Page 95 - Designing for Zero Carbon - Case Studies of All-Electric Buildings

Building Envelope
The original exterior walls were constructed of uninsulated reinforced concrete with an internal layer of red hollow clay bricks for running wiring and plumbing lines. With the removal of the unreinforced masonry, the concrete structural walls could be surfaced on the interior with furred wood framing holding R = 11 fiberglass batt insulation. The wood joist floor above the existing crawl space was repaired and insulated with R-19 fiberglass batt insulation, bringing its overall R-value to R = 21, while the existing concrete basement floor had to remain uninsulated.
The roof over the attic space was insulated with the same fiberglass batts and a layer of radi- ant heat barrier material attached to the sloping roof rafters. This radiant barrier prevents heat buildup on warm summer days, keeping the attic space cool. It’s equivalent R-value is R = 15, producing a nominal R-value for the roof of R = 30.
The single-pane glazing in the historic window frames was replaced with low-e double-glazed units (transmissivity 0.62). Because the window frames were considered historic, only the glass could be replaced. It was not possible to consider entirely new high performance windows with thermal breaks.
Daylighting and Electric Lighting
The design team located each of the two large labs (teaching rooms) in the main area of each of the two wings of the main level of the building. (See Ground Floor Plan.) This allowed opti- mal daylighting from two sides of the room as well as possible top-lighting from the ceiling. The original building had been built with a large skylight in each of these two main roof areas, but they were removed in a later renovation. Re-introducing this form of daylighting for the teaching rooms was seen as a desirable restoration measure for the historic building as well as a good energy design strategy.
Three possible configurations of skylights1 were studied: (1) two skylights centered in the room, (2) two skylights separated for more even light distribution in the room and (3) two pairs sepa- rated for higher daylight levels overall. Daylight analysis was done for each option to determine the number of hours per year when the daylight levels would exceed or equal the IES2 recom- mendations for classrooms and also to visualize the light distribution in the rooms under overcast and clear sky conditions. Some results are shown in the illustration on the next page. Based on this analysis, the design team opted for the two separated skylights (Option 2) for best light qual- ity and performance.
Option 1 Option 2 Option 3
(Below) Three options for sky- lights above the classroom spaces. (Courtesy of Carrier Johnson)
REDFORD CONSERVANCY AT PITZER COLLEGE CASE STUDY NO. 4
(Opposite) Upper wall section at existing wall and roof show- ing retrofitted insulation and finishes. (Courtesy of Carrier Johnson)
1 Velux VSE S01 Roof Window, with diffusing glass, visual light transmissivity = 0.50.
2 Illuminating Engineering Society. For a short list of IES recommended light levels see: https:// waypointlighting.com/uploads/2/6/8/4/26847904/ies_recommended_light_levels.pdf
Designing for Zero Carbon: Volume 1
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