Replies

1. 
   Kopper37 | Jun 15, 2011 05:12pm | #1

   Mary,

   I'm in Virginia. Here, the local building inspection department requires a 50' setback between a "treated" foundation and a cased/sealed well. This assumes that the exterior of the foundation will be treated with a termiticide. Usually, for these types of treatments, they trench around the exterior of the foundation wall, then inject the termiticide into the soil. Depending on the length of the foundation and type of chemical, they can inject > 100 - 250 gallons of pesticide (diluted per mfg. instructions). That's probably a much bigger issue than treated foam.

   The setback requirement also assumes the well casing has been sufficiently sealed / grouted. Well drillers typically use a cement based product, or bentonite clay to seal the well.

   I've looked into the same issue. I don't think there is much data out there. I couldn't find any data on the long term leaching that occurs from treated foam. The product is fairly new, and has a limited market share.

   You might inquire with your local building code official, see if they can provide any information on setback requirements, and how they were developed.

   Regarding your price for 2" EPS, that's high compared to what I was recently quoted, but that might be related to order size / sheet quantity. If you haven't already, check with Mid-Atlantic Foam in Winchester, VA. Here's the link:

   http://www.mid-atlanticfoam.com/home.asp

   They manufacture and sell the Perform-Guard Type IX EPS. If you're in South-Central PA, they are probably closer than any other manufacturer.

   If you're in a Zone 1 area for radon, then you'll need passive sub-slab ventilation, or active depressurization, depending on your local code. This would help with any off-gassing, but would probably not change the groundwater dynamics.

   One other thought . . . you could choose to use a less toxic termiticide like Bora-Care, go with untreated foam. However, my experience with below-grade foam and insects is not encouraging. Although they don't ingest the material, they will burrow and chew their way through EPS and XPS.

   http://www.nisuscorp.com/portal/page/portal/Nisus/categories/homeowners/products/boraCare

   Good luck!

2. 
   qHNVm6qn8J | Jun 15, 2011 05:43pm | #2

   Hi Daniel, Thanks for your input.

   On the termiticide - the treated soil type - I was thinking of skipping it altogether. Instead, I was planning on using a borate spray (the brand name escapes me at the moment) on the frame lumber (DIY). Also, I was intending to keep the sill plate 16” above grade, have a 2’ to 3’ no vegetation zone around the house, and possibly a flashing piece extending out below the sill plate as helpers in discouraging termites - or at least in helping to detect them soon after they set up shop. I just feel weird about putting the pesticides in the soil around the house … but maybe I’m over-reacting because I really don’t know.

   Re: wells
   In PA there are very few regs on how wells are drilled or installed. I installed my well last October, as we’re doing the project in phases and I had the money for it at the time…Then just a few weeks back I saw an ad for a “safe well water workshop” put on by PSU and I attended. It was VERY informative and I was so sorry I hadn’t thought to put more research into that aspect of my build. Living on city water all my life and not reading much about this issue, it was just an item that passed my by. I picked the highest spot on our rual property for the well, so that’s good. But in PA, hardly any wells are grouted (or sealed) - since it is not required. I relied on the well drillers quotes to guide me. None of the contractors even mentioned it as an option. I would have happily paid a premium price for it, had I known about it. Now that the well is in and it’s too late. But really, in PA, I’m in a lot better shape then many of the wells discussed in that workshop - some it you would not believe! Wells in barn yards, in pastures with only 10’ of fending around them, even through septic drain fields - because if the well is drilled after the septic, there are no codes that prevent it from being drilled there. You would think common sense would prevent it … And yet people treat the water (or not) and go on with life …

   So anyhow, that is why the well is on my mind I guess - since the workshop. And with the cost of the under slab insulation, and the hassle the supplier is giving me … it sorta makes me want to just put in the basement slab with NO underslab insulation. We have no plans to ever finish the basement - not sure what a future family would do. The contractor, designer, and even an architect I worked with briefly at the start of this project all laughed when I talked about underslab insulation (since I have no plans for radiant in the basement). The supplier in Winchester refused to sell to me and insisted I go to a distributer. The distributer had never heard of the underslab product (their exp. is with using it in their own SIPs). I tried again to buy direct from Winchester, offered to pay anyway they want, to rent a truck and pick it up (only 2 hrs from my building site) - but they would not sell to me. Geez, you would think in this economy, with state of the industry, they would be more interested in a potential sale!

   But even if I do drop the under slab insulation, there is still the water proofing product all over the outside of the building, in terms of well water impact. And I don’t think going without that would be a good idea.

   OK, so I’m still sitting on the fence and needing to make a decision and move on …

3. 
   jklingel | Jun 16, 2011 03:17am | #3

   Mary: "...it sorta makes me want to just put in the basement slab with NO underslab insulation...." I'd sure reconsider insulation under your slab, unless your soil temps are near 70 F. With no insulation, you'll be heating China 24-7. Rigid foam is not cheap, but neither is heating China. I would at least do a coarse heat loss analysis, using your average soil temp, and see what it looks like. It may surprise you.

4. GBA Editor
   Martin Holladay | Jun 16, 2011 03:48am | #4

   Mary,
   My opinion: you are overthinking the issue, and are dangerously close to making a bad decision.

   Omitting sub-slab insulation is not a good idea. It's an expensive error to fix. The time to insulate your slab correctly is at the time of construction. Even if your basement is unfinished, it should be within the conditioned envelope of your house. Most basements have heating equipment, and stay warm -- and without insulation under your slab, you will be paying to heat the soil under your house, every winter, forever.

   I can't imagine that the quality of your well water (drawn from 200 or 300 feet below grade, from a well that is 65 feet away from your basement), is going to be negatively affected by sub-slab foam.

   We all accept many risks in our lives -- the most significant is probably driving a car. Don't waste your precious hours on this planet obsessing over fears of harm that have not been proven scientifically. Drink your well water and enjoy it.