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Old Oct 17, 2012, 02:53 PM   #1
Huntn
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Calling Insulation Experts

I'm thinking about putting more insulation in my attic. The possibilities are more insulation on the floor of the attic, spray foam or cellulose, or radiant barrier under the roof deck.

Several weeks ago I got an estimate: $3700 to spray 5" of open foam up under the roof deck. This is supposed to keep the attic about 10 warmer than the house. Wow, sounds great because the attic becomes a more usable storage space instead of baking stuff at 140F! However when I called another contractor, I was told that open/closed foam was not allowed with gas water heater/furnace in the attic. (That's how they do it in Houston, no basement, furnace and water heater in the attic, although I'd prefer it in my garage but those are not big enough to put them there). So that's why this contractor offered cellulose insulation. And then there is radiant barriers, aluminum foil stabled to the bottom of the rafters that keeps heat out of the attic.

Anyone familiar? I'm about to launch some net research to educate myself, but thought I'd ask here.
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Old Oct 17, 2012, 04:05 PM   #2
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Several weeks ago I got an estimate: $3700 to spray 5" of open foam up under the roof deck. This is supposed to keep the attic about 10 warmer than the house. Wow, sounds great because the attic becomes a more usable storage space instead of baking stuff at 140F! .
140F Is your attic ventilated? My attic was in the 130-150F range before I installed some soffit vents and baffles to help with air circulation. Now it's down to 10-15 higher than outside temperature. The AC has to work less with a cooler attic.
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Old Oct 17, 2012, 06:39 PM   #3
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140F Is your attic ventilated? My attic was in the 130-150F range before I installed some soffit vents and baffles to help with air circulation. Now it's down to 10-15 higher than outside temperature. The AC has to work less with a cooler attic.
My attic does have soffit and roof vents and I've never measured it's temp. I just threw that out as a generality. Still looking for info online.
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Old Dec 5, 2012, 11:50 AM   #4
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I live in a hot and humid climate (central Texas) and I currently have a poorly installed combination of fiberglass batts and blown fiberglass. After months of casual research, I have been inundated with data and differing opinions about the best way to insulate my attic. I have even found myself dreaming about attic insulation... Cost is not the issue here, it is cost efficiency, how long to pay back the investment. This is where I am today:

Spray foam insulation: Nope. Although it is described as a miracle solution, especially with your furnace in the attic, because it reduces the temperature in the attic greatly . However in a retro fit, there are substantial risks. Ideally with foam, you seal off your attic from the outside keeping the heat and moisture out. This requires that it be installed correctly, no, if, ands, or buts. It also requires a retro fit on your furnace if it is up there (mine is), adding more expense to the project. If it is installed incorrectly, or if it deteriorates over time (pulls away), and moist air can find its way in, you are setting yourself up for mold issues in an unvented attic. I'd consider using spray foam in a vented attic to reduce radiant heat off the shingles, but it's so damned expensive, $4-5000 dollars, I question it's cost effectiveness (pay-back time).

I also considered using a radiant barrier. This is foil stapled across the underside of the roof rafters. The idea is to channel the heat coming in up and out through a ridge vent. This would cost about $2500. Articles like this one place doubt on its cost effectiveness.

Best Option? I have settled for beefing up the attic insulation with cellulose and adding some solar powered attic fans. They are expensive, $400 each, I'd need 3 of them, but they currently have a 30% tax credit on them. Increasing air flow through the attic is always good, but still you might question the cost effectiveness of them.
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Old Dec 5, 2012, 12:13 PM   #5
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I just went through the process of adding insulation to my attic. I am in a completely different climate than you (Central Ohio) so my required r-value is likely going to be higher than yours.

I ended up doing the blown in cellulose insulation myself. I put 60ish bags of the green fiber from home depot into my two attic spaces, about 1100 sq. ft. all told.

If you are not afraid to get up in the attic yourself you can do the cellulose blown in yourself. You just need a helper to feed the hopper, some goggles, a good mask and about 6 hours.

I was able to pick up, blow in 1100 sq. ft., clean up the machine, and return in all in one day. I am now around an R-60 value in my attic space... much better than the R-20ish I started with.
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Old Dec 5, 2012, 12:56 PM   #6
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Quote:
Originally Posted by Huntn View Post
Best Option? I have settled for beefing up the attic insulation with cellulose and adding some solar powered attic fans. They are expensive, $400 each, I'd need 3 of them, but they currently have a 30% tax credit on them. Increasing air flow through the attic is always good, but still you might question the cost effectiveness of them.
I agree that this is your best option.

Radiant barriers are sketchy at best. The concept of reflecting heat away from the house is pretty elementary, but to be truly effective it should be on the outside of the house - namely, replacing your shingles. I wouldn't bother.

A good insulation value for a roof is somewhere between R-22 and R-30. Anything more is a waste of money, unless IECC requires it.

Quote:
Originally Posted by prostuff1 View Post
I am now around an R-60 value in my attic space... much better than the R-20ish I started with.
There's a big misconception surrounding R-values in insulation. There are diminishing returns.

Conductive heat transfer is square feet times cooling load temperature difference times U-value, and U-value is the reciprocal of R-value. Per 100 square feet, on a typical summer day where the CLTD is around 40, the benefit of upgrading from R-22 to R-60 isn't all that much:

No insulation (R = 0.75):
100 * 40 * 1/.75 = 5,333 Btuh

Standard insulation (R=22):
100 * 40 * 1/20 = 200 Btuh

Extra insulation (R=60):
100 * 40 * 1/60 = 67 Btuh

Sure, it's some level of energy savings, but it's generally quite small compared to the cost of the insulation (not to mention it taking up three times as much thickness in your attic).
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Old Dec 5, 2012, 02:01 PM   #7
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Your math might be correct, but I can tell a huge difference in my house from the R20ish i started with and the near R60 that is up there now.

I don't need or use my attic for storage so the extra space it takes up is irrelevant in my case.

The ability to keep my house warm with the increased insulation is much easier. My heat pump does not have to run nearly as long or as hard to get the house up to temp.
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Old Dec 5, 2012, 02:11 PM   #8
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Our house is more vertical than horizontal so that might be the difference but adding more insulation to our attic was something like $700 for spray foam. I can't remember the R rating other than it was what was recommended in our area. Granted we got a discount because we were doing other house work but it would've only been a hundred dollars or so.
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Old Dec 5, 2012, 07:59 PM   #9
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Originally Posted by prostuff1 View Post
I just went through the process of adding insulation to my attic. I am in a completely different climate than you (Central Ohio) so my required r-value is likely going to be higher than yours.

I ended up doing the blown in cellulose insulation myself. I put 60ish bags of the green fiber from home depot into my two attic spaces, about 1100 sq. ft. all told.
Guess I could look it up, but do you remember what material cost for your job? For about a 2300 sf attic, to have R49 installed is about $1900.

Quote:
Originally Posted by Tomorrow View Post
I agree that this is your best option.

Radiant barriers are sketchy at best. The concept of reflecting heat away from the house is pretty elementary, but to be truly effective it should be on the outside of the house - namely, replacing your shingles. I wouldn't bother.
Thanks!

You don't know the gyrations I went through making a decision on the attic and spray foam. My initial impression was "this is great!!", then I started reading about the potential problems with foam, especially for retro fits and it was "oh my God!!" What really bothers me is that a sealed attic requires electrical power and available A.C. to avoid build ups of moisture in a sealed attic with no where to go. And although unlikely, there is the hurricane scenario where power could be out for a couple of weeks. Moisture will work its way into the house. There are cases even with power and incorrect applications of spray foam where home owners ended up putting a dehumidifier in the attic to control moisture up there. I don't want to think about it.
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Old Dec 5, 2012, 10:38 PM   #10
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I spent right around the $600 dollar mark in material (before the rebate coming back from my electric company).

That was to put in about 12 inches of insulation in about 1100-1200 sq. ft. of area.

Without looking at what you have up there now, I don't know how much needs to be added to get you to that R49 value.

The stuff I used is here. They rent the blower to you for free if you buy a certain number of bags. There is also a couple of pdf files at the end of that page that give info on the insulation and install instructions.
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Old Dec 10, 2012, 08:26 AM   #11
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I spent right around the $600 dollar mark in material (before the rebate coming back from my electric company).

That was to put in about 12 inches of insulation in about 1100-1200 sq. ft. of area.

Without looking at what you have up there now, I don't know how much needs to be added to get you to that R49 value.

The stuff I used is here. They rent the blower to you for free if you buy a certain number of bags. There is also a couple of pdf files at the end of that page that give info on the insulation and install instructions.
Thanks for the info! I have to think about messing with this myself. At one point I thought I might.
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Old Jan 27, 2013, 11:11 AM   #12
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The price of cellulose insulation may have gone up. A single bag of the Green Fiber is running just under $10 a bag at Lowes. By my calculations, if I do it myself the savings will be minimal as compared to the quotes I have received. I plan on pumping up the attic insulation to about R50.

In my attic insulation research I discovered the concept of attic door boxes or tents that insulate around the attic steps, one of the main areas of heat/cold transfers due to the lack of insulation associated with an attic door. I ended up purchasing the Battic Door and am very pleased with it. The R50 model cost $100. It consists of a cardboard box, insulation, and a aluminum type reflective cover that did not cost much more than if I tried to make one myself. Of note, one of the quotes I received from an insulation contractor included a stair tent/box for $250.

Battic Door Attic Stair Insulation:
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Old Jan 27, 2013, 11:58 AM   #13
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Originally Posted by Huntn View Post
I'm thinking about putting more insulation in my attic. The possibilities are more insulation on the floor of the attic, spray foam or cellulose, or radiant barrier under the roof deck.

Several weeks ago I got an estimate: $3700 to spray 5" of open foam up under the roof deck. This is supposed to keep the attic about 10 warmer than the house. Wow, sounds great because the attic becomes a more usable storage space instead of baking stuff at 140F! However when I called another contractor, I was told that open/closed foam was not allowed with gas water heater/furnace in the attic. (That's how they do it in Houston, no basement, furnace and water heater in the attic, although I'd prefer it in my garage but those are not big enough to put them there). So that's why this contractor offered cellulose insulation. And then there is radiant barriers, aluminum foil stabled to the bottom of the rafters that keeps heat out of the attic.

Anyone familiar? I'm about to launch some net research to educate myself, but thought I'd ask here.
I'm in DFW and I have a sprayed insulation in the attic and have my gas furnace and 55gal water heater in the attic. House was built in 03, I just purchased it in Sept 12 and had the house inspected inside out and passed with flying colors. My previous home(built in '01) a few miles away had a similar setup with a gas furnace in the attic but the water heater is in the garage.
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Old Jan 27, 2013, 09:58 PM   #14
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I'm in DFW and I have a sprayed insulation in the attic and have my gas furnace and 55gal water heater in the attic. House was built in 03, I just purchased it in Sept 12 and had the house inspected inside out and passed with flying colors. My previous home(built in '01) a few miles away had a similar setup with a gas furnace in the attic but the water heater is in the garage.
I assume your sprayed insulation in the attic is under the roof deck? After some research, due to relative cost and some concerns I have about moisture, I decided that I'd just put in about 2 feet of cellulose up there. I've also installed 3 solar powered attic ventilation fans.
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Old May 1, 2013, 04:45 PM   #15
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24" of cellulose insulation installed, 3 solar powered attic fans, new Trane heat/ac unit and initial savings indications are very good. My last elec bill (April 2013) is $130, as compared to $260 last year at this time.
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Old May 6, 2013, 02:44 PM   #16
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Quote:
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24" of cellulose insulation installed, 3 solar powered attic fans, new Trane heat/ac unit and initial savings indications are very good. My last elec bill (April 2013) is $130, as compared to $260 last year at this time.
Need more data points to make firm conclusions, but that is definitely a good sign. Congrats!
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Old May 6, 2013, 02:47 PM   #17
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Need more data points to make firm conclusions, but that is definitely a good sign. Congrats!
Caveat I forgot to mention- this Spring has been much cooler than last year... I'll report back when real HEAT kicks in.
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Old May 6, 2013, 02:55 PM   #18
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We just put some insulation (sunny southern cal). It has made a huge difference. We had the original insulation from about 40 years ago and it was probably at about r-20 ish due to it being flattened and we could see some of it below the rafter in the attic. We had a company add r-30 going perpendicular across the beams. In some area's the old insulation was replaced and then a second level was put across it.

It has made a huge difference for us. Right now we have not turned on the AC or Heater since we got it. We have ran a fan in the living room a couple nights but we have been pretty much hovering around the 72-76 degree mark inside the house (according to our thermostat).

The house is much much cooler and doesn't get nearly as hot as before. We just had a heat wave and yet we did not turn on the AC at all!

We also have two roof fans and one gable fan. A couple of whirlie birds also!
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