On Feb 27, 12:29*pm, (fwfrog)
wrote:
(I had been posting in another thread, but I kept getting error messages
when I tried to add another reply. *As such, I'm seeing if a new thread
will take my submission.)

We are thinking of adding insulation to our old home in Fort Worth, Texas..
*There's a subsidy program where the state pays for part of the insulation
if you use a participating vendor.

Here are the price breakdowns for blown-in fiberglass*:

R-30 (12 inches) - $200
R-38 (17 inches) - $460
R-49 (18.5 inches) - $709

*I don't know any more about the composition of the fiberglass, other than
it's blown-in, it's white, it's non-itchy, and it's very lightweight.

The 1,000 sq. foot house is 80+ years old with maybe a couple of inches of
old cellulose in the attic. *The attic is completely "open".

There's a gas furnace in the attic and a new electric A/C unit (14 SEER)
outside. *We're more concerned about insulating for the heat vs. the cold.

What's the best deal? *(I've used online savings calculators--but they
don't seem to give consistent answers.)

Maybe I'm a little confused on R-values. *Is the value # determined by how
many inches you have blown-in? *In other words, 12 inches provides R-30
protection. *I couldn't have 12 inches of R-38... I'd need more inches to
get the stronger R-value, right?

Or is the R-value an inherent quality of the fiberglass (like the SPF
value of sunscreen) where a higher R-value equals more "protection"? *In
other words, 18.5 inches of R-49 is greater than 18.5 inches of R-30.

Thanks again for everyone's help. *I think I'm eventually going to
understand all this -- but you've got to start somewhere, right?

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A different perspective is, Google, Fiberglass Loosing and "looses"
R Value At Low Temperatures, its reported to be up to 50%. 20-30% is
proven. So I over insulated, insulation is cheap labor is not. But I
go to -22f. The theory still applies, into you wallet.