We often discuss the merits of full-frame window replacement. It is simply the best, most complete installations for new windows.

So today, we’ll shift gears and talk a little about retrofit installations. More specifically, about aluminum capping (also called cladding).

Aluminum cladding is bent and put on top of the existing brickmould to complete the exterior look of the windows in a retrofit installation or on top of a vinyl brickmould. The cladding is not applicable to full-frame window replacements as the brickmould gets taken out and replaced with a new one. Vinyl brickmould acts both as a barrier and an esthetic finish.

Capping has been traditionally used on wooden windows, but a lot of window installers today, would not recommend it even for retrofit replacements. And for a good reason.

While it seals the wooden frame of your window from the outside, aluminum capping can also cause the wood to "sweat." This can lead to moisture damage or rotting.
While it seals the wooden frame of your window from the outside, aluminum capping can also cause the wood to “sweat.” This can lead to moisture damage or rotting.

 

As with most things window replacement, it’s all about keeping the moisture out of and away from the wood in your windows and walls.

Aluminum cladding actually contributes to the rotting of the wood underneath, often twice as fast as if it was left unfinished.

Once the capping is put on around the window it seals the air out but also seals the moisture in. As the temperature changes and the aluminum warms up and cools down, the moisture underneath has nowhere to escape and stays on the wood. This greatly contributes to rotting.

As a result, your retrofit installation may have to turn into a full-frame replacement in just a few years.

Capping also has an esthetic disadvantage to wood or vinyl brickmoulds. Because it has to be bent by hand, there will be some discrepancies to how the external finish looks between different windows. Even the best installers have to commit a considerable amount of time to get the capping to fit and look just right.

Which brings us to the final issue. Though it shouldn’t affect the final outcome of your window replacement, windows with capping take almost twice as long to install as ones with vinyl brickmoulds. Because capping has to be cut and fitted on site at the time of the installation, it takes considerably longer to change each window in the house.

Although aluminum capping is still a preferred finishing option for many installers, it is far from an ideal solution when it comes to keeping the moisture out of your windows and wall structure.

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