Should I agree to have more insulation added to my attic?

Question

I have a 6 year old home with about 12 inches (R-30) of blown-in insulation in the attic. Recently door-to-door sales representatives for an insulation company offered a free inspection and quote to add additional insulation. The pitch was that the R-value at the time of construction was sufficient, but that codes have been revised and more insulation is better.

I was provided with options for adding 8 or 12 more inches to attain R-49 or R-60 respectively.

Sure, insulation materials improve with technology, but should I agree to have additional insulation put in? Will adding more somehow pay for itself? Is there such a thing as too much?

I live in a desert climate with temperatures ranging from -20°C (-5°F) in winter to 32°C (90°F) in summer.

Answer 1

Good question. First off, there is no "code" requirement that would mandate adding insulation to a 6 year old house. The current standard in new construction is to try to achieve a R-42 in attic spaces. Adding more insulation to your R30 is not a bad idea, however I have a few questions for you. What kind of insulation do you currently have installed there now? What are the dimensions of the space and style of house and source of heat and A/C.

Adding more insulation is almost always a good long term investment, but before I would trust a sales pitch from a door to door vendor, I would investigate alternate routes. If a DIY project, costs to simply add a layer of R 13 or R19/23 fiber glass blanket over my existing insulation.(assuming it is also F/G blanket style). I would also seek quotes from a couple of reputable energy conservation/insulation contractors in your area. A good contractor will ask you the same questions I have, and ask about your energy costs now, then calculate the potential energy reductions in hard numbers or percentages and expected pay back period. Some energy audits are offered at a reasonable fee or even free and address several aspects of comprehensive energy savings in the home. It can be amazing what a little caulking, joist/wrap box insulation, weather stripping, hot water conservation methods and increased attic insulation can make in your total energy picture. Does your state require a professional license or certification for this kind of work? Be cautious and seek a trusted professional opinion.

Answer 2

OP, in your case adding insulation to bring the average up to r 38-40 is a good idea. At 1500' feet you will notice a lower energy bill. How much? Tough to say since I'm not there to see it. You will gain a greater improvement in the ceiling then what you would by changing windows even. It's probably the most cost effective way to lower your costs.

Over 38 it starts to not do much. Never batt over blow. I prefer batt 19 and blown 19 over the batt myself.

Air infiltration around outlets, top and bottom plate penetrations and weather stripping do make a big difference for very little.

Radiant barrier is nice if you can get to it with existing construction. If you chose this, obviously do it first before retouching blow.

Last, if you have cellulose, fiberglass above is ok, never let anyone blow cellulose over fiberglass. Batts or blown.

Answer 3

US Department of Energy recommendations are R-49 to R-60 for 85 percent of the country. The best source of info would be the Department of Energy website. Make sure your contractor air-seals the home too, or else you aren't doing anything.

Answer 4

R-value is not a good metric of real world insulatitive capabilities as it fails to account for air flow, heat emission, and moisture.

With respect to airflow and moisture, this why a wind-breaker can keep you warmer on a windy or rainy day than a sweater can, or why a thermos will keep our soup warmer than 6" of cellulose fill (especially if you were use a solid lid vs a lid made out of cellulose fill)

This means a thin layer of spray-foam insulation could actually do more for you than a thick layer of batt.

If you have batt or blow insulation that's in good condition, it is likely that the best thing you can do increase your energy efficiency is to seal airflow!!