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Timothy Miller
vapor barrier life

Howdy, been reading vapor retarding as barrier seems to be a misnomer. If i understand the tyvek web information it has only a 10 year warranty and insists acoustic caulk, special fasteners, and special tape of seams to keep the warranty; Moreover, furrowing strips need installed with wood or cement siding.... so i am wondering if i install 1/2" Styrofoam 4by 8 panels and caulk the seams with 50 year silicone caulk under the wood siding and over OSB would this not be a longer life and thermo break too? Also want to insulate the unfinished basement ceiling but do not want fiberglass raining down so can i install if and tyvek on the joists- my concern is not wanting to trap moisture in the joists cavity. Any heads up, suggestions? Home in heating zone in Nebraska...

JLMCDANIEL
Re: vapor barrier life

Timothy,
Tyvek is designed to pass moisture out but not in. The furring strips provide and air gap for that moisture to escape. Styrofoam is not going to accomplish that. When warm moist air enters the wall cavity it will be trapped and probably condense.

Jack

canuk
Re: vapor barrier life

It doesn't sound like you have understood the concept of house wrap material like Tyvek.
It's not a vapour barrier ----- it's an air barrier.

The microweave of the material allows vapour to pass through but prevents liquid water to pass through on inital contact.
This is what is meant by " house wrap breathes ".

Timothy Miller
Re: vapor barrier life
JLMCDANIEL wrote:

Timothy,
Tyvek is designed to pass moisture out but not in. The furring strips provide and air gap for that moisture to escape. Styrofoam is not going to accomplish that. When warm moist air enters the wall cavity it will be trapped and probably condense.

Jack

Hi Jack I was planning on installing a plastic vapor retarder between the studs and the drywall. But likely to install lath on the Styrofoam. The Styrofoam will be a vapor and moisture retarder and a thermo break which seems an important consideration. But was consider installing cellulose in the walls but the cellulose manufacturer recommends not using a vapor retarder with it. So the trade offs seem to conflict with each other as i do not think the Tyvek ads any thremo break itself. Might go with lock tight foam in the wall but finding an installer in rerual Nebraska is a issue.

Timothy Miller
Re: vapor barrier life
canuk wrote:

It doesn't sound like you have understood the concept of house wrap material like Tyvek.
It's not a vapour barrier ----- it's an air barrier.

The microweave of the material allows vapour to pass through but prevents liquid water to pass through on inital contact.
This is what is meant by " house wrap breathes ".

Howdy, i am just not clear in my attempt to combine different products. Reading about Tyvek i am disappointed how little of warranty life it has when when using the expensive fasteners and tape. An how challenging it is to retard air and moisture flow with the fasteners penetrating the wall surfaces. Then adding high and low pressure aspects of wind affecting the flow of air and moisture threw the retarders and walls has me in need of more insight and suggestion. Then after reading a book about moisture travel wind blown rain really ups the infiltration aspects. Thanks for your feedback..
It seems that loc tight foam inside the walls may be the superior method?

canuk
Re: vapor barrier life
Timothy Miller wrote:

Howdy, been reading vapor retarding as barrier seems to be a misnomer. If i understand the tyvek web information it has only a 10 year warranty and insists acoustic caulk, special fasteners, and special tape of seams to keep the warranty; Moreover, furrowing strips need installed with wood or cement siding.... so i am wondering if i install 1/2" Styrofoam 4by 8 panels and caulk the seams with 50 year silicone caulk under the wood siding and over OSB would this not be a longer life and thermo break too? Also want to insulate the unfinished basement ceiling but do not want fiberglass raining down so can i install if and tyvek on the joists- my concern is not wanting to trap moisture in the joists cavity. Any heads up, suggestions? Home in heating zone in Nebraska...

canuk wrote:

It doesn't sound like you have understood the concept of house wrap material like Tyvek.
It's not a vapour barrier ----- it's an air barrier.

The microweave of the material allows vapour to pass through but prevents liquid water to pass through on inital contact.
This is what is meant by " house wrap breathes ".

Timothy Miller wrote:

Howdy, i am just not clear in my attempt to combine different products. Reading about Tyvek i am disappointed how little of warranty life it has when when using the expensive fasteners and tape. An how challenging it is to retard air and moisture flow with the fasteners penetrating the wall surfaces. Then adding high and low pressure aspects of wind affecting the flow of air and moisture threw the retarders and walls has me in need of more insight and suggestion. Then after reading a book about moisture travel wind blown rain really ups the infiltration aspects. Thanks for your feedback..
It seems that loc tight foam inside the walls may be the superior method?

Timothy,
One main role of the house wrap is to provide a weather barrier ----- basically a modern material that performs better and intended as a replacement to common felt or tar paper.

Depending on the materials that exist for sheathing the dynamics of this product becomes more or less important.

For example ---- if the sheathing is plank then the air barrier function of house wrap becomes an important feature and less so than for plywood or OSB sheets.
Mainly because of the many gaps that exist between planks ---- with sheet goods it does help since there are still gaps at butt joints--- far less than plank.

The other dynamic of the material is providing a moisture barrier whenever water penetrates behind the exterior siding ---- regardless of plank or sheet goods it's equally important .

In the event moisture was to get in behind the house wrap this moisture has a chance to escape in the form of vapour that is allowed to pass through so as not to be trapped and rot the sheathing ----- opposed to felt or tar paper that's less effective in performing that function , especially when that material easily reaches saturation.

On the other hand that's why air gaps between the exterior siding and the sheathing are recommended ---- providing isolation and drainage from moisture penetrating the exterior siding.

The older conventional thinking is the house should breath vapour from the inside to out.
In some cases this remains true ------ however by tighter sealing and insulating can greatly change the dynamics of the structure.

If you create a higher resistance to thermal heat transfer and bridging on the exterior and increase the thermal resistance on the interior you are raising the temperature in the wall ----- a good thing.
Once this reaches optimum there will be considerably less chance of condensation occuring since this also raises the dew point for condensation to form.
In the science study of buildings when this condition occurs the home can breath into the interior making the interior vapour barrier redundant ---- which is advantageous in very cold climates.

Timothy Miller
Re: vapor barrier life

Thanks for the information, Canuk.

...diffused in the atmosphere- vapor. The Tyvek web page says it's a air retarder not a barrier. So i think i will use a plastic air retarder and fiberglass on the inside and OSB then Styrofoam then furrowing strips and finally wood lap siding.

Any one know how thick the insulation has to be to stop the thermal bridging of the wood framing members in walls ?

canuk
Re: vapor barrier life
Timothy Miller wrote:

Thanks for the information, Canuk.

...diffused in the atmosphere- vapor. The Tyvek web page says it's a air retarder not a barrier.

Not sure where your source is for that but from DuPont's site.........

Quote:

Air Barrier Code Requirements

The 2005 National Building Code (NBC) of Canada (Sections 5.4 and 9.25.3) requires air barrier systems to be included in thermally insulated wall assemblies.

The materials “intended to provide the principal resistance to air leakage shall have air leakage characteristics not greater than .02 L(s•m2) measured at an air pressure difference of 75 Pa”. DuPont™ Tyvek® air barriers perform as air barrier materials as recognized in the following CCMC evaluation reports:

• CCMC 12857-R DuPont™ Tyvek® HomeWrap® – Air Barrier Material™
• CCMC 13253-R DuPont™ Tyvek® CommercialWrap® – Air Barrier Material™

Air barrier systems shall be continuous across junctions between different building assemblies and around penetrations in the building assembly.

........... for what it's worth.

Quote:

So i think i will use a plastic air retarder and fiberglass on the inside and OSB then Styrofoam then furrowing strips and finally wood lap siding.

If you go with conventional 6 mil poly vapour/air barrier over interior insulation then sure that works.

Quote:

Any one know how thick the insulation has to be to stop the thermal bridging of the wood framing members in walls ?

Depending on your climate ---- around here it's common to go with 2 inch exterior applied ---- sometimes it'll be 1 inch --- depends.

Timothy Miller
Re: vapor barrier life

Howdy Canuk , again great information.
Vapor as Webster's Dictionary describes . I think more of air then water when stating vapor- my mistake.

The web information found at:
http://www2.dupont.com/Tyvek_Weatherization/en_US/assets/downloads/InstallGuideWRB_K16282.pdf\

So while i consider what to use to retard air and water infiltration and reduce the termal heat loss from framing members to the exterior of my home. I an enlightened by reading the numerous other web pages that dupont has regarding tyvek. It's need to have an air space between the product and exterior siding. It's short warranty, the need to uses in my opinion pricey tape, acoustic caulk, fasteners. Has caused me to pause pondering other choices. The dupont information states it is a "excess water barrier" and a wind retarder. So when using with lap wood siding and the numerous nail preparations while installing the siding moisture infiltration from the exterior is a valid concern. I have learned that each nail penetration can allow one cup of moisture to enter the wall in a year. So it is not the wonder cure all that i thought . Again thank you for your responses. Tim

canuk
Re: vapor barrier life
Quote:

I have learned that each nail penetration can allow one cup of moisture to enter the wall in a year. So it is not the wonder cure all that i thought

Your statement is something that's associated when an interior vapour barrier ( like 6 mil poly ) is punctured ---- I'm not familar with that statement being associated with exterior house wrap.

Somehow I'm getting the impression your confusing the dynamics of interior vapour barriers and exterior weather barriers.

canuk
Re: vapor barrier life
jkirk wrote:

hey hey hey now!!!! no cut and pasting from the 2005 canadian building code now canuk, you should know these codes by hear now!!! come on :D

LOL ....... are you kidding ???
I can barely remember what day of the week it is.;):D

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