Install Energy Efficient Windows without being Afraid of Breaking Your Home

By Vernon Trollinger, March 28, 2013, Energy Efficiency, Home Improvement, Save Money

Use Energy Efficient Low-E Window Coatings to Keep Your Home CoolIt’s no secret that installing newer energy efficient windows can save you money. Likewise, it’s no secret that installing energy saving windows sounds drastic, messy, and expensive. Most homeowners cringe at the thought especially if they’re going to take on the job themselves.

In truth, installing an energy efficient window is usually no big deal. The key is to learn how the job gets done and what to expect. So, let’s walk through a very basic version of how to retrofit an energy saving window into an existing window frame. If you are doing it yourself, you’ll need to take the time to learn about what you’re going to be working with and plan ahead. Know what kind window you are going to replace. READ the manufacturer’s instructions for the energy saving window you are going to install. Many top brand window makers (Pella, Jeld Wen, Andersen, Marvin) post window specs and installation instructions online for all their energy saving window products. Lastly, make sure you’ve got the right tools (sharp tools are safer), that you can physically perform the job safely (e.g., standing on a bucket on top of a step ladder is NOT safe), and that you also wear the right kind of protection for your eyes and hands.

Use Energy Efficient Low-E Window Coatings to Keep Your Home CoolChoose the Right Window

First of all, decide what kind of energy efficient window you need. This depends on where you live and what direction the window is facing. Energy saving windows (including skylights) gain and lose heat through drafts, conduction, and radiation.

Drafts: Outside air is pulled inside your home due to incomplete sealing of the window itself or from around its frame. Over time, moisture from drafts can rot the window frame and lead to other problems.

Conduction: Heat travels through window materials including glass, glazing, and frame. Windows are rated in U-factors. The U-factor measures the rate at which the window conducts heat through it —either from the inside or the outside. The lower the U-factor, the better the performance. Most low-U windows are double-glazed (two sheets of glass) and contain an inert gas that acts as an insulator. Low-emissivity coatings (Low-e) involve a thin coating on the glass panes that reduces conduction, lowering the U-factor making them energy efficient. These add to the cost of the window but substantially reduce energy loss by up to 50%. Low-e windows are EnergyStar approved and are eligible for energy efficiency tax credits.

Radiation: Heat enters the home via sunlight. Heat also exits the home by radiating from things inside such as people, walls, and furniture. Windows with solar heat gain coefficients (SHGC) help control the amount of radiation that is transmitted through the window (mostly from the sun). A product with a high SHGC rating is more effective at collecting solar heat during the winter. A product with a low SHGC rating is more effective at reducing cooling loads during the summer by blocking heat gain from the sun.

Use Energy Efficient Low-E Window Coatings to Keep Your Home CoolThe climate of where you live effects your window choices. So, too, does the orientation of the window. For example, when I installed two new energy efficient windows in my home last year, I chose to place a low-U, low SHGC window in the west wall and a low-U, high SHGC in the north wall. The reason was that I wanted more control of the radiation in the west wall due to hot summer sunshine. The north wall didn’t need as good a rating because it wouldn’t face the same onslaught from the sun.

Next, choose a window-frame type. While mostly it’s a matter of aesthetics, different materials have their own insulative benefits, construction requirements, and costs. For example, wood frames might be the best insulating, but they have relatively higher maintenance and cost more than vinyl. Vinyl might be cheaper, waterproof, and maintenance-free, but it still needs attention during installation for expansion in hot weather.

Sizing It Up

Let’s say we’re going to retrofit a new double hung sash window into an existing wood-framed sash window. It sounds complex, but it isn’t. What we’re going to do is clear out the old sashes and hardware and then insert a new energy saving window in that space.

Let’s get started:

  1. We first need to know the opening size. The window sash is kept in place by a pair of sash stop on either side and a head stop at the top. Removing these pieces will let you measure the space of the opening (or pocket) available for the new energy efficient insert.
  2. Remove the sash stops and head stop. Use a utility knife to score any paint on these pieces and then using a putty knife or chisel, carefully remove them from the window frame.
  3. Measure from the sill and to the top of the window (where the head stop was nail in) for the height and then measure the width. The sill is the part that the lower sash rests on and is the actual bottom framing member of the window frame. Even though it’s sometimes called the window sill, the stool is actually the piece of the window where your cat likes to sit and watch birds.
  4. Tack the stops back into place. You’ll remove them later.
  5. Our window measures 37 7/8 by 33 7/8 inches. Retrofit windows usually require 1/8 to 1/4 inch of extra space (depending on the manufacturer). That means, we’re looking for a replacement energy efficient windows that measures no bigger than 37 3/4 x 33 3/4 inches.


After double checking your existing window frame measurements with the new energy efficient window, it’s time to pry out the old sash stops and head stop.

  1. At this point, you should be able to swing the lower window sash out of the window. Old windows are attached to sash cords with counterweights that help open and close the sashes. Cut the window free of the sash cord and carefully let the counterweight slide down inside its pocket. Large sash windows can be heavy so have an assistant help hold the sash as you work. Remove and dispose of the sash.
  2. Next, remove the parting stop. This piece is attached to the window frame between the lower and upper sash runs. If it has lots of old paint globbed on it, it can be very hard to pry out. Once again, score the paint with a utility knife and then remove it. Don’t worry about breaking it but make sure all of the pieces are removed.
  3. If you find the upper sash is loose while removing the parting stop, have your assistant help hold it in place —even if it has been painted in place from both the inside and outside. Again, use the utility knife. Once the upper sash is loose, you should be able to pull it inside and remove the sash cords. Dispose of this sash as well.
  4. Remove the exterior sash stop as well as any window stops that helped hold the upper sash in place. Next, look for a pair of access panels cut into the lower part of the sash runs. These are typically kept closed with a screw. Inside these panels are the counter weights. Remove and dispose of them. Leaving them inside could block a mounting screw from the new window. Also remember to remove the sash cord pulleys on either side of the window. Some are screwed in place, others just pop right out with a slotted screwdriver.
  5. Finally, clean up any loose material or dirt as this could interfere with caulk or other sealants.

Remember, you can do this same job by working inward from the outside. It all depends on the window you’re working on.

By the way, there is also a version of double hung sash window that used a galvanized metal ribbon-spring to help raise and lower sashes. Dating roughly from the 1950s, the ribbon retracts into a coil in the wall above the window. Cut these ribbon-springs free from the window sash with a pair of tin snips and let the ribbon retract up into the wall.


Once the sill is clean, we can now get around to the business of installing the new window.

  1. Apply flashing tape the entire length of the sill, tucking it up tightly against the edge of the stool, and burnish it into place so there are no openings. There are many different kinds of flashing tape available and window manufacturers may or may not include a roll with a window installation kit. Needless to say, the flashing tape is important because it helps seal the underside of the window against leaking rain water and condensation.
  2. Use a level to check and see that the sill is level or if it bows. Set the spacers and shims until level. Carefully, dry fit the window, checking that it is level and plumb. Adjust shims as required. Some energy efficient windows come with sill adapting kits that let you custom fit a sill cover over the existing sill; others might require that you fabricate something yourself. So consider your own carpentry skills as you decide on what window to buy. Be sure to drill a pair of weep holes in your sill adapter at either end to allow condensation to drain.
  3. After you’ve made all your adjustments and marked how the window will sit inside the frame, remove it so you can begin applying sealant to the frame.
  4. Different manufacturers use different ways of securing their energy efficient windows in place but all require that they are sealed into place with caulk usually where the new window meets the stool as well as the sill and along the head. Use shims along either side of the new window to help keep it secure and plumb before you fasten it in place with screws or whatever the manufacturer recommends.
  5. From the inside, fill the gaps between the new window and the frame with expanding foam. Avoid using a foam formulated to fill big gaps since it can expand enough to deform the new window’s sides. Instead, use a foam that doesn’t expand as aggressively.
  6. On the outside, insert backer rod (a rope-shaped foam) into the gap and then caulk into place. The expanding foam and the backer rod will allow the window to expand and contract as well as eliminated drafts and keep out moisture. Caulk and seal any other gaps on the outside along the window frame as well.
  7. When everything’s dry and the excess foam has been cut off, apply the finishing trim according to the manufacturers instructions.

You’re done! That wasn’t so bad, was it?

One thing you’ll notice is that replacement insert windows like these do have a slightly smaller area than your original window. But, you’ll also notice right away that air near your energy efficient window isn’t as chilly on a cold winter night nor as hot on a sunny summer afternoon. Because of better draft sealing, you also should see less condensation forming on the glass as well. As you install more energy efficient windows around your hp,r, rooms will feel more comfortable and whole your whole home will be more energy efficient — which means you save money.

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  1. […] this year, I wrote a blog post on how to install Energy Efficiency Windows. In the article, I outlined that energy efficient windows are rated in “U-factors” to describe […]