Comments on: A Visual Guide to Why Fiberglass Batt Insulation Underperforms

By: FHFurr

FHFurr — Tue, 14 Aug 2012 19:11:41 +0000

I agree, regarding spray foam
I agree, regarding spray foam... customers should get an air tightness commitment (ACH50) in writing that is verified for home insulation.

By: Home Insulation

Home Insulation — Thu, 12 Jul 2012 14:44:33 +0000

Yet more proof that foam
Yet more proof that foam spray is the best solution for the loft insulation. It eliminates many of the gaps that allow air to seep through, though it isn't totally infallible.

By: Mr. C

Mr. C — Thu, 24 May 2012 02:49:17 +0000

This a good on how not to
This a good on how not to install. But for the most part air infiltration happens equally with all forms of insulation unless the whole wall cavity is sealed.

By: Lucy

Lucy — Mon, 26 Dec 2011 09:41:02 +0000

Mr. Bailes,
Mr. Bailes,

I used your picture of a class I batt installation on my blog. I hope that is ok. It was the only one I could find on the interest that did not have kraft paper. I included a link to your blog so people would know where I got it from.

Thank you.

By: Chris Brown

Chris Brown — Thu, 20 Oct 2011 23:18:01 +0000
David B.

David B.

Simply put, if the foam material in the cavity is not in direct and continuous contact with the back of the drywall, then the cavity is not full. That should be the goal of any defined cavity insulation, to fill the cavity. I meant nothing more.

By: David Butler

David Butler — Thu, 20 Oct 2011 21:37:08 +0000
Regarding spray foam... since
Regarding spray foam... since it's promoted and sold as a means to achieve a tight envelope, I tell clients they're wasting their money if they don't get an air tightness commitment (ACH50) in writing, verified by a 3rd party. Otherwise, they're just buying snake oil. In my experience, the only foam contractors who consistently live up to their promises are the ones who test their own work.

Chris wrote:
> If the contractor does not completely fill the cavity... there is no direct and continuous contact with the interior air barrier.

I agree with your point about inconsistent R-value, but there's no benefit from the foam being in contact with the drywall.

By: Allison Bailes

Allison Bailes — Thu, 20 Oct 2011 17:09:42 +0000
Chris B.:
Chris B.: Yes, you're absolutely correct that RESNET's insulation installation grading protocol applies to all insulation types. Although I don't think I discussed grading in that article, see my post from last year called 4 Pitfalls of Spray Foam Insulation for some of the problems I've seen with that type of insulation.

That said, it's not just that problems with batts are easier to see. They're also easier to get. Sprayed and blown products are certainly not infallible and don't get grade I every time, but it's a lot easier with them.

I've written quite a bit about insulation here in the EV blog, and you can see some of the other articles in the list of Related Articles at the bottom of this article.

Regarding codes, you're absolutely right. Improving codes definitely help move things forward, but adoption and enforcement are the keys.

By: Chris Brown

Chris Brown — Thu, 20 Oct 2011 16:57:21 +0000
There is no doubt that the
There is no doubt that the attention paid to the quality of insulation applications is long overdue. RESNET's grading scale is a good start. While I can't argue with the photos of poor applications of fiberglass batts that you posted, in all fairness batts are not the only insulating material subject to poor workmanship. Granted, the problems are easier to spot, so criticism is easy. RESNET requirements apply to all cavity insulations. From my field experience, I would hazard a guess that there are significant amounts of spray foam jobs these days in new construction that would also fail to meet a Grade I of Grade II requirement. If the contractor does not completely fill the cavity (which means overfilling and shaving off excess), there is no direct and continuous contact with the interior air barrier, nor is there a consistent R value delivered in each respective cavity. It might look better than a sloppy batt job, but is it really delivering what was paid for, or what should have been done? If netted loosefill applications in walls aren't applied at the required density (not easily spotted or determined by most inspectors), then once again what appears to be a good insulating job really isn't! Its not just about batts, or how any material "looks". Its about understanding why any insulation application is important, how insulation works (and what doesn't), how insulation relates to the other "systems" in the structure, the significance of air sealing etc.

Although there are many top notch insulation contracting firms working today across the country, there are still far too many that not only undersell their value each and evey day, but underperform as well. Its no longer about just putting something in the walls so the drywaller can hang rock tomorrow. The good news is that the improving codes and inspection requirements will act as a filter as well when its all said and done. By the way, don't leave the builders or framers out of the equation either. The best insulation application in the world (regardless of the insulating product used) can't make up for a house filled with thermal shorts, unbacked kneewalls, open chases, open ended floor structures under cold floors (Gee, I wonder where the term cold floor came from anyway?)bad design, etc.

We are making progress no doubt, and blogs like yours make it easier to educate oneself, but we still have a significant fight in front of us. Code adoption is one thing, code enactment and enforcement is where it really happens, and to a very large degree, we aren't there yet. Here's hoping!

By: David Butler

David Butler — Thu, 20 Oct 2011 00:12:54 +0000
Rocky, adding to what Allison
Rocky, adding to what Allison just said, I would only consider placing a vapor retarder on the OUTSIDE in a climate without a significant heating load (e.g., Miami)

In climates with both heating and cooling loads, the vapor retarder should (ideally) be in the middle of the insulation sandwich. For example, R13 in walls, R5 XPS on exterior and two layers of 15lb felt over the OSB. This is the configuration Dr. Joe recommended for my previous home in Charlotte (although R-values were different). This approach also mitigates thermal bridging. Joe and wife Betsy were largely responsible for getting NC to change its codes so that plastic or kraft facing on interior walls is no longer required, except in a few counties in the mountains.

By: Allison Bailes

Allison Bailes — Wed, 19 Oct 2011 23:58:34 +0000
Gene W.:
Gene W.: Thanks for the extra info.

Rocky: Ah, the old vapor barrier question. This should probably be the topic of my next article because it confuses so many people. The short answer here is that yes, in hot, humid climates with little heating load, vapor "barriers," officially class I vapor retarders (<0.1 perm), should be on the outside. Asphalt-impregnated kraft paper on batts has a perm rating of about 1, which means it's barely in the range of being a Class II vapor retarder (between 0.1 and 1 perm), so trapping moisture isn't as big a problem.

Also, many parts of what's called the Deep South, like Atlanta, have both significant heating and cooling loads, but we don't often find the condensation issues that the truly cold climates can have.

Finally, in the Southeast, most water vapor problems in building assemblies can be controlled with air-sealing. (Well, if that was indeed the short answer, there's definitely an article or two in there.)