insulation compression?

[1930artdeco]

Hi All,

Slightly off topic in that I am going to gut my room and put insulation in-finally. My question is I want the highest R value I can get and all I see at the big box stores is R-13.

Is there going to be a problem is I stuff R-19 in the walls? The R-13 is 3.5" thick and the 19 is 6.5". I have regular rough cut 2x4 walls so I should have about 4" of play.

What about some of the reflective foam boards and then the R-13?

Mike

 

[DekeT]

This topic is not new and has been the subject of lots of debate. Lots of charts, graphs, links, etc. on compression and its effect on R values. I suggest you do a search on fiberglass insulation and you will get more than enough info to answer your question.

 

[volleyball]

Put 2" of foil hi den foam on the outside of the studs and r 13 in the walls

 

[DekeT]

Put 2" of foil hi den foam on the outside of the studs and r 13 in the walls

Well to answer his question about the highest R value he can attain you would be wrong on R-13 in the walls.

 

[Scott H in Wheaton]

Highest R value would probably come from spray foam, but he probably isn't considering that due to cost.

How cold or hot does it get in Oakland? If you were in the snow belt I could see going for the max possible, but your temps are probably pretty moderate, so you're chasing a vision.

According to the pro's you should have an R13 - R15 in the walls and R30 up to R60 in the attic. Any more than that and you won't really see much if any benefit other than a lighter wallet.

http://www.naima.org/insulation-kno.../how-much-insulation-should-be-installed.html

 

[volleyball]

Well to answer his question about the highest R value he can attain you would be wrong on R-13 in the walls.

He mentioned foil foam. I mentioned putting it on the outside. It will give him better bang for the buck.

 

[1930artdeco]

Thanks guys, I did look but I entered 'insulation', maybe I needed to enter 'fiberglass insulation'. I figured it was talked about but I did not see much in the way of topics. So either I did not go far enough in the search or like I said I entered the wrong phrases.

Scott: I really only gets into the 30's very rarely here. I just like to stay nice and warm in the winter. But if I won't notice that much difference between 13 and 19 I won't bother. However, if I put the foil backed foam boards on the outside and then R-13 and I can get R-20 or more that is an option if it does not cost to much more.

 

[rsanter]

You have rated R value and actual or effective R value
The R value of fiberglass insulation depends on the install quality and the fluff.
If you compress it it will lower the effective R value.
Air leaks will reduce the effective R value.
Ideal install is that you want max fluff and 6 sided contact for fiberglass to work it's best.
Any compression or gaps drops R value a bunch.
On the cheap you can use caulking around the perimeter of the outside of the wall and do a quality install of the fiberglass. Minimize external openings and seal with foam any holes for wiring into the wall from the attic.

Bob

 

[megalo]

You can get R15 fiberglass insulation at some stores. Menard's has it here in St. Louis. It's probably 30%+ more than R13 - but still pretty cheap.

Also, a 2x4 wall is 3.5" deep.

 

[GYPSY400]

Put 2" of foil hi den foam on the outside of the studs and r 13 in the walls

X2 this would be the best bang for his buck..
But In Oakland, freezing is not a concern like Me up here in Sudbury, Canada.. So I think R13 by itself would be "good enough".. Also, this would help keep the heat out in the summer.

 

[volleyball]

I lived near Oakland years ago. The insulation is used for more than just saving heat.
Even putting a thin foam board on the inside, and then the R13 will help, especially with radiant heat.
If you don't have to reside, it isn't as cost effective.

 

[ddawg16]

You can put R19 in the walls....but the additional benefit is minimal.

On the walls, thermal bridging is more of an issue....hence, any increase in insulation is negated by the thermal bridging....i.e., thermal transfer through the studs.

If it was me...and you were really worried about it....R13 in the walls and then at least 1" of foam on the outside....assuming your doing siding. The 1" of foam will drastically reduce heat loss due to thermal bridging.

But also remember that a majority of your heat loss is through the ceiling and windows. If you have not upgraded your windows....well, your not going to see much improvement.

 

[DENALIAKITAS]

Mooney Wall, eliminates thermal bridging and increases R Value greatly in a 2x4 stud wall. http://www.builditsolar.com/Projects/Conservation/MooneyWall/MooneyWall.htm

 

[NUTTSGT]

Did these walls lack insulation before ? If they had none, anything you put in there will drastically change it for the better.