Tag Archives: dripstop condensation control

Water Damage to Girts, A1V Replacements, and “Sold Comps” in WA

This Wednesday the Pole Barn Guru answers reader questions about concerns that water might damage girts with use of spray foam, a replacement for A1V, and a request for “sold comps” in the state of Washington.

DEAR POLE BARN GURU: Hello, I am very early in the stages of considering self-building a post frame home. Spending a lot of time researching and learning as much as possible, mostly on Hansen Buildings since you provide such a wealth of information, thanks! My question: How do you go about weather protecting the girts against potential water intrusion from the siding/windows when using closed cell spray foam? I know with other insulation types, a weather barrier like Tyvek is used but this is not usually advisable for spray foam. My concern is that I build my home and water finds a way in and then rots away at my girts since the girts are on the outside of the vapor barrier but under my steel and it can’t dry out well enough. Am I worrying about something that is a non-issue? I am not 100% sold on closed cell spray foam for this reason, however, I do seem to gravitate back to it due to its ability to air seal well and high R value for the thickness. Thanks, CALVIN in HARTFORD

DEAR CALVIN: Appreciate your kind words.

Closed cell spray foam does provide a 100% water seal. If you are using bookshelf wall girts (highly recommended), then vinyl window’s 1-1/2″ nailing flange entirely covers framing around window openings. Even if water where to somehow penetrate steel siding around a window, it would be stopped by closed cell spray foam at juncture with nailing flange – so no way for water to ever get to wood.

While I used closed cell spray foam to insulate when I added an elevator shaft to our barndominium in Northeast South Dakota, I am just not convinced it is economically practical in northern climates.

 

DEAR POLE BARN GURU: Tried to buy the A1V radiant barrier you suggest in your blogs. Apparently it’s no longer available. What product do you suggest in its place? Is there something that can be applied after metal installation that can be sprayed on? I have seen some products that claim to be a condensation stop and sprayed on after the fact which seems like a great idea if it works and is more cost effective than close cell spray foam. Thanks TIMOTHY in CLINTON

DEAR TIMOTHY: You are oh-so-close to my favorite stop for cinnamon rolls! (shameless plug here: https://www.rivercitygrillmissoula.com/)

We discontinued A1V radiant reflective barriers several years ago – as shipping six foot wide rolls became a challenge and trying to install in even moderate winds resembled juggling cats. Every effort has been made to remove older blog articles recommending this as a possible option.

We have been offering to our clients factory applied integral condensation controls (read more here: https://www.hansenpolebuildings.com/2020/09/integral-condensation-control-2/).

As far as products able to be sprayed on after roofing is installed, only two inches or more of closed cell spray foam appears to actually work.

 

DEAR POLE BARN GURU: Our lender is asking for sold comps in order to put together our loan package with land and building costs. Do you keep a list of comps in Washington State? Thank you! SANDRA in GALLUP

DEAR SANDRA: Your sold comps will be any custom designed home, they do not have to be steel roofed and/or sided or even post frame. If your lender cannot grasp this, it might be time to seek a different lender. Many of our clients have used https://www.ffbkc.com/borrow/build-a-home/barndominium-financing/ as they understand barndominiums (and loan in Washington state).

Finding Which Way is Up

Finding Which Way Is Up

Avid reader DAVE in BLUFFDALE writes:

As I told Trey, I’ve been reading and reading and reading your blog posts until I don’t know which way is up!  Don’t get me wrong, you’ve done an amazing job with your blog posts, but it can be a bit overwhelming.  I think part of the problem I’ve had is that your posts span a wide time period and some technologies and techniques have changed over time, so it’s hard, sometimes, to figure out what the latest recommendations are.  Here’s some customer feedback regarding this:  Unless a post has comments under it, it’s impossible to tell when it was written.  The comments are date stamped, but the blog posts are not…take that for what it’s worth, your posts ARE an incredible resource!

Anyway, our building will be 30x60x10 and we don’t (currently) have any plans for heating/cooling the workshop, other than fans & space heaters as needed.  My big concern here in our area of Utah is the summer heat.  

After reading a number of your posts on reflective barriers, I get the impression that you are not (anymore) a big fan.  The other thing I haven’t been able to figure out is how you would put a reflective barrier between the steel roof panels and the purlins and be able to have an air space for the reflected heat to dissipate in.  Is there a way to do this, or is it just not worth it?

My current thought is that we would just use Drip-Stop on the roof panels and put unfaced fiberglass bats between the purlins and hold it in using 6 mil plastic.  I talked with Trey about having an increased heel height on the trusses to allow proper eave to ridge venting in this scenario.

We would do the same for walls…unfaced bats with 6 mil cover.

And, per your recommendation, a good plastic sheet under the slab.  

Which just made me think of another thing…we are planning to put a partial basement under the last 20′ of the building for some cold storage.  I figure we’ll be putting some kind of tar waterproofing product on the basement walls, but should we also put a plastic barrier under the basement floor?  We’ll have a wood joist floor over the basement, so moisture could come up from down there…thoughts?

TIA for any insights you can provide to help us nail down our order!”

Thank you for your kind words. You are correct about changing technologies and techniques and my 2000+ blog articles cover a dozen years of progress.

We’ve provided literally millions of square feet of reflective barriers however they basically function as little more than a condensation control, provided they are properly installed. There is just no realistic way to achieve totally sealed dead air spaces to take advantage of their ability to reflect.

Integral Condensation Controls (Drip Stop) are very effective for condensation control, are affordable, and do not have installation challenges associated with other alternatives. (For extended reading on Integral Condensation Control please see: https://www.hansenpolebuildings.com/2020/09/integral-condensation-control-2/) Placing batts between roof purlins is not your best choice, as Codes require a minimum one-inch of continuous air flow above batts from eave to ridge – impossible to achieve in this scenario. Raised heel trusses, with blown in fiberglass above a ceiling, and properly vented eave and ridge is your best design solution. In your climate zone, I would recommend at least R-49 with 18″ heels.

For walls – I would use a Weather Resistant Barrier (Tyvek or similar) with R-20 or greater batt insulation. I am really liking Mineral Wool batts as they are unaffected by moisture. https://www.hansenpolebuildings.com/2013/03/roxul-insulation/

You should have a vapor barrier under any slab inside of a building, so yes to below your basement floor. Your basement walls should be insulated down to top of slab floor with either R-15 continuous insulation boards or R-19 batts.