These gas savings are a solid achievement. However, there is room for even deeper savings with some additional work. The following issues still need to be addressed: resident behavior, management/ownership decisions and construction flaws that went unnoticed for too long because a commissioning agent wasn’t part of the team.
LEED for Homes doesn’t require a commissioning agent and it was skipped at a detriment. A commissioner was finally hired in summer 2013 and he has identified mechanical issues that will improve gas performance.
The team achieved the goal of monitoring gas savings almost immediately after construction. As a result, the team identified opportunities for enhanced performance quickly and began troubleshooting shortly thereafter.
In summer 2012, hot-water usage seemed high. After troubleshooting, the team identified a bubble in the solar-hot-water system that was blocking solar-heated water from serving many apartments. A repair was made in March 2013. The solar-thermal system wasn’t working properly for 10 out of the 13 months of the subject period. With the system repaired, overall gas performance should be much improved in 2014. By summer 2013, hot water savings was 45 percent.
Although heating savings from August 2012 through July 2013 was respectable, improvements can be made. Some of the areas for improvement include the following:
Thermostats: Because of resident demand, a decision was made in December 2011 to heat apartments to 75 F, despite the energy penalty. Unfortunately, this higher temperature was maintained after construction completion. Energy modeling assumed apartments would be heated to 71 F. Thermostats weren’t limited to 72 F until January 2013. This higher temperature setpoint affected gas consumption for five of the nine heating-season months in the study period. Some residents
continue to override their thermostats to enjoy tropical temperatures in their apartments.
Window operation: The other major issue affecting heating savings is open windows. Typically, windows were used in the winter to vent excess heat. Despite Energy Star thermostats in every apartment and an excellent ventilation system, residents frequently leave their windows open—even in freezing temperatures—for temperature control and ventilation. Occupants are expected to get used to the ability to control temperatures with the thermostats instead of windows as they become accustomed to their new systems. To help, Winn Management, the property’s residential manager, plans to conduct educational seminars for the residents.
As a DER, the bar was set exceptionally high for energy savings. The energy-savings projections became the design goals for the project. However, this simple approach to estimating energy savings was based on adding up individual-measure savings. Though the individual-measure estimates may have been reasonable, they could not be accurate when added because of their interaction. It is well known that adding individual savings reduces the size of the energy target for the next measure. In addition, some measures that save heating energy also have an effect on cooling or other electrical use, not captured by simple calculation. Thus an overestimate of total savings is inevitable.
In the chart above, the computer model shows consistently lower estimates for each measure. In the case of the computer modeling, savings for each measure was calculated by eliminating that one measure from the final design (a subtractive rather than additive method), so it was more likely to be closer to the mark. Computer modeling was begun after the design phase when it was too late to inform the process.