Insulation survey

Started by John Raabe, December 17, 2009, 01:33:04 PM

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pagan

doug,

Still go tight and then crack a window in the winter when you want some fresh air.

OlJarhead



OK still looking for an answer here (maybe I'm just dense and didn't see it?)....

I have two options available to me (do to location, experience, knowledge, funds, and oh ya, location) so was wondering which is better.

1.  As pictured: 1" foam board insulation and 4 1/2" Fiberglass batting with 6mil plastic vapor barrier
2.  No foam board with 5 1/2" Fiberglass batting with 6mil vapor barrier.

My thinking was that maybe the foam board would increase the R level and cut down on air movement.

Thanks


poppy

Jarhead, I don't like the idea of foam board between the studs.  You still have a thermal bridge across the studs, plus more joints for potential leaks.  Plus how do you secure the foam board?

Instead of 1" board between the studs, how about 1/2" board across the face of the studs with 5 1/2" between the studs.

The effective R value is what you're looking for, not just adding up 4 1/2" of fiberglass plus 1" of foam.  The thermal bridging reduces the effecive R value of the wall system.


pagan

#53
I would use a sandwich of 1 inch Hi-R foam board on both sides of the stud wall which will give you R14 right there.

MountainDon

The question is first, how much insulation is required? In many ways a I agree that more insulation is better. However....

My main criticism with insetting the foam panels like that is twofold actually. 1. it is a lot of work cutting those to fit snug within the stud bay. That also will involve a lot of foam edge to stud sealing. That comes from experience on a small trial project years ago. 2. With the cost of foam the results are much better using the foam panels over the studs to break the thermal leak at the stud.

Just because something has been done and has not failed, doesn't mean it is good design.


bmafg

I wonder if anybody makes a paper surfaced foamboard that could be used and finished in place of drywall.
Jim

RainDog

Quote from: bmafg on February 16, 2010, 03:57:07 PM
I wonder if anybody makes a paper surfaced foamboard that could be used and finished in place of drywall.
Jim

Dow manufactures a product, Thermax Heavy Duty (HD), that I believe fits the criteria. Runs about 30 bucks a sheet.

http://www.silvercote.com/PDF/ThermaxHDLit.pdf

NE OK

OlJarhead

Thanks all -- good points.

In truth I don't know that I need anymore then the 5 1/2 batts but it was something I've been wondering.

I suspect my actual installation won't include the foam but many topics here made me consider it -- I guess it comes down to the need more then anything.

In my case I'm less worried about winter cold as I am about summer heat -- which lead me to consider this.

So, perhaps the real benefit would be in the ceiling since it will get more direct sunlight in the summer?

MountainDon

Quote from: OlJarhead on February 16, 2010, 05:25:24 PM
In my case I'm less worried about winter cold as I am about summer heat -- which lead me to consider this.

So, perhaps the real benefit would be in the ceiling since it will get more direct sunlight in the summer?

Good point there. I believe any dollars and time you spend installing the highest R-value in the roof will give you the greatest comfort payback. My nearest neighbor in the mountains has a 16x24 cabin with a loft design similar to yours. In summer his cabin is always warmer (some days Hot) than ours. I think he has 2x6 rafters, maybe 2x8, and I'm not sure on how it is insulated other than he used fiberglass.
Just because something has been done and has not failed, doesn't mean it is good design.


eggman

Quote from: RainDog on February 16, 2010, 05:09:59 PM
Quote from: bmafg on February 16, 2010, 03:57:07 PM
I wonder if anybody makes a paper surfaced foamboard that could be used and finished in place of drywall.
Jim

Dow manufactures a product, Thermax Heavy Duty (HD), that I believe fits the criteria. Runs about 30 bucks a sheet.

http://www.silvercote.com/PDF/ThermaxHDLit.pdf



This is a great thread.

Never heard of this thermax stuff. Where do you get it?

Here's my situation. I have a cabin with 2x4 walls that I will never let fiberglass touch again bcause of the mice. They love the stuff. And I don't like sheetrock. So now you have me thinking I can nail this thermax stuff on the 2x4's, fill the cavity with loose pack cellulose diy if there is such a thing. Then I can put my reclaimed barn board over the thermax.


Thoughts? Concerns?

RainDog

Quote from: eggman on February 16, 2010, 08:37:46 PM


Never heard of this thermax stuff. Where do you get it?



Gee... tried looking for distributors, I'm curious myself, and this is about the best I could come up with. From Dow's "Find Answers" database:

http://dow-styrofoam.custhelp.com/cgi-bin/dow_styrofoam.cfg/php/enduser/std_alp.php?p_prod_lvl1=15&p_cat_lvl1=50

Question
     Where can I purchase THERMAX*, TUFF-R*, or other polyisocyanurate foam insulation products made by The Dow
        Chemical Company?

Answer
     There are hundreds of distributors across the United States for THERMAX, TUFF-R, STURDY-R, or other 
         polyisocyanurate foam insulation products. However, these polyisocyanurate products are not sold in Canada or     
         Mexico.

         Call 1-866-583-2583 for information on the distributors nearest to you.
_______________

  Well, guess you could call the number? Good luck, and let us know if you find a dealer, please.
NE OK

eggman

Thanks for the link raindog.

eggman

Does anyone know where to get diy cellulose?


pagan

eggman,

Most lumber supply companies carry cellulose.


eggman

Quote from: pagancelt on February 17, 2010, 07:53:59 AM
eggman,

Most lumber supply companies carry cellulose.

Thanks. Do you need to have a blower? Here's my latest idea. I want to put barn board walls up and leave the top open. Then I want to hand load cellulose into the wall from the top.

Do I need sheet rock since cellulose won't burn?

The walls are 12 x 24.

pagan

You don't need sheetrock. You do want to use a blower though and you should be able to rent one from a local rental company. Go to youtube and do a search for dense packed cellulose and a whole bunch of videos should come up. It's not complex, but it can be messy and you'll get a far better pack using the blower. I would recommend using 6 mil poly on both sides of the wall if you're going to be using barn boards because this will keep the cellulose from blowing through the cracks when you dense pack. It isn't really necessary as a vapor barrier because moisture cannot transfer through dense packed cellulose. You don't need to leave the top sill open, rather you drill a hole in the sheathing, it doesn't matter if it's interior or exterior, to access the cavity and then you snake the tube up into the cavity. As the cellulose dense packs it'll back up into the tube and you pull it out a little bit, repeating this step as it backs up. You continue doing this, periodically shoving the tube back up as far as it'll go, until the cavity is completely packed. By shoving the tube up and down into the packed cavity you ensure a complete and thorough dense pack.

You can also use a sandwich of Hi-R foam board. If you use foam board you can cut your access hole through the foam, sealing the hole with some spray foam when the cavity's dense packed, and then put your siding up over that.

RainDog


Lowes will lend you the blower for free if you buy a certain number of cellulose bricks. 25, maybe? Then you can return the unused packages. *wink wink* *nudge nudge*

  :D
NE OK

poppy

pagan
Quotebecause moisture cannot transfer through dense packed cellulose.
Are you sure about that?  ???

pagan

That's what the literature states. Air cannot travel through dense packed cello so moisture has no method of movement. This link is from a manufacturer recommending against vapor barriers with cellulose.

http://www.paulseninsulation.com/docs/vaporretarder.pdf

JRR

Quote from: eggman on February 17, 2010, 08:15:20 AM

Thanks. Do you need to have a blower? Here's my latest idea. I want to put barn board walls up and leave the top open. Then I want to hand load cellulose into the wall from the top.


I personally hope you will try this scheme ... and report back on results!  I've thought of giving it a try myself ...

The very top section may need some cut-to-fit sections of foam board, against the outside sheathing, to back up the cellulose.


MountainDon

Re: the info letter on cellulose and vapor....

I note the author is referring to "spray-applied cellulose insulation". To me that means wet blown cellulose, sprayed into open bays in new construction. I also find him a little confusing as he mentions polyethylene sheeting but talks about vapor retarders, not barriers. I think of polyethylene being a barrier, you can carry water in it. Kraft paper is a retarder, water will pass through it.

I do recall reading that a vapor retarder is usually not recommended by most manufacturers of cellulose insulation in walls.  I believe this is more important when the interior spaces are air conditioned, that is cooled in summer. That was the point of that post on vapor Barriers for Dummies.

I take issue with the claim that water vapor will not pass through cellulose. In a way that might be true, but in a real world situation I believe the cellulose material will absorb the water vapor much like a piece of solid wood will absorb water from the air. At that point the water is no longer a vapor and can wick through the packed cellulose in one direction or the other depending on where the colder side is located.

In the case of a barn board wall I would recommend applying something like kraft paper or building paper before applying the boards, not polyethylene.

The machines available at my Lowe's and HD are only suitable for loose fill blow in jobs as in an attic. They do not have the smaller hoses that are required for dry blowing cellulose into wall cavities. Here thay have a 15 bag minimum to get the machine free for 24 hours.

Cellulose is treated with a fire retardant. That does not make it fire proof. It makes it burn slower and in a wall can turn the wall into a two hour firewall.
Just because something has been done and has not failed, doesn't mean it is good design.

poppy

Thanks Don, what you report makes sense to me.

Speaking of insulation, I scanned the March issue of Fine Homebuilding magazine today.  There is an article on zero-energy houses.

A couple of things that I noted was that all of the examples used some kind of closed cell foam, either spray or board, and one used SIP's.
No fiberglass or cellulose to be found.

Another thing noted was that a couple of them used earth based heat pumps (I may not have the terminology correct).

And lastly, none of the examples had air conditioning.

pagan

Don,

The ability of cellulose to hold embers is one reason firefighters don't care for the stuff. I've read reports where they've been called back to the same house more than once because the fire flares back up, presumably from the interior wall cavity where the cello held live embers it until they got some air. When we did weatherization work on old houses we never used vapor barriers or retarders. I've spoken with some builders who don't use cello because they say it holds moisture.

Poppy,

I've noticed the same thing regarding net zero homes. Reading about the PassivHaus movement in Germany I've seen that they're using a double stud wall with a sandwich of foam boards and dense packed cellulose in the cavities.


OlJarhead

Quote from: MountainDon on February 16, 2010, 08:08:19 PM
Quote from: OlJarhead on February 16, 2010, 05:25:24 PM
In my case I'm less worried about winter cold as I am about summer heat -- which lead me to consider this.

So, perhaps the real benefit would be in the ceiling since it will get more direct sunlight in the summer?

Good point there. I believe any dollars and time you spend installing the highest R-value in the roof will give you the greatest comfort payback. My nearest neighbor in the mountains has a 16x24 cabin with a loft design similar to yours. In summer his cabin is always warmer (some days Hot) than ours. I think he has 2x6 rafters, maybe 2x8, and I'm not sure on how it is insulated other than he used fiberglass.

Interesting.

I wonder if it would be worth using reflecting (aerofoil type) insulation at the top, then the fiberglass, or perhaps the other way around....thoughts?  I can try to draw up a couple ideas.