In last month's article, I promised that we would look at the major items contributing to the energy consumption reduction of The Learning Source building located in Lakewood, Colo. The students, as a part of their evaluation, actually visited the site, and performed a commercial energy audit on the building, including a survey of lighting/energy consumption, a blower door test and a physical plant inventory. They evaluated the buildings current performance and compared it to local buildings of similar age and construction to establish a "base line" of energy consumption. Much to their surprise, they discovered that their subject building had an energy consumption profile that was very similar to a multi-family housing project. In other words, the building was an energy hog — 24 hours a day, seven days a week.
Much of the energy consumption had to do with the archaic air handling system, which ran 24 hours per day. The introduction of outside air was on a fixed damper basis. Evidently, economizer cycles were not available at the time of construction, and fixed shutter outside air inlets were the norm. In addition to this, the students discovered that a significant portion of the electric consumption was going towards the interior lighting. The footprint of the building was such that window aperture was minimal at best (remember, it was a library originally) and required a lot of inefficient lights in order to maintain reasonable lighting for the occupants. Above and beyond that, the students discovered that the building's exterior shell was basically a double wythe brick wall with approximately 1" of dead air space between the two wythes. Not much room for additional insulation. The ceiling was also problematic in that there was a vaulted ceiling that was not conducive to additional internal insulation. The students modeled the building using state of the art energy modeling software, and played numerous "What if" games, using different combinations of energy conserving measures. They eventually settled on the following decisions:
1. A complete wrap of the building exterior, including the roof, with an extruded poly styrene insulation and stucco finish (Exterior Insulation Finish System).
2. Installation of solar tube sky lights to introduce natural light throughout the interior core of the building, and increased the size of exterior openings to enhance natural day lighting.
3. Installation of a direct digital control (DDC) energy management system to turn lights off whenever the building is unoccupied, or when free lighting is available to reduce electrical waste not only for lighting, but also for heat rejection requirements.
4. The existing HVAC systems duct work was repaired, and modified to reflect the application of newer technologies. In particular, the blower motor serving the air handler was retrofitted with a Direct Current Electrically Commutated Motor (DCECM) and interfaced into the new DDC control system, to allow the blower to move air based on time of day, need for ventilation and cooling versus heating.
5. The building's air cooled compressor/condenser package was replaced, and right sized to reflect the buildings newer low energy demand profiles. They installed a state of the art evaporative pre-cooler on the air cooled condensing unit to reduce the energy consumed for cooling by 40%.
6. The introduction of outside air is no longer a fixed damper situation, but is now an adjustable damper, which is controlled by the DDC system, with operation based on the time of day, outside air temperatures, and the presence of carbon dioxide generated from the occupants.
7. Installation of an 8 kW grid tied solar photovoltaic electricity generation system.
Tune in next month as we continue to look outside our proverbial mechanical box in our efforts to reduce energy consumption and increase overall energy efficiency. Until then, happy think outside the box hydronicing!
All Mark Eatherton material on this website is protected by Copyright 2011. Any reuse of this material (print or electronic) must first have the expressed written permission of Mark Eatherton and CONTRACTOR Magazine. Please contact via email at: [email protected].