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How to Install A New Flanged Window in an Old Wall 1: Overview

Replacing a 30-Year old replacement window in a 100-year-old wall that was upgraded with exterior foam insulation 25 Years ago (part 1 of 4)
January 31, 2022

So here’s a window replacement opportunity you don’t get every day.

This is a window in a wall in a house. It has an inside and an outside, and both of them look like classic New England architecture because that's what it is.

The surprising thing about this wall is what’s behind the siding

This is the house of Betsy Pettit and Dr. Joe Lstiburek, the founders of Building Science Corporation and two of the most influential building scientists in North America.

Around thirty years ago they did an exterior insulation retrofit to this classic New England house with two inches of Styrofoam added to the outside and ¾ inch furring strips screwed into the framing to attach the siding to.

Beneath the foam is Tyvek Home Wrap, which is the first layer of the air barrier system.

The windows in the house were replaced before the exterior foam retrofit, and now they are replacing them again with triple-glazed double-hungs from Marvin.

Today, we are going to dig into that 30-year old deep-energy upgrade and install a new construction window in an old wall with an existing hole.

Replacement windows fit inside an old window frame, so the viewable area gets smaller.

Today, we’re removing the old tilt-in replacement windows, and we’re also removing the original frame and recapturing the weight pockets for more glazing area.

David will reframe the opening doing his best to not disturb the interior plaster.

He’ll flash the opening and then he’ll install the flanged window in the hole, tying into the existing Tyvek and replacing the exterior foam before trimming out the window with AZEK Trim stock.

He’ll also seal it inside with canned foam and trim it out after the camera is off.

Other parts of this window replacement series:

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