Put the money into insulating the roof.

As I explained, we can't afford to re-insulate at this time. A whole house fan will help us make our children's rooms more comfortable at a fraction of the cost. Anyone familiar with whole house fans, please let me know what I should be looking for feature wise. Are there any specific features or brands that we definitely need or should avoid? Thanks!

I don't think you will be able to install a whole house fan in the section of the house you want to.

You state that you do not have an attic or crawl space above the rooms. As far as I know, that leaves out the fan option. In two of the three house we have owned, I installed the whole house fan. The fan is installed in the ceiling between the ceiling joists. When the fan is turned, the shutter on the fan opens and the air is exhausted out the gable and sofit vents of the attic.

Without an attic, you have no way to exhaust the fan and you can't leave the fan open to the outside because of the weather elements.

Enjoy the journey.
eal51 in western CT

We have an attic above and NEXT to the kids' rooms. Their rooms simply have vaulted ceilings.

Sure, why not.
A couple of fly chasers (ceiling fans) and open the windows in those rooms in the late afternoon, should help substantially.
As for equip., $100-$300 for the run of the mill or $800-$1200 for the super quiet and efficient.

Traditionally, whole house fans were used before air conditioning and insulation was so prevalent. You had a louvered section in a main hall that opened when the fan was turned on and an exhaust port in the gable. The fan blew the hot attic air out the gable and set up a bit of a breeze by pulling in air from the open windows through the house and up through the louvers and out through the attic. Nothing really helped when it was 100 out side except the house being located in the shade of some tall trees. I grew up with a whole house fan, and we were still miserable in the summer. It was quite the memorable day when we got the first window unit AC!

With the advent of modern air conditioning (and modern isulation) whole house fans fell into disuse in most of the country except those with very mild climates. When the house is shut up and the fan is turned on, it will pull conditioned air out through the attic. This can lead to a big condensation problem (not the mention the $$ going out your attic) where the cool and dry air meets the warm and moister attic air. My cousin thought she had a leak in a pipe in the attic, only to find it was because her "thrifty" husband had turned on the 1952 whole house fan while she had turned on the AC.

Whole house fans can work, but the circumstances have to be just right. The climate must be a relatively mild and not very humid one and you can't have the AC on in the rest of the house and use a whole house fan to exhaust also. They can't make the rooms any cooler than the outside air already is.

If the excessive heat in the house is from solar gain (through the windows) and therefore the outside air is cooler than the inside air, a central fan might help but the warm air will stay in the vaulted ceiling unless you find a way to exhaust it to the outside at a high point or supply cooler air directly to the room. In my opinion your options are: an operable skylight, a thru-the-roof (or high wall) exhaust fan, or a window air conditioner.

sr - you mention that the other parts of the house get too cold. Do you have dampers accessible on your ductwork in your basement? If so, you have the best way to alter airflow and redirect your cool air to the hottest rooms. If not, then start redirecting air by dampering back at the registers in the coolest rooms. Anything you can do to force more of the air conditioned air to those upper, hot rooms will help. It's a balancing act but remember it's harder to push that cold air up - more volume moving, more will reach it's destination. We have hot and cold rooms, too and totally close off the register in one room during the summer to redirect. That room gets it's cooling largely from falling cold air above it (hot air rises, cold air sinks) We have to adjust during heating season - not sure if you'll have that same situation being in your climate.

You're probably getting heat gain from the windows, the attic next to the kids' room & the roof. I'd try reflective window film for starters. (Bouncing the heat back out is a better approach than the black-outs.) And radiant film on the wall (on the attic side) adjacent to the kid's room. Then, some sort of lo-tech mister (lawn sprinklers on a timer to run at multiple short intervals) on the roof over the kid's room. Plus working on exhausting the hot air that collects at the highest point in the room--perhaps by ducting it out thru the adjacent attic? Or adapting one of those powered attic ventilators?

dlm -- we live in So. Cal., so no basement, just a crawl space. All of our ductwork is in the attic/ceilings, and our vents don't have good adjustable dampers.

My understanding of the whole house fan is that it would exhaust the hot air out of the attic through vents. Isn't that the same thing as a "powered attic ventilators?"

"sarschlos"
Only if you have powered ceiling vents.
The Ideal method of using a whole house fan is to draw cool air off a shaded landscaped area, through the house, into the attic, and because of the pressurization, the hot air is forced out of the attic. This limits the affect of the accumulated hot air being radiated through the ceiling into the house.
In the installations that I preform, I recomend operating the equip. from 3-7pm and adjusting for their needs.

I have a recommendation for whole-house fans, and that is to go with the ones made by Triangle Engineering of Arkansas (made in the USA!).

These things move more air than any other brand. As an example: the 36" belt-drive model sold at Lowes & Home Depot moves 6,900 CFM on its highest speed. The 36" one that Triangle makes moves 10,600 CFM.

I just put one of these in last week and am so taken with it that I'm evangelizing for Triangle now.

These things are much higher quality than the other brands too -- these are made with very heavy-gauge solid welded steel (as opposed to the thin, flimsy metal - often aluminum - that other brands use). They use a very solid motor made by Emerson, the best of the top three motor-making companies (the other two being Fasco and A.O. Smith). They come pre-framed on a wood frame for installation, AND they have sponge-rubber noise-dampening material between the fan and the frame, so they are much quieter than the other brands. Also, Triangle holds a patent on an automatic belt-tensioning system these things use, so you don't have to worry about getting the tension right when you install the fan (or in the years thereafter as the belt loosens up).

Also, they come in more sizes than the other companies -- from 24" all the way up to 48" blade diameter (which moves a ridiculously whopping amount of air; no one else makes one that big).

They're sold online at Southern Tool amongst other places that ship nationwide, so they're available wherever you live.

Also, Triangle re-brands some of these as a private label for Dayton, which is the "store brand" of Grainger - so if you have a Grainger store near you (check your phone book or their website), you can buy one there. I will say this, though - Grainger/Dayton makes their own shutters, and those shutters are much better than the one Triangle makes. Triangle makes great fans, but crappy shutters. Luckily, they're sold separately -- so buy a Triangle fan and Dayton shutters; money can't buy better products.

They also re-brand some for a company out in San Francisco called "Fanman" (a/k/a "Delta Breeze").

A word to the wise -- these fans move a lot of air, so make sure to install at least the recommended minimum amount of attic exhaust space (gable vents, soffit vents, roof vents, some combination thereof, whatever works for you) - if you don't have enough, the fan will operate at reduced capacity, and there will be a backpressure which will cause the shutters to rattle when the fan is in operation (any time you hear whole-house fan shutters rattling, you know there isn't enough exhaust space). Oh, and one other thing -- only buy a belt-drive whole-house fan, don't EVER buy a direct-drive model...the direct-drive models are at least five times louder, they sound like standing on an airport runway next to an old prop plane getting ready to take off.

Several of the dedicated whole-house fan installing companies have chosen to use Triangle fans; that should tell you something. These companies want satisfied customers, so they use Triangle and only Triangle.

Refer to http://www.trianglefans.com/wholehouse.html for more info