Page 87 - Zero Net Energy Case Study Homes-Volume 1

The heating and cooling loads were modeled in advance to right-size the equipment, which de- termined that only a 3-ton system would be required in general for these ZNE houses.
Domestic Hot Water
The ZNE houses use a 50-gallon, highly energy-efficient electric water heater that is designed based on heat pump technology rather than normal electric heating elements. It uses approxi- mately 50% less energy than a standard water heater of the same size. The houses also utilize water-efficient features such as high pressure/low flow shower heads and faucets to reduce overall consumption of hot water.
Daylighting and Electric Lighting
All of the homes were originally specified with LED light fixtures that provide energy-efficiency, longevity and dimmability. Buyers were allowed to substitute or add specialty light fixtures. Plug- in lamps were also not controlled as part of the research study.
Plug Load and Equipment
All appliances are EnergyStar®, including refrigerator, dishwasher, microwave, washer, dryer, range hood and electric oven. However, due to consumer preference, buyers could opt for a gas range, which was selected in most cases.
Control Systems
The control system monitoring and operating the heating, ventilating and cooling system was Nexia XL824®. In addition, because the research study included detailed energy monitoring of the house energy consumption and PV system production, the data collected was made visible to the owners at the house. Although the system involved only passive monitoring, the owners were able to see real-time data and possibly adjust behavior or system operation in response.
A separate Energy Management System (EMS) is used to obtain the lowest utility rates by op- timizing the use of the battery storage. To avoid peak power charges, for example, the system may be programmed to charge the batteries in the early morning hours to make sure that there will be enough battery power available during early evening hours when there is no output from the solar PV system and utility rates are high. This is discussed in more detail in the section on Battery Energy Storage below.
Zero Net Energy Case Study Homes: Volume 1
75
MERITAGE PRODUCTION HOUSES CASE STUDY NO. 4
(Opposite page, top) Interior view of Great Room in the ZNE Model Home.
(Opposite page, bottom)
Interior view of Kitchen/Dining spaces.