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Old 09-30-2013, 04:14 PM
 
Location: Austin, TX
527 posts, read 1,044,929 times
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I'm in the process of purchasing a new construction house. The attic insulation is R-30. DOE recommendation for my climate zone is R30-60. I'm wondering whether I should add more insulation before I move in. I realize the ROI diminishes quickly, but I'm thinking perhaps I can bring it up to R-45 or so. Is this a worthwhile investment, or am I wasting my money?
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Old 09-30-2013, 04:33 PM
 
Location: Johns Creek, GA
12,587 posts, read 48,935,127 times
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Quote:
Originally Posted by phoenix_down View Post
Is this a worthwhile investment, or am I wasting my money?
Yes.
And, it depends. Look at the energy-efficiency of the home as a system- Doors, windows, wall/ceiling insulation, HVAC (the top 4) then there are other smaller variables.

Then you have to look at feasibility. A 2X4 framed wall with batt insulation (R-13 max.) yields just so much R-value, sheathing, siding make little to no additional benefit. If the walls were framed with 2X6 you could go to R-19. Same theory goes for the attic; depending on how it is framed you're not going to get R-30 or R-60 around the perimeter (soffit area)- as with most truss roof systems; there just isn't enough space.

For TX- I'd get the most efficient HVAC system I could afford. Then make the house as air-tight as possible (blower door test)- that will have a better effect on your wallet than just "adding more insulation in the attic".
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Old 09-30-2013, 04:42 PM
 
Location: Austin, TX
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I know the door is insulated and has seals around the edges. The windows are double pane low-e vinyl frame ones. Wall is R15. And the HVAC system is SEER 14 I think. I believe the house is pretty air tight.
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Old 09-30-2013, 06:49 PM
 
433 posts, read 1,092,137 times
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You might look at a radiant barrier material that "bounces" the heat back through the roof.

This really helps in very warm climates.
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Old 09-30-2013, 11:49 PM
 
Location: Austin, TX
527 posts, read 1,044,929 times
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Quote:
Originally Posted by qdogfball View Post
You might look at a radiant barrier material that "bounces" the heat back through the roof.

This really helps in very warm climates.
Thanks The house already comes with radiant barrier installed. I also forgot to mention that polycell foam sealant is used around switches, plugs, and other air infiltration sites. So I think in general it should be pretty air tight.

Basically I think the house is fairly energy efficient as it is, but I'm wondering if it would be be worth the investment to add more insulation to the attic. Also now it's a more convenient time since I'm not living there yet.

I found this page:

Home Power Saver: Adding Attic Insulation - Part II - DIY Projects and Energy Saving Products

Using his analysis data for Dallas, it looks like I'd only be saving around $15/yr going from R30 to R49. Using his figures of adding R20 worth of insulation ($394), it would take 26 years to recoup my investment. Although utility cost will go up, so likely it will take less time than that. Based on his data, it doesn't seem like it's worth it to me. But I wanted to get a second opinion here.
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Old 10-01-2013, 06:50 AM
 
1,403 posts, read 3,131,767 times
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Quote:
Originally Posted by phoenix_down View Post
Thanks The house already comes with radiant barrier installed. I also forgot to mention that polycell foam sealant is used around switches, plugs, and other air infiltration sites. So I think in general it should be pretty air tight.

Basically I think the house is fairly energy efficient as it is, but I'm wondering if it would be be worth the investment to add more insulation to the attic. Also now it's a more convenient time since I'm not living there yet.

I found this page:

Home Power Saver: Adding Attic Insulation - Part II - DIY Projects and Energy Saving Products

Using his analysis data for Dallas, it looks like I'd only be saving around $15/yr going from R30 to R49. Using his figures of adding R20 worth of insulation ($394), it would take 26 years to recoup my investment. Although utility cost will go up, so likely it will take less time than that. Based on his data, it doesn't seem like it's worth it to me. But I wanted to get a second opinion here.
Are you looking at the R-value of the insulation alone, or are you taking into account the radiant barrier as well? R-30 may be more than enough with the radiant barrier in place.

What is the insulation type in your attic? Batts or blown cellulose? Dumping more blown cellulose may be a good DIY option.
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Old 10-01-2013, 08:36 AM
 
Location: Austin, TX
527 posts, read 1,044,929 times
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Quote:
Originally Posted by broadbill View Post
Are you looking at the R-value of the insulation alone, or are you taking into account the radiant barrier as well? R-30 may be more than enough with the radiant barrier in place.

What is the insulation type in your attic? Batts or blown cellulose? Dumping more blown cellulose may be a good DIY option.
I'm just looking at the R-value of the insulation alone, not considering the radiant barrier. You could very well be right and I don't need any more insulation. That's why I'm asking here

It's blown cellulose in the attic right now.
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Old 10-01-2013, 08:49 AM
 
Location: Cold Springs, NV
4,575 posts, read 9,664,589 times
Reputation: 5037
Quote:
Originally Posted by phoenix_down View Post
Thanks The house already comes with radiant barrier installed. I also forgot to mention that polycell foam sealant is used around switches, plugs, and other air infiltration sites. So I think in general it should be pretty air tight.

Basically I think the house is fairly energy efficient as it is, but I'm wondering if it would be be worth the investment to add more insulation to the attic. Also now it's a more convenient time since I'm not living there yet.

I found this page:

Home Power Saver: Adding Attic Insulation - Part II - DIY Projects and Energy Saving Products

Using his analysis data for Dallas, it looks like I'd only be saving around $15/yr going from R30 to R49. Using his figures of adding R20 worth of insulation ($394), it would take 26 years to recoup my investment. Although utility cost will go up, so likely it will take less time than that. Based on his data, it doesn't seem like it's worth it to me. But I wanted to get a second opinion here.
Sounds to me like you answered you're own question. Pretty mild Winters, so your real battle is the Summer heat. I know, somebody will say it can cold there, but it's only for a short time compared to other parts of the country.
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Old 10-01-2013, 10:33 AM
 
Location: Somewhere in northern Alabama
17,925 posts, read 54,281,810 times
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Blown cellulose will compact over time. Wait ten years or so and THEN add more.
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Old 10-01-2013, 12:24 PM
 
Location: Queen Creek, AZ
5,212 posts, read 7,907,933 times
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Quote:
Originally Posted by harry chickpea View Post
Blown cellulose will compact over time. Wait ten years or so and THEN add more.
That could be the reason why our builder used wet spray cellulose insulation in the walls but Owens Corning pink loose-fill fiberglass insulation in the attic. In addition, fiberglass weighs less for the same R-value.
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