Wood Frame with 2" Rigid Exterior Insulation & Stucco or Veneer

Flanged Window Detail with 2" Exterior Insulation & Stucco

R-25 Wall

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Head

(Detail 1/3)

Sill

(Detail 2/3)

Jamb

(Detail 3/3)

Notes

This window detail uses a two stage seal to insure no water or air can infiltrate into the building. The exterior seal is installed by applying WRB tape over the window head flange. No tape should be applied over the window sill flange to allow the window to drain. The interior seal is added by installing a full perimeter backer rod & sealant joint. Expanding foam or special tapes can be used instead of sealant, however a backer rod should still be installed to prevent the foam from completely filling up the cavity and preventing the system to drain. To create a continuous air barrier, the pre-assembled plywood extension box needs to be sealed to the wall's fully adhered air barrier and the window with sealant joints.

A drainage mat covered with building paper or vented airspace needs to be installed between the stucco and the sheathing in climates that receieve more than 20" rain per year to allow the wall to properly dry. See the Cladding Notes section below for more info.

* Whether or not you need a Class II or III Vapor Barrier depends on your climate zone, location and amount of exterior insulation. Refer to Wall Barriers Notes section below for more info.

Building Science Courses on Acelab

How to detail drainage mat with stucco

How windows manage water

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Wall Barriers Cladding Windows

Wall Barriers

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Climate Zone

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County

Wood Frame Wall with Exterior Insulation

Design Requirements

Should you use a vapor retarder?

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Recommendation & calculations are based on the methods described in the Builder’s Guides from the Building Science Corporation and are only valid for residential occupancies.

Notes

This wall is designed with a vapor semi-impermeable stucco finish. Whether a Class II or Class III Vapor Retarder needs to be used depends on the project's climate zone and the amount of exterior insulation that is installed. Class II Vapor Retarders can be either a separate membrane, like a 'Smart Vapor Retarder' (SVR), or kraft facing on the cavity insulation.

A Class III Vapor Barrier, like Latex Paint, can only be used when the R-value of the exterior insulation is larger than the R-value of the cavity insulation multiplied by a climate coefficient. The formula above shows the climate coefficient after you've selected your state and county.

Product Options

Browse curated materials for this construction detail.

XPS

Rigid foam panels that are water repellent and offer good thermal performance at mid-range prices.