1950's house attic fan

[MayDay]

Our house is a rambler, built in 1952.

Today we were climbing around in the attic for the first time, installing a bathroom vent fan. We discovered that we have an attic ventilation fan. It's pretty big- maybe 18" diameter. However it doesn't have a duct connecting down into living area. And there isn't a switch on the main level- you have to climb into the attic to turn the fan on and off.

Any idea what the purpose of this would be? Are we supposed to be letting it run all summer, for example? Fwiw we almost never run the A/C, so if it does something to cool the house I the summer that would be great.

The attic hatch is just a panel in a bedroom closet.

[Mother Fussbudget]

This all depends on what area you're in, and what summer heat is normal for your area,  In the deep south, we had a large attic fan that had it's own exterior vent near the peak of the roof.  It was attached to a thermostat, and would come on anytime the attic temperature reached 100 degrees.  The idea is to blow hot air OUT of the vent, and draw in cooler air through the soffit vents to try to keep the attic temperature down to desert air temperatures, and less "burning lava / volcano" temperatures.

[MayDay]

We're in Minnesota. 90's on and off all summer.

I could definitely see running it whenever the attic temp gets high- but why wouldn't they have wireda switch to the main level? Was it typical to climb up into the attic to turn on/off? That is the most puzzling thing to me.

[Mother Fussbudget]

That is odd - yes.  Sounds like a homeowner DIY fan.

First thing I would try is turning the fan ON, and allow it to run on some 90+ degree days.  Measure the ambient house temperature before, and during the test.
If the temperature is cooler on days the fan runs, OR if the A/C runs for fewer minutes during the day, then change out the fan's manual switch for a temperature control switch, and let the temperature in the attic decide when it's time to turn the fan on. (and save yourself a trip into the overhead sauna)

[MayDay]

That is odd - yes.  Sounds like a homeowner DIY fan.

First thing I would try is turning the fan ON, and allow it to run on some 90+ degree days.  Measure the ambient house temperature before, and during the test.
If the temperature is cooler on days the fan runs, OR if the A/C runs for fewer minutes during the day, then change out the fan's manual switch for a temperature control switch, and let the temperature in the attic decide when it's time to turn the fan on. (and save yourself a trip into the overhead sauna)

An auto switch is a great idea. To get to it, we have to empty out a closet and drag a huge ladder inside, so we aren't going to be climbing up there every time it's 90 degrees. But it would be great if it auto switched on.we ran it all yesterday and it helped in the half of the attic closer to the fan.

[onlykelsey]

I'm not sure I understand exactly what you're describing but I lived in a huge old house in upstate NY, and we would shut down the house during the day (closing windows and drawing shade) and then open them all and use the attic fan as an exhaust fan to pull cool air through the windows and out of the attic.  That probably won't work if you can't turn it on and off easily.  Was quite effective though.

[Mother Fussbudget]

We're talking about Two DIFFERENT types of house / attic fans here.

1) [OP's fan] only blows air within the attic - it has no vent into the living space.  The thinking was to keep the attic cooler, and thereby keep the living space below cooler. (like this )
They play a role similar to those passive spinning 'turbines' that look like chefs caps on some commercial buildings.  Older buildings had attic gable-vents near the roof peak, and soffit vents along the lower portion of the roof - still seen in roofs today.

2) The living-space "whole house fan"  - these mount centrally in the house - in the living space - and with the windows open, draw air into the house from outdoors, and because it's mounted HIGH, tends to draw hot-air out of the house.  It works best when the house has a basement with windows, and cool air from the basement can be drawn upward into the house, but also works well in the evenings when temperatures cool down.  (like this)

[catccc]

A simple solution, if it is plugged in to a regular outlet someplace, is to leave the fan switch on, and use a regular old outlet timer to have it run for a portion of the day when it is hottest.   Then you are only going up there at the beginning and end of the summer.  A house that old probably isn't that tight, and pulling hot air out of the top of your house will probably help keep the rest of it cooler.

[MayDay]

A simple solution, if it is plugged in to a regular outlet someplace, is to leave the fan switch on, and use a regular old outlet timer to have it run for a portion of the day when it is hottest.   Then you are only going up there at the beginning and end of the summer.  A house that old probably isn't that tight, and pulling hot air out of the top of your house will probably help keep the rest of it cooler.

It is hardwired,so either way we need to fuss with it. But it is a good idea to consider that option. I will look into the cost of the thermal switch.