[slowjo]

Hello everyone. We are remodeling our 1880 home. Tore out plaster ect. Has 2x4 wall studs. We have been useing the r-19 rated 2x6 (15"x96") insulation becausee its about 10 dollars less expensive than the r-13 15"x6'5"for some reason.

Anyway are we going to get the theoretical r-13 or is the compression actually reducing the r-value beyond that?

In other words, is that just fine or am i shooting myself in the foot?


Thanks!
Josh

 

[Aggie67]

Compressing the insulation will reduce the R value.

 

[Clutchcargo]

You will still get R-13. Unless you really stuff the void, pink insulation will give you R-3.5 per inch. There is a point where you actually get less than R3.5/inch, I'm not sure how tight it needs to be before you get diminishing R-values/inch.
Are you sure you're not getting less linear feet of R19 insulation than the R13?
Another thought, use expanding foam behind the electric boxes on exterior walls.

 

[drtbk4ever]

Are you sure you're not getting less linear feet of R19 insulation than the R13?

My question too.

 

[Gary in WA]

Since fiber glass blankets compress so easily, can I increase the effectiveness of my insulation by squeezing a 5 1/2", R-21 blanket into a 2 x 4 wall instead of using 3 1/2", R-15 blankets?
No. Compressing fiber glass blanket insulation into a smaller wall space will not necessarily increase your insulation's efficiency. Fiber glass insulation works on the principle of trapped air pockets. By compressing fiber glass insulation, you decrease the amount of air trapped in the material. For example, compressing R-19 into a 2x4 wall will give you an R-13 value. It would be better to buy the product that best fits in the space. R-13 or R-15 batts are the best products for a 2x4 wall.
To see a general compression chart, click here.



This from the manufacturer. http://saveenergy.owenscorningblog.com/2006/04/frequently_asked_questions.html Be safe, G

 

[Wildie]

The Owens-Corning web-site states that compression reduces he R value. R20 pressed into a 3 1/2" cavity will result in an insulation value of R13.
There's no harm, but you will be getting less value for your dollar, as R20 is more expensive than R13.

 

[Scuba_Dave]

I'd buy R15 for a 2x4 walls
R19 compressed will give you R13

I doubt heating costs long term are going down anytime soon
So pay now for better insulation, or pay more every year

 

[slowjo]

We purchased the insulation at lowes. the r-19 is actually more linear ft. It may have been a sale of an over stock. I will look into the r15 for the rest of the rooms. We did one room like this so far.

Does anyone have any experience with the cotton bassed batting? Does any of it have a vapor barrier? Hows it perform? I hate fiberglass.

thanks again!
Josh

 

[texas115115]

wrong

There is the same number of air pockets per square inch of r- 11, r-13, r-19,r-30 batts. If you compress a r-19 into a 3.5 inch space you will end up with about r11.5. Reason for it is there are not as many air pockets pre square inch any more. :thumbup:

 

[Clutchcargo]

Good info Gbar.

Texas115, Owens claims R13 for compressed R19 insulation.

Slowjo, If you already bought the R19, I'd use it and stuff it in there. Otherwise go for the R15 as ScubaDave mentioned.
Correcting air infiltration issues (windows, doors, whatever) will give you a better return than insulation alone and with leaky old houses there's a lot of places that can be tightened up.

 

[slowjo]

Correcting air infiltration issues (windows, doors, whatever) will give you a better return than insulation alone and with leaky old houses there's a lot of places that can be tightened up.

Since you mention this, is there a better way to get spray foam? If I use the cans I have to use the whole can up once I start using it or the tip gets plugged up. Is there a reusable product?

 

[paredown]

Funny, I was saying the other day that they are missing a market opportunity--sell the stuff in a case of 24 small cans, enough for a couple of little areas & then you pitch it. Instead HD is all proud of the "new larger can"

The only other thing I've seen (but not tried) is the larger commercial type cannisters that come in various sizes--then use replaceable tips and toss them each time you spray a little...at least that's the theory.

 

[Clutchcargo]

Since you mention this, is there a better way to get spray foam? If I use the cans I have to use the whole can up once I start using it or the tip gets plugged up. Is there a reusable product?

I always think of my route before I start using the spray foam. Window -> Window -> Door -> crack in foundation -> etc.
I think I saw at HD that Hilti makes a reusable spray foam can. I haven't tried it yet though. It was in the Hilti tool section.

 

[jimmy21]

Naw. The can is probably more expensive than the contents. They need to work on just making them reusable. But that would lower sales.

Funny, I was saying the other day that they are missing a market opportunity--sell the stuff in a case of 24 small cans, enough for a couple of little areas & then you pitch it. Instead HD is all proud of the "new larger can"

The only other thing I've seen (but not tried) is the larger commercial type cannisters that come in various sizes--then use replaceable tips and toss them each time you spray a little...at least that's the theory.

 

[concretemasonry]

Everyone is missing the real point when they are talking about the R-Value of the insulation being the R-Value of the wall itself.

The studs are a big part of heat loss reducing the wall R-Value. 2x4 studs at 16" o.c. only reduce the wall R-Value by 10%. Steel studs at 12" o.c. can reduce the wall R-Value by about 40%. Even at 16" o.c., steel studs will still reduce it by 25-30%.

As an example, in a 6" thick wall with fiberglass (R-19) with steel studs could give you a WALL R-Value of about R11.

None of these examples are heavy enough to give you the "mass credit" you get with heavier construction.

Dick