Maximizing Attic Ventilation for Cooling: Tips and Considerations

[Ronnin]

It is absolutely miserable here. Me nor the kids will dare venture outside until after 7pm due to the heat and humidity. The AC runs almost non stop unless I shut it down for brief periods during the day. Once the outside temperature is sustained at 90+ F on average (from 11am-6pm), in the hottest part of the day the lowest my AC can cool the house is between 80-82 degrees. I have a 2.5 Ton unit cooling about 1600 square feet. Is this just normal in this kind of heat? I'm home all day so that may be the biggest reason I really notice how hot it gets in here now.

I have gone up into my attic to grab stuff during the summer and can just imagine how much of that attic heat is heating the house. I access my attic through the garage. If I were to keep the access open and rig a fan up to vent the attic air into the garage (I would crack the garage door) could this possibly help or would it undo what my ridge vent is suppose to be doing? I am very poor right now so running out and dumping a bunch of money on Low E windows and the like is out of the question. Any cheap suggestions?

 

[turbo]

Your best bet might be to install large passive vents high in the gable ends of your attic, and let natural breezes/convection evacuate the hot air. No fans to buy, no additional electrical load... Ridge vents are not awfully effective because they tend to have narrow openings and they need to be balance by additional venting at lower levels. Depending on how your house is constructed, you might be able to get some additional passive cooling by installing soffit vents. If you have a friend who is handy with carpentry, you might be able to get help without breaking the bank.

Edit: BTW, when energy prices start getting high, lots of people add more fiberglass batting to their attics. Unfortunately, if they don't know what they're doing, they can restrict any previously-installed soffit vents to the point that air in the attic is even more stagnant than before.

 

[Mike_In_Plano]

In an emergency, you can section the house and buy a few fans. I keep the Southern side of my house much warmer than the northern side. I just close down the vents on one and open them wide on the other.
Fans are great, but I wouldn't buy the oscillating ones. My ex wife was in corporate for a major insurance agency and a good many fires were attributed to the wires fatiguing in the arm of these fans.
As measures become more desperate, I've seen folks use a sheet to block of a hot section of house. Then, when I was a kid, it was very desperate, because few people had AC. A moist hand towel draped behind the neck was good help.

I wouldn't stomp around up in the attic until the season's cooled. Then, make some upgrades. A good one is to find leaks in the ducting and seal them with tape. Also, you may want to un-kink ducting and re-size it according to you needs - most people have rooms that get very little flow due to poor duct work.
The passive vents at the gables sound like a great idea - if you have gables. Just remember to include screen to keep the mice, rats, and squirrels out.
els

 

[below_ground]

Why not install a couple of roof exhaust vents like pop vents?

 

[OmCheeto]

It is absolutely miserable here. Me nor the kids will dare venture outside until after 7pm due to the heat and humidity. The AC runs almost non stop unless I shut it down for brief periods during the day. Once the outside temperature is sustained at 90+ F on average (from 11am-6pm), in the hottest part of the day the lowest my AC can cool the house is between 80-82 degrees. I have a 2.5 Ton unit cooling about 1600 square feet. Is this just normal in this kind of heat? I'm home all day so that may be the biggest reason I really notice how hot it gets in here now.

I have gone up into my attic to grab stuff during the summer and can just imagine how much of that attic heat is heating the house. I access my attic through the garage. If I were to keep the access open and rig a fan up to vent the attic air into the garage (I would crack the garage door) could this possibly help or would it undo what my ridge vent is suppose to be doing? I am very poor right now so running out and dumping a bunch of money on Low E windows and the like is out of the question. Any cheap suggestions?

This may sound very peculiar. But I'm from the northwest, so that goes without saying.
On 100+ degree days here, with no air conditioning at all, my house rarely gets above 80'F.

Do you have any insulation in your walls or attic?

Never mind. Let me try and figure it out.

According to http://en.wikipedia.org/wiki/Air_conditioner#Equipment_capacity", a "ton" = 12,000 BTU/hr

So you are running through 30,000 BTU/hr.

Assuming a single level house: 1600 ft^2 --> 40 ft * 4 *10 (perimeter area) + 1600 * 2 = 4800 ft^2 (surface area).

R-values are given in units of ft²·°F·h/Btu.

R=4800*15/30000 = 2.4

You have no insulation in your house.

As a pauper like yourself, I bought a dirt cheap house about 20 years ago, and progressing room by room, each year, tore down the interior sheet rock and installed R-13 insulation. Then I added R-23 insulation to the attic, and finally added R-13 insulation to the interior of my foundation.

But that's a lot of work.

With no insulation in your attic, I'd say stuff a fan in some orifice to suck out all that hot air. It's like a big radiator up there right now.

While you are thinking about next summer, just remember that if you upgrade your R-2.4 house to an R-13 house, you will be sitting in a living room, at the same energy consumption, at:

oh crap, math:

R = ft²·°F·h/Btu
delta °F=R/(ft²*h/Btu)=13/(4800*(1/30000)) --> 95'F -82'F = 13'F

something equivalent to a freezer.

 

[pantaz]

I installed "turbine" style vents on my roof a few years ago. HUGE difference! There are several varieties of attic venting. The best choice depends on the size of your house, the roof design, etc.

 

[DaveC426913]

I installed "turbine" style vents on my roof a few years ago. HUGE difference! There are several varieties of attic venting. The best choice depends on the size of your house, the roof design, etc.

Are they noisy? I sleep in my (finished) attic.