Page 70 - Zero Net Energy Case Study Buildings-Volume 1

CASE STUDY NO. 3
IDeAs OFFICE BUILDING
Post-Occupancy: Controls and Monitoring
As noted above, the early measurements of electricity use in the building circuits were flawed by some meter malfunctions and by the inaccuracy of some meters with regard to low energy flows because of characteristics of the current transformers (CTs), as was also observed with Case Study No. 2 and No. 3. When the data was analyzed and compared, the apparent inaccuracy of the meters was detected. The issue was resolved by replacing meters and verifying that the new results were internally consistent.
The accuracy of energy use metering is a consistent issue with low-energy buildings that are being monitored and analyzed. It would be useful to include metering system checkout as part of the regular commissioning process.
The lighting control systems presented a number of problems and issues with regard to energy use that were eventually solved. The lighting control industry has advanced in the past five years to correct and avoid some of these issues, but it is useful to note the experience with this building and how the owner and occupants, with their expertise with these particular systems, worked to resolve them.
When the meter accuracy problem was solved and accurate data on energy use for each of the circuits was analyzed, the IDeAs staff found that the lights were still consuming a base level of electric energy even when full daylight was available and the lights should have been off. Study of the issue revealed that the dimming controls never shut off the lights completely but main- tained a low level of power that was not discernible from the lamp appearance.
The staff worked with the light control system manufacturer to develop controls that completely shut off the power to the light fixture without adversely affecting lamp startup or the continuity of light level change. Since the operating system for the controls is located with a device at the elec- trical panel, it was relatively easy to change out the system to the new version that completely shut off the lights in adequate daylight conditions.
The problem was the same with the second type of light fixture and control system, where the dimming controls were built into the light fixture rather than a separate device at the electric panel that communicated wirelessly with the light fixture dimmer. This type of fixture made it impractical and costly to retrofit or replace the dimming control system. In addition, the occupant control of the light schedule was executed through proprietary software that was installed on a specified laptop in the office. The software compatibility with the Windows operating system be- came an obstacle to operation of the lights since the upgrades to the operating software always lagged behind Windows operating system upgrades and there was no backwards compatibility.
To solve both of these problems, the IDeAs staff decided to abandon the built-in light controls at these types of fixtures and to replace them with a new wireless dimming system with the central operating system located at the panel box and with an online site for scheduling the lights. The online site removed the software compatibility issue by moving the maintenance of the software to the manufacturer rather than the user. Replacing the dimming system for these fixture types incurred an expense for the owner but removed the energy drain at the fixtures under good day- light conditions.
Conclusion: wireless, web-based dimming control systems with the dimming operating system located in a hardware device at the electric panels is a “best practices” approach to daylight- responsive lighting systems.
Post-Occupancy: HVAC
After routine commissioning of the HVAC system was completed, the IDeAs staff noticed from the metering data that the ventilation fan was operating at night. Looking into this, the staff found that the operation of the fan, which is intended only to provide fresh air for the occupants, fol- lowed the operation of the radiant floor system. In other words, rather than operate in response to the occupancy of the space, the fresh air ventilation fan would turn on whenever the radiant floor system was operating to provide heating or cooling to the space.
Because of the time lag effect of the mass of the concrete slab, the radiant floor system would often start operating several hours before staff were scheduled to occupy the space so that
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Zero Net Energy Case Study Buildings: Volume 1