Elephant in the room (kitchen, in this case)
Mechanical air exchange is rightfully part of every plan in energy-efficient buildings. A lot of effort and no small expense is devoted to choices of HRV or ERV balanced air. The house I am building is 3 bdrm. & 2,000 sq.ft., thus: ((2,000 sq. ft /100) x 3) + (4 x 7.5) = 90 CFM. And this is intermittent, i.e. not necessary during shoulder season months when windows are open (six months here in zone 4A), or during other months when the occupants are working all day or traveling for business. Installing such a balanced system may take 20 years to overcome the cost of simply conditioning outside air that comes through a supply hole in the wall (which would of course come through an MERV 13 filter…)
Okay, most readers will likely advocate for the investment, and I will not argue the legitimacy of their choice. I remain dismayed however that there is no similar discussion about options for makeup air for the dryer (about 200 CFM per load) or the range hood (250–1,500 CFM). Depending on the family, these could equal the ventilation load, and because they come all at once, they may have a larger impact on comfort. And the cooking stuff not adequately ventilated is likely more harmful than stale air. Martin, your last article on the subject was published in 2010; comments date to 2016 but are mostly, “What if I do this…?”
So can anyone tell me how to provide makeup air in an efficient home? I am opting to widen the range hood to 36” over a 30” induction cooktop for a fuller capture. Vent-a-Hood says their 250 CFM is equivalent to 360 CFM because air is moved more efficiently with their squirrel cage design. Choosing induction over gas should make this adequate.
The best “What if I do this…?” so far seems to be to bring in outside air through a pipe that has a flapper with a controller tied to the range hood exhaust (ccbinnovations.com RMAS06 or similar). Several suggest dumping it into the toe kick in front of the stove. Others have put registers on the counter on either side of the stove! Matt Risenger put the range on a platform that acted as a plenum, allowing air to escape up the front and back of the range (https://www.youtube.com/watch?v=NsSvMB9bJeE).
Q1: What is best practice today?
Q2: Would it be less effective if I simply dump the air into the central stairwell, allowing the large volume to act as a mixing plenum?
Q3: If I go with some version of a plenum below the stove—given that it is simply exterior air—do I need to wrap the plenum with metal? Could I not simply build an airtight box our of rigid foam?
Thanks for any help!