Green Building Library
Daylighting

Squeeze More Light From Windows

Natural light isn’t exactly free, but you only do pay for it once– during the design phase. Since capturing natural light is mostly a design issue, there’s little or no cost for extra materials. So a little thought during design creates a cheery house that’s comfortable and saves a little energy on lighting.

Daylighting is a major factor in many new commercial buildings. Designers spend countless hours calculating window to wall ratios, figuring control systems and selecting glazing materials. While houses would benefit from all that attention, it’s unlikely that many home designers would invest the time. Instead, here are a few simple ideas that you can adapt to your own house designs.

Daylighting doesn’t necessarily require more windows and skylights. It’s really just squeezing the most light out of the glazing that you’ve already got. Three principles should guide you:

  1. Allow daylight to penetrate as far as possible into the house.
  2. Distribute light evenly through reflection, borrowing and placement of openings.
  3. Concentrate your efforts on living spaces where people are likely to be during daylight hours.

<house orientation>

Orient the house so that the living space–and their windows–face south. Winter sun will make the windows energy gainers instead of energy losers. Keep east and west windows small to prevent overheating.

<window positioning>

Position glass in the top two-thirds of the wall. This allows light to penetrate deep into the space. Glass below three feet doesn’t contribute light to the room.

<light direction>Bring light into the rooms from more than one direction whenever possible. This could be as simple as placing windows on different walls in a corner room. Also consider borrowing light from adjacent rooms through partial walls, glass blocks, or transoms. Of course, skylights are a great way to bring light into areas without exterior walls.

glazingSelect glazing materials with a high visible light transmittance (VLT). Higher numbers mean more light gets through. This number should be listed on the product literature. Low-emissivity (low-e) coatings reduce unwanted summer heat gain and reduce fading of drapes, upholstery and carpets.

<skylight>

Install small skylights. The spacing between skylights should be no farther apart than the distance from ceiling to floor. Flare deep skylight wells or install a diffusing lens at the bottom of the well to spread light over a larger area.

light colored paint

Choose light colors for walls, ceilings, furnishings, and other interior surfaces to bounce light around. Also, paint interior window trim a light color to reduce the contrast between the indoors and the outdoors.

 

This article appeared in Energy Source Builder Vol. III No. 4, August 1991,
©Copyright 2008 Iris Communications, Inc.

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