How to: Install Replacement Windows…The Easy Way!

by luke on June 24, 2011

How to: Installing Replacement Windows...The Easy WayInstalling Replacement Windows

Replacement windows are one of the most common upgrades to an older home. There are two good reasons for this:

  • Energy Efficiency: The cost of the energy saved, quickly overtakes the cost of the initial investment. Especially in extremely warm or cold climates, an older window will make your heating/cooling system work harder due to cracked glazing or seals, single pane glass, or improper operation leading to drafts.
  • Home Value: Beautiful, energy efficient windows are a selling point for any home. Often, older, wooden-frame windows are cracked or split beyond repair and look worn even with fresh paint. There’s a lot of curb appeal to new, sparkling windows.

Choosing a Replacement Window

Choosing a Frame

Your choice of frame should be based on the styling of your home, as well as your budget. The four common frame types are: wood, vinyl/metal clad wood, and all vinyl or all wood.


Wood Frames

If the exterior of your home features natural wood siding, a wood frame will complement your home nicely. Wood frames are generally more expensive, but they do offer a low heat transfer and can be very energy efficient. If you’re looking for low maintenance, they don’t exactly fit the bill. They must be properly primed and painted, as well as repainted every few years to maintain their appeal.

Vinyl/Metal Clad Windows

A lot of replacement window manufacturers offer a wood frame window with a metal or vinyl “wrapping” on the exterior of the window. As long as the “wrapping” is sealed, the window is relatively maintenance free. You can also choose a color that complements the exterior of your home, without having to repaint every few years.

Note: Although the window unit is maintenance free, you will still have to either: paint the exterior trim to match the window wrapping or replace the trim with a vinyl product like Azek.

Metal Frames

If you’re looking for low maintenance as well as low cost, a metal frame might be a good choice. Metal windows are becoming a thing of the past, along with metal siding, thankfully 🙂 But, depending on the look of your home, they may be an option. I’m not a fan of them for several reasons, among which is the high heat transfer, resulting in a lower efficiency window.

Vinyl Frames

Vinyl replacement windows are extremely popular for several reasons.

Quick and Easy to Install

Even someone without relatively no carpentry experience can learn to install a vinyl replacement window,(we’ll get to the trim later),  in less than an hour. With experience, a window can be installed in less than twenty minutes!

Cost Effective

Vinyl replacement window are definitely on the cheaper end of the scale. Ranging from $120 – $300, they often come with great warranties too!

Energy Efficient

Vinyl has a relatively low heat transfer, making it an efficient option; while still being cheap and low maintenance. They are also available with energy efficient and light blocking glass.

Note: Choosing a dark colored vinyl frame may be aesthetically appealing initially. However, vinyl expands, as well as fades, quite a lot in direct sunlight. This expansion can be extreme on a dark window and can lead to broken seals and warped frames.

Replacement Window Frame Graph

“Windows are thermal holes. Most are 10 times less energy efficient than the wall area they replace. An average home may loose 30% of its heat or air-conditioning energy through its windows. The good news is that window technology is improving by leaps and bounds. There are even some cases where new windows can be net energy gainers. Selecting energy efficient windows is cost effective in any climate. The payback period for selecting energy efficient units ranges from 2 to 10 years.”

-Paul Fisette (2003) UMass, Amherst

Full article here.


Measuring for a Replacement Window

A correctly sized replacement window makes the installation easy, and maximizes the effective size of the window. (Less frame and more glass!) Measuring for a replacement window is easy.


Replacement Window Jamb Parts

The width measurement should be taken from the inside-to-inside of the window frame.  (See above picture)

The height measurement should be taken from the bottom of the window frame to the top of the window frame.

Note: Some people take the height measurement from the top of the sill. This leaves room to attach a “header expander” to the top of the new window. I really dislike using header expanders because they decrease effective window size, and complicate the trim process.

Check the window frame for plumb and level. Since the new unit will need to be installed at least close to plumb, adjust your measurements accordingly. This will ensure that you have the largest size window that can be installed plumb, and level in the opening provided.

Since replacement windows are made to order in increments of 1/4″, you will reduce both the width and height measurements by 1/4″, and you have your window size!


Removing the Old Window

Removing the old window parts is usually very easy. However, there are a few steps you can take that will save you time and minimize damage to pieces that are part of the frame, or being reused later.

  • Use a utility knife to score the paint along the edges of the window stops. This will keep the paint from chipping or peeling away from the casing when you remove the stops. This will also make removing the window stops easier; paint is a surprisingly good adhesive.
  • Use a thin flat-bar or even a putty knife to separate stubborn joints. This will minimize denting or marring other parts of the window trim.
  • After the stops are removed, tug on the top of the individual window to loosen them. Using a hinging motion, swing the top of the window into the room until it is horizontal. Then, twist the window into the opening by lifting up one side and pressing down on the other until the window is free.

Note: Every window is different…some might take a little muscle to remove. Don’t worry about scratching the inside of the jambs while removing the window; it’ll all get covered anyways.

If the window is cracked or particularly stubborn, wear gloves and eye protection in case it shatters while removing it.

Preparing the Window Opening

Use a putty knife or flat-bar to remove any old sealant or paint chunks from the inside of the jambs, the exterior window stops, and the inside edge of the window sill. If the old window was an older, weighted window, there may be pulleys at the top of the jamb that need to be removed. Clear any dust from the bottom corners of the frame to ensure a good bond with the sealant.

Installing the New Window

After unwrapping the new vinyl window and discarding of that pesky header expander, locate the sill flashing and the four long installation screws. Sill flashing for a vinyl window is an “L” shaped piece of vinyl that is the same width as the replacement window unit. The vertical part of the “L” shape is slotted, allowing it to clip onto the bottom, outer edge of the window unit and shed water away from the bottom of the window.

  • Lay the sill flashing centered on the window sill and mark both sides where it hits the exterior window stops. Remove the lower part of the “L” shape on both sides as marked to allow the sill flashing to fit into place. Once trimmed, lay the sill flashing back in place and trace the outside edge with a pencil.
  • Apply a 3/8″ bead of silicone or silicone fortified sealant to the inside surface of the exterior stops; both sides and top. One the sill, apply a 1/4″ bead directly to the wood sill on the inside of your pencil line.
  • Snap the sill flashing onto the bottom, outer rim of the new window unit.
  • Lift the new window into the opening with the top angled into the room, and the bottom angled away, and into the opening. Once the  bottom of the unit has cleared the sill and is against the exterior stops, press down on the window and swing the top into the frame.
  • Press the window firmly and evenly against the stops to ensure a good seal.
  • Using the four provided screws, fasten the window to the frame at the four pre-drilled locations. (These are usually located about four inches from the top and bottom on both sides.
  • Tighten the screws until they hold the window firmly in place, and centered in the window opening. (Keep in mind that vinyl is much softer, and more flexible than wood. Over tightening the screws can damage the frame of the window.)

Window Adjustment

Although you may have read or heard about leveling and squaring the window unit, I prefer to use a faster, more effective method. A replacement window needs to be functional and beautiful – not necessarily level!

  • Fully close and lock the window.
  • Fully open the window by lifting the bottom sash.
  • NEARLY close the window; leaving about a 1/4″ gap along the bottom. A correctly adjusted window will operate smoothly AND close evenly.
  • If the gap is larger on the right side:
    • Loosen the top right screw and tighten the top left screw, or,
    • Loosen the bottom left screw and tighten the bottom right screw.
  • If the gap is larger on the left side:
    • Loosen the top left screw and tighten the top right screw, or,
    • Loosen the bottom right screw and tighten the bottom left screw.
  • Once the gap is even, you are done adjusting!

Cleanup and Final Sealing

Use a rag with water or paint thinner (depending on your choice of sealant) to clean any excess sealant from the frame of the window. Check the perimeter of the window for good contact with the exterior window stops. If necessary, apply a thin bead around the perimeter to eliminate any voids, and leave a smooth, weather-tight seal.


Coming soon: Tips on selecting and installing trim on your new replacement window!

{ 1 comment… read it below or add one }

Anonymous July 1, 2011 at 12:05 pm

Thanks! Where are your windows available? What frame types do you offer?


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