I just bought two city row homes, both have a flat roof. One is an end of group. I am going to fix them up and rent them. Because these older homes (one built in 1915 and the other in 1937) have little to no insulation, I am going to take the second floor ceiling down and insulate them. At first I thought about foam, but that is so expensive. And since the roof is watertight and therefore airtight, I don’t know if there will be any benefit.
Therefore, I am thinking about spraying a layer of foam along the inside perimeter of the exterior wall in the space between the finished ceiling and roof along with fiberglass batts. Will there be any problems with moisture with this plan? Does anyone think that this added step won’t be needed? I want to help keep my tenant’s utility bills as low as possible so that they will have an easier time paying me.
Thanks
Kevin
Replies
Can be a tough call. What is the ceiling? Sheetrock on the bottom of roof joists? I assume the ceiling cavity is not vented (some are). Where are you located (my gues is the Northeast ... NYC?).
Biggest issue ... continuous vapor barrier on warm side. If you have ceiling penetrations, they would have to be sealed ... ALL of them. Any moisture going through the ceiling will condense on a cold plywood roof deck.
I would think filling the cavity FULL would be a good choice ... insulation all the way up against the roof deck ... deters condensation.
Also ... make sure you have good bath fans for ventilation ... getting rid of moisture. Remember MINIMIZE flex duct. Don't be cheap. If you have humidity issues (weather or tenant wise), good exhaust fans will serve you well.
A tight house needs to be ventilated. If these are e.g. 2-3 stories ... their is a lot of 'pressure' in the top level ... cool air moves in low warm air looks for a high place to go out.
It's all in the details. Hope this begins to help you out, get you thinking.
Thanks.The ceiling will be sheetrock against the ceiling joists and the houses are in Baltimore. The ceiling cavity is not vented. So, do you think I should seal the openings in the ceiling electrical boxes, like those for the smoke detector? I could spray some closed cell foam around the openings where the wire goes in before we put the sheetrock up.
right ... seal the ceiling penetrations and really all boxes. Technically you shouldn't e.g. silicone all the holes in an electrical box ... voids U-L listing maybe (installing any U-L product in a manner other than as manufactured voids the U-L listing). People do it. There have been discussions about compatibility of e.g. silicone w/ NM wire insulation, but again ... it is often done, I think. A typical J box has lots of 'holes' in it, not just where the wire goes through. You can get sealed boxes and then just seal where the wire goes in. Carefully seal the box around the sheetrock. My sheetrocker made my drywall TIGHT to all my boxes ... no sloppy work with him ... he was amazing ... I'm wandering, though ...
Good vapor barrier on the ceiling, seal it. Think exhaust fans for ventilation (what you exhaust must come in). A healthy house has to breath a little.
sorry ... overlooke your ceiling condition. What is the ceiling ... suspended acoustical tile (e.g. my office)?
Good idea to insulate the walls above the ceiling ... great place for condensation.
Do I assume insulating the roof deck is not an option? If you ever replace the roof ... adding insulation can be a great way to go .... that is most standard in flat roof construction.