Energy required for water heating accounts for approximately 40percent of national residential natural gas consumption in California. With water heating contributing such a substantial portion of natural gas consumption, it is important to pay attention to water heater efficiencies. This paper reports on an investigation of a patented, buoyancy-operated flue damper. It is an add-on design to a standard atmospherically vented natural-draft gas-fired storage water heater. The flue damper was expected to reduce off-cycle standby losses, which would lead to improvements in the efficiency of the water heater. The test results showed that the Energy Factor of the baseline water heater was 0.576. The recovery efficiency was 0.768. The standby heat loss coefficient was 10.619 (BTU/hr-oF). After the damper was installed, the test results show an Energy Factor for the baseline water heater of 0.605. The recovery efficiency was 0.786. The standby heat loss coefficient was 9.135 (BTU/hr-oF). The recovery efficiency increased 2.3percent and the standby heat loss coefficient decreased 14percent. When the burner was on, the baseline water heater caused 28.0 CFM of air to flow from the room. During standby, the flow was 12.4 CFM. The addition of the damper reduced the flow when the burner was on to 23.5 CFM. During standby, flow with the damper was reduced to 11.1 CFM. The flue damper reduced off-cycle standby losses, and improved the efficiency of the water heater. The flue damper also improved the recovery efficiency of the water heater by restricting on-cycle air flows through the flue. With or without the flue damper, off-cycle air flow up the stack is nearly half the air flow rate as when the burner is firing.

Residential building practice currently ignores the losses of energy and water caused by the poor design of hot water systems. These losses include: the waste of water while waiting for hot water to get to the point of use; the wasted heat as water cools down in the distribution system after a draw; and the energy to reheat water that was already heated once before. A feasibility study and an action plan for a proposed research project involving residential hot water distribution systems is being developed. The feasibility study will use past work to estimate of hot water and energy loses caused by current hot water distribution systems in residences. Proposed research project, or roadmap, will develop recommendations for improvements to residential hot water distribution systems. The roadmap addresses the technical obstacles and gaps in our knowledge that prevent water and energy reductions and market adoption of water- and energy-efficient technologies. The initial results of the feasibility study are presented here along with a discussion of a roadmap to improve the efficiency of residential hot water distribution systems.

Residential building practice currently ignores the losses of energy and water caused by the poor design of hot water systems. These losses include: combustion and standby losses from water heaters, the waste of water (and energy) while waiting for hot water to get to the point of use; the wasted heat as water cools down in the distribution system after a draw; heat losses from recirculation systems and the discarded warmth of waste water as it runs down the drain. Several technologies are available that save energy (and water) by reducing these losses or by passively recovering heat from wastewater streams and other sources. Energy savings from some individual technologies are reported to be as much as 30 percent. Savings calculations of prototype systems including bundles of technologies have been reported above 50 percent. This roundtable session will describe the current practices, summarize the results of past and ongoing studies, discuss ways to think about hot water system efficiency, and point to areas of future study. We will also recommend further steps to reduce unnecessary losses from hot water distribution systems.

The Home Energy Saver (HES, http://HomeEnergySaver.lbl.gov) is an interactive web site designed to help residential consumers make decisions about energy use in their homes. This report describes the underlying methods and data for estimating energy consumption. Using engineering models, the site estimates energy consumption for six major categories (end uses); heating, cooling, water heating, major appliances, lighting, and miscellaneous equipment. The approach taken by the Home Energy Saver is to provide users with initial results based on a minimum of user input, allowing progressively greater control in specifying the characteristics of the house and energy consuming appliances. Outputs include energy consumption (by fuel and end use), energy-related emissions (carbon dioxide), energy bills (total and by fuel and end use), and energy saving recommendations. Real-world electricity tariffs are used for many locations, making the bill estimates even more accurate. Where information about the house is not available from the user, default values are used based on end-use surveys and engineering studies. An extensive body of qualitative decision-support information augments the analytical results.