So your house is getting on in years, and you’re thinking it could use a face-lift. One of the projects you’re considering is replacing all the windows in your house. Where to start? The purpose of this article is to give you the tools you need to make an informed decision.

Ask Yourself Why?

What are you hoping to accomplish by replacing your windows? Are you looking for energy efficiency? Or is the reason principally cosmetic? Are your windows rotting or damaged?

The Technical

In existing homes owners are often given the choice between “replacement” windows, and “new construction” windows. What do these terms mean?

Replacement windows are typically set in an existing window jamb. Most replacement windows are vinyl, both inside and out (although Marvin makes a wood replacement window).Installation requires removing the existing window sashes and operating hardware, installing a track or jamb inside the existing window jamb, and installing new sashes. (see drawing)

New construction style windows are installed within a framed opening. The term “new construction” is misleading as these windows can be installed in older homes.These windows are often fastened through either casing or flanges from the outside of the window opening.

Which One?

Replacement windows are inexpensive and easy to install. Sounds good, right? As with so many things, the harder path usually yields the best results.What’s wrong with replacement windows?

1.Replacement windows often fail to deliver on promised energy savings because they don’t address the most crucial spot for air infiltration, the jamb to framing connection. In NJ, the overwhelming majority of builders do not seal the connection between framing and a window jamb during construction (I may write about this more in the future). Instead, they choose to either stuff this void with scraps of fiberglass, or (gasp) do nothing.

2.Replacement windows do not address most weather-related problems. If you’re trying to address the root cause of your rot problem, replacement windows will most likely be a poor decision. Moisture penetration through compromised (or non-existent) flashing, poor siding/trim details, or ineffective housewrap will not be solved by using replacement windows. To make matters worse, what if the rot has spread or gone undetected in the framing of your home?This will only be detected by removing window trim – not going to happen with replacement windows.

3.Vinyl windows are ugly. You probably thought beauty was in the eye of the beholder. Well you’re wrong. Vinyl might be OK on the outside of your home, but on the inside? That’s like eating Filet Mignon with a plastic fork!

Well what’s so great about new construction windows? I can think of a few things:

1.You’ll have the opportunity to address the causes of moisture.

2.Properly installed new construction windows generally seal both the window trim/flange to the framing and then the jamb to the framing.

3.A myriad of exterior cladding and interior finishes are readily available in new construction windows.

What’s the downside? Well for one, there is the pesky matter of the bill. Expect to pay considerably more for new construction windows. I generally recommend that people install windows while they’re replacing their siding, as it makes for an efficient installation. Also, you’ll be required to replace and paint all window casing. But heck, you probably needed new casing about as much as you needed new windows!

*Builder tip – Window construction, especially sill construction, has changed a lot since the ‘50’s. However, windowsizes have largely remained unchanged. Be sure to remove the existing window’s trim so you can accurately measure the opening size. You’ll be surprised how often a ‘stock’ window size fits an old opening.

Thanks for reading,



  1. Isn’t it true that there’s no such thing as a completely zero air infiltration? I mean every window would leak air, albeit at different amounts. Just a thought.

    replacement windows consultant

  2. Sure, and there are probably some regional construction practices that make replacing one’s windows more or less viable. However, my experience, and the experience of many people who test things with blower doors across North America has been that replacement windows reduce air leakage in homes negligibly, or not at all, or in some instances make it slightly worse. Furthermore, if the goal is to reduce air leakage, there are usually more effective ways to spend money.

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