Home & Design

Ultimate Double Hung windows by Marvin adorn the rear façade of a traditional home. Photo: Marvin

Checklist: Build

Marvin’s guide to the changing world of window technology

When purchasing windows, most homeowners think about aesthetics and operation, while very little consideration is given to the glass itself. Below, Brenda Brunk, product portfolio strategist at Marvin, provides a rundown of glass types and their performance to help you decide which product is best for your home.

Double Panes—In the 1950s, residential-glass manufacturers devised double-paned glass, in which two panes are separated by an air pocket. It acts as an insulator and reduces condensation buildup in winter.

Low E Coatings

  • Radiation from the sun, in the form of infrared light, can shine through a window and heat up the objects in a room—not desirable on a hot day. Also, warm objects themselves can emit heat radiation, which means a room can lose heat by radiating it outdoors through the window. Glass alone will not reduce the effects of radiant heat transfer, but low emissivity (Low E) coatings can.
  • Low E coatings are made of microscopically thin metal on the surface of the window. They reflect radiant heat, reducing heat gain and loss, and block ultraviolet light, which causes flooring and furniture to fade.
  • A Low E coating is only noticeable as a slight tint. Adding layers and switching their surface application will change the performance of the glass.

Insulation—The first examples of dual-pane glass contained an eighth-inch of air in between the panes. Eventually, manufacturers began separating the panes by a half-inch and filling the space with argon, an inert gas. This type of assembly is referred to as an insulating glass unit (IGU). Krypton is even more effective than argon but is much more expensive to create. While insulating glass helps thermal performance, indoor comfort levels are still mostly controlled by Low E coatings.

Glass Ratings

  • U-FACTOR—Measures how well a window keeps heat inside. Lower numbers mean greater insulating capabilities.
  • SOLAR HEAT GAIN—The Solar Heat Gain Coefficient (SHGC) measures how much radiant heat enters your home. The lower the number, the less heat a window lets in.
  • VISIBLE TRANSMITTANCE—This describes how clear the glass is. The higher the number, the clearer the glass.

Climate Questions

  • The colder your climate, the less heat you want escaping your home and the more radiant heat from the sun you want entering. This means you should seek out a lower U-Factor and higher SHGC.
  • If you live in a warmer climate, escaping heat is not as important as preventing radiant heat from entering, which means a higher U-Factor and lower SHGC.

Pro Tips

“We create a balance between modern and traditional in a home by preserving charming existing features while layering in sleek elements that impart modern appeal.”
 — Maryam Tabrizchi, AIA, Elie Ben Architecture, LLC

“The architect’s role is vital during the construction phase. He or she resolves questions from the permit office, construction team and homeowner, and assists with design details throughout.”
—Bruce Wentworth, AIA, Wentworth, Inc.


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