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Mister Sonny 06-27-2010 08:36 PM

Some questions about attic insulation and improving it.
Hi everybody,

I have a house I have lived in a little over 10 years. It was built in 1964. Normal construction for Texas, single story house around 2400 sq ft. It has around 8" of blown in cellulose which has apparently compacted down from whatever the previously owners originally blew in. There are two of the gable style vents on the ends of the house (triangular at the peak of the roof), and two "mushroom" non-powered rotating vents on top along the ridge.

I have noticed that my AC is struggling. It's in good shape, good on freon, and not an old unit. (installed 4 years ago). What I did notice is that the temp of air coming out of the vents changes substantially the longer the vent run in the attic is. Which makes me think my duct work is getting too hot and heating up the air in it. I am looking at options and trying to get ideas on how much it would cost and how DIY friendly the various options are.

a) Blow in more insulation - An obvious choice, but I don't know if this is something I could do myself. I'm also just now starting to look at costs on it.

b) Add soffit vents. There are no soffit vents on the house and plenty of overhang on which I could install them. This looks like the easiest option, possibly the cheapest, I am just not sure how much of a difference it will make.

c) Wrap the ducts. They are insulated, but I have seen where you can get a product that looks like foil covered bubble wrap and wrap them for better efficiency. Anybody here have any personal experience with this? It looks pretty inexpensive and like something I could knock out assuming I can stand the heat up in the attic long enough (it's brutal up there with the daytime temps hitting 100 in Texas already this year.)

d) Staple in a radiant barrier. This looks like something I could do, and I found a company called AtticFoil ( that sells what looks like the right stuff and they are only around 20 minutes from my house so I could pick it up at their warehouse. Again, probably something I would have to do over time as there's only so long I can hang up in the oven of an attic I have right now.

e) Upgrade my mushroom vents to solar powered so they actively pull air through. Looks pretty easy, and I admit I just saw these while getting things at Sam's today so they're just the newest idea in my head.

I am not sure if one of these is the right answer for me, or if a combination would do the trick. I am price conscious (just finished redoing my wife's whole bathroom), but have what I consider a decent level of DIY skills. What do you experts and other semi-experts think?

beenthere 06-27-2010 10:43 PM

What size gable vents, and what size is the opening in the mushrooms.

Might want to consider doing both, adding more attic insulation and radiant barrier.

Mister Sonny 06-28-2010 05:21 PM

The mushroom vents on top are around 18" around for the opening, there are two of them.. The gables are around 2 ft tall and 10 ft wide, there are three of them total (L shaped house). These are approximates because I didn't get a chance to go up there and measure today.

So around 30 sq ft of gables, and around 9 sq ft of output vent. My concern with the gables is how much that helps get air around to cool off the vents and insulation since they are below the level of the gables obviously.

My concerns are the temps inside, but measurements of temp, and measurements of vents will be tomorrow probably for me.

beenthere 06-28-2010 09:57 PM

3 2X10 gables would be 60 sq ft.

2 18" rounds is only 3.54 sq ft.

The mushrooms aren't doing much.'

Mister Sonny 06-29-2010 09:31 AM

That's what I was thinking as well.

My first thought was adding soffit vents on the overhangs to increase the airflow in, and allot the gables to be predominantly warm air out. Second would be to add an additional vent on top, or possible look into doing a ridge vent. I will be putting sensors up there tonight to monitor the heat levels better and also getting some measurements.

beenthere 06-29-2010 10:00 AM

Might want to consider solar powered mushroom fans. 2000 CFM each, or more.

2 of them would pull a lot of air in your gable vents.

Uses no house electric to operate.

Not sure, but they may even qualify, for a 30% tax credit, since they are solar powered. If so, then they don't cost much to buy.

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