Looks like I’m the only one here who actually has a whole house fan available to test. Right now, the central A/C is on, but I’m turning it off just to test the fan. Here goes. . .
(Two minutes later) Pretty much nothing. The louvres on the fan opened a little, but there was no discernable breeze. Then I opened a large window in the house. A nice breeze came through and the louvres opened wider. Then I closed the window, the breeze stopped, and the louvres dipped to their previous level.
Windows did not pop in, water did not come gushing out of the toilets, nor did my attic rafters shudder under the strain. And you’re going to need one hell of a shop vac to move as much air as a whole house fan is capable of doing.
If I had continue to let the fan run, I would guess the fan motor will run hotter, but there’s still enough air going past it to ventilate it somewhat.
I’m careful not to run my whole house fan with windows closed because I have a gas furnace. I’m worried the pressure differential could lead to increased gas flow and inadvertently extinguish the pilot light.
My parents have a brand new house (modular construction build this winter) with a whole house fan. The house has all new windows, door and seals, so it closes up pretty tight.
Mom turned on the fan a couple of weeks ago, forgetting to have any of the windows open. She said there was a noticable strain on the fan, enough to change the sound of the fan. She noticed that and hurried over to turn it off.
So no imploding windows, but definately strain on the fan.
I’m intending to get one pretty soon. I don’t have central air, and it should probably actually suffice around here. The manufacturers claim that if you run it without sufficient open windows, the motor may have to work too hard, and eventually burn out.
If you didn’t do it for too long, I suspect it would be a good way to test your weatherproofing. Shut everything up, turn the thing on, and wander around the house feeling for where air is coming in around windows and doors.
There are so many holes in even an energy-efficient house… air gaps to let showers and baths drain, vent holes for bathroom and kitchen fans, exhaust holes for chimneys, furnaces and water heaters, etc. There’s just no way implosion is a risk. Frankly, I don’t think the fans have enough strength to cause implosion in even a worst-case scenario. (Paging Myth Busters!)
The biggest problem? Carbon monoxide. If you turn the fan on and have gas furnaces or water heaters, you can pull the exhaust back in. Since CO is undetectable by humans, it can be very dangerous.
I suppose blowing out a pilot light would be possible, and that would clearly be the biggest risk in terms of damaging the house.
Chimney smoke or ash is also a definite concern, though closing the flu or fireplace doors would probably prevent that. If we were aiming for an airtight house, I’d assume those would be closed.
I haven’t heard about sewer gas bubbling up, but I’m sure that would happen long before anything imploded.