HERS Water Heating Systems 3

Question 1

Which RESNET/ANSI standard governs water heating energy calculations in HERS ratings?

Accepted Answer

ANSI/RESNET/ICC 301-2014 (and subsequent amendments)

Answer

ANSI/RESNET/ICC 301 is the core standard that establishes the calculation methodology for HERS ratings, including all water heating energy use calculations.

Question 2

What impact does replacing a gas storage water heater with a gas tankless (on-demand) water heater typically have on the HERS Index?

Accepted Answer

Tankless heaters typically lower the HERS Index by eliminating storage tank standby losses

Answer

Gas tankless water heaters eliminate standby heat losses from maintaining a hot storage tank, which typically results in higher efficiency and a lower (better) HERS Index.

Question 3

A HERS rater evaluating a home with a water heater located in an unconditioned garage should ensure what is accurately modeled?

Accepted Answer

That the ambient garage temperature is accounted for, as it affects standby heat losses from the tank

Answer

Ambient temperature affects standby heat losses from the water heater tank; a colder unconditioned garage results in greater standby losses than conditioned space installation.

Question 4

From an energy perspective in HERS ratings, what is the primary purpose of a hot water recirculation system?

Accepted Answer

To ensure hot water is quickly available at fixtures, reducing water waste from purging cooled water

Answer

Recirculation systems keep hot water ready at fixtures, reducing both the water and the embodied energy wasted purging cooled water from pipes before hot water arrives.

Question 5

In HERS rating calculations, how is an electric heat pump water heater (HPWH) treated differently from a standard electric resistance water heater?

Accepted Answer

The HPWH's higher UEF is credited, resulting in lower modeled water heating energy consumption

Answer

The HPWH's significantly higher UEF (typically 2.0–4.0 vs 0.9–0.95 for resistance) is entered into HERS software, directly reducing the modeled energy consumption for water heating.

(HERS) Certified Home Energy Rating System Rater Practice Test

(HERS) Certified Home Energy Rating System Rater Practice Test

HERS Water Heating Systems 3