Tag Archives: integral condensation control

How To Vent An Attic Below A Lean-To Porch

How to Vent Attic Below a Lean-To Porch

Long time reader JON in SPRINGDALE writes:

“Hi Mike, long time reader. Thanks for the info you provide. These questions come from your

home town area. I was talking to my local building department and attic ventilation came up. He

said that using a ridge vent and vented soffits isn’t enough, because the purlins restrict the

natural air flow between the two. So he suggested powered gable vents. I believe code calls for 1″ minimum clearance between insulation and sheeting what would you recommend as this affects the size of the heel on the trusses. Still on attic ventilation, so I want a porch covered by a lean to with a continuous roof line peak to eave. My question is if the underside of the lean-to is open, how do I vent the attic with no overhang to put vented soffit on? Thank you.”

Mike the Pole Barn Guru says:

I have been unable to find any published research to back up your inspector’s theory, nor would anything in written Building Codes support use of powered vents as a method of either intake or exhaust to meet Code requirements. Code does require a minimum one-inch space between top of blown or batt insulation and bottom of roof deck.

To ventilate eaves on side of building with continuous roof and covered porch, you could oversize eave strut (purlin at top of wall between enclosed portion and porch) to say 2×10. Cut notches into top edge of purlin an inch deep, by whatever length would be necessary collectively to meet proper ratio of eave air intake to exhaust. Notches would need to be covered with Code compliant screen to restrict entry of small, flying critters and wall steel stopped below bottom edge of notch.

In summary, ventilation requirements in IRC’s 2018 edition are as follows:

Provision of one square foot of NFVA for each 150 square feet of attic floor. One important note – attic floor area is just as it reads – area – not volume. This is a minimum requirement and does not stipulate required ventilation openings provide intake (low), exhaust (high), or both.

Provision of one square foot of NFVA for each 300 square feet of attic floor if both following conditions are applicable:

A Class 1 (≤ 0.1 Perm) or 2 (> 0.1 to ≤ 1.0 Perm) vapor retarder is installed on warm-in-winter side of ceiling when the structure is located in climate zone 6, 7, or 8.

At least 40%, but not more than 50% of NFVA is provided by vents located not more than 3 feet below roof’s highest point.

Provision for a minimum one-inch air space between roof sheathing and insulation in attic at vent location.

There are a few items I would suggest, after looking at your provided portion of plans.

Do away with all of expensive OSB sheathing. Order roof steel with an Integral Condensation Control factory applied. 

Increase ceiling height to 10′ 1-1/8″ from top of slab to bottom of trusses. This will allow you to use 10-foot sheets of gypsum wallboard (sheetrock) run vertically without cutting.

Use bookshelf wall girts to create an insulation cavity and for ease of interior finish.

Have your engineer check purlin spacing on each side of ridge to account for drift loads. Purlins at high side of dropped right side porch also need to be checked for slide-off and drift loads.

Code requires a minimum 6mil vapor barrier under concrete slabs on grade in conditioned areas.

Hart and Home YouTube Episode IV-The Final Chapter

Hart and Home YouTube – Episode IV The Final Chapter

If you missed our previous episodes, please go to bottom of this article, on left, and click on arrow thrice to go to Hart and Home YouTube – Episode I. Moving forward:

While individual results may vary, our clients have generally had good experiences using windows with integral J Channels and following our Construction Manual installation processes. I have several of them on my own post frame shouse (shop/house) and leakage has never been an issue.  When I was a full time post frame building contractor, roughly 10% of all of our standard flanged windows had call backs due to leakage. Once we went to integral J Channel windows, our warranty claims disappeared.

Just this past year, we have gone to including Climactic specific requirements for insulation to our engineer sealed building plans, this includes window U values.

Kevin Hart had some excellent points on splash plank installation and for those who will be taking extended times for installation, we will be adding other recommendations to our Construction Manual. For buildings with ceiling loaded trusses and ceiling joists, “Most Common Mistake #2” in Construction Manual Chapter 36, Ceiling Joists, is “Neglecting to install joist hangers prior to lifting trusses”. With hangars in place, it allows for permanent truss bracing to be located appropriately to avoid having conflicting locations. Language has since been added to Construction Manual Chapter 9, Roof Truss Preparation, to encourage installation of ceiling joist hangers, prior to lifting trusses into place.

We have edited our Construction Manual in regards to orientation of truss notch and placement for the first pair of trusses closest to the front endwall in order to aid in ease of lifting the entire bay closest to each endwall.

Having owned or managed prefabricated wood roof trusses for 20 years – truss builders are not carpenters. When allowed to nail trusses together into pairs, more often than not results are less than what most clients would find acceptable. Due to weight, it is also far easier to move trusses around on jobsites as singles.

Language has since been added to our Construction Manual for applying temporary bracing to tops of purlins if roof steel will not be applied immediately following purlin installation. We also have discontinued offering reflective radiant barriers as an option, instead we have gone to roof steel with factory applied integral condensation control (more about Integral Condensation Control here: https://hansenpolebuildings.com/2020/09/integral-condensation-control-2/).

We had already been having discussions internally in regards to adding an externally mounted girt below windows, just like Kevin did. Right now, it is just a matter of programming in our system and getting instructions and drawings into our Construction Manual.

Many builders like to use F and J trims at top of sidewalls with enclosed overhangs – mostly because they then do not attach soffit panels at all on the inboard (wall) side. While it makes for a quick installation, soffit receiving portion of “F” is wider than soffit is thick, allowing soffit panels to vibrate in wind. Builders using F and J are not placing any solid wood backing above it, again saving them money, but not providing anything of substance to attach soffit panels to.

Trims butting or overlapping – we have struggled with non-uniformity of press broken trims and have had better luck with how they lie when butted than trying to make laps look smooth. On fascia trims, we’ve used a plethora of different variations before settling on our current model. With properly placed inside closure strips at the extreme downhill edge of fascia, we have never experienced water getting behind fascia L trim. We did try a shorter height L fascia trim, with an eave trim and found the angle of eave trims caused drip edge of eave trim away from fascia trim. When screws were placed thru eave trim to prevent this – eave trims puckered out away from fascia trim between screws.

On the end of sidewall soffit level trim, with soffit panels installed per Construction Manual, underside of base trim at end. Downside is it does leave a cut edge of the soffit panel. We believe we have found an improved trim option. It would allow soffit panels to slide in at each end and would have a finish painted side down.

Thank you again to Kevin and Whitney for allowing our team at Hansen Pole Buildings to participate in their incredible journey. We look forward to assisting you with yours!

My Barndominium Attic Has Moisture Issues!

My Barndominium Attic Has Moisture Issues!

Reader DAVID in CHICAGO writes:

“Greetings – I’ve got a pole barn style home that’s about 2.5 years old and I’m having moisture issues in the attic. Hoping I can talk with someone to get a consult or second opinion to resolve as quickly as possible. Let me know if it is something you can connect on. Attached is an image from the attic where you can see moisture on the underside of the metal roof. It freezes at night and then during the day when the sun is out, it melts and drips into the attic insulation. 

Attic space is dead, image below. Vented through passive soffit vents and ridge vent, with a few solar blaster ridge vents to help with active venting when the sun is out. Attic insulation is R50 blown in at 20 inches deep. Image of exterior attached. It’s sheet metal that’s then spray foamed on the inside and additional R25 batts. Image below from when we had this same issue earlier this year in February 2021 when the drywall walls and ceilings had to be torn out due to water damage. We purchase in January 2021 and the home is now 2.5-3 years old. There is a solid concrete slab that has in-floor heat. I believe it has a vapor barrier underneath from an image I saw. “

Mike the Pole Barn Guru writes:
You are victim of what is such a simple and economical solution, when planned for in advance. Why builders and building providers fail to address steel roof condensation initially drives me to consider alcoholism!

I do realize they are just ‘selling on a cheap price’, rather than providing a best solution for their client.

Easiest solve is to have two inches of closed cell spray foam applied to underside of roof purlins. Any other solutions will take removal of roof steel panels, adding a thermal break, and then reinstalling roofing.

At time of construction I would have recommended roof steel with an Integral Condensation Control (ICC) factory applied. Investment then would have been a fraction of having to solve it now.

For extended reading on ICCs https://www.hansenpolebuildings.com/2020/09/integral-condensation-control-2/.

Texas Post Frame Barndominium Insulation

Reader KIMBERLY in LINDEN writes:

“We are building a 52x40x10 post frame home in East Texas.  The entire thing will be living space.  I have been researching as much as possible on the best way to insulate a post frame home with metal siding and roof.  The information is overwhelming and you get a completely different answer depending on who you talk to.  I know not to skimp on insulation, but the consensus on most “barndominium” FaceBook groups is that spray foam is the only way to go.  I have reservations about that, because it may be a superior way to insulate, but it depends almost exclusively on who is doing the actual foam application.  On top of that you need to spend more money on your HVAC system to add the proper ventilation/air exchange.

I want a well insulated home that is specific to the type of building material and location we live in.  To me, “not skimping” on insulation doesn’t mean that it has to be the most expensive insulation either.  

I also know the insulation world is constantly changing and evolving, but what would your recommendation be to insulate our home in East Texas?

Thank you so much for your time!”

Mike the Pole Barn Guru responds:

Your insulation requirements will vary depending upon where you are in East Texas. Climates zone 1 (closest to Gulf) require R-30 ceilings, R-13 walls. Zone 2 requires ceilings to be R-49 and zone 3 (farthest north) goes to R-20 walls. You can look up you county’s climate zone here: https://codes.iccsafe.org/content/IECC2021P1/chapter-3-re-general-requirements#IECC2021P1_RE_Ch03_SecR301. I will cheat for you and tell you Cass County is Climate zone 3A.

For sake of discussion we will assume you have a dead attic space and will be insulating directly above a finished ceiling.  I would ventilate your dead attic space at the eave (air intake) and the ridge (air exhaust). Make provisions for preventing condensation on the underside of roof steel by having some sort of a thermal break. My personal preference is by using an Integral Condensation Control (https://www.hansenpolebuildings.com/2020/09/integral-condensation-control-2/).  You will want to order roof trusses with raised heels (https://www.hansenpolebuildings.com/2012/07/raised-heel-trusses/), so you can get full insulation depth from wall-to-wall with blown in fiberglass. Heel height should be R value of insulation divided by three and add two inches so you can achieve adequate airflow above insulation.

Should you want to condition your attic – delete ventilation, raised heels and the Integral Condensation Control. I would apply closed cell spray foam two inches to the underside of roof steel, then add open cell spray foam to desired R value.

For walls – best results will be from two inches of closed cell sprayed to inside of wall steel, then fill balance of wall cavity with either open cell spray foam, or unfaced batts (ideally stone wool https://www.hansenpolebuildings.com/2013/03/roxul-insulation/). You could also use BIBs to fill (https://www.hansenpolebuildings.com/2011/11/bibs/). Do not place a Weather Resistant Barrier (WRB) under wall steel or a vapor barrier on inside of wall.

As an alternative to spray foam, you can use a WRB between framing and wall steel, then BIBs with an interior vapor barrier or faced batt insulation.

Energy costs are not going to go down, so I would encourage you to err towards more insulation rather than less – and (since most heat loss is upward) invest more into added ceiling insulation than walls.

In warmer, humid climates like yours, your HVAC system should include an Energy Recovery Ventilator (ERV) regardless of what your choice of insulation systems ends up being.

Don’t Let Valleys Get You Down

When it comes to post frame barndominiums, rooflines run from simple gabled roofs, to complex designs including hips, valleys, reverse gables, etc. Basically, if you can imagine it, post frame can provide a design solution.

Loyal reader (and my Facebook friend) RUSS in PIPERSVILLE writes:

“Hello Mike. As we get a little further along with our design I would like to ask for your opinion. I read in past blog topics that you don’t recommend designing roofs with valleys when going metal over purlins. Our current plan has a large reverse gable on the front of the house covering the entry and porch and our utility mechanical room is a reverse gable room attached at the rear. All roofs are 6/12 pitch. I’m a bit worried about getting the details right. Is it that difficult to install the metal roof correctly over purlins, or should I just consider installing solid sheathing with metal over? Perhaps forego the metal and return to wood deck and shingles? Tom Z. has been a help in explaining how the gables must be framed but I must confess that the details don’t leave me all warm and fuzzy about the roof construction. Any insight you can offer is always appreciated.”

Mike the Pole Barn Guru says:
If I led you to believe I have issues with valleys on steel roofing over purlins I somehow took you astray.

In order to have a successful valley, these steps are followed:

Main roof is framed up, including purlins across area where reverse gable will intersect. 2×12 blocking is then placed between main roof purlins, centered on what will eventually be the middle of the valley. This provides a landing point for intersecting roof purlins from reverse gable (next to be installed). Once these purlins are in place, any reflective radiant barrier (RRB) is installed (I prefer using roof steel with Integral Condensation Control to a RRB). Valley flashing is then installed. We furnish Emseal® self-expanding foam closures to seal between valley flashing and roof steel, following slope of valley flashing. Roof steel is then applied and you are buttoned up tight.

Most challenging parts of assembly are cutting intersecting roof purlins (besides cut being at a 26.6 degree angle along wide face of purlin, cut also needs to be done at 26.6 degrees from perpendicular to compensate for slope of intersecting purlins from vertical) and cutting roof steel at valley to end up with a nice straight line up valley. Neither one is actually beyond most people’s abilities.

There really is no structural advantage to solid sheeting your roof and even the best of shingles have a very poor warranty and I cannot, in all good conscience recommend them as a practical design solution.

For extended reading on Emseal® closures: https://www.hansenpolebuildings.com/2016/03/emseal-self-expanding-sealant-tape-closures/

Must Do’s for a Worry Free Barndominium

My Facebook friend RICK in MALDEN messaged me:

“I have never built a building like this. I have seen many bad experiences with concrete, poor quality metal work and many more issues. I would just like to know if there is a list of things to make sure I get a quality home. I saw the other day you said osb under the roof metal could help with condensation issues. I’m also worried about gaps where the metal meets together. I don’t want to just shoot spray insulation and call it good. You have said that is not the way to do it. I guess I’m looking for something to tell me the quality method for the most common mistakes people or contractors make. I am using a contractor because I don’t have the skill or experience to DIY. I also don’t want to rely on the contractor to tell me the right way. If I had it my way I’d have you do it. You are the most knowledgeable and in-depth person I have found on the internet about the Barndo building subject.”

Thank you for all of your kind words. 

There are days when I think what a joy it would be to be out building. I do truly love to build, smells of earth from freshly dug holes, lumber being taken out of a wrapped unit, sawdust – all of these give me warm, fuzzy nostalgic feelings.

I have kept myself in great physical condition and at 63 years-old I could certainly be out building. And I do know there are folks who would gladly pay my rate to have me do their construction. However this would allow me to properly assist only one client at a time. What I do now allows me to help thousands of people every year to get better buildings.

Enough of me waxing poetic – let’s get down to business!

(Side note – much of this advice is expounded upon in detail in previously written articles. Please visit www.HansenPoleBuildings.com, navigate to SEARCH at upper right corner, click on it, type in a word or phrase and ENTER)

Plan tips – consider these factors:

Direction of access (you don’t want to have to drive around your house to get to garage doors).

‘Curb appeal’ – what will people see as they drive up?

Any views? If so, take advantage of them.

North-south alignment – place no or few windows on north wall, lots on south wall.

Overhang on south wall to shade windows from mid-day summer sun If your AC bill is far greater than your heating bill, reverse this and omit or minimize north overhangs.

Slope of site.

Work from inside out – do not try to fit what you need within a pre-ordained box just because someone said using a “standard” size might be cheaper. Differences in dimensions from “standard” are pennies per square foot, not dollars.

Put up the largest building you can economically justify and fit on your property.

Plan for accessibility – 4′ or wider hallways and stairs, an ADA bathroom with a roll in shower. 3′ wide interior doors.

Walk-in (roll-in) closets for bedrooms, even secondary ones.

Consider if you truly want to live on a concrete floor. Crawl spaces are roughly the same investment.

Kitchen – two dishwashers, two microwaves, two ovens, trash compactor. Separate side-by-side refrigerator and freezer units. A good sized pantry.

9′ or 10′ finished ceilings in living areas.

Onto building construction itself….

Probably most important (and most often neglected) is proper site prep.

Make sure there is a vapor barrier under any slab-on-grade (and use 10-15 mil).

For slab-on-grade at least have pex-al-pex tubes run.

Personally I like flash & batt for walls – two inches of closed cell spray foam ideally with BIBs insulation to fill balance of insulation cavity. In this circumstance, you do not want a WRB, however you do want to order inside closures for top and bottom of every wall panel.

Order raised heel trusses so you can blow in fiberglass insulation to full depth from wall-to-wall.

For condensation control – use steel panels with Integral Condensation Control.

Vent sidewall overhangs and ridge.

Use all 5/8″ Type X sheetrock.

Make sure you and your contractor have a written agreement covering everything – it keeps feelings from being hurt and clearly outlines expectations. I will have a series of articles soon outlining some important inclusions for agreements, please watch for them.

Post Frame Building Insulation

Pole Barn Guru’s Ultimate Guide to Post Frame Building Insulation

When it comes to insulating any building (not just post frame ones – like barndominiums) there is a certain point of diminishing returns – one can spend so much they will never, in their lifetimes, recoup their investment.

Here my ultimate guide to post frame building insulation is based upon practicality and obtaining the best possible value for investment.

There are some basics applicable to any steel covered building:

Under any concrete slab on grade inside a building, place a well-sealed vapor barrier. Read about under slab vapor barriers here: https://www.hansenpolebuildings.com/2017/11/vapor-barriers-slabs-grades/.

Between roof framing and steel roofing – please do not assume condensation is not going to be a problem. At some point in time it will become one and if precautions are not taken regrets will happen. Condensation under roof steel is maybe number one of the issues I am asked to assist with.

Least expensive financially, but does take some extra labor hours, especially if it is windy – a single air cell layer reflective radiant barrier. Six foot widths will install much quicker than four foot. Make sure to order with a six foot width NET COVERAGE and an adhesive tab along one edge with a pull strip. Without an adhesive tab all butt edges will require seam tape, not expensive, but adds lots of time. Do not waste your money on adding an extra approximate R 0.5 for double bubble (two layers of air cells).

For a slightly great investment in materials, hours of labor can be saved by the use of an Integral Condensation Control bonded to roof steel. This would be my product choice. https://www.hansenpolebuildings.com/2017/03/integral-condensation-control/.

Next higher cost would be sheathing the roof with either OSB (Oriented Strand Board) or plywood on top of roof purlins. Roof purlins will need to be spaced appropriately so sheathing seams fall on purlins (16, 19-3/8 or 24 inches on center). Roof truss top chord live load must be increased to allow for greater dead loads. Either 30# felt (asphalt impregnated paper) or an Ice and Water Shield must be placed between sheathing and roof steel. Roof screws must still be placed to go into purlins, as thin sheathing is inadequate to adequately hold screws.

Bigger financial investment, but no extra labor involved is to have two inches of closed cell foam sprayed on the underside of roof steel. This will prevent condensation and is noise deadening. As a rough budgetary figure, plan upon spending roughly two dollars per square foot of roof surface.

Storage/Utility Buildings

If you ever believe anyone might ever have a future desire to climate control your building then provisions should be made for making it easiest to make future upgrades.

For now we will assume this building is totally cold storage. If it might ever (even in your wildest dreams) be heated and/or cooled include in your initial design, walls with a Weather Resistant Barrier (https://www.hansenpolebuildings.com/2016/01/determining-the-most-effective-building-weather-resistant-barrier-part-1/) between framing and siding. 

Taking walls one step further would be ‘commercial’ bookshelf wall girts (https://www.hansenpolebuildings.com/2011/09/commercial-girts-what-are-they/).

In roof – have trusses designed to support a ceiling load, ideally of 10 pounds per square foot (read about ceiling loaded trusses here: https://www.hansenpolebuildings.com/2016/03/ceiling-loaded-trusses/). 

Trusses should also be designed with raised heels to provide full depth of future attic insulation above walls (https://www.hansenpolebuildings.com/2012/07/raised-heel-trusses/).

Make provision for attic ventilation, by having an air intake along sidewalls using enclosed ventilated soffits and exhaust with a vented ridge.

Any overhead doors should be ordered insulated – just a good choice in general as, besides offering a minimal thermal resistance, they are stiffer against the wind.

Equine Only Use

Same as storage/utility however ventilation is essential (and often overlooked). (Read more on stall barns here: https://www.hansenpolebuildings.com/2012/08/stall-barn/)

Garage/Workshop/Man Cave/She Shed/House/Shouse/Barndominium

Many previous recommendations are going to be repeated here. Ultimately it is going to depend upon willingness to include higher R values in initial budget, rather than having increased utility bills forever.

Start with a Frost-Protected Shallow Foundation – post frame version (https://www.hansenpolebuildings.com/2016/11/frost-protected-shallow-foundations/) with sand on the inside rather than a thickened slab. This makes for an excellent and affordable design solution.

For walls, we will again work from generally ascending price and R values.

On low end would be having installed a weather resistant barrier beneath wall steel, in conjunction with commercial bookshelf wall girts. Fill insulation cavity with unfaced batt insulation and cover inside face of wall with a well-sealed six ml clear visqueen vapor barrier. As an alternative to fiberglass would be mineral wool insulation as it is not affected by moisture (https://www.hansenpolebuildings.com/2013/03/roxul-insulation/). This method can be entirely done D-I-Y.

I have personally used BIBs (https://www.hansenpolebuildings.com/2011/11/bibs/) in several buildings, including my current barndominium home. It does require a certified installer.

A Weather Resistant Barrier can be eliminated by the use of a ‘flash coat’ of two inches of closed cell spray foam against the inside of wall steel. Balance of wall cavity can be filled with batt insulation. (https://www.hansenpolebuildings.com/2016/07/advantages-spray-foam-over-batt-insulation/).

For added R value and a complete thermal break, add two inch rigid closed cell foam boards to inside of framing. To maintain thermal break integrity, glue foam boards to inside of framing and properly seal all seams. Gypsum wallboard can be glued to the face of foam boards.

After ceiling has been installed, have insulation blown into dead attic space, following Energy Star™ guidelines (usually R-45 to R-60).

Other I.C.C. Benefits

My last article discussed Integral Condensation Control (I.C.C.) solutions for steel roofing.

When Hansen Pole Buildings’ Designer Dave Gross constructed his own post frame building, I convinced him to utilize I.C.C. for his roofing. A testimony to how much he liked it – virtually every building his clients have invested in since has I.C.C.!

 Reduced Noise
A common concern for owners considering steel roofing is increased noise caused by rain and echoes. Steel roofing with I.C.C. offers significant sound deadening abilities, often decreasing rain impact and reflected noise levels by twenty percent.

Fire Rating

Most building codes require faced metal building insulation to have a flame spread rating of 25 or less and a smoke developed rating of 50 or less when tested according to ASTM E84 or UL 723. Steel panels with I.C.C. attached meet these standards.

Rot Resistant

The two components of I.C.C. are synthetic polyester fiber and rubber-based adhesives, neither of which is susceptible to decomposition from bacteria, mold or mildew. These materials are also well suited for cleaning with a hose or pressure washer in the event that they are soiled.

Additional Protection in Corrosive Environments

An unexpected benefit of this product is offered by its rubber adhesive membrane. The adhesive layer acts as a barrier which adds additional protection, isolating the washcoat of the panel from corrosive vapors often found in structures used for animal confinement. In light of this, an experiment was performed on bare galvanized and Galvalume® steel to determine the actual amount of protection offered by the extra layer. The experiment consisted of a 1000 hour test which exposed the interior of panels (with and without I.C.C.) to condensation from heated liquid manure. The results showed a clear indication steel panels are in fact shielded from the corrosive compounds. These findings strongly suggest panels with I.C.C. will offer a greatly extended service life in conditions which typically void the paint system warranties.

Planning your new steel roofed post frame building? If so, be like Dave. Dave is smart, his steel roofed post frame building doesn’t drip!