What are the issues with breaks/holes in the foundation?
user-1124821
| Posted in PassivHaus on
We are building a near passivehaus in Northern Vermont (6 inches subslab foam and trying to strategize surrounding the footers). I have concerns and questions about breaks or holes in the slab/foundation. Which are needed and which are not? It seems anything that only communicates with the outside should be OK: septic venting/ air intake for wood stove…. but what about others such as slab/foundation drain or venting for radon mitigation?
1) Slab/ foundation floor drain
2) Radon mitigation pipe for venting
3) Septic venting
4) Finally what are strategies to avoid thermal loss through footers?
Thanks!
Phil
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Replies
Phil,
Many Passivhaus builders -- especially those who want a slab -- are building raft foundations. For more on raft foundations, and questions surrounding the use of rigid foam under footings, see Foam Under Footings.
A floor drain isn't necessary. If you want one, include a trap.
Your radon mitigation piping should be under your foam -- in other words, outside of the thermal boundary of your house.
Martin
How can your radon mitigation not penetrate the foam? You need the ability to vent the gas out through the house? All radon control strategies I have seen include perforated pipe below foam/ slab and then venting it out the house. Can you pull it outside only and how?
Phil
Phil,
Just because a pipe penetrates your slab, doesn't mean you'll have an air leak. The key to a tight house is to seal all penetrations. Pipe penetrations can be sealed with caulk, with EPDM roofing, with modified roof flashing (vent pipe boots), or with high quality tape.
Most slabs have many pipe penetrations. However, if these penetrations are sealed, you won't have much (or any) air leakage at the penetrations.