Another Hole(s) in the... Wall
My Northern zone 5a home can't be a Passive House (PH) because it was built in the 50's. But I'd guess that imitating PH practices where possible as projects are done will help the house be the best it can without a gut rehab.
We're putting in a 95+ efficiency furnace in the basement and the HVAC contractor will put a PVC combustion air intake and PVC combusted air exhaust through the 8" brick wall a few inches above the concrete foundation (I imagine each will be about 4' long). Not knowing enough to ask for specifics, I voiced a complaint about cold radiating radiating from the intake pipe and he said he'd wrap both pipes in bubble wrap insulation from the furnace to the brick. The current plan is to make each hole through the brick as small as it can be and still fit the PVC and then seal the outside and inside with expanding foam, which will expand into some of the 8" between.
My question is, if you were making two plastic pipe penetrations in a PH retrofit to a historic building (this one isn't, but the brick on the outside can't be covered over with a new PH insulated shell), how would you do this?
With respect to the wall, is the plan above (which probably involves foam voids and PVC-to-brick thermal bridges) as good as it gets or would it be better to make a larger hole such that insulation can be put around the pipe so that 1) those 8" are insulated and 2) they are thermally broken from the brick (again in this case spray foam would seal the outside and the inside)? The contractor is against larger holes because he thinks it likely the insulation will break down eventually and allow more air infiltration.
Is bubble wrap insulation along the 8' length (two 4' PVC pipes) between the brick and the furnace as good as it gets?
Is there a better sealant for this job than spray foam (I've read it develops cracks over time, but we can't very well use high quality primer and tape on the decorative brick outside)?
Seems like the following Building Science Corp/Dep't of Energy comment would apply. Do people agree? "Penetrations through building enclosure elements that also perform rain water management functions must be properly flashed. It is critical that airs sealing not interfere with drainage"
Other ideas? Maybe it would help to think about how fresh air intakes or plumbing penetrations in real PH retrofits where the exterior brick stays visible are put through the brick walls?
Thanks you for your time.
Posted Mon, 06/23/2014 - 16:43
Edited Mon, 06/23/2014 - 16:54
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