Lessons Learned - Brock Environmental Center
Photo by David Chance
Rainwater is intrinsically soft and corrosive, potentially reacting with distribution or storage systems, resulting in water quality issues and impacting the service life of copper pipes. After observing unusually high copper levels in the water supply, a calcite contactor was added to the Brock design to harden rainwater so that it would be less corrosive.
Alternatively, we might have pursued non-reactive piping materials, like PEX-a. While the issue was observed because of the aggressive monitoring triggered by drinking rainwater, the issue would be prevalent in nonpotable rainwater harvesting systems as well.
Predicting wind turbine output can be challenging, especially compared to the effort in predicting photovoltaic output. Wind is greatly impacted by terrain, and often the closest wind data available is from nearby airports with very different terrains than the building site. An on-site anemometer is a good idea, but often impractical or challenging to erect. Solar insolation is far more predictable and less impacted by localized site factors.
Wind speeds are far less predictable for a specific site, which left our team with a lower level of confidence about correctly predicting the expected output of the turbines versus the photovoltaic system.
During the first year of operation, the wind turbines actually produced 99.6% of their targeted output, but the wind output varied dramatically from historic averages (Figure 3). Despite the annual power generation matching the predicted output, our team still saw some large variations in actual versus predicted output from month to month. Also, using a turbine certified and tested for its output is important—most small-scale turbines used for individual buildings are not.
While photosensor dimming can greatly reduce electric lighting when daylight is present, the lower limit for the dimming is typically 10%. In the case of Brock, the office space has such consistent daylight in the middle of the day (even on overcast days), that the client decided to turn the office lighting completely off during the middle portion of the day to save additional energy. In spaces with consistently even daylight, consider designing photosensor dimming down to 1% or simply turning the lighting off during a consistent block of time.
The natural ventilation modeling during design was based on ASHRAE Standard 55 thermal comfort recommendations. The client has reported that the occupants actually use natural ventilation to much higher indoor temperatures. Providing users with several options for adjusting and fine tuning indoor environmental conditions can dramatically expand perception of comfort.
Designers need to be more engaged during the first year of a building’s operations. This helps to diagnose problems, especially control sequence problems, but it also helps the team learn about how building systems work.
A good example of this is with packaged controls that were provided with the VRF system. The energy model assumed the units would be able to turn the indoor fans off whenever space temperature was satisfied. The wall-mounted VRF units are set up in the factory so the fan runs continuously anytime the system is enabled. These controls can’t be overridden by the BMS or altered at the factory. This had a direct impact on fan energy compared to what was expected.
Packaged controls present challenges with integration into the building controls system. The VRF system and packaged DOAS unit both came with factory controls and had limited BMS control. Not all desired sequence of operation may be achievable through the BMS.
A good example was the factory controls on the wall-mounted VRF indoor units mentioned above that prevented fans from turning off. A fairly simple control strategy to turn off equipment when not needed was not possible due to the factory controls. This resulted in an extensive exercise of troubleshooting a problem with the controls contractor and the mechanical contractor. In the end, the team had to accept the factory controls as installed.
As issues like this were discovered during the commissioning process, the design team worked with the factory engineers and the controls contractor to identify solutions that allowed the systems to be controlled as closely to the design intent as possible. If packaged controls are used, designers should work directly with the factory applications engineers during design to be sure the desired sequences are attained and all the systems are modeled properly.
The design team worked diligently with the building owner to understand building use and loads and built schedules for each space covering people, lighting and equipment load profiles for virtually every day of the year. This gave the design team better comfort with rightsizing systems and understanding the energy consumption during the modeling process. It also allowed the owner to see how their decisions impacted building energy consumption and resultant renewable needs.
The building has more use than the design team and owner expected, especially in the large conference room. In spite of that, the energy model was within 2% of the predicted energy use for the year. Initial thoughts attribute this to feedback from the owner that the building operates in natural ventilation more than expected and the occupants have expanded the indoor cooling temperature to 80°F.