Hi –
I live in the San Francisco Bay Area (Los Altos). It’s starting to get really hot here, enough that I want to run my AC. But early in the evening, say around 7pm, it starts to cool off outside. The humidity is no problem here, so ideally I’d like to get the outside air in. But opening doors and windows is just too slow, and a big fan in a doorway is just too noisy for my 16 month old.
I’m considering a novel solution – my return air ducting is in my attic, so I’m thinking about adding a air intake on an electronically controlled damper into a big roof vent. That way I can flick a switch and my nice-and-quiet central air will suck the air in, filter it, and distribute it.
What do people think? Seems simple enough to me. The only gotcha that I can think of is that maybe I need to put a extra filter so my ducting doesn’t get clogged.
Thanks, Sean
Replies
In theory that should work but the air above the roof might not be as cool as you think it is. The building will radiate heat for several hours after sunset and the roof area is usually hottest. Also, as the air temperature falls and gets closer to the dew point, you will perceive less cooling effect because the relative humidity is increasing.
I don't know the answer. I have considered it, and arrived at the same direction as you are considering.
I live near Atlanta, high humidity, and my HVAC sub talked me out of it. Given your dryness, it may work.
I say do it, and tell us how it works
Not a novel idea at all. It's what's known as an "economizer". Done all the time in commercial work.
Sean -
As a neighbor (San Jose), I recommend that you do a quick test before you try this.
Poke your head into the attic around 5:00 pm, 6:00 pm, and 7:00 pm. You will probably be amazed at how hot it is up there - and how little it cools off late in the day. From long experience, I just don't go into attics after around 9:00 am during the summer. When I'm doing attic work, I start as early as possible - but I'm outta there by around 9:00, or so!! - lol
I've lived here for 34 years and never had AC. It's nice, but we just don't usually get that much hot weather - and it seldom lasts more than a few days when we get it.
About 8-9 years ago, I worked my house over, replacing all the windows and the patio door with low-e double glazed units. I added some insulation to the attic and put ceiling fans in every room. During hot weather (like yesterday), the windows are wide open and the fans run all night. First thing every morning, the windows are closed and the drapes/blinds/shades are closed. The place stays comfortable all day. Late in the afternoon, we begin opening windows on the east side of the house and by sundown we're wide open again.
Oh yeah, those windows and fans also made a huge difference in our winter time PG&E bill. Every fall, I clean the fans and reverse them so they blow up instead of down. They run on low speed 24/7 and gently circulate the warm air throughout the house.
A better idea might be a whole house fan.
You install it in a central area of the house in the ceiling. Some of the nicer ones have a motorized insulated cover over the fan. Then you open a few windows and with a large enough fan will have quite a breeze flowing in. The fan will also push out the hot attic air.