According to the LEED for Homes Reference Guide, “as much as one-third of a home’s total energy bill is spent on heating water.” That's why the LEED for Homes green building program rewards projects that incorporate strategies for reducing the energy use associated with heating water.
Energy associated with water heating may go to waste in several places between the source of heat and the tap:
- Inefficient plumbing design, which increases the distance that hot water needs to travel to get to the tap
- Heat loss from uninsulated pipes
- Inefficiency of the hot water heating equipment
The LEED for Homes program addresses each of these potential energy efficiency losses:
- Distribution System Design. Projects that include an energy efficient hot water distribution system design may earn up to two points toward certification. Such designs include structured plumbing systems with demand controlled circulation loops; central manifold systems that minimize the length of hot water branches from a central trunk; and compact design of conventional systems, which meet criteria limiting the length of plumbing branches and the diameter of plumbing pipes.
- Pipe Insulation. Projects may earn one point toward certification by installing R-4 insulation on all hot water piping. Pipes must be completely insulated – even where they pass through the home’s framing. Sunset Green Home will earn this point.
- Efficient Domestic Hot Water Equipment. The greatest point-earning potential comes from specifying efficient hot water hearing equipment. Sunset Green Home will earn two of three possible points by using Rinnai’s tankless hot water heaters (a project can only earn the full three points by installing solar or heat pump hot water heaters – which were not practical or cost-effective for Sunset Green Home). Sunset Green Home’s Rinnai hot water heaters far exceed the 0.8 Energy Factor required to earn the points. With an Energy Factor of 0.95, the ENERGY STAR qualified RUC98i models installed in Sunset Green Home lead the industry in terms of efficiency.
Rinnai's RUC98i tankless hot water heaters on the left and an insulated hot water pipe in the wall on the right.
We selected Rinnai for its industry leadership in tankless hot water heating technology. Federal efficiency requirements were enacted in 2010 with an adoption date of April 2015, just one month ago. But Rinnai’s tankless hot water heaters already met the standard. And Rinnai’s Ultra Series tankless hot water heaters that will be used at Sunset Green Home also meet the more stringent requirements of 2015 updates to the ENERGY STAR program.
Sunset Green Home’s builder consulted with Rinnai to design a system with two hot water heaters connected together to serve the home’s hot water needs. The second heater will only fire if the first one is unable to meet hot water demand.
Sunset Green Home’s hot water heaters were installed last week. We can’t wait to take them for a test drive!