Tag Archives: unfaced batt insulation

Avoiding Condensation When Insulating an Existing Pole Barn

Avoiding Condensation When Insulating Existing Pole Barn

The last thing people want to have to deal with would be condensation dripping in their pole barn. When an originally unheated cold storage building becomes repurposed to be climate controlled, possible condensation poses some new challenges.

If you are reading this article and plans are to construct an unheated building, I implore you to consider taking steps so it could be repurposed to be heated and/or cooled later. Please browse through some of my previous articles regarding this subject, such as: https://www.hansenpolebuildings.com/2018/06/pole-barn-insulation-oh-so-confusing/.

Reader JOSEPH in ALPINE writes:

“We have a pre-existing pole barn that we want to turn into a insulated building. Knowing that condensation would be a problem, I’m looking for a professional to consult with so it is done correctly. Is this something you do and what are your rates?

 

The building is 15×15, on a pad. There is no attic- 1/4” plywood is nailed to the ceiling 2x4s. We’d like to keep this height since it affords space for a loft. There is a single central roof vent. I read your response to one customer about using unbatted insulation on the walls and punching holes in the plastic to allow venting. But how does one allow for venting when there is no attic space? Our main house (1937 farm home, remodeled to modern code in 2003) is a metal roof with the upstairs rooms opened up, no attic, no roof vents. How can one replicate what is done in the house with this pole barn?

Thanks.”

Mike the Pole Barn Guru writes:

I am deeply flattered to have someone offer to hire me for a consultation. Here is my response to Joseph:

I am a bit geographically inconvenient to be able to come and see your building. However, based upon experience and what I would do if it was my own building, I will give you some free advice. You are welcome to use it, or discard it as best you see fit.

As you do not know if a vapor barrier exists beneath your existing concrete slab, I would use a high quality surface sealant over it. Your major water source for potential condensation will be through this slab. I’d close off roof vent, and have inside surface of siding and roofing closed cell spray foamed. Your local installers can give you recommendations for thickness, however I would not go with less than two inches thickness. If possible or practical, unfaced fiberglass insulation may be added to the inside to increase R value. However, it might be most practical to just pay a little extra for thicker spray foam.

 

 

Insulating a Post Frame Home Crawl Space

One of our clients has been erecting a post frame home in Colorado Springs, which is over a crawl space. Here is our discussion in regards to insulating the crawl space.

“While I have your ear, I had asked you a question earlier about getting the code required R30 in the 2×6 floor joists of my raised floor. I looked into your suggestion of spray foam and I got some quotes from local companies and I was shocked! One company quoted me $16,000 to do 3″ in the floor and walls with some performance charts showing that the 3″ would satisfy the code (I’m a bit skeptical). I got another general quote of $1.10/board foot and that it would take 5″ (i.e. $5.50 / sq ft)  or $12,650 just for the floor. The second company did suggest though that El Paso county allowed the R30 around the crawl space perimeter and no insulation in the floor… which leads me to my question…

What would be your thoughts of a non-vented crawl space using something like 15 mil plastic on the ground and up the sides the 18″ to the floor and the R30 spray foam from the ground to the floor level?  I could get that done for around $2500. I’m still haven’t completely decided if I will used dense pack cellulose or BIBs for the walls but I’m pretty sure I don’t have the budget for spray foam in the walls.”

Mike the Pole Barn Guru Responds:

When I moved to Oregon from Eastern Washington in 1979, I was amazed at how different the construction techniques were from what I had grown up with. Eastern Washington was the land of full basements, whereas Western Oregon was predominately crawl spaces. The typical crawl space would have 6 mil black visqueen draped down the sides of the foundation and covering the ground, with R-19 unfaced batts used to insulate directly beneath the floors.

A variant of this was to use the crawl space as an air plenum, eliminating the need for heat ducts, and placing the unfaced insulation against the foundation.

This variant is basically a very slight spin away from what you propose to do.

Performance charts always frighten me as they general require some hocus pocus involving dead air space. Closed cell spray foam is R-7 per inch, so a claim of three inches in a system making R-30 sounds bogus unless the balance of the cavity is going to be filled with something like unfaced fiberglass batts. There is no question about closed cell spray foam being expensive, even the work I had done when we added the elevator shaft on the back of our home ran $2.80 per square foot for four inches thick.

Personally, I have no issues with what you propose to do and would probably take it a step further and utilize the principles of Frost Protected Shallow Foundation insulation below the base of my wall steel. https://www.hansenpolebuildings.com/2016/11/frost-protected-shallow-foundations/.

How Insulation Works

I so enjoy clients who truly care about the outcomes of their post frame buildings. In this case, I’ve been back and forth with reader Eric and today we are discussing how insulation in walls works.

Eric writes:

“Mike,

Thanks again for the input. I read those articles you mentioned on the BIBs and the white liner panels. The liner panels are very common and popular around here but the article had very good points and gave me more to think about. As for the insulation, I was not familiar with the BIBs system and was impressed. I have done some more reading and reached out to a few contractors for quotes on the BIBs system. I do prefer to do things myself whenever possible however, so the option of installing fiberglass myself is still on the table. This is where I still have a question. You mentioned to fill the entire wall cavity with unfaced fiberglass and then cover with Visqueen. Is there an issue if the cavity is not completely filled and an air space is created between the fiberglass and the Tyvek® behind the metal sheeting? I ask because my walls are roughly 5 1/2” deep and obviously R13 is only 3 1/2” thick and R19 is 6 1/2” thick. If I go with R13 (cheaper) I end up with an air space. If I go with R19, I end up compressing it and losing r value anyway. Also, I have diagonal bracing in the corners which will also make it near impossible to tightly fill with fiberglass batts. I would love to go with the BIBs system but am waiting to see if it is within budget. If I can save considerable money insulating myself with batts I would most likely do so but need to be sure I am not causing problems down the road. Sorry for being so long winded and thank you very much for all your help and information.”

Mike the Pole Barn Guru responds: How Insulation Works

Fiberglass itself has little resistance to heat flow. The actual insulator is the air trapped in the tiny spaces between glass fibers. The tiny air voids slow conductive heat movement, while the glass fibers reduce radiant losses and impede air movement to block convective heat flow.

Don’t be fooled by so-called dead air spaces. Small air voids slow heat flow, but large voids don’t. A dead air space is one in which air does not move — once a gap gets larger than 3/4 inch, convection kicks in and overrides the insulating effect. Even though they contain air, uninsulated framing cavities have little or no R-value.

Making contact.

This understanding should govern the way batts are installed in the field. They should make good contact with wall and ceiling and nestle snugly against the sub-floor at the base within wall cavities. If the batts don’t touch the inside face of the drywall and the housewrap, convection coupled with air leakage will seriously undermine their thermal performance. Use only unfaced batts in exterior walls, because we’ve found inset stapled kraft-faced batts tend to create gaps between the insulation and the drywall. (Using unfaced batts also prevents the drywallers from complaining about the presence of stapling flanges on the surface of the framing.)

In other words, even though shoving batts into a wall girt cavity may seem like a no-brainer, doing it right takes some care. If a batt is simply jammed into place, its edges tend to drag along the sides of the girts on either side, which often prevents the rear corners of the batt from coming into contact with the exterior sheathing.

Moral of the Story

If your budget does not include closed cell spray foam insulation, then BIBs is a great solution and is effective.