Thanks for the great info and recipe. I look forward to more posts like this one.

Question on this...If doing 1-4 listed above, is there any additional benefit to adding the air ducting and return to feed the cooling/heating to the crawlspace?

I live in Brentwood, TN in a home we just recently bought and it has a decent sized crawlspace and I have been investigating ways to reduce the "cold floor symptom" we are having now that winter is here.

Thankiossk Cool!

Alan,

The short answer is YES. Adding conditioned air to the crawl space, in my opinion, is a great idea. Doing this makes it a conditioned space and it is then called a conditioned crawl space. The advantage in the winter is heat rises and in this case rises into your home making your floors warmer. It may seem that it will be more expensive to do this but actually it is the opposite. With an open crawl space your home is attacked from all six sides, but once you close and condition the crawl space one of the largest square foot surfaces is no longer in contact with the outside.

Hope this helps,

Matt

HaHA! I have already seen the great thing!!!

Wow, thanks for the insightful post. I look forward to reading more from you.
My cousing was looking for this last night. Glad I found your article :- )

Ok, I see what you're saying. That's truly interesting to consider, though I think I'd have to research it a little more to fully understand.

Thanks for posting this. It's good information and frankly, a lot of it needed to be said.

Glad that you shared this! It's some pretty great info, I know some people that will really enjoy this.

So your not worried about ventalation at all not even in the summer time.How do you feel about heavy duty plastic for a vapor barriers.
Thanks Randy Meade

Randy,

Thanks for your comment. This article was directed to insulation only and not to the full procedure in a crawl space encapsulation. Ventilation is very important once you seal the foundation vents, but the ventilation is not coming from the outdoors any more. Once the crawl space has been sealed, insulated and encapsulated it has to have a way to control moisture. This can be done by conditioning the crawl space or installing a crawl space dehumidifier.

You asked about heavy duty plastic. There are many products that fit into this category. Do you have one in particular in mind? I can better answer your question if I have this information.

Matt

I've been offered a job in insulation on the pay scale of piece work .Is there any real money to be made at this.In the state of Washington

You cannot believe how long ive been looking for something like this. Through 6 pages of Google results without finding anything. One search on Bing. There you are!.... Gotta start using that more often

I just had one of your recommended contractors install Dryspace (20mil on floor, 12mil on walls) and close off our vents. He also trenched and installed a sump pump a month before coming back and installing the Dryspace. I've been monitoring temp/humidity levels for months and it dropped 18 percentage points after the liner installation and closing the vents. Nothing but praise for the product and the contractor.

As I understand it, the reason the top 5 inches of concrete block is not covered by foam board is to allow easy access for termite inspection whenever the house is to be sold.

As I plan my crawl space job, I think I see one slight modification (a tweaking of steps 3 and 4 in your recipe) that would allow this band to be insulated and still make it accessible for termite inspection - please inform me of any reason it should not be done this way:

After installing the rigid foam board to the walls (putting the top edge of the board 5 inches below the joists), and then taping and pinning the top edge of the DrySpace vapor barrier just above the foam board, THEN install the un-faced R-19 fiberglass insulation in the rim joist area, cutting the pieces long enough that they hang down over the top of the foam board. A staple or two near the top should keep each piece in place.

This would have the advantage of insulating this top 5-inch band of concrete block (hence making it less prone to have moisture condense onto it) while still allowing easy access for termite inspection to be done (the inspector would merely lift the freely-hanging lower ends of the fiberglass).

In order to work on this after the first piece of vapor barrier has been installed, I am guessing that it would be best to keep the lower part of the vapor barrier folded or bunched up at the base of the wall - until the fiberglass work has been finished; then proceed with extending the DrySpace across the dirt floor and adding the adjacent piece. Otherwise, the installer could potentially cause damage to the first piece of DrySpace.

Would this alternate order of steps be beneficial or not?

Thanks a bunch for your feedback.

Dave,

Thanks for the comment!

Before I can give you my opinion on this I would need to know; what region you live in and is your foundation poured wall or block?

Matt

Matt,

I live in East Central Illinois (Champaign), and have a block foundation. Since posting my question, I have had an Energy Audit done on my home and discussed the crawl space project with the inspector. He said, "don't use fiberglass for the rim joist/sill plate area, use rigid foam caulked or glued in place." The reason, he said, was to provide an additional barrier against air infiltration, which fiberglass would not do. This seemed to me like a good suggestion.

I asked him what distance requirement (down from the joists) existed in Illinois for termite inspection, and he did not know - he said to just make certain that the sill plate itself was unobstructed. He did understand the concept of encapsulation (he said it is much more common in the South), but was quite adamantly set against making the crawl space a conditioned space. I couldn't get him to explain why he thought this was a bad idea, and I suspect he just hadn't had any experience with it.

As I move closer to committing to the project (I plan to fax you the measurements early next week and place an order for materials before the "no shipping costs" special expires on July 30), I have 3 additional questions:

1. Your suggestion (I read it here somewhere, I believe) to encapsulate, then to monitor the humidity for an extended period before proceeding if necessary to add a dehumidifier or supply and return vents in the crawl space seems like an approach I should adopt. I have a very lengthy duct system under the house, with about 100 feet of duct between the furnace and the most distant vent in the house - that means lots of pinhole leaks are already adding conditioned air to the c.s., and if the c.s. humidity does not stay in the desired range, I am thinking I might get by with only the addition of one or more return vents. Am I thinking correctly?

2. The foundation vents (on the outside of the house) are surrounded left and right by the brick exterior. For cosmetic reasons, then, closing the vents off with a cinder block would not be desirable. I am thinking of using a 4-inch cinder block inside the vent cover, and leaving the vent in place - basically creating a dummy vent. It would be a whole lot easier, cheaper, and probably even better looking than mortaring in bricks that are not quite the same in appearance as the rest of the house. Would there be any shortcoming to this approach?

3. I have had poor results over the years with any kind of paneling adhesive. So I am interested in finding a really good adhesive, or in adding some fasteners that are driven through the 2-inch pink board into the cinder block or mortar. What are your suggestions on this - can you recommend an adhesive that I can rely on for the next 'x' decades, or can you suggest a mechanical fastener (maybe a concrete nail with a washer-like head) that can work in tandem with the adhesive?

Dave,

(Sigh!)

Needless to say I would not take this inspectors advice.

In response to your question 1; I recommend you consult with a HVAC contractor to guide you with your local code on conditioned air in a crawl space.
Your question 2; when we close foundation vents that have a brick exterior we usually leave the vent in place and close the hole in the block wall with a new block. Your right it will be nearly impossible to match your brick.
Your question 3; We sell an adhesive that will give an instant grab for the foam board to the foundation wall without mechanical fasteners. Its made by Loctite. If you don't see it on the site you can call our office to order.

Matt

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

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

That was intriguing . I like your finesse that you put into your work. Please do continue with more like this.