Attic fan? Whole house fan? Neither? Both?

[trader4]

I second the good advice given by Ed, Paul and Heathcliff. For the WHF to be effective, you need periods where the outside air is around

70 or below and not excessively humid. In the Philly area, that limits their usefulness to night usage in mostly the Spring and early Fall. You could also use the WHF in summer if the AC has been off and it's 85 inside, 75 outside, to drop the temp, then turn on the AC, But if the humidity is too high, it's questionable if it's worth it. If you have enough days where it works out for you, then it can be worth it.

The attic fan is there to move air out of the attic so that it doesn't get excessively hot. Before going with a fan, I'd make sure you have maximum natural convection venting, ie ridge, soffit, gable etc. If you can't get sufficient cooling that way, then a fan may be worth it. However, either type of fan needs adequate attic ventilation to be able to move the air volume.

[willshak]

Another use for a whole house fan is to remove smoke or odors from the house. Burn something on the stove? Dog comes in after an encounter with a skunk? Refinish a floor?

[Phisherman]

Listen to your friend. You might consider additional insulation.

[Andrew Barss]

Malcolm Hoar wrote: : In article , Heathcliff wrote: :>Also I will say using a :>whole house fan requires a little bit of operational savvy; you get a :>nice breeze wherever you open a window, but you may have to prop the :>door open in that room so it doesn't slam shut.

: Solution: magnetic door stops. You open the door fully and a : magnet in the door stop keeps the door from moving.

: They may be hard to find and/or expensive but are well : worth the effort.

: I first saw them in several homes in China and thought : they were bloody terrific. They're easily available and : extremely cheap there so I brought a bunch home. I just : love these little suckers; best thing since sliced bread!

They're available from Lee Valley.

-- Andy Barss

[Andrew Barss]

Kyle wrote: : inside the window.

: (2) In our area of the country (I'm west and slightly south of you, in : western MD) the optimal insulation level in attic space is R50. Being : your house looks fairly new, I'm going to guess you have the paperwork : to check it out, or can contact the contractor who built it. The : reason R50 is helpful is not simply for holding heat in during cold : months, but for keeping the 120 degree heat of the attic in Summer : from penetrating to the upper floors of the interior.

: (2a) Ventilate the living daylights out of the attic space in the : Summer, which means making sure you have enough soffit vents as others : have mentioned, and perhaps having a thermostatically-controlled vent : fan installed at one of the gable vents.

I'm in a similar situation as the OP, except for living in Tucson, AZ, where the big problem is the attics getting extremely hot (160+ degrees) and radiating heat down into the living space. (I've come to realize peaked roofs make utterly no sense in Arizona).

The consensus seems to be that getting the built-up air out is the key, with air coming in from as low as possible (i.e. the soffet area), exhausting it passively at or near the peak of the roof, and making sure to have enough square feet of area in the inflow and outflow.

But there's remarkably little information out there about products, especially

a) soffet vents, other than cheap 16" x 8/10/12" perforatd metal, and

b) ways of getting the inflow of air from the soffits up above the attic floor and insulation (in an existing house).

I've been to three home centers and two roofing supply specialists, all in Tucson, and no one has any range of alternatives for (a), and none has a clue about (b). I was particularly struck by the fact that the roofing supply guys really had no idea there was even a problem in getting a clear pathway from a soffet vent to the airspace up above the insulation. (In my house, the roof slopes down enough that the sofets are about 3-4 feet below the attic floor, and so 4-5 feet below the insulation up there).

If anyone has any sources, even mail order, I'd appreciate the tip. What I'm looking for for soffet vents is a continuous length of peformated metal, that looks fairly nice, that could span a 24" wide and 23 foor long area.

-- Andy Barss

[gfretwell]

If you look at the old Florida "cracker" houses before they had AC here you will see a steep pitched pyramid shaped roof with metal roofing (reflective) and a cupola at the top that acts as a natural exhaust fan. They also have a porch roof all the way around the house to keep the sun off the walls and out of the windows. They have lots of windows and the cupola pulls the air in from the shaded porch and out the roof. If you translate that to an air conditioned house you have an insulated ceiling above the conditioned space. The air intake for the attic is generous air intakes in the soffits above the porch.