Air recovery ventilators

Old 01-22-15, 02:44 PM
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Air recovery ventilators

I have a 10 year old Energy Star certified home when purchased we were told to run a ventilation fan in the upstairs bathroom about 11 hours daily to help with moisture, I have faithfully done this but every year we get excessive condensation in the upstairs windows, I am considering an ERV or an HRV unit but not able to determine what would be best for the house. Do either help with heating the house, the upstairs living space is about 10 degrees colder on average.
Old 01-22-15, 06:17 PM
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Welcome to the forums.

I don't see how running a venting fan can possibly control moisture..... except during and right after a shower. You are discharging expensively heated air outside and drawing moisture laden air into the house from anywhere it can squeeze in.

Neither unit will "help" with the heating but an HRV may save more heat.
I can't offer much help choosing between an ERV or an HRV but here is an interesting piece on it.
HRV or ERV? | Green Building Advisor
Old 01-22-15, 07:16 PM
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Hi adamn and welcome to the forum.
PJ, up here in very cold country, that cold winter air that replaces the air being exhausted is dry as a desert.

But PJ is correct, an exchange unit doesn't really help heat the house, other than recovering some of the energy being lost. In a tighter home where you already have too much moisture the HRV would be the better choice as an ERV recovers moisture as well.

In addition to watching for condensation on those windows it would be good to have a humidistat to read relative humidity (RH) directly. When you say the upstairs is 10 degrees cooler that by itself increases the RH reading.

Controlling the source of the moisture is #1 priority and again, as PJ said, run the fan for 20 or 30 minutes after every shower. But how about a kitchen fan and what type of range are you using, gas or electric. A gas range generates a lot of moisture.

Any other moisture generating activities?
Drying clothing inside?
Exhausting a dryer somewhere inside?
How many family members and pets (live beings exhale gallons of water)?
Firewood stored inside?
Lots of house plants and/or fish tanks?
Moisture issues in a basement?

Pick up an RH meter and take some readings around the house. If you find one that reads temperature at the same time, better as we need both numbers.


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