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All experts agree that you should update your windows & doors for energy efficiency. Windows and doors can account for up to 25 percent of total house heat loss. This makes a difference on both our environment and on our energy bills when heating our homes in the winter or cooling our homes in the summer with air conditioning.

This article, with some content provided by Natural Resources Canada, deals with upgrading or replacing windows and doors to save energy.


There are a number of options for upgrading the energy efficiency of your windows. Windows can be repaired by servicing hardware such as latches, cranks and locks or retrofitted with caulking and weatherstripping or adding glazing and storm windows. At times the best choice is total window and frame replacement with new, high-performance ENERGY STAR® certified windows.

Replacing glazing, sashes and windows

Properly installed energy-efficient windows make homes more comfortable by reducing drafts and increasing the temperature of the interior side of the window, reducing condensation. Energy-efficient windows will have many of the following features:
• double- or triple-glazing
• low-emissivity (low-E) glass
• inert gas, such argon or krypton in the sealed unit
• low conductivity or warm-edge spacer bars
• insulated frames and sashes
• good air tightness

If your inspection has revealed serious problems with a window’s glazing, sash or the entire unit, your best option will be to replace all or part of the window.

If the frame is in poor condition, it may be time to replace the unit.

Taking stock

Check each window for signs of damage: rot, mould and/or staining on or around the window, the condition of the glass, putty and paint, weatherstripping and the operation and condition of the hardware. Some windows may need only minor air sealing work, while others require major upgrading or replacement. Check for air leakage around the frame and at all movable joints.

Condensation problems

Interior surface condensation and frosting are common complaints. Sometimes the problem is light fogging on some windows; at other times, there may be persistent and heavy frost covering the glass. Many homeowners buy new windows only to find that the problem becomes worse because the old, leaky windows actually helped to reduce humidity. The new windows seal the house more tightly, causing a rise in humidity. One solution is to reduce humidity levels in the house.

Interior caulking

Air leakage around a window can be reduced by applying a continuous bead of caulk around the window trim where it meets the wall, at the mitred joints of the trim, and between the trim and the frame. Make sure the caulk is intended for indoor use (do not use exterior caulking indoors), can be painted and is of good quality.

If a window is particularly leaky and the trim can be easily removed and re-installed, remove the trim, add insulation and seal the gap before reapplying the trim. If the gap is small, 6 mm (¼ in.) or less, insulating the gap followed by caulking may suffice. Larger gaps may require either a backer rod with caulking or low-expansion foam.

To further reduce air leakage, apply a layer of red technical tape to cover the joint between the wall and window frame. Ensure that the tape will be hidden by the trim as it cannot be painted and red adhesive may remain after excess tape is removed.

Exterior caulking

Exterior caulking is the last and weakest defence against rain entering a wall from the outside. The best defence against window and door wall leakage includes the following two items:
• properly applied flashing (i.e. top window flashing is underneath the air barrier, while side and bottom flashings are on top of the air barrier)
• a properly detailed drainage plane

Caulking on the outside of a window should be done only after interior sealing is complete. If the exterior is caulked first, it can trap warm, moist air in the wall, which over time, can damage the wall.


Weatherstrip windows around the sash to reduce air leakage. If the windows do not have to be opened and do not serve as emergency exits, they can be locked and caulked. Where storm windows are installed, seal the inside window more tightly than the outside window to reduce condensation problems.


Even the most well engineered window won’t perform effectively if it has been improperly installed. Purchasing a highly efficient window is the first step in obtaining high efficiency performance. The window must be professionally installed correctly to industry standards to make sure that the window achieves the efficiency it was rated to get. Improperly installed skylights can suffer from water leakage and condensation around the frame and curb or tunnel. For operable skylights, ensure that hardware is working and all seals are in good order. Keep them in perfect condition by quickly repairing exterior seals and flashings if damaged. Proper installation will ensure curbs and interior tunnels around the skylight are well insulated and air sealed to reduce condensation. Reduce summer overheating by purchasing light-reflective glazing and, if desired, blinds.


Poor installation, years of hard use, shifting foundations and seasonal warping can often force hinged doors and sliding glass patio doors to become out of square with their frames.

If doors do not fit snugly, fix or replace the door, frame, hardware, gaskets and weatherstripping.

The same techniques for preparing windows apply to all doors including any needed repairs or adjustments, surface preparation and cleaning for the weatherstripping.

Weatherstrip the top and sides of the door frame. The easiest and most effective weatherstripping for a door frame is a good quality V-shaped vinyl type. It makes contact with the edge of the door and provides a good seal even when the door warps from season to season. For increased protection, attach weatherstripping to the stop so that it presses against the face of the door.

There are also many types of combination metal and foam or rubber weatherstripping that are screwed to the stop. They should be adjusted regularly to conform to the changing warp of the door.

Apply weatherstripping to either the door sill or to the door itself. Although this can be a difficult area to seal well, it is worthwhile doing because this is often a source of major drafts. Use durable material that can withstand traffic and is flexible enough to conform to changes in the door caused by fluctuations in humidity and temperature. The weatherstripping should also be easy to replace. A good seal can usually be obtained with gasketed door-bottom weatherstripping that attaches to the door, or with full or partial threshold weatherstripping that is attached to the door sill.

When the weatherstripping is applied to the door itself, a very durable material is necessary. The most effective choice is the combination type, which is simply tacked or screwed along the bottom inside surface of the door. There should be slots that allow for some adjustment of the weatherstripping.

There is a wide variety of door weatherstripping on the market, including kits that include weatherstripping and threshold or door bottom seals. Some products come with replacement seals. Look for high-quality, durable products.

For sliding patio doors, replace weatherstripping and hardware when worn. Replace poor condition sliding patio doors with ENERGY STAR® certified units or with French or garden-style doors and additional energy-efficient windows. In the interim, older patio sliding doors not used in winter can be sealed with removable sealant or covered with heat-shrink film.

Contracting the work

A typical window will last up to twenty years or more. Whether you are replacing one window, completely renovating your home, or building a new home, the decision to purchase new windows is an important one. Here’s list of questions you can ask before selecting a window replacement company.

When getting estimates, make sure the contractor has experience in the type of work you want done. Ask the contractor if the company offers a comprehensive warranty on products and services. Aaben Windows and Doors offers contactless, hassle-free quotes.


Author Michael

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