4" diameter since that's what it takes. Rigid or semi-rigid (plastic flexible hose is a fire hazard, at least when used with dryers). Don't think you need to insulate it (except for soundproofing where it may rattle). Just make sure there are as few angles/turns as possible, and that any are large radius.

I have 2 Panasonic fans. The secret to any fan noise is proper duct work. This means as long a run as possible directly off the fan without changing direction or reducing size. Avoiding 90 degree bends - multiple 45's are better. Avoid flexible duct work like the plague. It's horrible stuff. Not only will it collect dust and moisture, the turbulence of the air caused by all those ridges contributes a lot to the noise level. Both my fans are exhausted to the outside with rigid duct work properly installed, taped (not duct tape - silver foil tape) and of course screwed together. They're very very quiet. Any fan is going to be much quieter with no ductwork attached, which is how they're demonstrated in big box stores which also are massive, tons of ambient noise etc. all making the fans seem quieter. Also don't oversize the fan for the cubic feet of the room. Very important, as is ensuring there is enough supply coming in under the closed door etc. to feed the fan. As much air as it pushes out of the room has to be replaced with new air coming in under that small crack under the door. If it's not getting enough replacement air, it will be noisier.

Auzzy, I haven't been happy with the color of the CFL's I've tried so far, but something still sounds fishy to me that you're finding it too dark. A 32 watt CFL should be brighter than a 150 watt incandescent bulb -- which should be very bright in your shower. So I'm still wondering if something could be wired or configured wrong such that you're not getting the full power of the 32-watt CFL. Or could the bulb which came with the fan accidentally be a lower wattage one? Or could there be a problem with the transformer in the fan unit. Unless you have a super high ceiling, or a huge room, I don't think you should be perceiving the light as too dim. You might want to call Panasonic tech support to see if they can tell you anything that might be causing the light not to reach full power. As Brickton says, changing to a warm color temperature CFL bulb -- more yellow light instead of blueish-wite light -- could improve the overall feel. -- Eric

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 Here is a link that might be useful: Triangle whole-house fans