Installed by Side-Pro Exteriors across Seattle, Bellevue and Tacoma
Tyvek is the most vapor-open wrap in common use. The number nobody quotes is 120 days.
Tyvek HomeWrap is DuPont’s flashspun polyethylene housewrap and the default weather-resistive barrier on most residential walls in the region. Its case rests on permeability: 56 perms, against Typar’s 11.7 and Henry WeatherSmart’s 8. A wall behind Tyvek dries outward faster than a wall behind almost anything else, which is exactly what you want on an older Seattle or Tacoma house where the assembly is going to get wet at some point regardless.
It is also a Type I air barrier material at under 0.004 cfm/ft², but only once the seams and penetrations are sealed to DuPont’s instructions. The sheet on its own is not an installed air barrier, and the difference shows up in a blower-door test.
The limit worth putting in front of you is ultraviolet exposure. DuPont gives HomeWrap, StuccoWrap, DrainWrap and ThermaWrap 120 days — four months — before the cladding must cover them. Only CommercialWrap gets 270. Wrap routinely sits open longer than that on jobs across Bellevue and King County, and when it does, the wall is outside what DuPont published.
Water holdout is 250 cm of hydrostatic head. That is a genuinely lower figure than Typar’s 500-plus, and it is the trade you make for the permeability.
Typar BuildingWrap · Henry WeatherSmart · Protecto Wrap self-adhered · All siding products
If you are cladding in cedar or redwood, this page is not the end of the conversation. DuPont publishes no surfactant-resistance figure for Tyvek HomeWrap, and for cedar its own guidance points to DrainWrap rather than HomeWrap, with the cedar primed on all surfaces including the back and ends, and furring strips to promote drainage. Tannins leaching out of unprimed cedar are a well-documented route for water to get through a wrap that would otherwise hold. Ask us about the detail rather than assuming the standard wrap covers it.