Should I add more insulation?


Old 02-15-14, 11:37 AM
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Should I add more insulation?

Had a free home energy audit today from power company. The report says I have equivalent of r-37 blown in cellulose insulation in attic. The report said no recommended improvements. However from what I have read online we need 38-60 r-value for attic (live in central indiana). Would it be worth the cost to add extra insulation?

We have a 4 year old tempstar heat pump around 17 seer and 8.5 hspf.
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Old 02-15-14, 07:08 PM
Join Date: Mar 2006
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Insulation follows the law of diminishing returns. What this means is that starting from no insulation the first amount will save you huge amounts of money and will pay for itself in a single season but for each additional amount the savings are diminished significantly. Adding something like R-12 where there was no insulation might save you 50% on your heating/cooling costs but adding an additional R-12 will NOT save you an additional 50% of the costs after the initial R-12 but may save maybe 10%. The more you add the less the savings and for that reason retrofitting additional insulation over an "adequate" amount of existing insulation will take several years to several decades to realize any true saving when the capital cost of the additional insulation has been amortized.

This is an old story and the numbers are skewed compared to today but the ratio is what is important. I had a co-worker that had no insulation whatsoever in his Seattle house. He wondered if it would pay to insulate the attic and I told him it absolutely would. His oil bill had been running around $900 a season and he spent $100 to insulate just the attic (DIY). His oil bill dropped to $600 that year and it was a typical year so he saved $200 that year and then $3oo the next year and so forth.

Another ancient story; when ,my parents bought the house I grew up in it had no insulation. The first winter it cost $250 for oil and my daddy said that was ridiculous. He paid $1,000 to have the house fully insulated with blown-in mineral wool and also all the exterior doors and windows fitted with interlocking metal weatherstripping. He said the salesman for the insulation company tried to talk him out of doing the walls and the weatherstripping but my daddy insisted. The oil bills following that work and up to the oil embargo of 1973 ran about $50 a season. In other words he saved over $4,000 in fuel costs during that 20+ year period. He never added to the insulation and never installed double-pane windows. The boiler (baseboard heat) had a gas input of about 40,000 BTUs/hr and that house was never cold.
Old 02-16-14, 08:49 AM
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1) is the house now comfortable
2) what is the cost of extra insulation
3) what is your present heating cost
Old 02-16-14, 08:59 AM
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Red face

The only reason I would do if is if it would reduce my heating cooling bill enough to pay for itself in 2-4 years.
Heating costs probably around 300-350/month in the cold months. Cooling 100$ per month.

According to lowes website I need about 4-500 in materials alone. Doesn't sound like it will be cost effective.
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