Transfer fans from hallway to bedrooms
I’m looking at a few different heating and cooling options for a (very) efficient two storey house with no basement. An option I like is using one ductless minisplit air handler per floor. Simple, inexpensive, fairly easy to size properly, pretty efficient.
My question is this: is anyone familiar with (or have an opinion on) using small through wall fans to transfer air from a hallway to bedrooms? I’m picturing two fans. Possibly, one near the ceiling and one near the floor, on a single switch. One fan would transfer air from the hallway, one would transfer air from the bedroom. To get fancy, they could even be reversible (heating season and cooling season).
Kind of like the Lunos concept, without heat recovery.
I think the National Research Council (of Canada) may have tried something like this, but I haven’t been able to track it down.
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Replies
First, only one fan per bedroom, the return path can be a simple duct through the wall. Second point is heat is only moved by air movement if there is a temperature difference which means all the fans can do is reduce the temperature difference, never eliminate it. Assuming the mini split is in the hallway, it would make sense to move the air from the floor level of the hall into the bedrooms and return air from the bedrooms to the ceiling of the hallway because the mini split takes air from the ceiling and sends the heated or cooled output toward the floor. My opinion is it will help but predicting how much is very difficult.
Graham,
For more on transfer fans, see this article by Marc Rosenbaum:
https://www.greenbuildingadvisor.com/blogs/dept/guest-blogs/practical-design-advice-zero-net-energy-homes
Where are you building?
If the heating loads are sufficiently low, it's unlikely that transfer fans would be necessary for the bedrooms.
If the cooling loads are sufficiently high, it's unlikely that transfer fans would be effective.
Thanks for the replies - they have been helpful.
I'm building in southern Ontario - cooling loads shouldn't be too great, with decent window shading and orientation part of the plan.
We use the Tjernlund fans. They are cost effective and can be on a switch or a thermostat, whichever you want. But it is a nice complement to a minisplit, especially where our cooling load is low. I have seen one 1-ton head do a 2,000-square-foot home (built correctly), with the transfer fans moving air and using exhaust-only ventilation to help move air.