Page 29 - Designing for Zero Carbon-Volume 2_Case Studies of All-Electric Multifamily Residential Buildings

IVY SENIOR APARTMENTS
CASE STUDY NO. 1
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Domestic Hot Water System
A central heat pump water heater (HPWH) system is used to heat all the domestic hot water (DHW) for the complex, including all apartments, administrative spaces and shared facilities. (See system diagram on the previous page.)
The water is preheated using a solar thermal system, which was required for the prescriptive path of the California Title-24 energy code for multifamily housing at the time this project was ap- proved (2019). The preheated water is then circulated to the two HPWH units located outside the water heating room on the ground floor. The heat pumps raise the temperature of the water and direct it into the large hot water storage tank. The water distribution system is a typical central water heating system, with the main distribution piping installed first horizontally in the ceiling of the first floor, then vertically to the apartments above.
The solar thermal panels (shown in Photo 1 above) actually utilize a “working fluid” that transfers the captured solar heat in the panels to a potable water supply via a heat exchanger. The heated water is circulated to a dedicated solar storage tank (shown in Photo 2 above), though it is not fully at the necessary temperature for use in the building. This water source, however, serves as an effective preheated supply for the central system.
Two heat pumps (shown in Photo 3 above) are used for the water heating system to ensure a redundancy in the supply system. These large pieces of equipment must be located outside and produce a certain amount of noise during operation (85 dBA). The water heating room was therefore located as far as possible from the apartments, which consequently positioned the heat pumps on the back side of the building complex, where the noise would be least intrusive.
Appliances
Typical electric appliances are used in each apartment, including an ordinary electric range. Induction ranges were not selected because of comparative cost and lack of familiarity with this type of appliance among this particular occupant group.
The common laundry facility is outfitted with conventional electric dryers with direct venting to the outside, rather than heat pump dryers, which are more energy efficient.
Lighting and Plug Loads
Daylighting design was emphasized for each apartment unit. As noted above, the ceiling height could be kept at a relatively high 9’-2” because no ceiling space is needed for ductwork. The exterior windows for each unit could therefore be set at 8’ tall, which gives much greater daylight penetration into the interior of the units. In addition, light from two sides of the unit is possible because of the windows on the circulation decks (entry sides of the unit). This not only reduces potential glare from the large window, but encourages turning off electric light sources because of the high visual comfort resulting from the good daylighting design.
Another noteworthy amenity is that the infrastructure for electric car charging was installed in the common parking area, so that the project is “EV-car ready”. The car-charging units can be attached to the designated locations near each parking space, providing this service to staff and visitors.
Battery Storage
None included or planned for future installation.
Designing for Zero Carbon: Volume 2
(Above) Tall windows could be used in all units because of the relatively high ceilings, provid- ing good daylight penetration to the interiors of the units.
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