Page 29 - Zero Net Energy Case Study Homes-Volume 1

cant use of energy outside of heating and cooling is that of the equipment, or “plug loads”. These include electric appliances, TV and stereo systems, computer and network equipment and any- thing else that “plugs” into a household outlet. Both homes feature Energy Star appliances and the owners are aware to check the label for the Energy Star certification of any equipment pur- chased for use in the houses.
The house at 703 Heliotrope has the added energy loads of an indoor elevator, an intermittently used type of equipment, as well as charging equipment for an electric car.
Natural Gas Use
The two houses were designed with a dual-fuel kitchen range, namely an appliance with a gas cooktop and an electric oven. The owners decided that this combination minimized the carbon generation while at the same time satisfying their preference for gas stovetop cooking. In addi- tion, the two houses are equipped with gas clothes dryers in each laundry area.
In each case, the solar PV system is so over-sized that this carbon is easily offset by the renew- able energy generated.
In general, the choice of energy source for cooking is often seen as a choice between gas and electric stovetop units, where the reasonable selection is gas because of food-cooking characteristics and capabilities. But there is a third choice, namely electric induction5, which is a magnetic technology that is prevalent in northern Europe and arguably has food-cooking advantages over gas-fueled cooktops. This carbon-free type of appliance will be discussed in more detail in subsequent case studies in this book.
Domestic Hot Water
Domestic hot water is supplied in each house using a 50-gallon heat pump water heater. To conserve water, the sinks at 703 Heliotrope are equipped with an automatic recirculating pump that saves water when the hot water tap is about to be opened, as signaled by a motion detector when someone enters the room. The operation is initiated by the control device at the pump to use the cold water line as a return pipe to the hot water tank until the water in the hot water line reaches high temperature rather than let the water from the hot water tap go down the drain while the water heats up.
703 Heliotrope has a soaking tub in the master bathroom, which is heated by a dedicated tankless (“instant hot”) water heater. The instantaneous hot water device is also used in the small powder room in this house.
Construction
During the construction of both houses, the contractor paid particular attention to details that would affect the airtightness of the construction (see above) and continuous insulation characteristics (no thermal breaks or thermal bridging), which might appear inadvertantly during the course of construction. A basic sequence of the milestones of the construction of the house at 703 Heliotrope is shown on the facing page.
5 See the following article for a technical comparison of cooktop alternatives:
(1) http://ovens.reviewed.com/features/induction-101-better-cooking-through-science;
(2) https://www.consumerreports.org/electric-induction-ranges/pros-and-cons-of-induction- cooktops-and-ranges/.
Zero Net Energy Case Study Homes: Volume 1
17
CORONA DEL MAR NEW HOUSES CASE STUDY NO. 1
(Opposite page) Series of photos, top to bottom, of construction sequence at
703 Heliotrope from forming for foundations to framing of second floor. (Photos courtesy of John Steed Homes.)