Lets talk insulation

[Sledhead00]

Soo Ive got some insulation work ahead of me after a water line freezing and bursting... Here's my scenario...
This is in my attic where it meets up against the warm side... It's studded out with 2x4 and they(someone before me) put r-19 in the cavity and then put up basic white Styrofoam to the cold side...
I was going to take it all out and replace it with r15 roxul and a r10 foam board but then I got to wondering that even though your not suppose to put r19 in a 2x4 cavity I wondered just how compromised is r19 in this situation...I mean is likely to still have a higher value than the recommend r13 or will it be lower...(It's not super crammed or pressed in there tightly but )
Secondly, not all of the r19 got wet and I do have a spot where I could use it what's still good, but having been in a slightly compressed state for at least several yrs is no longer going to be effective even in the right setting??

 

[Isaac Carlson]

I quit using fiberglass long ago. It is a mess and does not stop air movement. It does not insulate once wet and is a pain to mess with. I had to put some in today for a friend and it was a nightmare for me. I have started using foil covered bubble wrap stuff and love it. It is easy to work with, no mess and works great. You can put multiple layers in with air spaces between and multiply r-value.

Do not tell me it only has an r value of 1 or 2. I have used it. It is good stuff. It reflects heat back and is also a good thermal break. I insulated my op up ice house with it and can fish in a t-shirt in freezing temps. I was cold in my arctic gear without it.

 

[billb3]

Some claim 6 inch thick R-19 compressed into a 3-1/2 in space is R-13 effectively and squeezed into a 5-1/2 inch space is only R-16.

Dunno if I like the foam on the cold side if it actually acting as a seal (taped seams ) and vapor barrier unless you run an air conditioner in the Summer.

 

[Sledhead00]

I quit using fiberglass long ago. It is a mess and does not stop air movement. It does not insulate once wet and is a pain to mess with. I had to put some in today for a friend and it was a nightmare for me. I have started using foil covered bubble wrap stuff and love it. It is easy to work with, no mess and works great. You can put multiple layers in with air spaces between and multiply r-value.

Do not tell me it only has an r value of 1 or 2. I have used it. It is good stuff. It reflects heat back and is also a good thermal break. I insulated my op up ice house with it and can fish in a t-shirt in freezing temps. I was cold in my arctic gear without it.

What you said about fiberglass are my thoughts on why I don't care for it either.. From what I've read about the roxul stuff it cuts like butter not to mention the better R... I will certainly take a look at the foil wrap stuff this weekend though..

Some claim 6 inch thick R-19 compressed into a 3-1/2 in space is R-13 effectively and squeezed into a 5-1/2 inch space is only R-16.

Dunno if I like the foam on the cold side if it actually acting as a seal (taped seams ) and vapor barrier unless you run an air conditioner in the Summer.[/quote]

Could you explain that a little further... Not sure what you mean...

 

[DickRussell]

Here is a link to an Owens-Corning table showing R values of various fiberglass batt products when installed to various framing cavity depths. In general, compressing the batt increases the R per inch of thickness, but decreases the total R due to the decrease in cavity depth.
(broken link removed)
As you see, the batt labeled "R19" is what it is tested to be at a thickness of 6.25 inch. Installed in a 2x6 cavity (5.5 inches deep), it's only R18. Compressed into a 2x4 cavity (3.5 inch), it's R13. It works fine that way, but just has the reduced R resulting from the shallower depth, even the R/inch has gone up from 3 to 3.7 per inch.

Be sure that you have the batt enclosed on all six sides. You don't want the unfaced side of the batt open to the air, or you'll get air currents moving up slowly through the batt, cutting its effective R value. Having the white styrofoam (EPS) on the outside serves the purpose of enclosing the batt to avoid the convective looping. It also is sufficiently vapor permeable to avoid "wrong side vapor barrier" issues. Having a thicker foam board on the cold side decreases the permeability of it, but the approach works fine if it's thick enough to keep the warm side of it above the dew point of inside air. Here's an article on how much thickness you need: http://www.greenbuildingadvisor.com...lating-minimum-thickness-rigid-foam-sheathing.

 

[woodgeek]

I agree with what Dick said ^^^. Sometimes when you shop for FG, you can find the R-19 costs the same as the R-13 on a sq ft basis. Then I always get the R-19 and compress it.

Your plan for changing out the FG + EPS for Roxul + R-10 will not likely make a big difference in heat loss. If the EPS is 1", and thus R-5, (you don't say) you might be going from R-10 for the 2x4 section (due to thermal bridging) + 5 (EPS) = R-15, to R-20. I would never waste time ripping out and replacing insulation to take the R-value from 15 to 20.

There have to be lower hanging fruit, likely in airsealing. It sounds like a kneewall, have you checked that the joists under the kneewall are airsealed?

 

[Isaac Carlson]

On the subject of thermal bridging..... We will be insulating our house this year. I plan on framing 2x4 walls on the inside or outside of the existing walls with the studs offset from the original studs. I will be putting bubble foil insulation between the walls to make an air break and reflect heat. This would give me a double wall with no thermal bridge and would bump the r value from near zero to maybe 40. It will cost a bit but will be well worth it. I built a house for a friend and did something similar with an air break and he heats his place with an electric boiler for $100 month. It was 30-60 with 2 floors. Air movement is a big deal when you talk about insulation. Stop air movement and you multiply r-value. Fiberglass does not stop air movement or heat. It is only a bad conductor.

 

[Sledhead00]

I agree with what Dick said ^^^. Sometimes when you shop for FG, you can find the R-19 costs the same as the R-13 on a sq ft basis. Then I always get the R-19 and compress it.

Your plan for changing out the FG + EPS for Roxul + R-10 will not likely make a big difference in heat loss. If the EPS is 1", and thus R-5, (you don't say) you might be going from R-10 for the 2x4 section (due to thermal bridging) + 5 (EPS) = R-15, to R-20. I would never waste time ripping out and replacing insulation to take the R-value from 15 to 20.

There have to be lower hanging fruit, likely in airsealing. It sounds like a kneewall, have you checked that the joists under the kneewall are airsealed?

I should've worded my original post better. I'm replacing the insulation due to the water line bursting and soaking the insulation that was there. About half was destroyed so im just redoing the whole wall. I can use the remaining good r19 elsewhere.
I don't believe the white styrofoam board that was there had any r value to it. So the 1" tuff-r foam should be a upgrade.

 

[semipro]

I will be putting bubble foil insulation between the walls to make an air break and reflect heat.

Have you considered foil faced polyiso or xps sheets instead?-- probably more effective at less expense.
Also, if your radiant barrier is not facing an air space it is ineffective.

 

[ksc]

I'd skip the bubble wrap too...

http://www.greenbuildingadvisor.com/blogs/dept/musings/stay-away-foil-faced-bubble-wrap

 

[Swedishchef]

What about spray foam? The high density stuff?

Andrew

 

[midwestcoast]

I should've worded my original post better. I'm replacing the insulation due to the water line bursting and soaking the insulation that was there. About half was destroyed so im just redoing the whole wall. I can use the remaining good r19 elsewhere.
I don't believe the white styrofoam board that was there had any r value to it. So the 1" tuff-r foam should be a upgrade.

Not sure why you consider the existing foam board useless. That stuff is called EPS (expanded polystyrene). It is kinda fragile & flimsy compared to the pink board (XPS) but the r-values aren't much different. EPS about r-4 per inch. XPS = r-5 per inch. If it isn't busted up you can reuse it.
Priority #1 as Woodgeek states is air sealing the knee wall before re-insulating. Especially blocking the joist bays running from under the living space floor into the side attic. That may mean digging up some of the attic floor insulation to check.
Roxul should be easier to install perfectly & give you a bit better performance, but I'd spend the money on thicker foam. Same amount of work, more R-value, less chance of condensation in the wall.

 

[Knots]

My house walls are insulated with this stuff:

http://www.icynene.com/en-us

There's contractors that apply it to existing houses.

 

[Swedishchef]

Nothing can beat spray foam...

 

[Knots]

Nothing can beat spray foam...

It fills up just about every nook and cranny...

 

[brian89gp]

I had medium weight spray foam put into a house, . Night and day difference and will gladly pay the premium on all future projects to get spray foam.

 

[Swedishchef]

My entire basement was spray foamed with high density closed cell before I put up any walls. It was especially worth it in the rim joists.

Andrew