Opening Windows & HRV (Heat Recovery Ventilator)
I’m in rainy Oregon, with mild, (but often damp & chilly) winters. My heating plan is a woodstove, with a ductless mini split for back up heat. I’m also trying to make the house air tight to reduce temperature stratification in my high ceilinged spaces. Yes, I have 16 foot ceilings sloping down to 11.5 feet in the living room area, with a partial loft. So…as part of the energy efficiency additional measures required by code in my area, I selected an HRV with insulated ducting. My crawlspace will be conditioned, and the HVAC person who seems to be knowledgeable says he can install it in the crawlspace, and make the ducting work to circulate air between conditioned crawlspace and the home, ventilate the bathroom, as well as performing normal HRV duties. I like the idea of having a single system perform multiple things, simplifying/reducing the amount of machinery that is humming around me.
My home is in the woods in rural Oregon. My boyfriend pointed out that this HVAC system is modeled on the assumption that I keep my windows closed all the time. What about listening to rain, birds, wind, etc?
I’m motivated to protect my investment from the constant moisture, and the damp cold, but at the same time I don’t want to live in a bubble that is acoustically sealed off from nature.
So with one of these systems, when am I “allowed” to open the windows (aside from summer of course)?
If I have the woodstove cranking out a lot of heat, and I open a window, I’m creating a situation where the hot air will rise and I’ll have cooler air at floor level. But at the same time, it seems silly to build a system where I’m bypassing my investment everytime I open a window.
Can someone shed light on this? Thanks!!
Paula
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Replies
If you open a window during heating season, you will lose heat. The purpose of the HRV is to gain ventilation without losing heat, so yes, opening windows bypasses the HRV. That said, the purpose of HVAC is comfort. It's your house, do what makes you comfortable.
I'm more concerned about this statement:
"My crawlspace will be conditioned, and the HVAC person who seems to be knowledgeable says he can install it in the crawlspace, and make the ducting work to circulate air between conditioned crawlspace and the home."
I'm hoping he's talking about using the crawlspace as part of the duct system, and not as the source for ventilation air. Because the ventilation air needs to come from outdoors.
Cold and wet? I'll show you cold and wet! :-) Try 101" a year, and North of you! I'm in the foothills of the Cascades, about 90 miles or so north of Seattle.
During the winter I have little interest in opening up windows, in which case there's no concern over heat loss. During the summer, however, there is a slight need for cooling. And the summer also poses the highest humidity levels inside the house. Relative Humidity is the gauge to go by. Colder air cannot hold as much moisture as warmer air: sometimes it hard for me to think in these terms when it's stacking up 5" of rain in 5 days (like it has recently).
I've decided on an ERV. I'll also be utilizing a wood stove, if I can find a small enough one: the Manual-J I ran showed even a small one to be more than enough; but living in the country and with a lot of "free" energy in the form of downed trees (from my property) I will be endeavoring to have a wood stove, even if it means cracking a window (and, perhaps, turning off the ERV).
Share the results of your HVAC installer's Manual-J. This is data that folks here could scrutinize.