Energy-efficient Windows & Lighting

By Joyanna Laughlin

This ""Anatomy of an Energy-Efficient Window" diagram is courtesy

Shine a Light on Energy Savings
Make windows and lighting a priority in your energy-efficient home

When it comes to building your energy efficient home, it’s not just the big decisions (like orientation and insulation) that are important. Selecting the right lighting and windows has a bigger impact on your energy bill than you might think.

Choose High R-Value Windows
While windows let light and amazing views into your home, they are also a source of heat (energy) loss. A single pane of glass has an R-value of R-1 and a double-glazed window is R-2. According to David Johnston, Colorado-based green building consultant and author of Toward a Zero Energy Home, if your home’s walls are insulated to R-30, you could be losing 15 times more heat through the windows than the walls. And the low-emissivity (low-E) windows that are considered energy efficient are often only R-3. Johnston recommends shopping around to find windows with even higher R-values. For example, the windows in Johnston’s home and office range from R-7 to R-11. In addition, he suggests shading windows with awnings or overhangs during the summer to keep the sun out of the house.

Focus On Lighting
There’s more to energy-efficient lighting than buying a bulb and screwing it in. The most important things to consider when buying lighting include how light sources work, lumens, and color temperature, says Hyman Kaplan, IALD, PE, owner of the Tucson, Arizona-based lighting consulting firm Hy-Lite Design. Interior home lighting includes ambient (general), task, and accent lighting, and a standard bulb for ambient lighting illuminates differently than a spot light bulb. Kaplan recommends deciding how you intend to use each room in your home before selecting lighting with your design team. If you’re planning on watching TV in the living room, it will require different lighting than if you’re going use it for reading, Kaplan says.

Secondly, people are used to buying incandescent light bulbs by the watt, but it makes more sense to compare compact fluorescent (CFL), LED and halogen incandescent bulbs in terms of lumens, which measure brightness, Kaplan says. For example, a 60W incandescent bulb gives off 800 lumens of light. “Incandescent bulbs are obsolete,” adds Johnston. “CFLs are a transitional bulb, and LEDs are emerging as the bulb of the future.”
In addition, color temperature impacts quality of light. An incandescent bulb has a color temperature of 2,800K, providing what most people consider warm, comfortable light, whereas many people don’t like the cool, white light of a 4,100K CFL. Neutral light is 3,500K. Whichever lighting you prefer, don’t be afraid to speak up and ask questions, Kaplan says. It’s your home, after all. 

Tue Apr 29 00:00:00 PDT 2014