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Scott101
Registered Users
Posts:36
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| 12/14/2006 10:55 PM |
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| I have been doing a lot of reading about exterior basement wall insulation and under-slab insulation and have a couple of questions and am looking for advice.
First, I plan on building in a moderate but heating oriented region (4800 heating degree days) of Tennessee. I plan to construct a SIP envelope over a basement or crawl space with a slab and poured concrete walls. I have read that exterior slab insulation is a good idea. However, I have also read warnings regarding termites (we will also be building in a an area where termites are a concern. I have read that EPS insulation may provide harborage termites and carpenter ants and termites. Is this limited to EPS? What about rigid fiberglass? I plan on installing insulation to R-5 or R-6.
Being in an area that averages 50"+ annual rainfall, a good water drainage plane and waterproofing is also needed. Any way to combine the drainage plane and insulation? I read a lot. I have also read that fiberglass looses most of it's insulating qualities when wet. If buried underground in a relatively wet climate won't it always be wet?
Second question (or third or fourth...) is what type of insulation should be used under the basement slab? I plan on a 4"-6" gravel bed with a minimum Class B vapor barrier above the gravel and the insulation above the vapor barrier. As with the exterior basement insulation, I am only looking at a total of R-5 or R-6. Standard 4' x 8' x 1" EPS sheets? Did I say that I plan on installing a wet hydronic radiant heat system in the basement floor?
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Mark Fleming
Registered Users
Posts:188
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| 12/15/2006 8:30 PM |
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Just keep reading, as there's much to learn and not everyone agrees on the answers to many of your questions. Here's my ideas. On the exterior of your concrete walls, the emphasis should be on waterproofing, not insulation. Almost all foams are subject to insect attack (some with boric acid are supposedly okay). Use a dimple fabric, put in drain gravel all the way to the top, put in a drain at the footer and one in the middle on any wall over 5', slope the grade away, long roof overhangs, etc. Once you have the water issue taken care of, then think about insulation on the inside. If your wall only has "dry" soil against a vapor barrier, you won't have enough vapor transmission to cause any problems with your inside insulation.
Now, you can use foam or fiberglass on the inside between the furrying strips that you put up to receive the drywall. I'd be tempted to foam because of what you already pointed out. Fiberglass loses it's insulation value if very much moisture is present. Moisture would be the sign of a bigger problem, but why create the possibility of two problems? I'd even be tempted to try the DIY spray foams like TigerFoam. Because your basement wall will have soil behind it (usually 50 degrees unless you have a really deep frostline), 1.5 inches of spray foam would probably be fine, although the buiding inspector may not agree.
You will have to put foam on the outside for the underslab. In my area, R-10 is the minimum, which translates to about 2" of EPS foam. Hopefully, you don't have a boring insect that is so determined that it will dig under the footing to find a home.
Mark |
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Scott101
Registered Users
Posts:36
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| 12/16/2006 3:22 PM |
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Mark,
Thanks for the response. I anticipate that the basement walls will extend into the grade no more than 5’. Actually, I hope to get enough depth to the soil to even have a basement. The bedrock is shallow and I am not about to blast to get the depth for a full basement. The land does slope, but the building location is only slightly sloped.
The bedrock is exposed around the perimeter of the bluff and during the winter the water seeping from the soul above the bedrock freezes where it exits so I know that there is water movement in the soil. I had planned a spray-on waterproofing membrane and also a dimpled water plane over that as well as the footer drain and even a subsurface system to catch the roof drainage from the gutters. I have specified a 1:10 or steeper slope away from the house for final grading.
I currently live in Florida and don’t have to worry about basement drainage problems. I do have friends and family in the area in which we plan to build (Tennessee) and they do have basement water problems.
I will continue to research the issue.
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icfblocks
Registered Users
Posts:265
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| 12/16/2006 10:43 PM |
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| A product like Insul-Tarp® works great. |
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Thanks,
Tom
www.advbuildingtech.com |
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Cattail Bill
Registered Users
Posts:245
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| 01/31/2008 4:27 PM |
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Scott as stated not everyone agrees on the best methods to eliminate the termite problems in various areas and it changes depending on many differant climatic, vegatation, and soils.
We have carpenter ants in our area but no termites I would almost rather deal with the termites they at least stay below grade for the most part, the ants stay above grade and and have very easy access into the wood areas of most any home.
Yes it is true that termites will bore into foam products to nest it is not a food source so it is strictly for nesting. Buy the way if you built a house entirely out of wood they would still bore in and nest but now they also have a food source. In most of the areas where I have trained ICF construction and they have had termite problems, the little buggers have entered through a wood frame window or door openig and worked their way into the foam. Termites do not like day light and stay mostly hidden and find ways to travel where it is dark. There are sheilds available or that can be made to stop them from geting at the wood portions of a home such as wood bucked areas, or those areas can be built with V-Buck that is not a food source.
This only my opinion based on common sense but not insulating the concrete on the out side greatly reduces the effectiveness of insulation, specifficly if you are building the above grade portion with wood. You see if the concrete gets cold it projects the cold into the wood above and the wood only has an R value of 1 so nothing there to stop that cold from radiating up through the walls leaving cold surfaces.
I think Mark makes the most important point and that is a good seal coat on the exterior of the below grade foam surface, this can be done with a trowel on or spray on parging coat or cement coat that the little buggers can not get through in the first place, and depending on what you use you can either put the waterprooof on the outside or the inside of that check with the manufacturer of those products on the application.
Last fall there was an episode on the learning channel that dealt with this issue and termite traps that are sunk in your yard where used at regular intervals, if termites are prevalant in your area I would suggest you look into some back episodes on this issue they are very informative.
Don't give up on good energy practices just because of termites! |
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