Greenbuilt Construction Energy Efficiency Retrofit House Demonstration - Sacramento

One of the homes that was part of Sacramento Municipal Utility District's (SMUD) Energy Efficiency Retrofit Demonstration (EERD) project was a 1980's era home in Fair Oaks, California, referred to as the Greenbuilt house, as Greenbuilt Construction completed the retrofit of the home. The home underwent an extensive energy efficiency retrofit with a goal of achieving a 50% reduction in energy use to demonstrate the potential for other builders and homeowners in the area. The retrofit measures included installing: ENERGY STAR appliances high efficiency light roof radiant barrier additional ceiling and wall insulation double-pane, low-e windows external motorized shading and solar tubes a 16 SEER/9.75 HSPF heat pump improved ducts a whole-house fan a heat pump water heater (HPWH) integrated collector storage solar water heater (ICS SWH) and 3.2 kW of PV. In addition, the home was air sealed to reduce infiltration.

Researchers from the National Renewable Energy Laboratory (NREL) performed short-term tests on the major systems installed as part of the retrofit to ensure that they were performing as expected. The systems evaluated included the space conditioning heat pump, the air handler and ducts, the HPWH, the ICS SWH, and the PV array. Some ducts were untwisted after testing revealed that two rooms were not getting sufficient airflow. Afterwards, all systems were performing as expected.

In addition to testing to confirm adequate performance of all new systems, NREL was given the opportunity to use the Greenbuilt house as a laboratory house for a year. The space conditioning system and home water systems were subjected to a series of tests to determine optimal control strategies for lowering energy consumption and reducing peak (4:00-7:00 p.m.) energy consumption during the summer. The different cooling strategies considered included two different precooling schedules, drawing the external shades during the day and using the whole-house fan at night, and combinations of those. The most effective strategy for reducing overall energy consumption was the use of external shades, which cut the daily cooling load by 34% and reduced the energy use during peak hours by 40%. The different precooling strategies eliminated the peak load entirely but actually increased daily cooling energy use. The use of shades and the advanced precooling strategy increased the daily energy use by 5% but eliminated all peak use and maintained a comfortable home. These results were verified over the entire summer using an Energy Plus model of the home. The hot water system was tested in two configurations: the HPWH alone and the ICS solar water heater paired with the HPWH. Six hot water draw profiles, varying in terms of daily hot water volume, time of day for hot water use, and the duration of the draws, were imposed on the hot water system to test their effects on performance. When operating alone in the summer, the HPWH operated with a COP around 2.2, except for a draw that used a quarter of the averaged daily hot water usage, which had an average COP of 1.6. The combination of ICS and HPWH resulted in larger COPs, but also more variability depending on the draw profile. The standard, hourly draw profile produced the highest COP of 6.4. The quarter volume draw profile had the lowest COP of 2.8 for the combined system. Relative to a standard electric water heater, the HPWH operating alone reduced the peak load by 56% and the combined ICS and HPWH system completely eliminated the peak load.

萨克拉门托市政公用事业区（Sacramento Municipal Utility District, SMUD）的能源效率改造示范项目（Energy Efficiency Retrofit Demonstration, EERD）中，有一座位于加利福尼亚州费尔奥克斯的20世纪80年代建筑风格的住宅，被称为Greenbuilt house，由Greenbuilt Construction公司完成了其改造工程。该住宅经过全面的能源效率改造，旨在实现能源使用量减少50%，以向该地区其他建筑商和业主展示其潜力。改造措施包括安装：能源之星（ENERGY STAR）电器、高效照明屋顶辐射屏障、额外的天花板和墙体隔热材料、双层中空玻璃、低辐射率（low-e）窗户、外部电动遮阳和太阳能管道、16 SEER/9.75 HSPF热泵、改进的管道、全屋风扇、热泵热水器（HPWH）、集成收集储存太阳能热水器（ICS SWH）和3.2 kW的太阳能光伏板。此外，住宅还进行了空气密封，以减少渗透。

国家可再生能源实验室（National Renewable Energy Laboratory, NREL）的研究人员对改造中安装的主要系统进行了短期测试，以确保其性能符合预期。评估的系统包括空间调节热泵、空气处理器和管道、HPWH、ICS SWH和光伏阵列。测试发现，部分管道未扭曲，因为两个房间未获得足够的气流。之后，所有系统均按预期运行。

除了对所有新系统进行测试以确认其性能充足之外，NREL还获得了将Greenbuilt house用作实验室住宅一年的机会。空间调节系统和家庭水系统接受了一系列测试，以确定降低能源消耗和减少夏季高峰时段（下午4:00至7:00）能源消耗的最佳控制策略。考虑的冷却策略包括两种不同的预冷却时间表、白天拉下外部遮阳帘和夜间使用全屋风扇，以及这些策略的组合。降低整体能源消耗的最有效策略是使用外部遮阳帘，这减少了每日冷却负荷34%，并在高峰时段减少了40%的能源消耗。不同的预冷却策略完全消除了高峰负荷，但实际上增加了每日冷却能源消耗。使用遮阳帘和先进的预冷却策略增加了每日能源消耗5%，但消除了所有高峰使用，并保持了住宅的舒适性。这些结果在整个夏季使用Energy Plus模型进行了验证。热水系统在两种配置下进行了测试：单独的HPWH和与HPWH配对的ICS太阳能热水器。对热水系统施加了六种热水抽取配置文件，这些配置文件在每日热水体积、热水使用时间和抽取持续时间方面有所不同，以测试其对性能的影响。在夏季单独运行时，HPWH的COP（能效比）约为2.2，除了使用平均每日热水使用量四分之一的抽取，其平均COP为1.6。ICS和HPWH的组合导致了更大的COP，但也根据抽取配置文件的不同而具有更大的可变性。标准的小时抽取配置文件产生了最高的COP，为6.4。四分之一体积的抽取配置文件产生了组合系统的最低COP，为2.8。与标准电热水器相比，单独运行的HPWH减少了56%的高峰负荷，而ICS和HPWH的组合系统完全消除了高峰负荷。