Open-air barn
user-1147510793
| Posted in Mechanicals on
We are designing an unconditioned “party barn” in Central Texas for occasional gatherings for groups of various sizes. The barn has about a 1,400 sf footprint — 1,400 sf at the ground floor then there is a loft that is about 200 sf. We have Big Ass Fans for air movement but would like to add an attic fan to exhaust the warm air that will build up in the loft/attic space. How do we calculate the amount of CFM that the fan should be moving?
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Search and download construction details
Replies
Think about adding a cupola with electrically operated windows in it. Make it a design element in the middle of the roof.
Heather,
Another vote to consider Stephen's idea. Cupolas or roof monitors will do passively what the fan will struggle to do actively.
Heather,
I assume that the barn is not conditioned -- so there is no way to calculate the cfm of a fan. It's optional. It can be as small or as big as you want.
I agree with Malcolm; this situation has been solved over the past 200 years of barn design (and design for sugarhouses). The solution has nothing to do with fans. Your barn needs a monitor.
It doesn't need electrically operated windows (or windows of any kind). Just design adequate roof overhangs on your monitor roof -- enough to keep the openings dry -- and leave the ventilation openings wide open all year long. I suppose you could install insect screening if you wanted.
.
The above three suggestions are the most elegant solution, and I agree with that as a first choice. The fan option could be cheaper if you only run it on the few days a year that you have an event. CFM? I'd think in terms of making sure you could change out the air in that space about 3X in an hour. But that's just a guess, not based on any solid analysis, experience, or anything else you can count on.