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Basement Insulation/Moisture Control - Reading Comprehension Test

Posted by justus_atl (My Page) on
Wed, Dec 10, 08 at 18:45

Worthy and others,

Thank you for the information and help you provide. I have spent several hours this past month reading through posts as I get ready to kick off a basement finishing project. Now I'd like to make sure I have put together a decent strategy for getting the space insulated and ready for framing.

My house is a 50's ranch in Atlanta, and the basement walls are made out of solid granite blocks mortared with cement. The space is about 2,300 square feet, and the front half is below grade, while the back half has windows and doors. The previous owners installed a 1" drainage trench around the perimeter of the basement with a sump pump. It kicks on only during very heavy rains, but seems to work great, as the basement stays dry and has no musty odor.

This will be a full finishing project, and we plan to add 2 bathrooms, a laundry room, and a few regular rooms. We are starting from scratch. I will mostly act as general contractor, and will only do the light jobs myself.

So, having said that, as for insulation and conditioning, the plan is:

1) Foam spray directly onto granite walls - XPS not really feasible because of uneven walls. The professionals I have spoken to have recommended between 1.5 and 2 inches of closed-cell polyurethane foam, and quoted $1.30-$1.75 per square foot. The plan is to have them spray the walls down to within an inch of the trench, and spray up all the way and including the rim joist. Then, use low-expansion foam on doors/windows. Sound good?

2) For the floor, I plan on laying down DriCore or SubFlor panels wall to wall, right up to the trench, and using canned foam to seal any plumbing openings. I am working to see if I can get the new HVAC ductwork configured to blow both below and above the subfloor. Then, I plan to frame on top of the subfloor. Sound OK? I don't need XPS below the framing if installing onto the subfloor, correct?

3) Inside the 2x4 framing I will use unfaced batt insulation, which my local HD does have, then dryall and finish as normal

4) I plan to put batts in the ceiling/floor joists to help with sound proofing and further insulate. Should these be unfaced as well, or should I used faced with the paper against the main-level side?

5) The new HVAC system will be a heat pump with humidity control (Trane XL15i) - will this be sufficient humidity control, or should I have an additional dehumidifier? The HVAC guy is coming Friday to quote so I am sure he will have a recommendation, but the knowledge of the average HVAC salesperson leaves a little to be desired, so any thoughts/inputs would be appreciated.

6) Finally, back to moisture control for a minute. Building code requires a vapor barrier in my area. Will the foam insulation serve this purpose? Is it likely that the inspector insist on some rolled membrane? Would the MemBrain(r) material work in that case? Does anyone know how expensive that stuff is?

Sorry for the long post and laundry lists of questions. I'll only do this once so want to make sure all bases are covered. I want to save money where I can, but want to be sure not to cut corners that can result in disaster later on.

Please let me know if I am missing anything.

Thanks everyone!!!


Follow-Up Postings:

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RE: Basement Insulation/Moisture Control - Reading Comprehension

Sounds absolutely fine to me!

1)-3) No comment

4) The insulation will make little difference as far as sound proofing. If keeping the noise down is a big priority, use a damping system such as Quiet Rock, Green Glue or resilient channel and an extra layer of drywall.

5) If the heat pump doesn't keep humidity below 35% RH, you can always put in a portable dehumidifier.

6) If the inspector is uninformed and therefore insists on a polyvinyl vapour barrier, it won't hurt the system. There's no need to bother with Membrain, which is designed to be effective with fibrous insulation. On one project I did with cc on the walls, the inspector approved it without poly. On walls with XPS, inspectors have insisted on the poly.


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RE: Basement Insulation/Moisture Control - Reading Comprehension

Thanks Worthy! I really appreciate it.

I will make a note of the 35% RH and discuss with the HVAC rep. A portable unit, especially in the laundry room, wouldn't be a bad idea anyway.

I have looked at the other soundproofing options, will keep that in mind. The foam guys also suggested spraying an open cell foam insulation into the ceilings, and recycled blue jeans in the interior walls. I just have to weight the costs for a room that may or may not eventually become a media room.


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