Should I add celing cold air returns and close up my house fan? Which rooms and whats the benefit?

Question

I have only floor air returns in my house which was built around 1950. There is a house fan which is why I assume there are no celing cold air returns. The house has trouble cooling and I am going to probably plug the house fan because during the summer its very hot to the touch and probably another source of the problem. Its a ranch with 3 bedrooms, 1 kitchen, 1 dining room and 1 family room. Basement is finished always very cool. Probably more than 5 degrees cooler. House fans dont work in Michigan when its 95 out.

Answer 1

For a forced air heating/cooling system to function properly, each room should have a supply vent and a return vent. Supply air is air entering the room, return air is air going to the air handler. Your home being built in the 1950's would indicate that the homeowner was more interested in heating the home than cooling. The whole house fan is great when the outside temperature drops at night below the indoor air temperature, but in hot humid areas, this rarely happens in the summer. You might build a cover that is installed in the attic, such as a lightweight box covered with insulation that can be moved easily on days where the outside temp is cooler than inside. Since your basement is naturally cooler than the main level, you might put a return duct (air going to the air handler) in the basement to draw in the cooler air. Leave the basement door open so that the air can circulate as well.

Answer 2

Your vents in the floor are likely "supply" vents, not return vents, although it is difficult to guess based on location alone. It doesn't sound like you really know which vents are doing what. It was common in the old days to leave the bedroom doors cut off about an inch from the floor (take a look and see) to allow air to flow throughout the house, especially ranch-style homes. Your doors may be like this, and if they are, you may not have return air vents at all. For maximum efficiency, every room should have a return air vent -- think of it as blowing air into a water bottle compared to blowing air into a short length of pipe. The air can't go anywhere in the bottle, but the pipe is open on both ends so the air moves right through.

But, that is neither here nor there. It sounds like your attic may be trapping heat and making things worse. Like another poster said, the original builder was probably more worried about heat than cooling. You might check whether you have vents in your roof fascia, or that existing vents are not blocked by debris or insulation. Perhaps consider installing a ridge vent to help increase airflow through your attic also.

Basements are always cool, because cold air sinks. Use the house fan at night, not during the heat of the day. You might want to install a window-mount A/C unit or evaporative cooler. Unfortunately it would be ideal to install an evaporative cooler (swamp cooler) on your roof in place of the house fan, but in humid areas these are not efficient. An A/C system throughout the house, with proper return air vents installed, would be your only sure-fire cure for hot weather.