Attic Insulation Blown In Cellulose vs Fiberglass?

[NY_Yankees_Fan]

Thanks guys, love the knowledge here, very much appreciated.

 

[KennyG]

There really is no way to cool an attic other then encapsulating it and running cool air into that area. Venting is not for cooling. No amount of air flow in an attic is going to lower the air temperature up there. Venting is designed to keep the framing dry. Attics without proper venting have condensation, which leads to mold, rot and shingle failure. Adding a fan might increase air flow, depending on it's location, but it will never lower the temperature. It's one of those things people sell because people will spend money on it hoping it will do something when it doesn't.

Eddie

I'll agree that limiting moisture is the most critical benefit of venting, but while venting won't "cool" the attic, it will significantly limit the heat increase.

 

[Kyle_in_Tex]

In the old days, homes had attic fans which pulled air in thru the windows up thru the fan and out the attic gables. This kept the attic much cooler than a relatively dead convective air attic in many homes of today. Solar plywood is awesome if you have the opportunity to apply it when building. I have been in 2 homes on the same day, 1 with and 1 without. 145 degrees without, 110 degrees with. It really amazed me.

The hotter the air, the more moisture it can hold. Any ventilation will help cool the attic. Electric thermostatically controlled fans do help, If the solar powered fans were good, I'd look into one. I don't know if they are good or not. Let others chime in on that.

Back to the op, I would prefer the fiberglass. The attacat insulation if it is what I remember, does not itch you. The sales guy rubbed it up and down his forearm.

 

[rswyan]

I'll agree that limiting moisture is the most critical benefit of venting, but while venting won't "cool" the attic, it will significantly limit the heat increase.

Correct.

Last year or the year before I finally got around to installing a thermostatically-controlled power gable vent I had sitting around for 10 years.

Makes a very significant difference on the heat gain in the house - particularly on really hot, sunny days.

Before, the AC could not keep up ... and I could feel heat radiating from the ceiling ... now, it's able to maintain the temp set on the thermostat (usually 72F to 74F) throughout the entire day.

 

[EddieWalker]

How does moving the air cool the air? It just changes the location of the air. Don't confuse what a fan does on your skin to what it does to the air itself.

Eddie

 

[Gary Fowler]

Correct.

Last year or the year before I finally got around to installing a thermostatically-controlled power gable vent I had sitting around for 10 years.

Makes a very significant difference on the heat gain in the house - particularly on really hot, sunny days.

Before, the AC could not keep up ... and I could feel heat radiating from the ceiling ... now, it's able to maintain the temp set on the thermostat (usually 72F to 74F) throughout the entire day.

IF your feeling the heat in the ceiling from your attic, putting a 8-12" layer of insulation in over what you have now would likely pay for the cost in electric for heating AND cooling in a year, 2 at most. When we built our retirement home we put the solar radiating plywood in on the roof and walls, put in 8" bats in the walls, R52 in the ceiling, double pane glass in all the windows and doors. The AC rarely comes on even in 100F heat and then only runs a few minutes. We have a total electric home (2308 sq feet heated area) and electric runs about $150 per month average year round.
Insulation is your friend when it comes to heating and cooling.

 

[ovrszd]

How does moving the air cool the air? It just changes the location of the air. Don't confuse what a fan does on your skin to what it does to the air itself.

Eddie

Good point Eddie. Only living things feel wind chill.

Attic fan will not cool attic below outside temp. But it will, as someone mentioned, control heat buildup.

 

[Kyle_in_Tex]

It cools it the potential delta between 100 degree outside air and the 145 degree air you find in many attics. Simple heat removal.

 

[oldballs]

I'm with Kyle on this. Moving the air out of the attic keeps the attic "cooler" than the simple convection allows.

 

[KennyG]

How does moving the air cool the air? It just changes the location of the air. Don't confuse what a fan does on your skin to what it does to the air itself.

Eddie

In our area, outside (ambient) air temperature seldom exceeds 90 F. On a sunny day, an unvented attic can easily reach 150 F. Pulling in outside air controls the heat buildup.