Double-brick house in Toronto – how to deal with high indoor humidity after insulating?
Hi,
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.
我们尚未做到的是修复二楼的管道。那里的两个房间（浴室和儿童卧室）有足够的供应，但是第三个房间（主卧室）几乎没有空气出来。二楼没有返回空气。计划是在主卧室安装新的供应量，重新安置给儿童室以终止窗户下方而不是房间中部，并在两间卧室之间的中央走廊的天花板附近安装冷空气返回。这至少应该更好地散发房屋中的空气，但可能仍然不会照顾湿度问题。
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:
//m.etiketa4.com/book/export/html/15970
//m.etiketa4.com/blogs/dept/musings/designing-good-ventilation-system
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.
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Replies
Leif,
The first way to address your problem is to be sure that you have addressed all of your moisture loads.
Is moisture entering your house through your basement floor?
Does everyone in the house always use the bathroom exhaust fan when showering?
Do you introduce extra moisture in your house via lots of houseplants, or fish tanks, or drying laundry indoors, or bringing green firewood indoors?
假设您已经解决了这些问题,there is nothing wrong with upgrading your bathroom exhaust fans to Panasonic units (they are quiet) and running them as needed to lower your indoor humidity level during the winter.
Thanks for the reply, Martin.
Basement is finished and we put down a vapour barrier on the floor before putting in laminate, so there shouldn't be a problem there.
We use bathroom fans excessively, and usually leave them running for at least 30 minutes after taking a shower.
We do dry laundry indoors sometimes (about once a week) and obviously I notice a spike in humidity at that time. However, I figure that within a week it should return to normal levels, but it's still around 60%.
No problem with upgrading the fans and leaving them running. I just wonder if that will be enough to pull in air from other rooms in the house?
Also, do you categorically recommend against installing an HRV that is connected to the existing ductwork for the furnace?
Leif,
Running your bathroom fans for more hours per day during the winter will definitely lower your indoor relative humidity. After all, whenever a volume of air leaves your house, an equal volume of outdoor air enters your house to replace it.
The RH in your home will drop, even in rooms without a fan. Try it for a few days and see if your hygrometer can register a reduction in indoor RH; I predict you'll see a difference.
Of course, this ventilation incurs an energy penalty (although the energy penalty is not as severe as that exacted by a dehumidifier). Don't overventilate; only ventilate for as long as you need to to control your indoor humidity.
再次感谢马丁。昨晚，我整夜都跑了两个浴室风扇，浴室门敞开了。湿度实际上确实下降了约3-4％（降至55％）。今天早上，随着日常活动的开始，今天早上开始再次爬行 - 我想很自然。我将继续这样做几天，看看会发生什么。这显然是最便宜的解决方案，我不介意能源罚款，尤其是现在以如此便宜的天然气价格而言。我认为我可以以安装HRV的价格进行多年的这些粉丝多年！
Thanks again. I'll report back after a few days of running the fans.
Leif,
One more observation: it's always possible that you have a faulty hygrometer. It may be worth buying another one to double-check your RH readings.
# 5,马丁是我发现worth checking.
Hi there,
Just thought I'd follow up to let you know what I have observed so far after running my bathroom fans 24/7 for a couple of weeks.
Humidity has dropped. It actually dropped to around 52% (from 60%) within a few days. During those days we did not do much cooking and didn't hang any clothes to dry. Once we resumed those activities, humidity quickly climbed up to around 60% again within a few days.
So, we've changed some things. For example, we only hang wet clothes in the bathroom now, with the fan running. We also leave the kitchen fan on longer after we are done cooking.
The interesting thing is that the humidity level seems to have stabilized around the 54-55% mark over the last few days, even though it's been raining steadily outside. I thought that the humid outside air would be pulled in by the fans and would increase my indoor humidity, but that doesn't seem to be happening.
I'll obviously monitor this closely going forward, but so far, the simple trick of running the bathroom fans seems to be working. Thank you everyone!
And btw, I have double-checked my hygrometer with another model and it does seem to be fairly accurate.
Hi there,
Keeping the right humidity levels in your house is actually very important. Usually it's between 40 - 50%. Depending on where you live. Because of your high humidity you probably also have squeaky floors, since the wood contracts and expands in different seasons. I had that problem in my house too, so we fixed the humidity levels and found a firm that fixes the squeaks in our hardwood floors. If you do also have that problem google them. I believe they were called silent floor.
Cheers! Good luck.