Keeping a multi-story house cool using AC and attic fan?

[Mercula]

I may try to close ALL the vents on the 2 main floors to force the cool air upstairs.

Might as well. It’s gonna come down anyways to some degree.
I’m probably going to try the curtain. Unfortunately my furnace does not have a fan only option.

Hopefully Highclasswhitetrash jumps in here with some experience.

[beast556]

Does your office have a return in it?? Where are the returns for the upper level located???

[Great-Kazoo]

By "controller" do you mean the thermostat? If so, I don't think it has such a setting.

Question: It does have both "on" and "auto" fan settings. If I set the fan to "on" would the AC unit (i.e. the chiller) run constantly or just the fan? Seems to me if I can set it to where the fan runs but the chiller only comes on when the temp drops below a certain level, that should help even out the temp in the house, right?

Then the next question is, is the fan a big power draw? I know the chiller is.

On is just the fan. Depending on age of unit it will draw some power, maybe more. Again depending on age. I suggest you install ceiling fans to move that air around, as well as install a return on the upper level. If it's too cost prohibitive, go with a mini - split.

[thedave1164]

all I got is hot air rises

[jslo]

Attic insulation and/or attic exhaust fan (different than your whole house fan)

Decreased Temperatures in Living Areas
When the temperature outside is in the 80s, the temperature in your attic could skyrocket to 150 degrees or higher. Vents allow for a degree of passive cooling, but an attic fan is the best way to make a significant difference.

Running an attic fan during the hottest part of the day lowers the temperature in your attic by as much as 50 degrees. This translates to temperatures roughly 10 degrees cooler throughout the rest of your home.

[Gman]

Pulling warmer outside air in and blowing cooled inside air out seems to defeat the point of having AC. Shutting off the AC after the sun goes down also doesn't allow it to run when it can have its biggest impact.

I had my furnace and AC replaced a couple of years ago. My thermostat is set to reduce the indoor temp just before bedtime. The variable speed DC blower is also set to a 'circulate' mode where it will randomly come on to mix the air in the house periodically, even if the heat or AC isn't actively running, to keep temps more even.

Close registers in the lower areas and open them fully in the upper areas in summer. Reverse in the Winter.

I have a ranch with a full finished basement. The stairwell is open into the basement, so it ends up being pretty cool. My basement is warmest in winter and coolest in summer. I can live with that. ;-)

[jslo]

"Pulling warmer outside air in and blowing cooled inside air out seems to defeat the point of having AC. Shutting off the AC after the sun goes down also doesn't allow it to run when it can have its biggest impact."

Don't think the first part was suggested and, as for the second part, it seems perfectly logical and wise, to me, to take advantage of our cool evenings to cool your home as long as you don't have respiratory issues.

[Ramsker]

Our house is 2 story & a finished basement . . . central air, a whole house fan, and attic fans in the attic and in the gable above the garage on the south side of the house (where my office is on the 2nd floor). My office is by far the hottest room in the house. The furnace is in the basement on the opposite side of the house, so my office is also the furthest point from it pretty much. It just gets hotter than the rest of the house no matter what.

I have a ceiling fan in the office, which helps, but I also bought a portable AC unit and have it piped out the wall and through the gable to the outside. Works pretty slick if it gets too hot up there. If I was rolling in cash, I'd put in a ventless system to cool that part of the house better and quieter--but it's not so bad that I want to spend the $$ on that.



As far as the whole house fan, it's great at night when things cool down. If it's cool enough, I'll back off the AC and let the fan do its thing. On the hotter nights, it's not as much help . . . but in the spring and fall when it really cools down outside, it's amazing how fast and how much that thing cools the whole house.

[earplug]

Paint your roof with a reflective coating. Bright White. I'm in a Tri Level without AC. Coating reduced inside temperature a easy 10 degrees.

[Big E3]

Your house is almost exactly the same layout as mine even facing same direction. My house was built in 1996. My HVAC plan that works best for me is that every year I adjust all the vents on each floor depending on season. Open every vent on the fourth level and close most vents on lower floors in the summer. I do the opposite in the winter, heat rises. The fourth level basement is adjusted backwards, slightly open in the summer, closed in the winter. We use the basement as a wall in cooler.

I ran the whole house attic fan with windows open until it got too hot in the last few weeks. I have a thermostat on the attic fan switch because at times of year it can be freezing outside by morning, so I want the fan to go off while sleeping. Another advantage of the attic fan, when it gets hot, is to flush hot air out of the attic. Occasionally I run the attic fan for 15 minutes even with the AC on just to lower attic temps and it doesn't hurt to pull cool air to the upper level.

Another thing that works for me is to put a fairly large pedestal mounted fan at the top of the stairs blowing down the stairs to pull hot air from the upper level to the main level where the thermostat is located. I have a ceiling fan upstairs in the master bedroom and on main level in the formal living room that to move air. These rooms have vaulted ceilings, it helps to circulate air. The family room behind the garage has a small table fan just to move cooler air from that room.

My AC is set at 71, right now at 11 PM in my office in the northwest corner of the upper level, it's 74 and it's only down to 82 outside. I have lived here since 2001 and have tried just about every variation to determine what works best. Bottom line, what I find is to use low cost to operate fans to move air and it reduces AC costs and keeps things more uniformly cooler. FYI, I also had 18" of insulation blown into the attic and it didn't seem to make much difference in the summer.