Housewrap exposure time

[Danny Pritchard]

Does anyone know if housewrap has an exposure time before it has to be covered.I have a client who is building a new home.She has been having trouble with the builder and because of that little work has been done on the house.The housewrap has been on the home for over 90 days.I have left a message with the manufacturers represenative but have not received a response as yet.

Thanks

[Jim Katen]

Originally posted by Danny Pritchard

Does anyone know if housewrap has an exposure time before it has to be covered.I have a client who is building a new home.She has been having trouble with the builder and because of that little work has been done on the house.The housewrap has been on the home for over 90 days.I have left a message with the manufacturers represenative but have not received a response as yet.

Thanks

Tyvek says 120 days.

Personally, I'd go with felt.

- Jim Katen, Oregon

[kurt]

I'm becoming anti-housewrap; if I was building a new house, I'd also go w/felt. I don't think housewrap breathes like they say; I've torn a few up that had condensation on the inside surface.

Letting it degrade in the sun might be a good thing. But, that's just me.

[itsiceman]

I questioned our Tyvek rep. about the 120 day exposure because our home was open longer and they told me it is not automatically bad after 120 days. They ask for a 3 ft X 3 ft sample and Dupont will test it to see if is still up to their standards.

[Chad Fabry]

I'm a felt guy too. Well, except on other people's roofs. Then I'm a Grace 30 guy.

[hausdok]

Hi,

Danny didn't mention the brand. Some brands are limited to 90 days.

To contribute a little bit to the thread drift - a little building science explanation might be in order here. Kurt's comments about wrap are pretty much what everyone is experiencing. House wrap was never meant to be a moisture barrier - it was designed to be an air barrier.

Unperforated felt and wrap that's been properly applied perform similarly. However, when you introduce thousands of siding nails into the equation they're quite different. When water blows into siding with felt beneath, and water passes through thouse thousands of nail holes, the felt gets wet and it's perm rate increases, allowing air and water to more easily pass through it. That's the downside to felt. The upside is that, after the saturation stops, the felt allows the felt and underlying sheathing to thoroughly dry out.

However, when holes are punched through wrap and it's exposed to wind-driven water, the wrap's perm rate doesn't change. That's the upside to felt, it continues to do what it's supposed to do - prevent air infiltration. In fact, the only thing that changes is there are holes through it that will allow water to seep through. This is the downside. Though wrap is designed to keep out wind and is vapor permeable, it won't allow water molecules to to pass through, so any water that gets behind it through those thousands of nail holes becomes trapped between the wrap and the underlying sheathing, and this is what causes the sheathing, and ultimately the studs, to rot. Since there's really no way to effectively seal every single tiny hole and penetration through the wrap, thereby ensuring that absolutely no water can get behind it, the odds of trapping water in the walls are extremely high, no matter how carefully you apply it.

So, we're left with a choice, install a product that will probably only allow a little water through but will trap the water and promote rot, or install a product that will allow more water through but will allow the building envelope to more readily dry out, thereby preventing rot. Me? I'd choose the felt. It's been around for a century and there are a lot of old buildings still standing. I can't even begin to recount how many thousands of stories I've heard about rotting building envelopes that have been caused by wrap.

ONE TEAM - ONE FIGHT!!!

Mike

[NewInspector]

Good stuff - thx much hasdok, appreciate the lesson.

[Focal Point]

Here are some good videos on the topic of house wraps.

http://216.211.130.165:8081/code_college/Air_Barrier_OverviewO.wmv

http://216.211.130.165:8081/code_college/Air_Barrier_InstallationO.wmv

http://216.211.130.165:8081/code_college/Air_Barrier_Flashing_WindowO.wmv

http://216.211.130.165:8081/code_college/cc_thermawrap_overview.wmv