Index and Ratings Flashcards

A home receives a HERS Index of 0. What does this indicate?

Answer: The home uses no net energy on an annual basis

A HERS Index of 0 represents a net zero energy home that produces as much energy as it consumes annually.

Which of the following scenarios would most likely INCREASE a home's HERS Index score?

Answer: Increasing duct leakage from 4% to 10%

Increasing duct leakage wastes conditioned air and raises energy consumption, which increases the HERS Index score.

When a HERS rater upgrades a home's insulation from R-11 to R-19 in the walls, what is the expected effect on the HERS Index?

Answer: The HERS Index decreases

Better insulation reduces heat transfer and energy demand, which lowers the HERS Index score.

The HERS reference home is set to an index of 100 and is modeled based on which standard?

Answer: RESNET/ICC 301 standard

The HERS reference home is defined by the RESNET/ICC 301 standard, establishing the baseline for index calculations.

A new home scores a HERS 55 and its neighbor scores a HERS 85. Approximately how much more energy efficient is the first home?

Answer: About 30% more efficient

Each point on the HERS scale represents approximately 1% more or less energy use, so a 30-point difference equals roughly 30% greater efficiency.

What is the primary purpose of the projected HERS rating versus the confirmed HERS rating?

Answer: Projected is issued before construction; confirmed is issued after final inspections and testing

A projected rating is based on design documents before construction, while a confirmed rating is issued after the home is built and tested.

Which component of the HERS rating accounts for mechanical ventilation energy use?

Answer: It is part of the total annual energy consumption factored into the index

Mechanical ventilation energy use is included in the total annual energy consumption calculation that determines the HERS Index.

A HERS rater is evaluating an existing home built in 1985. Which type of HERS rating is most appropriate?

Answer: Confirmed rating with full field verification and testing

Existing homes require a confirmed rating that includes on-site inspection and diagnostic testing to accurately assess actual energy performance.

How does the HERS Index treat on-site renewable energy generation such as solar PV?

Answer: It reduces the home's energy consumption score, potentially driving the index below 100

On-site renewable energy offsets the home's consumption, lowering the HERS Index and potentially achieving scores below zero.

A home's HERS rating is listed as '52.' Which of the following statements is most accurate?

Answer: The home uses 48% less energy than the reference home

A HERS Index of 52 means the home uses 48% less energy than the reference home (which scores 100).

Under RESNET standards, which category of energy end use is specifically EXCLUDED from the HERS Index calculation?

Answer: Plug loads and process loads (in some rating types)

Plug loads and process loads are excluded from the standard HERS Index calculation, which focuses on regulated energy end uses.

What does a HERS 'sampling' protocol allow a rater to do?

Answer: Test a subset of similar homes in a subdivision and apply results to the group

The HERS sampling protocol allows raters to test a representative subset of similar homes in a development and apply those results across the group.

A builder asks a HERS rater why their HERS 45 home qualifies for the DOE Zero Energy Ready Home program. What is the best explanation?

Answer: The program requires a HERS score at or below 45 for most climate zones

The DOE Zero Energy Ready Home program requires a HERS score at or below 45 (varies by climate zone), making a HERS 45 home eligible.

How does window-to-floor area ratio affect the HERS Index in a hot climate?

Answer: Excessive window area in a hot climate increases cooling loads and raises the HERS Index

In hot climates, excessive glazing increases solar heat gain, raising cooling energy demand and the HERS Index.

Which ENERGY STAR certification pathway for new homes relies directly on the HERS Index as the primary compliance metric?

Answer: ENERGY STAR Performance Pathway

The ENERGY STAR Performance Pathway uses the HERS Index score as the primary metric to determine whether a new home qualifies.

A HERS rater is told a home has an infiltration rate of 3.5 ACH50. How does this value factor into the HERS Index?

Answer: It is used to calculate heat loss/gain from air leakage, affecting the energy score

ACH50 is used in HERS software to calculate the energy impact of air infiltration on heating and cooling loads.

What is the significance of the HERS Index value of 130?

Answer: It indicates the home uses 30% more energy than the 2006 IECC reference home

A HERS Index above 100 means the home uses more energy than the reference home; a score of 130 indicates 30% more energy use.

In HERS ratings, what is the 'rated home' compared against to generate the index score?

Answer: A computer model of the same home built to the RESNET reference specifications

The rated home is compared against a reference version of that same home modeled to RESNET/ICC 301 specifications to produce the index.

A HERS rater discovers that a home's HVAC ducts are entirely within conditioned space. What is the likely effect on the HERS Index?

Answer: The HERS Index may decrease because duct losses to unconditioned space are eliminated

Ducts located entirely within conditioned space eliminate thermal losses to unconditioned areas, improving system efficiency and lowering the HERS Index.

Which software tool is most commonly used by HERS raters to calculate the HERS Index for residential buildings?

Answer: REM/Rate or equivalent RESNET-approved rating software

HERS raters use RESNET-approved software such as REM/Rate or equivalent tools that meet RESNET/ICC 301 calculation requirements.