How To Measure Replacement Windows

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Replacement Windows

Harvey Tribute Double Hung Replacement Windows 225x300 How To Measure Replacement WindowsThis weekend I helped my dad install some new replacement windows. Installing replacement windows isn’t really that hard and it’s certainly a great DIY project for anyone with moderate DIY and construction skills. We replaced five double hung windows in about six hours.

Replacement windows are installed in a way that doesn’t require the old window frame to be removed. Because of this most replacement windows do not require exterior siding to be removed which greatly simplifies the process. This makes replacement windows a great do-it-yourself project.

Ordering Replacement Windows

Installing replacement windows is an excellent way to upgrade your home and make it more energy efficient and better looking. Replacement windows are designed to be installed inside your existing windows frame. This eliminates the need for costly siding repairs and also makes it a rather simple and quick project.

How To Measure Replacement Windows

Ordering the replacement windows is fairly straight forward if you know what dimensions you’ll need. You need to measure the height and width of the existing window opening.

Step 1 – Measure Width: First you need to measure the width of the window. See Figure 1 which shows how to measure the width of the unit between the left and right jambs.

Figure 1 Measure Width and Casing How To Measure Replacement Windows

Figure 2 Measure Window Height How To Measure Replacement WindowsIf your house had replacement windows previously then it’s likely you’ll have a plastic or aluminum jamb liner where the parting stop and jamb are shown in the photo above. Later in the article I’ll show a photo of a that jamb liner. I bring this up because the jamb liner is typically about 3/8 to 1/2 inch thick and you need to base your width on the fact that the jamb liner will be removed.

Once you’ve measured the width shown above you’ll want to order the replacement window approximately 1/4 inch narrower (each manufacturer actually recommends how much narrower to use).

Step 2 – Measure Height: Next you need to measure the height of the replacement window. Most (but not all) existing windows will have a sloped sill. This is important to note because you want to be sure to measure the “least” opening which occurs at the top of the sill. See Figure 2 for a sketch on how to measure the height.

Figure 3 Minimum Jamb Width How To Measure Replacement WindowsAgain you’ll want to take the vertical measurement and subtract about 1/4 inch for the height you’ll order. Be sure to check with the window manufacturer on the recommended size tolerance to use.

Step 3 – Unit Depth: The last dimension you need to check is the distance between the outside blind stop and the inside stops. Most older windows were built with a dimension of 3-1/4 inches to 3-1/2 inches. In order for standard replacement windows to fit you need a minimum distance of 3-1/4 inches (see figure 3).

Ordering Replacement Windows

Once you’ve got all the window measurements you just need to place your order. Today’s replacement windows offer lots of options and features. The following is a short list of options and features that replacement windows come in.

  • Material – Today you can order wood, vinyl, fiberglass, and aluminum clad wood (there may be other options as well ). A vast majority of today’s replacement window market features vinyl windows. For our project we used Harvey’s Tribute Vinyl Window.
  • Glazing – Today’s window manufacturers offer more glazing options than I care to cover in this article. You can choose from single pane, double pane and triple pane windows. You can also choose from Low-E/Argon filled glass to Low-E/Krypton filled glass. You can also order glass with UV protection to protect your furnishings from the suns damaging rays (I wish we had this in our home as our Brazilian Cherry Floors Darkened from UV light).
  • Screens – Screen options are plentiful with most manufacturers including full screens, half screens, aluminum, fiberglass and many companies are now offering “see through” screens which almost appear invisible when you look through the window.

Benefits of Replacement Windows

Installing replacement windows will improve the energy efficiency of your home. One of the best reasons to install replacement windows right now are the Federal Tax Credits / Home Improvement Stimulus. Right now you can get a 30% tax refund up to $1500 for windows that qualify under the Stimulus Bill. With the rising cost of energy it’s fairly easy to see the cost benefit of new energy efficient windows. Your home will be easier to cool, easier to heat and much more comfortable.

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  • Mark Morris says:

    Not everyone agrees that replacement windows are necessarily more efficient. A properly sealed and maintained wood window with a properly installed storm can in some cases provide more protection. This is not to mention the fact that older wooden windows, when properly maintained or refurbished, will far outlast any window on the market today. Many of them have already weathered a century or more and if kept properly maintained will outlive their owners.

    • Todd says:

      Mark – I don’t disagree…however…there are very few people around today capable of maintaining them and frankly very few of those windows are able to meet the performance of today’s windows. Thanks for sharing your thoughts

    • Mike says:

      I totally disagree, I have installed 1000′s ow windows and none of the wood windows can even match the performance and quality of a higher grade vinyl window for energy savings, sealings and ease of use.

  • matt says:

    I work in a glass plant that produces loE window coatings. Old non coated windows are not nearly as good as new energy efficient windows. Anybody who tells you otherwise does not know what they are talking about.

  • RIGO says:


    • Todd says:

      It’s not uncommon to have to make new jamb stops and trim. Replacement windows almost never match the original window dimensions.

    • To your direct question, yes there are windows that have a frame depth of 3.25″. These windows are built to meet the requirement for most replacement projects. I am not suggesting you bought an inexpensive window, but if one shops strickly on price then it is highly possible that there was a less expensive window that looked great, but close examination, or explanation by the sales person selling the window, could show that the savings was accomplished by a lighter (both wall thickness and frame depth) window. This also results in thinner glass units which affects thermal properties as well as sound transmission. It is prehaps to late for this to help you as it sounds like this is an after the fact question, but possibly can help someone in the future.

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