Double-brick house in Toronto - how to deal with high indoor humidity after insulating?
First time posting, but I have learned tons from reading many of the excellent articles and postings on this site.
Here's our situation. We live in a double-brick one and a half story house in Toronto that was built in 1949. We have done a number of energy efficient upgrades and are now experiencing consistently high indoor humidity (60%+) which leads me to believe that we have a ventilation problem.
The upgrades we have done:
-Closed cell spray foam insulation on basement walls (R12-R24). This was done after complete exterior waterproofing and weeping tile replacement around perimeter of house. Basement is dry.
-New high efficiency furnace (95%)
-3" closed cell spray foam on underside of roof between rafters. Spray foamed over rafters behind knee walls and at peak of ceiling. Put one inch (R5) of XPS rigid foam on top of spray foam where drywall was going on top. Roof is airtight where before there had been huge gaps - needed space heaters to keep room beside bathroom from freezing.
-No insulation added on main floor, but extensive air sealing has been done. Still a little leaky and drafty, though.
-Sealing of all ductwork that was exposed during renos.
-Home Energy inspector gave us a 75 EnerGuide rating after the latest upgrades (attic).
These upgrades have been done over the last three years. We always thought humidity was a little high in the house (no known plumbing leaks), but at least in the fall and winter it would drop into the low 40s or high 30s. Now it is consistently around 60%, and I'm getting concerned about mold. One cold night when it dropped down to around 0 degrees centigrade (32 F) we already had condensation build-up on our windows.
What we haven't done yet is fix the ductwork going to the second floor. Two rooms up there (bathroom and kids' bedroom) have adequate supply, but the third room (master bedroom) has hardly any air coming out. No return air on second floor. Plan is to install a new supply run to the master bedroom, relocate supply to kids room to terminate below window instead of middle of the room and install cold air return near ceiling in central hallway between the two bedrooms. This should at least circulate the air in the house better, but will probably still not take care of the humidity issue.
I also suspect that some cracked mortar between the exterior bricks contribute to more moisture entering the building envelope when it rains, so some repointing is planned and I have also considered sealing the exterior brick using a siloxane or silane based water repellent.
Now, I've considered an HRV, but after reading the following articles by Martin Holladay I'm not so sure:
An HRV might make my situation better, but there's no way that I can install it properly as outlined in those articles (separate ductwork hooked up to bathroom fans). I could install better bathroom fans (currently fairly noisy 70CFM units) in our two bathrooms and run them all day to create an exhaust-only ventilation system, but I'm worried that this might not be enough to benefit the whole house. I could of course also just open a couple of windows, but then why did I install all the insulation and do all the air sealing in the first place???
Anyway, I'm a little worried and frustrated at this point, so any advice would be greatly appreciated.
Posted Oct 10, 2012 1:45 PM ET
Other Questions in General questions
Is it advisable to use nail base insulation panels over a roof insulated with closed cell spray foam?