Keep Your Structure Sealed Tight
The selection of appropriate windows and doors which provide the owner with an energy-efficient, functional and durable installation while meeting or exceeding building code is only the beginning of a good door/window replacement project. The interface between the door or window with the structure is critical. Often original installations of doors or windows omitted proper insulation around the opening, bridged thermal barriers from the exterior to the interior, and failed to provide adequate backup waterproofing ad sub-pan flashings. Windows are common in aging homes and structures alike. After years of extreme temperatures, varying weather conditions, and building settling, windows are no longer air or watertight. Window frames can become damaged, glazing seals broken or the entire unit can become compromised. While older windows often experience water leaks, newer ones can also be at risk. Generally, there are three key areas that cause windows to leak: design, installation, and maintenance. Leakage from windows and doors can cause significant structural damage and hidden decay which ultimately inflates project costs far beyond the investment in new windows and doors.
Types of Window Framing Material:
Windows come in a number of different frames and glazing types. By combining an energy-efficient frame choice with a glazing type tailored to your climate and application, you can customize each of your home’s windows. Improving the thermal resistance of the frame can contribute to a window’s overall energy efficiency, particularly its U-factor. There are advantages and disadvantages to all types of frame materials, but vinyl, wood, fiberglass, and some composite frame materials provide greater thermal resistance than metal.
- Aluminum or Metal Frames – Although very strong, light, and almost maintenance-free, metal or aluminum window frames conduct heat very rapidly, which makes metal a very poor insulating material. To reduce heat flow, metal frames should have a thermal break — an insulating plastic strip placed between the inside and outside of the frame and sash.
- Composite Frames – Composite window frames consist of composite wood products, such as particleboard and laminated strand lumber. These composites are very stable, they have the same or better structural and thermal properties as conventional wood, and they have better moisture and decay resistance.
- Fiberglass Frames – Fiberglass window frames are dimensionally stable and have air cavities that can be filled with insulation, giving them superior thermal performance compared to wood or uninsulated vinyl.
- Vinyl Frames - Vinyl window frames are usually made of polyvinyl chloride (PVC) with ultraviolet light (UV) stabilizers to keep sunlight from breaking down the material. Vinyl window frames do not require painting and have good moisture resistance. The hollow cavities of vinyl frames can be filled with insulation, which makes them thermally superior to standard vinyl and wood frames.
- Wood Frames – Wood window frames insulate relatively well, but they also expand and contract in response to weather conditions. Wood frames also require regular maintenance, although aluminum or vinyl cladding reduces maintenance requirements.
Types of Window Glazing or Glass
In addition to choosing a frame type, you will need to consider what type of glazing or glass you should use to improve your home’s energy efficiency. Based on various window design factors such as window orientation, climate, building design, etc., you may even want to choose different types of glazing for different windows throughout your home.
- Heat-Absorbing Tints – Heat-absorbing window glazing contains special tints that change the color of the glass. Tinted glass absorbs a large fraction of the incoming solar radiation through a window, reducing the solar heat gain coefficient (SHGC), visible transmittance (VT), and glare.
- Insulated – Insulated window glazing refers to windows with two or more panes of glass. To insulate the window, the glass panes are spaced apart and hermetically sealed, leaving an insulating airspace. Insulated window glazing primarily lowers the U-factor, but it also lowers the SHGC.
- Low-Emissivity Coatings – Low-emissivity (low-e) coatings on glazing or glass control heat transfer through windows with insulated glazing. Windows manufactured with low-e coatings typically cost about 10 to 15 percent more than regular windows, but they reduce energy loss by as much as 30 to 50 percent.
- Reflective Coatings – A special type of low-e coating is especially selective, filtering out 40 to 70 percent of the heat normally transmitted through insulated window glass or glazing while allowing the full amount of light transmission. Spectral selective coatings are optically designed to reflect particular wavelengths but remain transparent to others. Such coatings are commonly used to reflect the infrared heat while admitting more visible light.