I've been searching for an answer to this question but have yet to find one that applies. I'm looking to put in a new thermostat on the 2nd floor where the bedrooms are that would take over in the summer to keep the rooms cool enough to sleep. The original thermostat is on the first floor and keeps the whole house warm enough in the winter. I'd prefer not to have to go into the walls and do crazy new duct work/rewiring. The house is my first home and was a foreclosure so I already have my work cut out for me and would like to get as simple of a fix as possible.
I would love for the new thermostat to be wireless and just able to communicate with the old already wired thermostat to tell the AC when to turn off and on again. Is this type of product out there? Or do I need to bite the bullet and re-wire/re-duct the whole house? I've looked into covering the registers but I've heard that can make the furnace/AC unit less efficient so would like to avoid that as well. There are no ducts towards the ceilings on the 2nd story. I've already ordered a new high-efficient roof in order to help with the heating/cooling issue, and am planning on putting new insulation in the attic when I get the chance. But with summer coming on I'd really like a quick fix if it's available.
Thank you all for your help!
Best Answer
You can't make your single-zone system behave like a 2-zone system just by changing the thermostat, unfortunately. What you're suggesting would be roughly equivalent to relocating the thermostat upstairs. To do this, you could either move your existing thermostat and wiring, or achieve a similar effect by getting a thermostat with a wireless remote temperature sensor. In the winter, you'd have the thermostat base its operation on the temp downstairs, and in the summer move the sensor upstairs.
But - this would just run the AC more. You'll still have the problem of upstairs being much warmer, even if it's 70 upstairs and 60 downstairs. You could probably achieve a similar effect by just turning down the temperature on your thermostat without moving it.
You mentioned your house was built in 1941. A common cause of poor upstairs cooling in older homes is the lack of a return air duct upstairs. This leaves no escape for hot air that has collected upstairs; the cool air pumped up there is going to settle down first. If you have a return upstairs, try closing your downstairs return in the summer so that your system is forced to pull more from upstairs. If you don't have an upstairs return, try closing some of your downstairs vents, so more of your cool air goes upstairs. Yes, this will make your blower work a little harder, but it's not uncommon and should be fine.
Finally, a low-tech but possibly helpful option would be to add a floor fan blowing air upstairs. Run it for a day or so and see if it makes a difference in equalizing temperatures.