Bill Warren2
The 19th century witnessed a game changer from gaslight to incandescent, which prevailed till the end of World War II. After the war, buildings like the UN Headquarters and Lever House used fluorescents. We are now experiencing another game changer – to LEDs, with more SSLs coming with white light at twice the lumens/watt than today’s. The DOE mandates we reach Net Zero Energy in 15 years, and based on their record for the last 15 years, they will get there day by day.

The best source for what to expect is the ASHRAE quarterly publication, “High Performance Buildings” (HPB). The cover story in last Spring’s edition entitled “Rethinking Daylighting”, was written by the A&E firm, CMTA of Louisville KY, who’ve done many NZE school buildings. They concluded that active day-lighting systems are difficult to maintain and schools systems are reluctant to purchase service contracts, which can negate the energy systems. On the other hand, manual dimming switches save energy by having the teacher or even the students balance the natural light. Their new classroom design adheres to the lighting section of ASHRAE/IES Standard 90.1-2013 which requires reduced artificial LPD requirements and where automatic control is not required because the lighting wattage within the primary side-lighted area is below 150 watts.

This Spring’s edition of HPB features the new Exploratorium Building in San Francisco, where the NZE goal was 36 kBtu/sf, which is equal to its solar PV panel generation. The HVAC and plug load energy consumption are equally at 37%, while the lighting is only 14%, the remainder is for the restaurant. When lighting becomes twice as efficacious, there won’t be economic justification for system control, only room control. The lighting power density is now so low that sophisticated central lighting savings are negligible. With the lighting load so small there might not be enough lighting heat on the coldest days so the Mechanical Engineer must add some supplementary heat source in the winter. If it’s a lighting upgrade with LEDs – add a room control dimming option.

Coordination between the A&E, HVAC and the lighting designer is critical. They must compare design concepts at the very beginning to avoid problems and wasted energy savings later. When PV solar load is being proposed, where will it be located? What restrictions will the local fire department have with respect to % roof coverage? How much carport roof is available for additional PV panels? Can we do DC Solar to DC LEDs in classroom lighting fixtures just below the roof? What will be the BMS cover? If not necessary for lighting, how about for surveillance cameras and intrusion alarms and lock-downs?

Teachers put student’s art work on window blinds that are pulled down if there’s not enough wall space. Make sure the architect provides enough wall space and window space to serve both needs, otherwise blinds will be down all the time losing daylight contribution. All of this should be coordinated with the local authority having jurisdiction regarding energy codes.

On the HVAC side, there are now low rise buildings being designed with fan-less ventilation, more reflecting and chromatically changing glazing to reduce sun load, while the DOE is working on increasing the efficiency of motors that drive fans and pumps. Using just fuel and electric bills as a guide and when our lighting load density goes below the tipping point of 0.5 w/sf, most facilities will be “managed by exception” not by sophisticated and expensive controls. Quoting James Brodrick, Lighting Program Manager of the DOE Building Technology Office, in the April issue of LD&A, “LED technology has been improving at a pace so rapid that it can outstrip long lead times for new construction.” And the arrival of SSLs for lighting has changed the ROI calculation for exiting building upgrades to months rather than years. And don’t be surprised when it pays to relight in 3-4 years rather than 15.

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