How Windows Sit in Thicker Walls


Thick walls help lower energy bills and create comfortable conditions in the home, but can make it difficult to install windows.

But what can be done overcome these challenges? This blog will give you some ideas on how windows can be properly applied to a home with walls on the thicker side.

Recessed windows

Windows have to perform the functions of both the water-resistive barrier (WRB) and the air barrier. It’s often easiest to keep the window flanges at the sheathing with WRB and airtight layers at the sheathing. This leaves the window recessed from the wall’s exterior plane and adds some shadowlines.

Before the continuous exterior insulation is installed, the process goes as it normally does. But when you add the insulation you have to make a sill extension and extension jambs toward the exterior. To keep time and material costs to a minimum, remove the exterior casing and leave the extension jambs as the exterior trim. It’s not for everyone, but some architectural styles make this strategy work well.

Recessed Windows with Traditional Casing

If exterior casing is required, you can do that—the other details remain the same. In all cases, slope the sill extension. The sill material does not have to match the jamb and casing material; it can be wood, fly-ash trim, stone, or metal. (Stone or metal have to be installed before the jambs.)

Recessed Windows with Shingled Returns

Another detail that works well is shingled returns. Instead of using extension jambs just install the sill extension and apply sidewall shingles around it. Flanged windows might allow a gap between the shingles and the sill as you apply them, so it’s best to first install a small casing, similar to using an inside-corner block when siding walls.

Windows curbed to the exterior

Windows located at the center of the wall depth are usually best for temperature regulation and are easier to use when making an airtight layer, but sometimes you have to set the windows closer to the outside of the house than to the inside. When using continuous exterior insulation, one option is to create a buck or curb around the rough opening. Windows must be sealed to the WRB, so this curb should be built and wrapped with self-adhering materials before installing exterior insulation. A wooden curb would work just fine. To reduce thermal bridging, first run a layer of foam, cork, or wood-fiber insulation behind an outer layer of framing lumber to create the curb. The furring would be hidden behind the casing, and you can seal the casing to the furring to help prevent water infiltration. This method creates a shadowline at the windows which many people enjoy.

Curbed Windows

A curbed window with ThermalBuck requires several steps, but ThermalBuck is premade, saving you at least one. ThermalBuck can match its depths to the thickness of insulation needed in any given home. A lot goes on in the installation process, so be sure to make the WRB consistent to the window flanges with sealant or tape. Long fasteners are required to secure the flanges completely through the buck and into the wall framing.

Need to Replace Your Windows?

Whichever style you’re interested in, proper window installation is very important, which is why when you’re ready to replace your old or damaged windows, you should call Little Buckaroo Construction. Little Buckaroo Construction is an experienced window installation contractor in Idaho that will let you know when your windows are ready to be replaced. We will also advise you on what type of window, coatings, glazes, etc. are right for your home.

Call Little Buckaroo Construction today and have our team inspect the windows that you’re concerned about. Our caring, friendly professionals will provide you with a free estimate.

Call us at 1 (208) 869-3926 or email us at We are waiting to help you!