Whole house fan, attic fan, no fan both fans?

[Borax]

Hi all,

I live in the great sSan Joaquin valley in northern California. Typical summer temps are mid 80's to high 90's with about 14 days of 100+.

My house is 12 years old, 2-story with 2,000 square feet.

During the day the central AC does a fine job of cooling, but frequently after the sun sets we get a nice cool delta breeze in the mid 70's. The problem is that the house seems heat soaked and with the windows and doors open and the ceiling fans going there is not enough circulation to cool the house and the AC will still try to run (set at

84).

I am thinking that a whole house fan would be able to change the air rapidly and bring in the cooler air. I am interested in real-worlkd experience about things like overall efficiency, run times, noise etc (we have a 3 & 1 year old that we'd really like to sleep sometimes...).

Thanks for reading and replying.

[Edwin Pawlowski]

Right, ceiling fans only circulate hte iar already in the house.

Yes, it will give you a rapid air change and keep the cooler air coming in.

Kids that grow up with absolute quiet have a herder time sleeping that kids with noise around them. They'll get use to it. Depending on location, there will be some noise. Two types of fans to consider. A fan mounted in the hallway blowing into the attic is efficient, but has the most noise.

A gable mounted fan and a louvered vent to the attic will be quieter. You need large gable to mount it though.

[jdk]

as a kid my dad put a box fan in the upper floor window, crack the other windows open just a little. it works.

[BobK207]

Borax-

An attic fan (or whole house fan) will work great, we had one in NJ & ran it during the summer at night to cool off the house. It was windy and kinda noisy but it really worked.

I have a 2 story (actually 1 1/2) story home in SoCal & we have some hot days but we almost always get the good night time cooling.

I've been too cheap / lazy to install a whole house /attic fan so I did the next best thing.

I put a couple of 20" box fans in windows of rooms that were unocupied, with the fans blowing outward. I opened doors & windows in the rooms I want to cool. The idea is bring the cool air into the rooms you want cooled first and exhaust through the rooms that matter least. The box fans are by no means as powerful as a whole house fan but you can give it a shot & see how it works,

In your case you might want to conider some sort of powered attic vents, this topic has been discussed before and with some disagreement. IMO venting the attic is good when ever the attic is hotter than outside. A superheated attic will drive heat into the house & make the AC work harder.

The whole house fan is an "old school" solution but it works

here is a link to a newer concept

Good luck w/ the kids. :)

I'm still working on one.

cheers Bob

[trader4]

The attic should be properly vented regardless of how you choose to cool the inside of the house. The best solution is a ridge vent with adequate soffit vents. You also need to make sure that the soffit vents are not blocked by insulation. It's very common for the attic insulation to be installed improperly so that it's covering the soffit vents and not allowing air to flow. There are plastic baffles available at home centers that can be stapled to the underside of the roof sheathing for a couple of feet near the soffit vents to keep the air channel open.

A whole house fan can pull cooler outside air into the home very effectively. However, I think they are most effective on days and climates where you can get away with them without using the ac. If you intend to use the AC during the day, then switch to the whole house fan at night, I tend to doubt it will save much or be worth it. By the time the outside air is cool enough to be of help, the AC load will already be greatly reduced and the system should not be running much. Also, the whole house fan will not deal with humidity, so you may be replacing drier air with air that is more humid.

[dadiOH]

I had the same idea, based on a window box fan that I used in college to great effect. Put in a whole house fan in my house when building it, sucks marvelously, makes so much noise we never use it.

I also have one in my shop. Vents outside, makes as much noise but I don't mind the noise there and it really clears the air.

I still think a fan for this purpose would be great but you need to work around the noise in some manner. Possibly enclosed in the attic, ducted for intake and exhaust.

-- dadiOH ____________________________

dadiOH's dandies v3.06... ...a help file of info about MP3s, recording from LP/cassette and tips & tricks on this and that. Get it at

[nicksanspam]

NREL's 30-year average temps for Sacramento:

Mar Apr May Jun Jul Aug Sep Oct Nov Daily max 64.0 71.1 80.3 87.8 93.2 92.1 87.3 77.9 63.1

24h avg 53.6 58.3 65.3 71.6 75.7 75.1 71.5 64.2 53.3 Daily min 50.3 55.3 58.1 58.0 55.7 These are averages. Some March days are warmer than 64, and so on. It's fairly dry, with a max 0.0088 humidity ratio in August.

So it probably has reasonable insulation, with a thermal conductance of about 400 Btu/h-F? You might improve the airsealing, and maybe add thermal mass.

Good idea. You might heat and cool your house for 9 months of the year with a whole house fan and a differential thermostat that also turns on ceiling fans at night to ensure the outdoor air reaches the thermal mass of the walls.

Lasko's 2155A 2470 90 W window fan seems nice... $53 from Ace Hardware stores. With average 84.5 and 66.9 day and night temps in July, your 75 F house might gain 12h(84.5-75)400 = 45.6K Btu/day with the windows closed and lose 45.6K Btu by running the fan for 45.6K/((75-66.9)2870) = 2 hours at night, using 180 Wh, vs about 45.6K/3/3.41 = 4.5 kWh with an AC.

The fan and a lower air inlet window might both have one-way plastic film dampers, hinged at the top, to stop airflow during the day.

Nick