Fiberglass bats vs roll prices

Pa_Kettle · November 07, 2007, 11:29:21 PM

The Home Depots out by me have rolls of 15"x32' (40 sq. ft) R-13 insulation for $9.68. This comes out to $.24 per square ft. They have R-13 bats in 15"x93" in groups of 11 (106.65 sq. ft.) for $42.62. This comes out to $.40 per sq. ft.

So, am I missing something here? Why is one so much more than the other? They are both kraft paper backed, R-13 fiberglass insulation.

BTW - I noticed the r-19 in either bats or rolls were about the same price.

Thanks,
PK

glenn kangiser · November 07, 2007, 11:31:48 PM

Looks like it's cut it yourself and save.

November 07, 2007, 11:32:34 PM

Possibly just the deals their buyers get.

MountainDon · November 08, 2007, 12:12:21 AM

QuotePossibly just the deals their buyers get.

You most likely hit that nail right on the head. Pricing does not always make sense, nor does it have to. It always pays to calculate all your options. You never know what might work best until you run the numbers!

MikeT · November 08, 2007, 10:04:14 AM

Related question:
Am I looking for trouble if I buy and install reclaimed/salvaged batt insulation?

I was looking at a huge house that was built my an engineer here in Portland, OR and the new owners demolished the entire thing and built an even bigger ode to opulence. Anyway, the new builders are trying to sell salvagable parts of the old house (it was built a decade ago). One of the items they have is all the fiberglass insulation. It is dry and is being kept undercover ( in a big barn). I think I can get it for next to nothing.

Thoughts?

November 08, 2007, 01:04:29 PM

Can't really hurt it if it's clean and dry and meets the insulation requirements the inspector will be looking for.

Redoverfarm · November 08, 2007, 03:54:43 PM

I priced R-19 at Lowes and they both (batts and rolls) came out to $.43 each sq ft. Go figure.

FrankInWI · November 08, 2007, 05:22:39 PM

insulation gets it's insulating value from the air cells left open between the fiberglass strands I believe. If you compress firberglass insulation it looses value. I wonder how compressed portions of salvaged insullation might be. May be a penny wise, pound foolish decision?

MountainDon · November 08, 2007, 06:20:24 PM

QuotePossibly just the deals their buyers get.

Further on pricing.... Today I needed some clear plastic to cover a wood pile. I've been buying 4 mil 10' x 25 ' rolls. Went into HD. As I was about to pick up a single roll I noticed that the twin packs were marked down. Single roll $13.something. Twin pack $9.98, marked down from $19.98. More "go figure". I bought 2 twin packs.

November 08, 2007, 06:45:34 PM

That's enough to build a house out of.

Redoverfarm · November 08, 2007, 07:25:04 PM

I was always told tht for every inch the insulation is compressed you loose 1 R-value. I'm sure someone can give the accurate formula.

MountainDon · November 08, 2007, 08:03:17 PM

Voila! From Owens-Corning

Redoverfarm · November 08, 2007, 08:21:18 PM

Hint, Hint I knew you would have it. It doesn't take long on the board to learn.

Pa_Kettle · November 08, 2007, 11:31:54 PM

Thanks everyone for the quick responses. I was primarily concerned that I had missed some major difference between the two. I'm going to grab all the R-13 rolls I need tomorrow.

We are finally going back up to the cabin this weekend, after a 6 week down time...

BTW - That's a very cool chart Don.

PK

November 11, 2007, 06:05:35 PM

So I thought too much and came up with a puzzler.

Looking at that chart I posted you'll note that installing R-19 fiberglass (nominal thickness 6.25") in a 2x6 framed wall (cavity depth 5.5") results in the compressed insulation having an R-value of 18.

Installing R-21 fiberglass (nominal thickness 5.5") in the same 2x6 wall retains the R-21 insulation value.

So why does my Home Depot sell R-19 and not R-21 when virtually all exterior wall construction around here is done with 2x6's?? For that matter why does Owens-Corning even sell the R-19 that's 6.25" thick??

glenn kangiser · November 11, 2007, 06:54:59 PM

...and does R21 cost more or less than R19?

MountainDon · November 11, 2007, 07:00:31 PM

Quote...and does R21 cost more or less than R19?

Breaking news....
I can't find a price listing on the R21 online. You would assume it would be more, but then,

?

More as this story develops.

glenn kangiser · November 11, 2007, 07:30:47 PM

JM lists R21 in their PDF brochure and I found Spider insulation I hadn't heard of before.

http://www.jm-builder.com/spider.php

http://www.jm-builder.com/products.php

No pricing though.

MountainDon · November 11, 2007, 08:59:38 PM

No JM retailers in my area; only an installation contractor. Spider looks interesting.

From the Owens-Corning website:
"Your exterior walls will be comprised of either 2x6 or 2x4 studs. 2x6 stud walls allow for more insulation because of their extra depth. Depending on local codes or your desired R-value for the wall, you may use 5 1/2" thick R-21. R-19 fiber glass batt insulation (6 1/4" thick) can also be used. Compressing it into a 2x6 cavity will lower the R-value to R-18. For 2x4 stud walls, the choices are R-15 or R-13, both of which are 3-1/2 inches thick."

I think there are a lot of folks out there with one less "R" than they think they have.

Lowe's website doesn't list any fiberglass products. :-/