My new house has a 20+ year old evaporative cooler on top of the roof. The cooler is ancient and rusted, difficult to service due to the location, and the forced air heating ductwork it feeds into is undersized for the volume of air it pushes. I would like to replace the unit with a (surprisingly inexpensive) new, highly efficient evaporative cooler mounted at ground level that blows air straight through a wall. The cooler would sit in the shade and have a short, straight duct going right through an exterior wall and into the main living/dining/kitchen area.
My hope is due to the direct installation, I could get a very low level of static pressure and choose a small, energy-efficient 1/3 horsepower motor. However, I worry about this installation being able to serviceably cool the entire house (≈ 1100 sf) with all of the air coming through only a single supply vent.
I think I would be able to get adequate airflow into the bedrooms by opening bedroom windows but NOT opening windows in the living/dining/kitchen area, thereby forcing the flow through the main living area, down the hall, and out through the bedrooms.
Does this sound like it would work? Is there some kind of chart or formula for determining the required CFM of the blower given a static pressure value, a square footage, and/or (pipe dream) a house layout? Should I just get a bigger cooler or motor for some wiggle room and be done with it? I would prefer the more efficient, better designed approach. 😉
Best Answer
The optimal CFM is related more to the cooling capacity than house size, since you have low pressure (usually the other major factor). The cooling capacity is related to house size, climate, and many other factors, so there is some indirect relationship. I couldn't tell you what that is. Consider this a verbose comment and not an "answer".
For the bedrooms to be adequately cooled with that setup, the living area would need to be colder than normal, assuming the unit is adequately sized for the whole house. On the average, your house will be kept properly cool, but you will find the temperatures will vary noticeably from room to room. Neither extreme may be all that comfortable.