ASHRAE Journal - December 2010 - 134

Solar NZEB ProjEct

Photo 2: Interior light with full sun entering Equinox House on September 20. The sun’s Photo 1: Equinox House near the fall equinox (September 20) with clerestory overhang elevation through most of the winter will and lower roof overhang allowing full sun to enter the house. move the direct beam radiation onto the upper walls and ceiling.

Windows & overhangs

By ty Newell, Member ASHRAE; and Ben Newell, Associate Member ASHRAE

indows, after people, are maybe the second most complex showing the main living space picture win-

Photo 3: North looking view of Equinox dows and smaller casement windows in the (6435 L) cistern access cover for rainwater

component affecting building performance. Windows impact master bedroom. Note the 1,700 gallon
for storm water retention in the foreground. ficiency or daylighting. Photo 2 shows area in Equinox House on September

comfort (both visual and thermal), capital cost, and operating cost. harvesting and adjacent rain garden area

Proper integration into a building for achieving good performance and

aesthetic appeal requires close cooperation of architects and engineers. the interior view of the main open living Chapter 31 of ASHRAE Handbook—Fundamentals.
Equinox House is defined by its windows and their protective overhangs. The house is named after its “equinox overhang” design protecting the clerestories in the summer from direct solar radiation, and acting as a solar energy reflector in the winter. Photo 1 shows the outside of Equinox House taken on September 20, close to the fall equinox. The top edge of the clerestory overhang was placed at a distance and angle from the top of the clerestory windows such that three weeks prior to the equinox, the clerestories were fully covered. From our simulation modeling, the equinox is the optimal time in our area (Central Illinois) to cover (spring equinox) and uncover (fall equinox) the clerestories. The optimal time to cover and uncover windows is dependent on other factors, too, such as the windowto-wall area ratio and internal activities. Too many buildings have been over windowed under the guise of energy ef-

A great source for learning about window performance is found in 20 when the first beam of sunlight has
penetrated into the space. The 5.5 m2 (59.2 ft2) of clerestory and 5.5 m2 (59.2 ft2) of picture windows in the main living area provide 400 to 500 lux (37 to 46 footcandles) during the summer and 800 lux (74 footcandles) in the winter with the admission of beam radiation. The movement of sunlight through the space is quite animated and fun in an unobtrusive manner to room occupants. The north-facing picture windows, shown in Photo 3, were chosen to view the backyard garden.

this is the fourth in a series of columns. Find previous columns at www.ashrae.org/ashraejournal.
134 ASHRAE Journal ashrae.org December 2010

ASHRAE Journal - December 2010

Table of Contents for the Digital Edition of ASHRAE Journal - December 2010