Finished basement insulation/drywall
Im in zone 4c, wondering if insulating the floor joists above in my basement is proper. If so, when using fiberglass, go with paper faced or non faced? If paper face – facing basement correct?
Will all pieces of Sheetrock that go in the basement need to be mold resistant?
also, when framing in divider walls, and particularly where the wood framed wall is perpendicular to and meets the concrete wall of the basement, should there be anything in between those? Should I insulate there w/ rigid first, or just make my last framing member PT, and insulate everywhere else on that wall except where walls come into contact with the concrete?
lastly, is any sort of vapor barrier on the concrete floor required before framing walls begins or can that be done after?
Any help appreciated.
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The only place you need pressure treated wood is on the floor. There is no reason for the wood to touch the foundation at any other point....even on the ends where the wood walls meet an intersecting foundation. Hold the wood proud of the foundation in all directions and insulate behind it. Insulating between floors does noting EXCEPT perhaps some sound attenuation. Other than that no reason to do it SO LONG AS YOU PROPERLY SEAL AND INSULATE THE PERIMETER. (Think about it. Any heat you would lose from your basement is simply going to rise to your first floor where you still benefit from it.) However, you should still air seal plumbing and electrical penetrations from below because that air will rise into you walls and it will increase the stack effect.
Once had a pipe in the middle of my basement freeze solid. It was running through a cold air return. In our area, the HVAC practice is to use stud bays and floor joists as the return duct (it is a box in theory anyway with two studs on either side and drywall on the other two sides.) In practice though plumbers and electricians come along and drill holes through the box. Well in any case, the holes drilled by the electrician for wiring that went through the air return actually connected one stud bay over to a soffit in the kitchen. The soffit had insulation above it at the ceiling level but was otherwise open and empty. It found outside air in several places and was pulling the outside air over the entire soffit down the stud bay through the wire penetrations and straight on to the pipe. This froze the pipe of course but more so than that my furnace was suctioning outside air into my cold air return and heating/colling that unconditioned air. The frozen pipe SAVED me hundreds. That is why on all my other houses I pay strict attention to the cold air returns. I put stops above every cold air return in my house and caulked above them to stop them hunting for air from out side the room the return is supposed to be pulling from.
Hi Kevin.
It is commonly a better approach to insulate the basement that to insulate the first floor. The first thing you should do is answer some questions.
Is the basement dry? If you can't answer yes to this question, start here: Fixing a Wet Basement. There is no use insulating or finishing a basement with water problems or excessive moisture.
If the basement is dry, you can start to ask these question; Are your basement walls insulated outside? Is your slab insulated? Is there a vapor retarder below the slab? The first answer should be easy to determine, but the two questions that deal with what's beneath the slab may not be so easy to answer. I suggest you read these articles to help with understanding the next steps you need to take: All About Basements , How to Insulate a Basement Wall, and Installing Rigid Foam Above a Concrete Slab.
And by the way, it is common to use pressure treated lumber where it will be in contact with concrete slabs, foundation walls, etc. and mold resistant drywall is not necessarily required for a finished basement that is dry and conditioned, but it's not a bad idea either, in any potentially humid area of the house.
Brian, thanks for the helpful information. I will learn about this stuff and pass this along.
I just wanted to double check with you on some things. You started off by saying “It is commonly a better approach to insulate the basement that to insulate the first floor. ” I don’t want to assume I know what you meant but here did you mean it is better to insulate the basement walls, floors, or both, than the first floor joists? Thanks.
At this stage (slowly going along saving money each step of the way), the customer simply wants me to put in a L shaped wall in the corner for a bedroom. Each end of the framed wall will be touching the foundation wall..
I think even if there are moisture related problems if I were to do just this job it wouldn’t hurt if moisture problems did need to be addressed later. To my knowledge there are none, but more testing is wise.
I think both responses I got contradicted one another, But Why? Said to leave a gap between foundation wall and last stud - and insulate behind - if this is what you’d do too - should I just leave a 1-2” gap to be able to fit 1” or 2” insulation later? And once it slides in behind the wall just tap on that last stud to the foundation? Or - what I heard you say I think, is to run the wall all the way to the foundation wall and butt the insulation up against the wall - and to make sure the last stud is PT. Want to help clarify?
If you wouldn’t mind as well... I’ve seen people create a new subfloor before any wall framing, using DMX, and plywood. Others however, frame to the concrete floor and, and just put a vapor barrier down before flooring... or a combination of the two, to frame in a wall, then butt up to the wall the dmx, and plywood. Does it depend on where you live (4c)? In other words can I frame in my wall before addressing flooring/sub flooring.
Thanks!
Hi Kevin.
Yes. Some people insulate the floor above the basement and leave the basement uninsulated, effectively putting the basement outside of the conditioned building envelope. It tends to be more efficient and healthier to insulate the basement floor and walls to bring the basement into the building envelope.
On the second question, I agree with But Why? Insulate the walls first with rigid foam and then the framing doesn't need to contact concrete and you don't need PT lumber. I was just making clear that if you don't insulate and you do put lumber against the concrete floor or wall, then it is wise to use PT because the lumber will wick moisture. Sorry to confuse the issue.
As far as the last question goes, I have seen it done both ways too. I think I like the idea of insulating the slab and foundation walls and installing the subfloor before framing walls. That way you have continuous insulation and all of the framing is isolated from the concrete. These walls are not bearing any weight, so I can't see an issue here.
I've only done a little basement remodeling myself, so maybe some others will chime in with their experience.
There is no need for a mechanical connection between the last stud and the foundation wall. The wal will be attached to the floor and to the first floor joists from above which is more than sufficient for a simple non-load bearing wall. More than likely, you will also secure that wall to a perpendicular stud wall as well. Essentially, you are building a double stud wall with no bridging between the first wall (the foundation) and the second wall (the stud wall). The only bridging occurs at the slab and at the joists.
I will differ to others to do the calculations but insulating the slab is not cost vs benefit a winner if I recall correctly. I oppose it on the grounds that it wont give you a return and because it will further restrict headroom. Additionally, adding more plywood (read food) for mold on the floor is going to simply add to the headaches when you have the inevitable leak inn the basement. I opted for vinyl tile over the slab and area rugs to increase comfort where needed. The area rugs can be removed if they get soaked and either pitched or cleaned. I also went with a high baseboard (6") with a rabbit that the drywall sits on. That leaves me a six inch gap between the floor and the drywall. If (when) I do get water, I can pull only in the baseboard and dry things out. I also didnt insulate all the way to the floor leaving a couple of inches un-insulated is no big deal performance wise and yet it allows space for the water to drain and will allow me to better spot the area where the water is entering and if the water is coming down the wall or entering between the wall and foundation. Insulate all the way to the slab and you will be destroying the insulation to find the source area.
The most important thing is if you are even considering a bedroom you have to have an egress window.
Any vapor barrier under the vinyl’s underlayment? (Probably cork)
We’ll probably go with the engineered vinyl planks.
So no insulating the first floor?
If the space above is conditioned wont really matter is what I’m hearing
Thanks
If you insulate they perimeter (read foundation) there is no energy benefit to insulating the basement ceiling/1st floor. The reason is that any heat or cold that migrates between the basement and the first floor is not WASTED in the sense that it is still inside the envelop of the conditioned spaces. That being said there MAY be reasons to insulate between the basementbin the first floor if sound is an issue. If you are going to locate a home theater in the basement blow bedrooms above, you may want to take steps to minimize noise tranmission which may include insulation. My wife demanded insulation plus other measures underneath our master bedroom and the basement because ....let’s just say she didn’t want anyone in the basement hearing us walk in the bedroom :)