CrawlSpace Concepts - Latest comments on Crawl space Insulation

Bob R. [Visitor] in response to: Crawl space Insulation

Bob R. [Visitor] — Wed, 01 Sep 2010 03:29:43 +0000

Thanks for the response. This is very helpful. When I proceed, I'll need to insulate the crawl space walls, but I have a "pier and curtain" style wall construction for about 70% of the crawl space making it very difficult to use a rigid insulation due to the constant intrusion of the block piers. Any thoughts on the Johns-Manville product "Basement Wall Insulation" that is a fiberglass insulation with a Polypropylene-Scrim-Kraft facing. One contractor I know uses this and it would eliminate 1,000s of cuts for the boards. In humid NC climate would you place the liner on the wall side of the insulation or on the inside of the crawlspace or would you just go up several inches on the wall and have the insulation drape over the liner? Thanks for your help.

Chase [Visitor] in response to: Crawl space Insulation

Chase [Visitor] — Sun, 29 Aug 2010 03:51:50 +0000

@chels I know what you mean, its hard to find good help these days. People now days just don't have the work ethic they used to have. I mean consider whoever wrote this post, they must have been working hard to write that good and it took a good bit of their time I am sure. I work with people who couldn't write like this if they tried, and getting them to try is hard enough as it is.

Matt Leech [Member] in response to: Crawl space Insulation

Matt Leech [Member] — Tue, 24 Aug 2010 08:44:19 +0000

Rob,

Thanks for the question!

Some building code do not allow you to have insulation in both areas so check with your local building dept. to be sure.

I personally don't recommend it in a sealed crawl because:
1. the floor joist insulation is neutered by the wall insulation
2. The floor joist insulation will hinder any positive geothermal exchange between the home and crawl
3. The floor joist insulation makes a nice home for rodents (even if they come in from the house and not the crawl)
4. The fiberglass insulation holds odor from the problem crawl
5. By having insulation in both areas and your HVAC in the crawl space you will create a refrigerator in the crawl during cooling season.

So those are the top five:D

Let me know if there is anything else I can do to help.

Matt

Bob R. [Visitor] in response to: Crawl space Insulation

Bob R. [Visitor] — Mon, 23 Aug 2010 18:50:23 +0000

You mention that insulation should be on the crawl space walls and rim joist areas or in the crawl space ceiling/floor joists, but never both. Why is it so important to remove the floor joist insulation when adding wall insulation and conditioning the crawl space. My floor joist insulation has no backing and could offer some quietness to the floors. Our HVAC is in the crawl space and I feel certain it will be louder with the insulation removed.

stair chair [Visitor] in response to: Crawl space Insulation

stair chair [Visitor] — Thu, 05 Aug 2010 03:01:41 +0000

With all the doggone weather we have gotten lately I am stuck indoors, fortunately there is the internet, thanks for giving me something to do. :)

Tattoo Removal Cream [Visitor] in response to: Crawl space Insulation

Tattoo Removal Cream [Visitor] — Fri, 30 Jul 2010 21:23:32 +0000

That was intriguing . I like your finesse that you put into your work.

Matt Leech [Member] in response to: Crawl space Insulation

Matt Leech [Member] — Thu, 29 Jul 2010 01:46:48 +0000

Hi Dave,

In response to your July comment regarding the process of hanging fiberglass insulation down over the inspection gap. In my opinion that will not hurt anything, but it is hard to say if it will actually improve the space. The real heat loss is going to be at the rim joist and at the top of the foundation block where the sill plate does not cover the block cavities. I understand what you propose will cover both of these areas but will continue past to cover 5" of the block face. I am in favor that there will be an improvement covering the rim joist, sill plate and open block cavity but it is very debatable if continuing the fiberglass 5 or 6" down the wall will actually help. I think our mind gets wrapped around the rest of the foundation being insulated makes it a must to find a way to insulate the last 5 inches. When in fact the greatest heat loss is from cold wind or cold air penetrating the space. For me I would say fiberglass insulation in the rim joist extending down to cover the opening in the foundation wall cavity. This is by far the fastest, cheapest and easiest way to insulate this area.

I do want to comment on the difference between using fiberglass vs rigid foam board for the rim joist area. There are some reports on the net that say it is best to use rigid foam and spray foam in the rim joist area. Because of this article there are people, like that inspector, that recommend this process. The problem is, it is not practical AND it is not the best way to insulate that area. For some reason guys like the inspector do not understand (even though they should!) why. They most often don't understand why to do it that way or why not to do it that way and I suspect it has to do more with lack of experience than it does anything else. So, here is my take on why fiberglass insulation is the better choice over rigid-

First the most obvious reason is that the installer has a much higher range of R values to choose from in fiberglass, reaching up into the R-38 range. Rigid foam board is only an R-10 in 2" if you get it in the pink or blue. The installation process is far easier with the fiberglass which makes it possible to do a better job. When one thinks about the rim joist area, what comes to mind is the part of the perimeter where the joist ends on the foundation wall. But there is the other two sides were the rim joist is one long joist cavity and rigid insulation would have to be nailed in place to keep from falling out. In addition to that the rigid will need to be fit tightly to work properly. Yes, you can spray foam around the areas that are loose but that is an additional step not to mention quite messy in a crawl space. The fiberglass insulation can be cut into identical size pieces and will work in almost every cavity while the rigid will need to be cut to fit, while in the crawl space, or cut small and spray foamed in. The idea behind why the rigid foam was a better choice in the article was based on the idea that it would stop condensation on the wood(Sigh!) and/or not allow air to penetrate the crawl space(Another Sigh). Here is why I reject that article's suggestions as being valid: 1. there would not be excess moisture to condensate (because the crawl would be sealed and according to the code, would need a mechanical means of ventilation to control moisture) 2. Both insulation types will stop condensation if installed properly. The purpose of the insulation is to provide a barrier between warm and cold air or surfaces. One will not out perform the other unless they are not of the same R value 3.The complaint in the article of the fiberglass getting wet and failing if there were condensation is only a true statement IF the fiberglass was installed IMPROPERLY. Remember we are talking about a sealed crawl space, that is what this article was written about 4.If there are air penetrations (gaps) in the rim joist allowing outside air in, well that would need to be fixed properly no matter what insulation was chosen and 5. Both insulation types will perform to their R value regardless of any gaps. If this were not true then every home in America would have rigid insulation in all of the exterior walls and fiberglass would no longer be used in homes.

I hope this answers your questions without getting to rambunctious. As always I enjoy your comments and I welcome them in the future.

Matt

Dave [Visitor] in response to: Crawl space Insulation

Dave [Visitor] — Tue, 27 Jul 2010 05:30:47 +0000

Matt,

thank you for your very helpful answers to the questions in my email of July 23, but please note that I was also attempting to provide you the additional information you requested after an earlier (July 16) email.

I am not clear now whether the inspector (home energy auditor) had it right to use 2-inch pink board in the sill plate/rim joist region instead of fiberglass (which you list in your "recipe"), to cut the air infiltration? Or (going back to the first of my 3 emails) was there any worth in what I was proposing in hanging the pieces of fiberglass down past the top of the foam panels on the wall - doing this step in the insulation AFTER the top edge of the DrySpace has been taped and pinned?

My gut says that insulating the rim joist with unfaced fiberglass will be much faster, easier, and cheaper to do - whether done as you cited in your recipe, or done after the vapor barrier has been attached (as I have described and am still considering). And I am uncertain just how big a problem that air infiltration into the crawl space happens to be (and how well it can be reduced by following the energy auditor's suggestion). One acquaintance who followed the pink board and adhesive step on the sill plate remarked to me that he was able to go very fast by pre-cutting all of the pieces of pink board he needed.

Thanks again, and I look forward to your next response.

Dave