doubling attic insulation - does it help?

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I have a 5 year old house. I can't remember the R-value, but I know I've got the yellow insulation batts in my attic. Its what is required for code, no more I'm sure :) The insulation has paper on 1 side (down), and nothing on the exposed side (facing up) in the attic. I was wondering if I buy the white insulation from H.Depot (higher R-value) and put it down ON TOP of the yellow insulation. I don't think it will compress it much - the bats are light. Perhaps that will provide me with $$ savings?
Thanks! jason shohet
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Great energy saving tips are at the following link. I would do everything you possibly can. For example I just got a new "Energy Star" refrigerator and it is saving me $10 a month on my electric bill. Strange that a new appliance could do the same thing while using less energy, but I guess they figured out some way to make these thing more efficient. These suggestions *really* help to lower energy bills.
Some things are expensive like replacing windows, others are cheap like sealing leaks - caulking, etc.
Energy saving tips... http://www.energystar.gov/
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Anything helps, but keep in mind there are diminishing returns. Before you jump into this, find out what you have and what is recommended for your climate. In general, more is better. You can probably find some chart showing what the potential savings are. http://www.eere.energy.gov/consumer/your_home/insulation_airsealing/index.cfm/mytopic360
Don't forget the basement http://www.bchydro.com/powersmart/elibrary/elibrary643.html
--
Ed
http://pages.cthome.net/edhome/




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I'm in FL, and blown in insulation is the big thing here. I had roughly 1800 sq ft blown in at an R19 value in fiberglass. Cost me $550 and I got a $100 credit frm the power company, so $450 total. It took about 30 minutes to be done, and the best part is that someone else was in the attic getting sweaty. These guys will blown in at any R value, it just costs more.
You can buy cellulose as HD/Lowes, and if you buy enough, the machine rental is free. I think I may have saved a few bucks if I did it myself, but even if it was $100 I could have saved, to not sweat in the attic, it was worth the cost. Doing it with rolled out insulation would have been far more costly.
Downside to blown in stuff is it settles over time. My house is 25 years old, had blown in fiberglass and it settles down to around an R10 value. Probably was R19 originally. So now I'm at R30 range.

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Attended a house building course years ago when I was building mine with sweat equity. On insulation calculations the data was that up to R30 the gain in insulation efficiency is a straight slope upwards. After R30 the slope flattens which is to say any gain in insulation efficiency ( reduction in heat loss) after R30 is very marginal. That is you won't get your money's worth beyond R30.
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This is Turtle.
Ed and other had some good replys but there is one thing to remember here. There is such a thing as over insulating the attic. a example of this is put 10 feet of insulation in your attic and then when the evening comes when the temperature cools off . your attic has this 10 feet of insulation which will still be transnitting heat into your house most of the nite. then when the morning comes you will have to start heating up the 10 feet of insulation from inside the home which will waste a lot of heat to just do this. So Too much is just as bad as not enough.
TURTLE
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On Mon, 17 Oct 2005 11:18:12 -0500, "TURTLE"

Insulation has that much thermal mass?
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Wes Stewart wrote:

No.
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Turtle, insulation needs vary upon locality-zone. You pay to heat or cool and more attic insulation helps. Many areas have heating as the major cost not cooling, but I always find nightime humidities to high during cooling season to open windows, although I agree in theory wth you as I noticed what you mention, but the winter and overall savings up north here negate what you experiance in your warmer locality. Uping R even cut my summer cooling bills as heat is not let in the attic. Ten feet of it you say, that would be upwards of R 420, kind of stupid for you to say Ten Feet. Facts and proof are out there that codes are insuficient minimums, there are guidlines that work to get optimal values. You don`t live where your new heating bills may be up hundreds a month or where a 90% furnace is not as good as a 94.5%. and a 80% efficiency is a joke.
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This is Turtle.
10 feet of insulation was a example of there is a limit to having too much and just as not having enought.
TURTLE
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This is Turtle
No the Air in the Insulation does have a good mass to concider but the insulation it's self would only very small in the effect. A example of this is the perfect insulation is a 1" block of a glass cube with a vacuum space in side it. Heat will not transfer in a vacuum except it is a radian heat. The vacuum cube would be the perfect insulation and put all the insulation companys out of business.
TURTLE
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TURTLE wrote:

Not from the above cause. Too much (or more likely, poorly installed) could be a problem if you were to block necessary air circulation, but any realistic amount would not be a problem as described by thermal mass and re-radiation back into the living space.
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No.
Nick
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Just be sure not to block your attic ventilation, especially if you're in a climate where you get snow & ice that hang around for long periods of time.
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Measure what you have and if fiberglass figure 3.5 per inch R value. All insulation settles.
Codes are minimums. Previous sites provided will give you optimal R values for your Zone., Also check out Owens Corning, Dow, and other R value energy sites.
Im Zone 5 , Code is R 35, optimal is stated at several sites R 60 - 70. I did R 100 and it has settled to R 80. My utilities are the lowest in the area confirmed by the utility co, but I did the walls , windows and basement also.
Up what you have past optimal ratings for settling and you will save big time. Remember Heat Rises, the attic is the cheapest place to start Be sure to instal side roof deck baffles.
Codes are basicly 30 + years old, minimums, and do not reflect todays utilities prices .
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On 16 Oct 2005 19:13:29 -0700, snipped-for-privacy@gmail.com wrote:

I have loose fill between the joists which had settled over the years. I "topped off" the loose fill and ran 6" unfaced perpendicular to the joists over it, making sure not to block ventilation to the eaves. Seems to have made a difference. Hard to tell how much because I did a number of potentially energy saving things that year. It sure didn't hurt.
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On 16 Oct 2005 19:13:29 -0700, snipped-for-privacy@gmail.com wrote:

Here's a (really) simple little thought experiment. Pretend you are in a cooling situation so that you are trying to minimize the internal heat gain.
Let's start with walls and roof with no added insulation and say that the construction materials give an R value = 1. The heat gain comes from the following sources:
1. Internal (appliances, hot bodies, etc.) 30%
2. Roof 40%
3. South wall (lots of overhang) 5%
4. North wall 5%
5. East wall 10%
6. West wall 10%
Assume the total daily heat gain for a typical day is 100,000 BTU, so the distribution is as follows:
Internal = 30,000 BTU
Roof = 40,000 BTU
South wall = 5,000 BTU
North wall = 5,000 BTU
East wall = 10,000 BTU
West wall = 10,000 BTU.
Now, let's stuff some R-10 (U = 0.1) insulation under the roof. This reduces the transfer to 10% of the starting point or 4,000 BTU.
The total heat gain drops to 64,000 BTU, or a 36% reduction. Hey, this is progress, let's double the amount and really save some dough.
Adding another R-10 layer for R-20 total reduces the roof heat gain to 2000 BTU, for a total of 62,000 BTU, or a 38% reduction from the starting point.
Wait a minute! We doubled the insulation (and its cost) and saved 2%. Clearly, the other sources should be addressed before going overboard with ceiling insulation. You can argue about the beginning distributions, but the trend is clear. Unfortunately, building codes sometimes take the position that if some's good, more's better, which is complete nonsense.
I also find it amusing that some builders, as I've seen here in Tucson, offer hype such has "R-40 ceilings, and R-30 walls" when 80% of an unshaded west facing wall is sliding glass doors. The 20% shear wall is R-30 alright, but the 80% is R-1.5 and might as well be a hole in the wall through which you pour money.
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wrote:

Consider the gross simplification where all 4 walls and ceiling had the same area and R factor (ignoring the floor). Doubling the amount of insulation would decrease the heat lost by 50% over 20% of the area or a total of 10% overall.
Since ceilings are generally better insulated than walls (which have doors and windows) and (especially in a 2 storey house) have less area than the total wall area, the actual improvement from doubling the ceiling insulation I would expect to be much less than 10%.
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So how did I get an 1800sq. ft. 110 yr old house to have an annual gas bill of 463$ last year, down from 1850 $, Which includes tankless gas water heater gas cooking and gas dryer. I did R 100 attic R 35 walls, dual and tri pane, and complete basement insulation, even Under the new concrete. But #1 I did not listen to the naysayers that I would never get a payback. My utility co was so sure I was stealing they were out twice. So all you who say don`t overdo it , it will never payback, I laugh to the bank this year and maybe pay 6-700 for a years worth of comfort. Oh Im Zone 5 Chicago area it goes to -20 here and im on the water, a very windy place indeed, so windows were purchased with test results.
Bottom line, insulate for your zone to the max.
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On Tue, 18 Oct 2005 15:24:21 -0500, snipped-for-privacy@webtv.net (m Ransley) wrote:

My, my, aren't we testy. Could you give us the savings attributable to increasing the attic insulation from R-50 to R-100, since doubling that value is the subject of the thread?
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