Author Topic: Foam Board Insulation Installation (between studs)  (Read 7893 times)

0 Members and 1 Guest are viewing this topic.

Offline DirtyLittleSecret

  • Full Member
  • ***
  • Posts: 166
  • This is gonna hurt...
Foam Board Insulation Installation (between studs)
« on: September 08, 2009, 05:18:58 PM »
Q: What is the "typical application" for installing closed cell foam boards within studs...I see alot of info for exterior or in conjunction of fibreglass, but how about "instead of fibre"?  I'm guessing its a cut to fit, add adhesive, and insert with some dimension of breathing space between walls, add vapor barrier, and then interior siding/gypsum board?
Thumb, meet hammer...hammer, meet thumb...

Offline MountainDon

  • Administrator
  • Journeyman
  • *****
  • Posts: 15,847
  • Jemez Mountains, NM; that's pronounced HEY-mess
    • My 15.75 x 30 Jemez Cabin
Re: Foam Board Insulation Installation (between studs)
« Reply #1 on: September 08, 2009, 05:39:04 PM »
Cut to fit is right. Cut very careully for a tight fit. Gaps must be filled; maybe use foam in a can to fill gaps. Installed tightly and sealed in place the foam is its own vapor barrier. It should be installed tight against the exterior wall and sealed with no air space between it and the outside wall. That is to prevent the formation of condensation against the colder outer wall.

For my money foam board is best used as it comes, in large sheets with the joints between sheets sealed with tape. Placed on the exterior usually it helps make a more air tight building and helps remove the heat loss through the studs. Solid wood has much less R-value than any other insulation.

If you are after wall insulation that is better, more efficient, than fiberglass batts have a look at wet blown cellulose. Done by an experienced installer it is hard to beat. It is not a do it yourself product.

Sprayed in place foam insulation like icynene is a great product, superior to most everything else. It also carries a superior price tag. It insulates and seals air leaks all at once.

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

If you didn't have the time or money to do it right in the first place, when will you get the time and money to fix it?

Offline MountainDon

  • Administrator
  • Journeyman
  • *****
  • Posts: 15,847
  • Jemez Mountains, NM; that's pronounced HEY-mess
    • My 15.75 x 30 Jemez Cabin
Re: Foam Board Insulation Installation (between studs)
« Reply #2 on: September 08, 2009, 05:43:28 PM »
Keep in mind that the above information does not necessarily apply to hot humid climates with air conditioned (cooled) interior spaces.
Just because something has been done and has not failed, doesn’t mean it is good design.

If you didn't have the time or money to do it right in the first place, when will you get the time and money to fix it?

Offline DirtyLittleSecret

  • Full Member
  • ***
  • Posts: 166
  • This is gonna hurt...
Re: Foam Board Insulation Installation (between studs)
« Reply #3 on: September 08, 2009, 06:58:59 PM »
Thanks Don,
Trees are changing colours and there was a bite of autumn in the air the other night.  Thinking its time to consider insulation and a vent free blue flame propane heater...
Last question if you dont mind: I was considering the foam with foil backing as it has a higher R value for the roofing and noticed that big pink sells "gap fillers" to keep the foam panels from touching the actual roof osb/zip panels.  Is there a different technique for installing foam insulation in floor joists and/or roof rafters?
Thanks again!
Thumb, meet hammer...hammer, meet thumb...

Offline MountainDon

  • Administrator
  • Journeyman
  • *****
  • Posts: 15,847
  • Jemez Mountains, NM; that's pronounced HEY-mess
    • My 15.75 x 30 Jemez Cabin
Re: Foam Board Insulation Installation (between studs)
« Reply #4 on: September 08, 2009, 07:40:57 PM »
I have noticed that roofs are frequently shown with an air space and walls are not. ???   Have you read anything on the Building Science website? It has a wealth of information on building and insulating for different climates.

Here's a link to the index page on climates...   http://www.buildingscience.com/doctypes/primer

Vapor barrier info link...  http://www.buildingscience.com/documents/information-sheets/3-water-management-and-vapor-control/info-sheet-310-vapor-control-layer-recommendations


One last note; [soapbox ON:] Maybe it's just me but I do not like vent free heaters at all. When operating properly they should not produce CO. They do consume O2 from the air. They do have O2 sensors that are supposed to turn the unit off when the O2 level is depleted to an unsafe level. Too many IF's for me, especially if you build a small air tight cabin. The smaller the enclosed space the less O2 there is to begin with. Low oxygen levels will cause even a perfectly tuned appliance to produce CO.

A side note; some tankless water heaters come with warnings against use in small spaces as they can quickly consume enough O2 to cause dangerous conditions.

A direct vent heater will involve more labor to install. I know that, I've been putting of the job in our cabin. However, I believe they are the only safe type of propane heater to use.

[soapbox OFF:]
Just because something has been done and has not failed, doesn’t mean it is good design.

If you didn't have the time or money to do it right in the first place, when will you get the time and money to fix it?

Offline DirtyLittleSecret

  • Full Member
  • ***
  • Posts: 166
  • This is gonna hurt...
Re: Foam Board Insulation Installation (between studs)
« Reply #5 on: September 08, 2009, 08:06:22 PM »
Thanks for the link.  I remember seeing that, but lost it before I could save it. [cool] Unfortunately it does not look as though they have anything of material use for foam insulation.   ???
I was also thinking of using a propane sailboat heater, but was told it would not meet any residential codes.
Wasnt planning to use the vent free as an all nighter, but rather just to take the chill off before bed and in the mornings while making coffee, etc.  I've also installed a combo detector as a last resort for redundancy.  Dont want to wake up purple. :-[
« Last Edit: September 08, 2009, 08:25:05 PM by DirtyLittleSecret »
Thumb, meet hammer...hammer, meet thumb...

Offline upa

  • Junior Member
  • **
  • Posts: 95
Re: Foam Board Insulation Installation (between studs)
« Reply #6 on: September 08, 2009, 09:47:36 PM »
One of the other draw backs to ventless propane heaters is they throw off a ton of moisture as a by product of combustion. I would seriously worry about mold from continued use in a tight cabin. I ran a heater in my garage one winter and all my tools started to rust.

Offline Squirl

  • Journeyman
  • *****
  • Posts: 2,153
Re: Foam Board Insulation Installation (between studs)
« Reply #7 on: September 09, 2009, 05:34:41 AM »
Thanks for the link.  I remember seeing that, but lost it before I could save it. [cool] Unfortunately it does not look as though they have anything of material use for foam insulation.   ???
I was also thinking of using a propane sailboat heater, but was told it would not meet any residential codes.
Wasnt planning to use the vent free as an all nighter, but rather just to take the chill off before bed and in the mornings while making coffee, etc.  I've also installed a combo detector as a last resort for redundancy.  Dont want to wake up purple. :-[

If you are worried about residential codes, ventfree sometimes does not meet them either, at least as a primary heater. It usually says so on the box and in the instructions "for backup heat only,  NOT INTENDED TO BE USED AS A PRIMARY HEAT SOURCE." Use in a well ventilated area.  Ventfree recommended use is 4hrs per day or less.  Some states they are illegal all together. This could be different with your individual code officer. 
You can check for compliance here.
http://www.ventfree.org/content/view/36/53/
« Last Edit: September 09, 2009, 05:53:49 AM by Squirl »

Offline Squirl

  • Journeyman
  • *****
  • Posts: 2,153
Re: Foam Board Insulation Installation (between studs)
« Reply #8 on: September 09, 2009, 07:14:15 AM »
Also on a cost per R Basis foam board does not usually compare to fiberglass or cellulose.  There is a reason that people usually put it on the outside.  I would take advantage of the space in between the studs for the most cost effective solution.  Plus the time savings would be tremendous.  
I break down my view.  So you have a 12 x 16 x 8 Chalet with a 12 x 6 area for the wall up to the roof.  Around 520sqr ft.  I did the estimates without windows and doors, but I will keep it consistent for comparison.  122 sq. ft. package of R-19 fiberglass costs $54 at the big box stores.  So it would cost around $200 for R-19 walls of fiberglass.  A 4x8 1" R6.5 sheet of foam insulation costs $20 at the big box stores.  So that would be around 50 sheets to equal the same R value (520 sqft / 32sqft per sheet * 3 layers) or $1000.  So to equal the price of fiberglass between the studs, foam would have to cost less than $4 per 4x8 sheet.  This does not even account for the amount of labor involved, or the cost of the cans of spray foam for gaps.  

The maximum R value you could get from rigid foam in a 2x6 wal is 5.5 in.* 6.5/R per in.= R37.5.  It would cost around $1800. (520 sqft / 32sqft per sheet * 5.5 layers * $20) In this method you would also not take advantage of the coverage of the studs for stud heat loss.  Or you could get R38.5 by putting fiberglass between the studs and 3 layers of foam on the outside for $1200.  This would save you the labor of cutting up the foam and it would give you the advantage of insulating the studs.  Also rigid foam is just what the name implies, rigid.  To a remote site, fiberglass is compressed in batts and much easier to transport in.

I just went through this with my shed. (8 x 12 x 8).  I was given foam insulation pieces for free from a local place (2x2x1/2).  After a few pieces I bought fiberglass. It was on sale this week at 20% off.  It would take up my entire vehicle to ship in a small amount and it took forever (almost 3 hours per stud).  I can fit almost the entire shed of fiberglass in my jeep and it will take about a day for $130.  I would have spent more on gas.
« Last Edit: September 09, 2009, 07:29:38 AM by Squirl »

Offline John Raabe

  • Administrator
  • Journeyman
  • *****
  • Posts: 5,388
  • Whidbey Island, WA
    • CountryPlans.com About Us
Re: Foam Board Insulation Installation (between studs)
« Reply #9 on: September 09, 2009, 08:22:49 AM »
I agree. The most cost efficient, time efficient and energy efficient strategy for stud wall framing is high density fiberglass batts well placed into the cavity and 1" foamboard on the exterior (or interior) of the walls. You can usually do this at a cost equal to or better than an all foam-board stud cavity fill that would meet the R-11 to R-21 that is code required (for 4" or 6" wall insulation).

Even if you are getting the cheapest fiberglass (R-19 for 6" walls) a 1" foam-board sheathing rated at R-5 will perform as if it were R-7 cavity insulation. It will up the overall wall to the equivalent of R-26. This is because the foam now insulates the R-5 framing as well as the R-1 or R-2 gaps, corners and imperfections of the batt job.
None of us are as smart as all of us.

Offline MountainDon

  • Administrator
  • Journeyman
  • *****
  • Posts: 15,847
  • Jemez Mountains, NM; that's pronounced HEY-mess
    • My 15.75 x 30 Jemez Cabin
Re: Foam Board Insulation Installation (between studs)
« Reply #10 on: September 09, 2009, 11:08:04 AM »
I'll add that I used some sheet foam insulation in a few small areas in our cabin, because I had some. It was crazy labor intensive.


For the do it yourselfer it is impossible to beat fiberglass batts in bang for the buck. For a contracted installation I still love the wet blown cellulose. The better builders around here use cellulose wet blown into the walls. There is no question in my mind it is superior to batts when it comes to getting in and around electrical boxes, pipes, odd shaped corners and the like.

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

If you didn't have the time or money to do it right in the first place, when will you get the time and money to fix it?

Offline DirtyLittleSecret

  • Full Member
  • ***
  • Posts: 166
  • This is gonna hurt...
Re: Foam Board Insulation Installation (between studs)
« Reply #11 on: September 13, 2009, 05:40:50 PM »
Figure'd that I'd add this link from Core a vent which has some great diagrams for those of us who think thumbs are targets...
http://www.cor-a-vent.com/pdf/S-4004P.pdf
Thumb, meet hammer...hammer, meet thumb...