Heating Make-up Air
First the details that I hope will answer questions you might have before considering this:
Zone 5a, R20/40/60 dense-pack cellulose, triple-pane and super tight. 3600sf interior floor space includes an in-law with its own laundry room. ERV pulling on bathrooms, laundry rooms and back corner closets. Air-source minisplits, sealed combustion water heater, direct vent gas fireplace and serious central vac blowing to outside. Very open floor plan with a 'command central' kitchen that will get a lot of use, and is adjacent to a wide opening to second floor (yes, I know, but can't change this). Electric oven and a gas cooktop around 52,000 BTU.
I would have gone with a carbon filter for the kitchen hood (and added an ERV return near the kitchen), but the range has to be gas, so I'm looking at the largest reasonable hood area with the smallest fan to suitably exhaust the cooktop (somewhere below 400 cfm). No appetite to push into the bleeding-edge of ductless dryers, and although line drying will be done, it won't always be done.
Even though none of the exhausting appliances by themselves push me into a code requirement for make-up air, it is conceivable that a total draw of around 900 cfm could occur if the kitchen hood, two (high-capacity) dryers and central vac are all running at the same time. I'm convinced that during such a perfect storm, somewhere around 600 cfm make-up air could be needed as the house is expected to be very tight.
I was originally planning to passively deliver all make-up air to the back of the refrigerator through a power-open damper, as I don't want that much air being delivered straight to the cooktop, but I'm doubtful that either of those solutions would satisfy code requirements for heating make-up air.
Because the laundry rooms can have their doors closed to create a self-contained system, I have been considering a dedicated, relay-driven, power-open make-up duct delivering air in close proximity to the dryer intake for each of them. If I take care of the dryers that could be running at the same time as the kitchen hood, perhaps I can just leave leakage to handle the kitchen hood's makeup air. Again, however, I'm doubtful such an approach would satisfy code requirements for heating make-up air.
If I bring _any_ makeup air into the building in Zone 5A, am I running a risk that the building inspector may require me to heat it?
I imagine there may be some alternative ways of looking at this, and will, of course, appreciate all of them :)
Posted Tue, 10/15/2013 - 07:44
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