Page 26 - Zero Net Energy Case Study Buildings-Volume 2

CASE STUDY NO. 7
DPR CONSTRUCTION OFFICE BUILDING
Daylighting and Electric Lighting
Given that the building is one or two stories with a large single roof area above occupied space, as well as the general abundance of natural light in a mild marine climate, daylighting coupled with LED electric light fixtures is the key low-energy design strategy for this project. Challenges were posed again, however, by neighboring site constraints, the blanketing of the roof with the solar panel arrays, and the desire for a light touch to the existing roof for historic reasons.
The roof included two very large industrial skylights over the central two-story open space and, while a source of (over-) abundant daylight locally, they were also a source of great glare. This would have caused an excessive use of interior electric lighting to overcome this problem, so some design modification of the skylights or their interior surround was needed.
These large skylights were to be preserved in appearance for historic reasons, so the company opted to replace the glazing with double-glazed panels rather than install solid diffusing panels or canopies. Great value was also placed on the ability for occupants to see the sky, with cloud movement and the change in light during the day. So, a solution was devised to replace the single-pane skylight glazing with insulated dynamic glass2 panels in the rectangular sections, which would still allow view out to the sky above while providing glare control and lower solar heat gain. After some post-occupancy tuning, the most comfortable and effective energy-saving levels of the adjustable tinting were set for the spaces below the two skylights.
2 Dynamic glass or electrochromic glass is electronically tintable, so that the solar heat gain and light transmission of the glass can be set at a pre-programmed level or through instant control via a portable device. A light sensor reading outside the glass panel is compared to the desired interior condition; the glass system then sets the tint based on the preferred interior light condi- tion for minimal glare and best daylight levels. The glass is therefore tuned to the space.
PHOTO: DREW KELLY
14
Zero Net Energy Case Study Buildings: Volume 2
ROOF PLAN
EXISTING LARGE SKYLIGHTS RETROFITTED WITH DYNAMIC GLASS
TUBULAR SKYLIGHTS, TYP.