each gable, a net free venting area of 360 square inches or more will be required for each endwall.

Hang 5/8” Type X gypsum wallboard on bottom of ceiling joists, leaving an attic access somewhere towards building center. Have a spray foam insulation installer apply closed cell foam along a two foot strip closest to each sidewall. Blow in fiberglass, cellulose or rock wool insulation across remainder of ceiling surface.

Dress for Winter Post Frame Success

Dress for Winter Post Frame Building Success

My most recent winter-time post frame building experience was a few years ago when my lovely bride and I assisted her brother Mark with construction of his 36’ x 48’ shop. Temperatures hovered around zero as we shivered our way towards getting a roof installed.

Given frigid temperatures recently affecting most of our country, now seems a particularly good time to discuss how post frame builders and do-it-yourselfers can best deal with jobsite cold temperatures.

First, have correct clothing and gear, and though it may seem clichéd, dressing in layers helps.

Right clothes can save you a lot of trouble and investing in expensive yet effective gear isn’t a waste of money. If I were to build in 0-degree weather (like today) I would be wearing five or six upper body layers. Take advantage of microfiber moisture wicking apparel (think Under Armour®).

Essential pieces to invest in are good gloves and boots. Gloves are particularly important because post frame builders need warmth but also enough dexterity to be able to pick up a nail or screw. Gloves offering a right balance can be difficult to find. I am still searching for a perfect pair of gloves. Closest I have found to keeping my hands warm would be layers, with a thin pair of gloves inside a heavier pair. When it comes to footwear you get what you pay for in work boots. Boots offering 400 milligrams of insulation are highly effective. Although I have not tried it, apparently some have experienced success with cutting pieces of radiant reflective barrier to use as insoles!

Overalls are particularly effective for trapping in heat. Often overlooked, is importance of keeping one’s neck warm. There are a myriad of options, although personally I wear a thick scarf.

While clothes are important, they of course won’t entirely eliminate cold as a jobsite factor. After right clothes, mental fortitude comes in second most as an important element of successfully post framing in the cold. Remember to keep moving around. You are less likely to become frostbit if you keep fingers and toes moving. Stay hydrated. A thermos of hot coffee or chicken noodle soup helps to keep the body core temperature set at “warm”.

It’s really easy to be defeated. And it’s really easy to be sitting in your warm truck in mornings, not wanting to turn it off. Most veteran post frame builders, when they’re going out to work near zero degrees, don’t talk about it. They don’t complain about it, they just go out and do it because they have this mental wherewithal it’s just another day.

 

Insulation, Snow Loads, and Best Choice for Condensation

The PBG answers questions about insulation, snow loads, and best choice for condensation.

DEAR POLE BARN GURU: I am wanting to finish the interior of my pole barn and have an cathedral like ceiling. If I were to follow the trusses up to the peak with foam board Insulation and use 2x4s spanning between the trusses for support would there be enough air flo between 2x4s and metel to prevent condensation? If not is there a way. I have a ridge vent along peak and soffit vents on both sides of 1ft eves. Thanks for taking the time to answer. TIM in PORTAGE

DEAR TIM: To begin with, I will surmise you have either a rather typical Midwest style post frame (pole barn) building with trusses spaced every four feet on top of “truss carriers” (headers) or a building with single trusses widely spaced somewhere from seven to 10 feet on center.

foam insulation installation

You have a couple of choices – if you are going to utilize the existing intake (soffit vents) and exhaust (ridge vents) then a minimum of one inch of clear airflow must exist above the insulation. The high ribs of the roof steel will not provide adequate ventilation and there is really no way to create it after the fact. An alternative would be to seal the vents and use closed cell spray foam on the underside of the roof system. The closed cell foam should take care of any condensation concerns from the underside of the roof steel and it provides approximately an R 7 insulation value per every inch of thickness.

 

DEAR POLE BARN GURU: Can your building be designed to handle a 40# snow load? 24 x 30. JIM in WISCONSIN RAPIDS

DEAR JIM: Any snow load is very possible to be designed for, even those at high altitude snow ski resorts (including this one: https://www.hansenpolebuildings.com/2014/04/2014-winter-olympics/). Besides the snow loads in excess of 200 pounds per square foot at ski resorts, I’ve also provided post frame buildings in places like Glacier National Park, where the snow is so deep the park roads close for months in the winter.

 

DEAR POLE BARN GURU: I am planning on a 24x48x12 steel truss pole barn for vehicle/toy storage. Would you recommend a radiant bubble material under the metal to keep the inside of the barn for becoming a convection oven sitting in the hot Florida sun? Best wishes, JOHN in FLORIDA

DEAR JOHN: My first choice would be closed cell spray foam. While it is going to be more expensive, you will save greatly in labor as opposed to using a radiant reflective barrier. Radiant Reflective Barrier, installed correctly, might give you the performance you are seeking. If you do go with the barrier, single cell will perform pretty much as well as single cell. Buy six foot wide rolls with a tab. The tabs should have a pull strip over adhesive, which eliminates the need for taping seams. The six foot wide rolls mean fewer pieces to handle and overlaps to seal.

 

 

 

3M VHB Tape

3M™ VHB™ Tape

Reader WILLIAM in DYER writes:

“I’ve been researching pole buildings, and the weak point for putting one up seems to be the screws and washers.  Have you looked into using 3M™ VHB™ tape instead of screws and fasteners for attaching the metal exterior sheeting? What are the pros/cons of tape only? Thanks.”

Personally the only way the screws holding the steel roofing and siding on would be the weak point would be if the wrong product is being used, or the right product is being improperly installed.

Here is the scoop on VHB™ tape straight from 3M™:

Details

  • Fast and easy-to-use permanent bonding method provides high strength and long-term durability
  • Virtually invisible fastening keeps surfaces smooth
  • Can replace mechanical fasteners (rivets, welding, screws) or liquid adhesives
  • Black, 0.045 in (1.1 mm), modified acrylic adhesive and very conformable acrylic foam core bonds to a wide variety of substrates including powder coated paints and irregular surfaces
  • Eliminate drilling, grinding, refinishing, screwing, welding and clean-up
  • Creates a permanent seal against water, moisture and more by offering better gap filling capabilities
  • Pressure sensitive adhesive bonds on contact to provide immediate handling strength
  • Allows the use of thinner, lighter weight and dissimilar materials

 

Dream, Design, Deliver with our 3M™ VHB™ Tape 5952. It is a black, 0.045 in (1.1 mm) modified acrylic adhesive with a very conformable, foam core. It can replace rivets, welds and screws. The fast and easy to use permanent bonding method provides high strength and long-term durability. It offers design flexibility with its viscoelasticity and powerful ability to bond to a variety of surfaces.

Convenience Meets Extreme Bonding Power 
Our 3M™ VHB™ Tape consists of a durable acrylic adhesive with viscoelastic properties. This provides an extraordinarily strong double sided foam tape that adheres to a broad range of substrates, including aluminum, stainless steel, galvanized steel, composites, plastics, acrylic, polycarbonate, ABS and painted or sealed wood and concrete. Our bonding tapes provide excellent shear strength, conformability, surface adhesion and temperature resistance. They are commonly used in applications across a variety of markets including transportation, appliance, electronics, construction, sign and display and general industrial. Reliably bonds a variety of materials with strength and speed for permanent applications. 

Dream, Design, Deliver with the 5952 Family of 3M™ VHB™ Tapes 
The 5952 family of 3M™ VHB™ Tapes utilizes modified acrylic adhesive on both sides of a very conformable, adhesive foam core. The combination of strength, conformability and adhesion makes this family one of the most capable and well-rounded 3M™ VHB™ Tapes. It is specifically designed for good adhesion to high, medium and lower surface energy plastics and paints, metals and glass. Applications for this tape include bonding and sealing polycarbonate lens over LCD, signage and windows to post-painted control panels. 

An Unconventional Foam Tape 
We invented 3M™ VHB™ Tapes in 1980 as the first of their kind. These unique tapes combine conformability with a strong, permanent bond. The result is a family of extraordinarily strong tapes that adhere to a broad range of substrates. 3M™ VHB™ Tape is a proven alternative to screws, rivets, welds and other forms of mechanical fasteners. Skyscrapers, cell phones, electronic highway signs, refrigerators, architectural windows and more all rely on this specialty bonding tape for one or more steps in the assembly, mounting, fastening and sealing process. This trusted and reliable tape offers a consistent bond, outstanding durability and excellent solvent and moisture resistance. 3M stands by all of its products and is there to provide you with design guidance and technical support when you need it. 

Proven Reliability from 3M™ VHB™ Tapes 
3M™ VHB™ Tape offers a durable bond in a way that mechanical fasteners can’t. This tape enhances the appearance of finished goods by eliminating rivets and screws while providing immediate handling strength. In most cases, fastening with 3M™ VHB™ Tape is a quicker process than drilling, fastening, or using liquid adhesive. Our versatile line of tapes can be used indoors or outdoors in a variety of applications, including window, door and sign assembly, electronics, construction and countless other industrial applications. Chemically resistant as well as UV and temperature stable, 3M™ VHB™ Tape can withstand the heat of Dubai to the cold of Canada. The unique acrylic chemistry is extremely durable and resistant to change over time, making this a long-lasting and powerful tape you can trust. 

Bringing Better Ideas to the Surface through Science and Innovation 
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Mike the Pole Barn Guru comments:

Why it might not be the best choice….

OLYMPUS DIGITAL CAMERA

In order to utilize it with the steel panels, it would need to be tested for shear strength by an independent engineer. It would preclude the use of Building Wrap (like Tyvek) in walls, as well as radiant reflective barriers or Dripstop/Condenstop in roofs.

While it sounds like an excellent product, the cost along may prove prohibitive, as the lowest price I am seeing is somewhere around 70 cents per lineal foot, making it around 10 times as expensive as the diaphragm screws we provide and even more expensive than the smaller diameter lesser quality fasteners used by most post frame suppliers and builders.


 

Condensation Under Roof Steel

Condensation Even With Radiant Barrier Installed Under Roof Steel

It seems every winter I get a few messages similar to this, So far, this winter, I have gotten two, both from newly constructed post frame buildings and from the same area of the United States (which is known for high humidity).

Reader SAM in GREENBANK writes:

“Hi there.  I’ve almost completed the building, and It’s been getting cold lately.  I noticed that every time we have a frost I have condensation drips all over inside the barn.  I was under the impression that the foil backed bubble wrap was supposed to prevent this.  Is there something I can do to stop it?   Is this normal?   I’m having to keep all my tools under cover even though they are inside.  Not ideal.”

Mike the Pole Barn Guru Responds:

The radiant reflective barrier does keep warmer moist air from contacting the underside of the colder roof steel and condensing. If it has been below freezing inside your building, and fairly humid, water vapor will freeze to the underside of the barrier as well as the roof framing members. Most often the excess humidity is a product of a relatively freshly poured concrete floor (tremendous amounts of water vapor are expelled from a concrete slab as it cures), a concrete floor which does not have a well sealed vapor barrier beneath it, or (in buildings without a concrete floor) the ground under your building will not freeze and when the ground outside starts to freeze the excess ground moisture rises inside of the building (think of a cork being removed from a bottle).

Possible solutions (may have to be used in combination): heat the building to just above freezing, open the doors to allow excess moisture to escape (especially in cases with a fairly fresh pour or no slab), if no vapor barrier under a slab – seal the surface of the slab to prevent moisture from coming through. Basically it takes a reduction of humidity inside of your building.

In cases where eave and ridge ventilation was not provided for initially, adding gable vents might help to alleviate some of the interior humidity. When I was a builder, we erected a boat storage building over (we found out later) what had been a pit where asphalt waste from old roads had been deposited. Water sat in between the chunks of asphalt – we had basically built over an underground lake!

The only solution was for the owner to install power vents to pull the humidity out of the structure!