wall insulation

[Mark Modrall]

Hi...

We're having some remodeling done that involves pulling off some drywall here and there. The house is not very well insulated, and we were thinking of re-insulating at least the parts that get exposed.

The contractor told me that r-19 is as high as you should go in walls and that taking a thicker bat of higher r-value would just get compressed in the wall and lose its efficacy.

It just sounded odd that we haven't improved the r-value of wall insulation in 30+ years.

What's the best you can do for wall insulation these days?

Thanks Mark

[dpb]

Mark Modrall wrote: ...

For fiberglass in 2x4 wall cavity, that's true.

Fiberglass is still fiberglass -- can't do much to change that...

There's a much higher R-factor per inch for solid foam products than fiberglass although I don't recall the number otomh, it's easily googled (just I'm not going to bother... :) ).

It's more expensive, of course, but then again, you get more, too. Unfortunately, though, unless you do something about the other areas that aren't insulated as well, you're not going to see anyways near the increase in overall effectiveness that you're hoping for.

Depending on what you do have, it could possibly be cost-effective to simply pull the walls at one time and do it all or investigate the fill-in systems that don't require access other than small holes to patch later. That, of course, depends on details not provided as to what is there now.

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[benick]

Not much you can do about R Factor of insulation in a wall just doing patch jobs here and there...Now if you were doing a total gut there are things you could do....Like spraying it with Polyurethane Foam....

[Rick Blaine]

How much money do you want to spend? Spray foam will get you in the 20s, but isn't cheap. Spray cellulose is also slightly more efficient than fiberglass and will also improve noise reduction over fiberglass.

[Paul M. Eldridge]

Hi Mark,

Assuming you'd prefer to stick with batt insulation, Roxul's Flexibatt is rated at R22. It's a really nice product that's easy to work with (it doesn't itch like traditional glass batt).

See:

If, however, you're looking for maximum R-value and money is no object, high density close cell polyurethane foam can't be beat, but it's not something a D-I-Y'er can tackle on their own.

See:

Cheers, Paul

[Edwin Pawlowski]

He's mostly right with 2 x 4 framing. There are some foam sheets that can top that, but they are very expensive by comparison. Fiberglass batts are at about the limit of technology for that material. If you add framing to make a 2 x 6 equivalent you can add more insulation.

Insulation depends on air to do the work and compressing thicker batts will reduce the amount of insulating value.

[Wayne Whitney]

For a given thickness cavity, denser insulation will have a higher R-value. For a 3.5" cavity, you can get low density (R-11), medium density (R-13) and high density (R-15) fiberglass batts. So if you took a medium density 5.5" batt (R-21) and stuffed it in a 3.5" cavity, you would lose R-value relative to the R-21, but you'd still be higher than R-13.

Cheers, Wayne

[hallerb]

closed cell spray foam about R6 per inch, plus its a self vapor barrier, and best of all it expands and seals all air leaks, making for a draft free quiet room, since air leaks carry noise...........

if it were me i would go foam since even though it costs more over time its bound to pay for itself

[S. Barker]

Fiberglass - R-13/15 in a 3.5" wall and R-19 in a 5.5" wall. Slightly better with cellulose. The new fangled closed cell foams claim a lot more, but i'm not up on those.

s