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

[brutal]

I have a brand new Carrier Infinity system - variable speed compressor, fan, smart controller with app (basically an ecobee4 built for Carrier) etc., and am still working to try to balance it.

My office is upstairs in a BR on the opposing end of the house from the evaporator. I have a fair amount of gear in it, so it's the warmest room in the house.

So far I have cut in another return vent in my office as suggested by the HVAC guy. The single return in the 2nd floor is in the hall on the other side of my office so that was 2 minutes with a multitool and covering it with a vent. That helped, but not as much as I had hoped. More return vents are better, but not an option for me.

While I have some registers closed off (living room, bathroom), we have new wood floors in the main level everywhere else with fancy wood registers that can't be closed and a toe kick register in the kitchen island that also can't be closed off.

Next step is to install dampers in the feed to each of those rooms and start closing them off. Since I have an unfinished basement, this is easy to do. You can hang meat on the main floor and the floor is ice cold, but it's 6-10 degrees warmer in my office by early afternoon. I'd rather close the ducts off near the source than cool off all that ductwork and close at the vent. Perhaps it serves the same purpose, but I can't close them anyway so that's my option.

I've also been running the attic fan when I feel it getting too warm in my office, and that helps pull cool air up from downstairs but my office still runs 3-4 degrees warmer with all the equipment in it.

My advice to MJ would be to see if you can get more return air from the upper levels and close off what you can on the lower. However, nothing you do will beat physics and the fact that cold air sinks and hot air rises.

ETA: One thing I forgot to mention. Make sure your floor registers are free to blow that cool air. If there's furniture in the way, you may be able to use some of the 90* clear plastic magnetic base vent covers to help. Our master has vents near both front windows and our king bed straddles both and covers a good portion of them and installing the vents helped both heating and cooling.

[DenverGP]

I installed one of these in my office (similar to yours, all the computer gear means it's the hottest room in the house):
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1



Needs to be close enough to an outlet, but it really pulls a lot more cold air from the vent than I got with just a low restriction vent. Has taken care of the hotter temps in the office.

[jslo]

Air flow is critical during cooling season. High MERV filters are great for removing pollutants but more restrictive the higher the rating. You might try using the inexpensive fiberglass filters, if you don't have sensitivities to particular pollutants, to increase the flow and increase the efficiency and life of your unit. This is what my HVAC guy recommends to me and I pass it on to my clients.

[Not_A_Llama]

Been balancing my house.

Don't go to crazy closing off vents - there's an expectation of a certain degree of flow, and excess backpressure will reduce the effectiveness of your system.
Go with a low resistance filter, and change often - the filter is there to protect the equipment, not to clean your household air. Get a dedicated air filter if that's your aim.
Keep your Evaporator coil clean. Bust out the old nut driver and take a look - improved my airflow significantly.
Keep your condenser coils clean. Hose em off.

Current thought on the outside-ducted AC units is that they're probably counter-productive from an overall house perspective - the air going out has to be resupplied from somewhere, and that somewhere is probably from the outdoors through wherever air infiltrates your house. OTOH, if your cooling is generally sufficient and you need localized cooling, it's maybe not a bad bargain.

[ray1970]

My house faces southwest. I used to have a giant cottonwood in the front yard that basically shaded my house in the afternoon. It was awesome. I had to take the tree down years ago and now the afternoon sun pounds the front side of my house. If technology would let me grow about a 60ft tree in a very short period of time I?d plant one today.

[FoxtArt]

I'm no AC expert by any means, just two random thoughts from my knowledge:

If your system has return air (it should) maybe reconfigure that to suck all your return from the upstairs. Pull the hot air and it'll replace it with air from the bottom. Idea two is to run a vent inline with the blower... You're supposed to stem them off the sides, top, bottom, etc, a vent inline with the blower (and the end of the main duct) will put out a disproportionate amount of air. It's also not hard to add more vents upstairs on most systems. Cut a 6-7 inch hole in the main duct, sheet metal screw the base, zip tie the inside of the insulated duct to the base, and then zip tie the other end to your vent-duct. Well....as long as you can get ducting up there somehow.... (Those instructions assume round flex ducting since it's a new install)

[Martinjmpr]

Update to this: First off, I discovered that our AC DOES have a "circulate" setting on the thermostat, so I set it to that. Closed off most (but not all) vents on the bottom two floors. Upper floor vents wide open.

Put an oscillating "tower" fan in my office - that way the air that does come out of the vent gets distributed.

Seems to be working well. We've abandoned using the Whole House fan for now - we are shut up tight as a drum to keep the heat out and the cool in. When we sleep at night we have an oscillating fan (actually the same fan I use in my office) that sweeps across us and keeps us cool.

It stays cool enough in my office that I'm quite comfortable and the family room (on the lowest non-basement level in the house) is almost cold.

The big question will be "how much will this cost?" but we won't know that until the Xcel bill comes early August. Last bill was $75 but that was for June when it was pretty cool and rainy. I'm willing to take a hit on the bill in exchange for comfort in the house - last Summer was brutal, I don't want to go through that again!

I just looked through my Xcel bills for the last 2 years (since we moved in here.) Winter's highest bill was $151, that was just for one month. I'm willing to go as high as that for a month or two in the Summer in exchange for comfort. Of course, the big difference between Summer and Winter bills is water - we have a yard and a sprinkler system so water bills can be as high as $75 or more a month when we water (May - Sep.)

It's too bad the wife is a green thumb who loves gardening. If it was just me I'd murder the grasss and replace it all with rock. No sprinkler system, no lawnmower, just a spray bottle of plant killer to keep my yard looking good!

[ray1970]

Luckily. My summer water bills are usually around $260.

[Martinjmpr]

Luckily. My summer water bills are usually around $260.

A month? How big is your yard?

[ray1970]

The back yard is a little over 100x100 and has seven zones . There?s another two zones in the front for a total of nine. Thirty minutes a zone means I?m watering for four and a half hours each time, three days a week.

Actually, we also had four people in the house using up water as well. Two of them have finally moved out so maybe this summer will be a little lower. I?ve only had the sprinkles on for about a month so we?ll see.