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Your Guide to Windows

 Windows are one of the major components of the building envelope and play an integral role in the overall energy efficiency of the home.  They visually join the interior to the outside, allowing you to enjoy the view while keeping out water, air, heat, and cold.  With so many options, selecting the best windows for your project can seem like a daunting task.  However, with a small amount of research and consultations with knowledgeable window representatives, the process can yield well-performing and great looking windows for your home.

 Installation Methodology:

If you are building new, your builder will be using full-frame windows in the rough lumber opening of the home’s framing.  However, if you are looking to replace existing windows in a home, two options can be employed.  In a full frame approach, the entire original window, frame and all, is removed.  It is a holistic approach that allows all aspects of the window to be dealt with, thus providing a more thorough replacement.  In an insert or “replacement” style installation, the original window fame is left intact and the sashes and jamb components are removed.  A new window with minimal framing is installed into the opening.  This is a great option if the frame is in good condition although one of the drawbacks is reduced day light opening, as a new, slightly smaller window is being inserted into the original opening.  It is less invasive and generally less expensive than a full-frame window replacement.  In all cases, installation should be according to the window manufacturer’s specifications with proper water management and insulation.

Frame Construction:

Several options are available in window construction, each with benefits and drawbacks associated with the materials used and how they are built.

Vinyl windows are easy to maintain, offer decent thermal protection, and are generally the lowest cost product option.  However, as vinyl is exposed to hot and cold temperatures, it expands and contracts which leads to an increased risk of seal failure in the window.  Strength of the frame is also a concern and racking or twisting of the unit can be experienced.  Color options for both interior and exterior surfaces can also be a limiting factor.

Composite windows are low maintenance and offer a wider array of color options.  Benefits of durability and strength are dependent upon the materials used in the composite (vinyl, glass, wood pulp, etc.), therefore is dependent upon the combination of products and the manufacturer. 

 All-aluminum windows offer strength, durability, and low maintenance.  With their low thermal performance and thermal barrier issues, they are often not the best fit for use in colder regions in which seasonal variations are strong.

 Fiberglass windows offer strength, low maintenance, great thermal performance, and low expansion rates.  Cost comparative to vinyl is the main drawback of this window type.

 All wood windows provide thermal performance with exterior architectural detail and unlimited color choices.  They do, however, require regular exterior maintenance and can be costly when looking at high quality options.  With proper maintenance, they can last the longest of any of the types.

 If homeowners want the benefits of a wood frame and interior, but without the maintenance of the wood exterior, several exterior clad options are available on the market.  Vinyl, composite, fiberglass, and aluminum clad versions are all readily available and offer lower exterior maintenance options.  Costs can range depending upon manufacturer and the quality of materials and construction.  Fiberglass and aluminum clad versions are generally higher performing, but also have a higher associated cost.

Glazing Options:

Although single pane windows are available, most homeowners choose windows with insulated glass options, allowing them to build the best performing window for their region.  Both double and triple pane insulated glass options are available with most manufacturers and provide the basis for building the window’s efficiency.  Low-emissivity, or LowE, layers on insulated glass surfaces help to control heat transfer.  LowE coatings lower the U-factor of the glass , thus making it more energy efficient.  Inert gasses, such as argon and krypton, can be used between the panes of glass to improve the thermal performance of the window.  Other glass coatings, such as tints and reflective layers can help to address the visible light transmittance inside the home.

 Energy Performance:

Overall energy efficiency of a window is determined by the interaction of all of the window components as well as how the window is installed.  Three main measurements are used to determine this: 

 ·         U-factor:  the rate at which the unit conducts non-solar heat flow.  The lower the U-factor, the more energy-efficient the unit.

·         Solar Heat Gain: is the fraction of solar radiation admitted through a unit and subsequently released as heat inside a home. The lower the SHGC, the less solar heat it transmits and the greater it’s shading ability.

·         Air Leakage:  the rate of air movement around a unit.  A unit with a low air leakage rating is tighter than one with a high air leakage rating.

 Window performance is also dependent upon the geographic area of the home and how the materials respond to the environment.  For example, tri-pane glass may not be the most energy efficient option for your region, even though homeowners may think that three layers of glass are better than two.


Style and Aesthetic:

While materials, construction, and performance are essential to selecting the best window for your project, homeowners should also pay special attention to the style and aesthetic of their window choices.  Most manufacturers offer several styles of windows, including double hung, casement, awning, picture, bays, and bows, allowing architects, builders, designers, and homeowners to make the best choice for the style of home.

Meg Connor

Executive Officer

Studio 4 Showroom