7 posts / 0 new
Last post
Timothy Miller
osb rott an insulation

Howdy, been reading and cogitating on what to use in retrofit & addition walls & insulation. Wanting to super insulate the walls with 10" of blown in cellulose. The catch is condensation possibilities. OSB and plywood almost stop any water transmission since the perm #s are so low. Was shocked to view Typek verses Tipar and OSB rot displayed by Tyvek....

The Tipar has a much lower perm # so it again does not allow water to transfer. So i think i'm going to use 1by8" diagonal planking leaving 3/8" spacing and wrap the outside with Tyvek perm rating about 70...
Then cementagous siding with a rain screen wall 3/4" air spaciong. But want some insightful opinions. What do you think?

canuk
Re: osb rott an insulation
Timothy Miller wrote:

Howdy, been reading and cogitating on what to use in retrofit & addition walls & insulation. Wanting to super insulate the walls with 10" of blown in cellulose. The catch is condensation possibilities. OSB and plywood almost stop any water transmission since the perm #s are so low. Was shocked to view Typek verses Tipar and OSB rot displayed by Tyvek....

The Tipar has a much lower perm # so it again does not allow water to transfer. So i think i'm going to use 1by8" diagonal planking leaving 3/8" spacing and wrap the outside with Tyvek perm rating about 70...
Then cementagous siding with a rain screen wall 3/4" air spaciong. But want some insightful opinions. What do you think?

Sounds like you were reading the marketing hype from Tyvek.
Those two have been in an ongoing mud slinging battle for some time --- 2 manufacturers claiming each other's product is better than the other.

To be clear --- Typar has a vapour perm of around 11 and Tyvek is somewhere in the high 20's. Typar does pass water vapour

The minimum standard (ASTM measurement ) is 5 perms -- so they both fall well above that minimum.

They both have pros and cons.

Timothy Miller
Re: osb rott an insulation

Howdy once again i stand corrected. Tyvek moisture vapor rating high typar water transfer low....

It appears there are 2 issues in house wrap keeping water from coming into the house and letting moisture vapor out. Typar and Tyvek have what seems to be apposing positions. Consider review of the comparison at

http://www.typar.com/pdfs/Typar_vs_Tyvek.pdf { Typar' info**\

But neither product has a warranty longer then 10 years... Odd if their so good and i need the protection for at least as long as the siding 10 years- falls way short in my opinion. If i read it correctly-Typar warranty only transferable to second owner{ that owner whom has no idea what wrap is on the house ** has 30 days to notify typar in writing..... give me a break .. Thank goodness my concern is more about how to let the moisture vapor out. Seems like most contractors have this concern if OSB is the sub siding and not get mold and rot based on the above not for a hundred years but for a whopping 10....

Check out the photo on this site about moisture an osb AN FIGHTING WRAPS.

http://www.scribd.com/doc/17741280/High-Perm-vs-Low-Perm-Tech-Talk

NO WONDER WHY ITS AN ONGOING ARGUMENT....tim

Timothy Miller
Re: osb rott an insulation

Other insights on a higher perm rated sub siding?

Sirhc16
Re: osb rott an insulation

The primary purpose of a house wrap (Tyvek, Typar, or even felt paper) is to keep any bulk water off the sheathing. It's often referred to as a secondary drainage plane (the primary being the siding, brick, etc). Any water that makes its way through the siding hits the house wrap and is drained down and out of the wall assembly.

Water vapor that accumulates in the wall should be able to dry. The perm ratings of tyvek or similar products are sufficient to allow water vapor to pass through.

A wall filled with cellulose, sheathed with osb/plywood, and covered with tyvek with drywall on the interior will be able to dry to the inside as well as the outside. Assuming the house wrap was installed properly with correctly flashed windows, etc - there should be no issue with rotting osb.

:)
nnerobi
Re: osb rott an insulation

I have a two story home. The entire upstairs is the master bedroom, which is not as big as the whole downstairs. The upstairs bedroom seems to be at least 10 degrees hotter than the downstairs. Now I realize that heat rises, but would more insulation help the problem? I have central air, bit it works pretty hard to maintain the constant temp.

Sponsored Stories

TV Listings

Find TV listings for This Old House and Ask This Old House in your area.