Insulation Question

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(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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fwfrog wrote: ...

The optimum price point depends on the heating-degree days and cost of fuel and the efficiency of the heat source as well as the other losses in the house. In general, it's undoubtedly better to err on the side of more rather than try to hit a current target as fuel costs are unlikely to do anything other than go up over the long haul.

The R value is a proportional to heat loss value--for any given material it goes up w/ additional thickness proportionally. Each material does, however, have it's own characteristic R-value/inch so one can get the same R value from different thicknesses if use different materials. Expanded foam, for example, has a much higher value than does fiberglass so for constrained spaces (like wall cavities) one can get a much higher total value in the same thickness than fiberglass would allow. In an attic where space isn't an issue, there's no point in the higher-priced solution.
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fwfrog had written this in response to http://www.thestuccocompany.com/maintenance/Re-Insulation-Question-361653-.htm : When you say "higher-priced solution", do you mean there's no point in getting foam (which I'm guessing is costlier than fiberglass)?
Or is there no point in fiberglass R-49 vs. the cheaper R-38/R-30?
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"In an attic where space isn't an issue, there's no point in the higher-priced solution."
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fwfrog wrote: ...

Bingo...
No. Although Ft Worth isn't cold enough that for heating >R30 may have a long payback. OTOH, it might pay on the cooling side depending on other factors as noted above.
I'd suggest looking at your utility companies' web sites -- often they have recommendations tuned specifically for their service areas and factoring in local costs. Many will have energy conservation services at low or even no cost that may include actual evaluation of your house itself, leak tests, etc., ... Such an energy audit may save well over its cost in short order, particularly when for older homes that may have significant leakage problems in particular. Depending on just how old "old" is, in Ft. Worth it's even possible it was built w/o much if any insulation at all in the walls although if it has the cellulose in the attic there's probably at least a minimal amount. But, if it's really marginal there as well, you'll not see nearly as much payback w/ the attic alone as you might think you will or the calculators imply.
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fwfrog wrote:

Heh! Foam is MUCH more costly. But, in addition to getting the greatest R-value per inch, it is superior to other methods in blocking air flow. That is, it essentially seals all the cracks and gaps (think "Great Stuff").
Plus:
R-values Foam insualtion - 3.6 per inch. Batt fiberglass - 3.0 per inch Blown in fiberglass - 2.5 per inch

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fwfrog had written this in response to http://www.thestuccocompany.com/maintenance/Re-Insulation-Question-361653-.htm : After much debating, I think we're going to go with company #2 and the R-49 of blown-in fiberglass. I was finally able to get accurate quotes on the number of inches and the total cost from the second company ($698 for 19.5 inches of blown-in fiberglass). As someone guessed earlier, with this second company, the cost per inch did indeed drop as you moved up from R-38 to R-49.
Here's my final question...
How important is it to have our home "weatherized" before we blow in the fiberglass insulation?
As many people have mentioned, it's a good idea to "fix" anything before the new insulation is blow-in. Although we don't need to do anything with our electrical wiring, I wondered if this logic would also apply to sealing leaks in the attic?
Since we're not getting the blown-in foam insulation, I know the fiberglass won't "seal" any leaks. Would we be doing ourselves a disservice by not having someone come out to "weather-proof" our house first? We're probably losing more energy through old doors, windows, and the chimney than anything. (We had a new A/C unit put in not even 2 years ago, so I'd think that the duct work would be solid.)
I'm not sure what leaks might be present in the attic - but I didn't want to go about this insulation process in the wrong order, if I could help it.
Thanks again!
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On Mar 23, 9:55pm, jessmprice_at_yahoo_dot snipped-for-privacy@foo.com (fwfrog) wrote:

The only air leaks you should be concerned about in the attic are those from the conditioned air space below up into the attic. Air from outside is supposed to move through the attic ABOVE the insulation. There should be soffit and either gable vents or a ridge vent, etc. Typically those air leaks that may need to be addressed are around recessed light fixtures, holes cut for plumbing vents, etc. I'd do an inspection and this is something you can probably DIY. Also, I'd be careful about calling in some company to "weatherize" your attic. That's so open ended, you could spend $$$ for nothing. The blown in insulation will cut way down on any leaks like this anyway, because it's going on top of most of them.

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It's very important to seal off all the "bypass" openings in the attic. That means all the plumbing that comes through the ceiling, the kitchen stove vent hood, the furnace vent, etc.
For the furnace vent, pick up some aluminum sheeting at the home center and cut it around the furnace vent. Seal the it to the actual vent using intumescent sealer (pick it up in the caulk section). Use intumescent foam to seal all the plumbing openings and around each electrical box the punctures the ceiling.
Intumescent foam will not burn up in a fire. It actually expands when heat is applied. Code requires that type of foam and caulk.
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In general, more is better. How cold does it get in your areas? We have about 6800 degree days of heating where I am so I'd to for the R-38, perhaps more if I was going to stay in the house a number of years. How much do you pay for heating costs? If you save 10% it would not take long to pay back the extra $260.
In your area, air conditioning also comes into play so be sure to figure some savings for that also. Even if you don't stay in the house, it will add to resale value.
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fwfrog had written this in response to http://www.thestuccocompany.com/maintenance/Re-Insulation-Question-361656-.htm : It doesn't get very cold here (or at least for very long). Our average heating bill is quite low (natural gas). In the winter, we might pay upwards of $80. In the summer, it dips to around $15.
Our average electric bill (which runs the A/C) is between $60-75 month. In the hotter months, it can soar two or three times the average. We get 15-20 days of 100 degree heat in these parts, so running the A/C is paramount. (It seems to get hotter every year. It was 91 yesterday!)
We might stay in the house several more years (if the economy doesn't improve). With my job, we might also get transferred at a moment's notice.
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On Feb 27, 12:29pm, jessmprice_at_yahoo_dot snipped-for-privacy@foo.com (fwfrog) wrote:

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.
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Am I the only one wondering how blown-in fiberglass at 17 inches is R38, yet at 18.5 inches it's R49? Something there doesn't compute because I don't think that 1.5 inches should make that big of a difference.
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fwfrog had written this in response to http://www.thestuccocompany.com/maintenance/Re-Insulation-Question-361705-.htm : I kind of wondered the same thing. Seems like a big price jump for 1.5 inches.
Also, I should edit a previous post... our average electric bill right now is $160-$175 a month (not $60-$75, as I mistakenly calculated).
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fwfrog wrote: ...

I really hadn't paid any attention to the actual quotes, etc., as it's such a generic question and I would still recommend the energy audit from an independent particularly if the utility company has them at minimal cost as many do.
But, the answer to the specific question is the estimates aren't right. I don't know the particular product but a typical blown fiberglass R value is 2.5/inch and that is fixed for a given product. So,unless they quoted a different insulation material the R values should be directly proportional to the installed thickness within roundoff.
As someone else noted, cost would be expected to go down on an incremental basis as the material cost goes up compared to the fixed costs as time differential is pretty small.
One additional thing to be noted in blowing into an attic -- be certain the soffet vents don't get blocked cutting off the necessary circulation.
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Perhaps both include the fixed cost of showing up.
Nick
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On Feb 28, 12:41�pm, snipped-for-privacy@ece.villanova.edu wrote:

expandiong foam is far better as it expands it seals air leaks that make up much energy loss.
fiberglass cant seal holes
the foam will seal the air leaks around wiring boxes
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On Feb 28, 12:41pm, snipped-for-privacy@ece.villanova.edu wrote:

Two points:
1 - He said the R values should be proportional to the installed thickness, which is true and costs don't factor into that
2 - If you allow for fixed costs, then getting 2X the inches of insulation should cost less than 2X the price. In his quotes, in one case, it costs MORE per inch for the thicker blown-in insulation.
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On Feb 27, 6:37pm, snipped-for-privacy@optonline.net wrote:

Good question , but I bet its not 17"
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fwfrog had written this in response to http://www.thestuccocompany.com/maintenance/Insulation-Question-361649-.htm : UPDATE:
Here's the breakdown for the original company that quoted us: R-30 (12 inches) - $200 R-38 (17 inches) - $460 R-49 (18.5 inches) - $709 All I know is that it is blown-in fiberglass of some sort.
Here's the breakdown for the second company that quoted us: R-38 - $548 R-49 - $698 (inches not verified) This is the material that will be used, I believe: http://tinyurl.com/blown-in
And from what I can gather, it looks like R-38 is a recommended minimum in our area. http://www.simplyinsulate.com/savings/index.html
I'm not sure, but I think perhaps paying for expensive foam (which no one quoted as of yet) would be overboard... but R-49 fiberglass from the second vendor would be a good deal in the long run (rising energy costs, resale value, etc.)
Thoughts?
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On Feb 27, 10:23pm, jessmprice_at_yahoo_dot snipped-for-privacy@foo.com (fwfrog) wrote:

So, just as I thought, something doesn't add up in the stated amounts here. According to the link you provided from JM, for that insulation:
R30 = 12.4" R38 15.3 R49 19.1
So, the first company's quote looks totally wrong. It's impossible for 1.5" more insulation to take it from R38 to R49. Plus, neither the R38 nor the R49 correspond to the JM datasheet. I'd get rid of them to begin with. If they can't see such any obvious discrepancy in their quote, I don't want them around my house.
The second one looks more consistent, but we don't know the inches. Assuming the are using the JM material, then you are paying $35.82 per inch with the R38 and $36.54 per inch with the R49. That wouldn't seem to be right either. One would think that with the larger amount of insulation, the cost per inch would be less, not more. I base that on the fact that there is a certain overhead for doing the job, regardless of the inches blown in. Meaning the time spent quoting you, travel time, set up time, clean up, etc are all independent of whether they blow in 15 inches or 19 inches. There may be some issues that make the extra 4 more difficult, so that it would drive up the cost per inch of the whole job, but I tend to doubt it.
I would insist on the following in ALL quotes:
Specify the material and manufacturer Specify the installed inches and R value.


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