Spray Foam Insulation

ubenhad4 · 01-23-2011, 11:36 PM

Quote:

Originally Posted by 4020power

I had a quote to do a 50'x100'x17. 5 1/2" in walls and 7" under roof, for around $11600

Closed or open cell?

4020power · 01-23-2011, 11:46 PM

Quote:

Originally Posted by ubenhad4

Closed or open cell?

Open cell

bluebird5 · 01-23-2011, 11:51 PM

by blanket insulation are you talking about cellulose?

ubenhad4 · 01-23-2011, 11:52 PM

Yes

bluebird5 · 01-23-2011, 11:58 PM

yea its good stuff but its not really a diy thing

ubenhad4 · 01-24-2011, 12:01 AM

Insulation isnt a DIY thing period. Everyone thinks if you DIY youll save money. I have seen a ton of insulation bid that were cheaper with install than I could buy the material from my supplier for. I get really good prices from my supplier to. Isulation is almost always cheaper to get installed than it is to just buy the material. That is for batt insulation to. Once you get to celulose and spray its even les comparable

bluebird5 · 01-24-2011, 12:06 AM

i thought that thats what this thread was about diy insulation

nap · 01-24-2011, 12:19 AM

Quote:

Originally Posted by ubenhad4

The r value of open cell is like 3.5 . In a 2x6 wall thats only 19.5. Blow in blanket is 23. Closed cell is 38.5. The advantage of spray foam is not so much r value as much as stopping air flow completely. If you spray a couple inches of open cell, blow in balnket insul, and then provide 1/2 ridgis insul on the exterior for a thermal break your super dialed. Way better than 5.5 inches of closed cell.

what did you use for a vapor barrier on the inside wall? I would also have to wonder about using the blown in insulation and then the spray foam with the spray foam on the outside of the wall. While open cell does allow moisture migration, it would seem you may inhibit the movement enough that you could trap moisture in the blown in insulation should any escape beyond your vapor barrier or had an leak into the wall for some reason.

ubenhad4 · 01-24-2011, 12:43 AM

No vapor barrier on the inside. I want the moisture to migrate to the outside the the drain wrap and go away. You have to allow moisture to esxcape, plastic behind drywall is not good.

**Gary in WA** · 01-24-2011, 01:03 AM

As long as it's not on OSB;
Practical Recommendations
• When using medium-density (MD) foam
in walls as both insulation and vapour
barrier, a minimum thickness of 40 mm
is recommended.
• When placing a foam product in an
exterior wall assembly, ensure that the
moisture flowing through the foam will
not affect other materials. This could
happen when moisture is trapped in a
moisture-sensitive material, such as
plywood or OSB, and drying is prevented
by the layer of SPF.
http://www.earthane.com/ctu32e.pdf

http://www.buildingscience.com/docum...d%20in%20walls

Gary

nap · 01-24-2011, 01:20 AM

Quote:

Originally Posted by ubenhad4

No vapor barrier on the inside. I want the moisture to migrate to the outside the the drain wrap and go away. You have to allow moisture to esxcape, plastic behind drywall is not good.

hhhmm, what do you do about the IRC code that requires a vapor retarder on the interior side of the studs?

Waymo · 01-24-2011, 11:37 AM

Quote:

Originally Posted by GBR in WA

As long as it's not on OSB;
Practical Recommendations
• When using medium-density (MD) foam
in walls as both insulation and vapour
barrier, a minimum thickness of 40 mm
is recommended.
• When placing a foam product in an
exterior wall assembly, ensure that the
moisture flowing through the foam will
not affect other materials. This could
happen when moisture is trapped in a
moisture-sensitive material, such as
plywood or OSB, and drying is prevented
by the layer of SPF.
http://www.earthane.com/ctu32e.pdf

http://www.buildingscience.com/docum...d%20in%20walls

Gary

So no foam on osb?

ubenhad4 · 01-24-2011, 11:04 PM

Quote:

Originally Posted by nap

hhhmm, what do you do about the IRC code that requires a vapor retarder on the interior side of the studs?

What do you think paint is?

ubenhad4 · 01-24-2011, 11:08 PM

Quote:

Originally Posted by Waymo

So no foam on osb?

Yes you can foam osb. Osb has more ability than ply to more moisture through it. You need to make sure you have a drain screen on the out side to let the moisture out. These systems are not that difficult to understand but there is a ton of misinformation out there based on opinions. Ive been to a number of classes and seminars on just this subject based upon sustainability. We go round and round about products and assemblies. Houses have to have the ability to shed moisture from condinsation inside the wall cavity. It has to either go into the house or outside. Paint and primer make it so it need to be able to escape outside.

**Gary in WA** · 01-25-2011, 12:53 AM

"So no foam on osb?" ------ I wouldn't use it again because it's like putting a vapor barrier on the outside wall;
p://www.diychatroom.com/f19/taping-osb-sheathing-joints-92133/

At 35% humidity ply and OSB are about the same, but at 85% plywood has almost twice the permeability of OSB; http://usgbchouston.org/files/1479_J450.pdf

Just make sure you have that rain screen or you will get mold especially in a hot and humid climate;
http://repository.tamu.edu/bitstream...pdf?sequence=4

Gary