Attic ventilation theory

[John Larkin]

I came up with this one from out of no where. Looking to see if anyone thinks it is feasible.

I have roof vents and eve vents. My attic is hotter than hades due to a black roof and probably not enough roof vents. Without adding a power ventilator in place of the roof vents, here is my proposal:

My garage has the pull-down stairs in it where you get access to the attic. The garage also has a window. I am thinking if I took the plywood covering off the pull-down stairs and replaced it with a screen or mesh I could provide a source of cooler air to the attic (supplementing the eve vents). Now, if I install a fan in the garage window, assuming the garage is closed I can effectively pressurize the garage and force the "cooler" outside air into the attic through my now mesh-covered pull-down stairs? Then this pressurized air should increase the flow through the roof vents and turnover the air in the attic faster, thus keeping it more in line with outside temperatures. I can't really put a fan up in the attic due to it having blown in insulation which would be flying around everywhere. My house has a hipped roof so I have no end gables to install a fan in either.

I guess this would almost be "turbocharged". Does this sound feasible?

 

[bishir]

My Father-in-law had a pull down staircase, but he replaced it with a sheet of plywood and a fan that blows air up into the attic from the house. Works great! Maybe that will work since it's just blowing straight up?

 

[Lee_Burough]

"Whole House Attic Fan"

Is what you need.

Mine is running right now. I put the fan in a choice spot in the ceiling (built a dam around the fan that is taller than my blown attic insulation). You can add a couple turbines near the top of the ridge of your roof to allow the air to escape. Air currents during the day will move the hot air out through the turbine vents even if you don't have the whole house attic fan or powered roof vents.

I turn the A/C off and open the windows at sundown to let the cool mountain air come in the windows of the house and up through the attic.

At 7,000 ft, that cools my house on all but the hottest 10 days each year

Look in a Sears catalog for your options

 

[John Larkin]

Thanks. I thought of the whole house fan also. I've seen them and hear good things about them. I'm satisfied with my a/c system and the cost is reasonable so I haven't seen a living space cooling need. What I do hear is that the house, maintenance-wise, performs better when the attic is as close to outside temperature as possible. Supposedly it helps the life of the roof, sheathing, etc. That's my goal: preventative maintenance. Translates into more "me time".

 

[Drew L]

screens

They can reduce air flow by 50%. Drew

 

[HRpartsNstuff]

The whole house fan in the attic stair hole will work fine, unless you get up/down there a lot, then it's always in the way. If you do the garage window fan (which should work about as well), then you also have a fan for the garage if you need it there (and close off the attic).

The downside of both ideas is that garages usually stay cool on their own. Now you let warmer air into it to offset the even warmer air in the attic. Results= attic cooler, garage warmer.

Either one of those ideas should be kept on low/med if you have the windows open in the house. I noticed on high, it blows enough that hot air comes out of the roof ridge vent and the eaves. As it comes out the eaves, it gets sucked into the house. Now the house is even warmer & smells like insulation.

Best way IMO is to have a roof vent/fan near the center of the house, high up on the roof. Then you can run it full blast, sucking cooler air in from the eaves. You shouldn't smell anything, and the garage stays cooler.

 

[Night Train]

You said you have roof vents. I presume these are the aluminum ones cut into the back of the roof. You could also add a ridge vent. This would allow the heat to escape through the highest part of the roof and should have a nice draw from the eave vents. Also, could make the eave vents larger, unless they already cover the whole eave.

 

[John Larkin]

Thanks for the feedback. I think I'll start with the lo-tech draft idea and work my way up to forced air.

 

[Matt Weiser]

Here's another idea I had. I was thinking of taking an electric radiator fan out of a junkyard, bolting it to an attic vent and powering it directly with a solar panel. You can buy kits for this but I figured I could save some money on a junkyard fan.

Solar panels put out 12 volts so it would be an easy hookup. I haven't done the math to figure out what size solar panel I would need, but I'd want to find a fan that draws minimal amps yet moves the air well. Solar panels are expensive, but I like the idea of making the heat source power the cooling effect.

 

[John Larkin]

I'm pretty sure that's the basis of gravity fans. Those sphere shaped ones on top of buildings that spin. The rising heat powers them so that is one free way to do it. Unfortunately I doubt they are very weather resistant meaning rain could come in.