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Question DetailsAsked on 5/25/2017

Should upgrading from R-19 to R-21 be double the cost?

New home construction. 2x6 exterior walls 16" OC, exterior wrap with vinyl siding.
Would I benefit going to R-21 insulation from R-19? It is quoted as double the cost and the subcontractor seems to think R-21 is uncommon, hard to acquire and unnecessary.

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1 Answer


I am going to assume no insulation is on-site or in yet, so this is just an option before buying - not a tearout and replace cost.

Well - R21 versus R19 is a 10% difference in insulation value, and for normal decently insulated new construction (with serious attic insulation) the walls comprise around half to 2/3 of your energy loss, so might add up to a 5-7% reduction in overall heating/AC energy consumption. So for a typical home with maybe $1000-2500 (lower end with gas, higher with oil and in most areas, with electric heat or a lot of AC use) per year total heating/AC bill, you might save around $50-200 per year with the better insulation. You would have to figure how long you intend to stay in the home, but at most your savings would be maybe $1000-4000 over a 20-year life, so spending more than about $300-2000 for the better insulation respectively (assuming project/mortgage financing at about 7%) probably would not pay off even over 20 years - one of the reasons R-21 is generally only used in the very hot or very cold states. Though considering the upward trends in power prices (especially if in a reltively non-competitive area or one that pays very high rates to "green" power which drives your rates up, if this is your "forever home" the added insulation would proably not be a bad idea - at a reasonable cost, not 100% more than R-19.

In our area (where good insulation is serious business, with real winters) R-21 is readily available at pretty much all building supply places, and Owens Corning EcoPack R-21 costs about 10% more than R-19 Pink for any of the facing options, so your installed cost difference (assuming it does not take special shipping to get it into your area) should be about a 5% to at most 10% total installed insulation cost difference, not 100%, since it takes very little more work and no special added effort to put it in.

Sounds to me like he does not want change orders or changes from normal routine - or maybe you are dealing with a major builder, who tend to grossly upprice any changes because they figure if the buyer is interested enough to ask for a price they really want it. In our area, I have seen upgrades priced commonly at 5-10 times what they should be becuase the builder figures the buyer is already on the hook, so if even a couple of them are selected at even a grossly higher markup, they have made a killing.

If going for a high energy efficiency rating, check the rules - generally you need R-21 in 2x6 ewalls for the highest ratings.

Also note - $ for $, about the best place you can spend your energy conservation money is in better energy rated windows - because an R-2 bump-up in wall insulation saves maybe 10% in the energy going through per square foot, whereas an R-2 bumpup in window rating is commonly a 30-40% reduction in per-SF energy loss. OF course, it can get out of hand - like some of the architectural monstrosities out there with so few and so small of windows that they look like a prison or hsower/bath house.

Answered 3 years ago by LCD

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