HERS Index and Ratings — Questions and Answers

Question 1: A home receives a HERS Index of 0. What does this indicate?

The home uses no net energy on an annual basis (Correct answer)
The home is 100% more efficient than the reference home
The home fails minimum code requirements
The home has no HVAC system installed

Correct 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.

Question 2: Which of the following scenarios would most likely INCREASE a home's HERS Index score?

Adding solar photovoltaic panels
Replacing single-pane windows with double-pane
Increasing duct leakage from 4% to 10% (Correct answer)
Upgrading to a higher-efficiency heat pump

Correct answer: Increasing duct leakage from 4% to 10%

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

Question 3: 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?

The HERS Index increases slightly
The HERS Index decreases (Correct answer)
The HERS Index is unaffected by wall insulation
The HERS Index doubles

Correct answer: The HERS Index decreases

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

Question 4: The HERS reference home is set to an index of 100 and is modeled based on which standard?

ASHRAE 90.1-2013
IECC 2006
RESNET/ICC 301 standard (Correct answer)
DOE Building America guidelines

Correct answer: RESNET/ICC 301 standard

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

Question 5: A new home scores a HERS 55 and its neighbor scores a HERS 85. Approximately how much more energy efficient is the first home?

About 30% more efficient (Correct answer)
About 55% more efficient
About 85% more efficient
Exactly twice as efficient

Correct 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.

Question 6: What is the primary purpose of the projected HERS rating versus the confirmed HERS rating?

Projected is used for tax credits; confirmed is used for financing
Projected is issued before construction; confirmed is issued after final inspections and testing (Correct answer)
Projected covers HVAC only; confirmed covers the whole building envelope
Projected applies to existing homes; confirmed applies to new construction only

Correct 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.

Question 7: Which component of the HERS rating accounts for mechanical ventilation energy use?

It is excluded from HERS calculations entirely
It is included under the lights and appliances end use
It is part of the total annual energy consumption factored into the index (Correct answer)
It is only counted if ventilation airflow exceeds ASHRAE 62.2 minimums

Correct 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.

Question 8: A HERS rater is evaluating an existing home built in 1985. Which type of HERS rating is most appropriate?

Projected rating based on blueprints
Confirmed rating with full field verification and testing (Correct answer)
Preliminary rating based on county records only
Design rating with no field inspection required

Correct 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.

Question 9: How does the HERS Index treat on-site renewable energy generation such as solar PV?

It is ignored entirely in the rating
It reduces the home's energy consumption score, potentially driving the index below 100 (Correct answer)
It is added to the index as a bonus multiplier
It only counts if the system is grid-tied and net-metered

Correct 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.

Question 10: A home's HERS rating is listed as '52.' Which of the following statements is most accurate?

The home uses 52% more energy than the reference home
The home uses 48% less energy than the reference home (Correct answer)
The home meets 52% of code requirements
The home has 52 energy-efficient features installed

Correct 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).

Question 11: Under RESNET standards, which category of energy end use is specifically EXCLUDED from the HERS Index calculation?

Space heating
Water heating
Plug loads and process loads (in some rating types) (Correct answer)
Cooling

Correct 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.

Question 12: What does a HERS 'sampling' protocol allow a rater to do?

Rate only one unit in a multi-family building and apply it to all units
Test a subset of similar homes in a subdivision and apply results to the group (Correct answer)
Skip duct leakage testing for homes above a HERS 70
Use projected data instead of confirmed data for new construction

Correct 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.

Question 13: 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?

HERS 45 means the home produces more energy than it uses
The program requires a HERS score at or below 45 for most climate zones (Correct answer)
HERS 45 automatically qualifies any home as net-zero
DOE ZERH requires HERS 60 or below, and 45 exceeds that requirement

Correct 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.

Question 14: How does window-to-floor area ratio affect the HERS Index in a hot climate?

More window area always improves the HERS Index due to daylighting benefits
Excessive window area in a hot climate increases cooling loads and raises the HERS Index (Correct answer)
Window area is not modeled in HERS software
A higher window ratio always lowers the HERS Index regardless of climate

Correct 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.

Question 15: Which ENERGY STAR certification pathway for new homes relies directly on the HERS Index as the primary compliance metric?

ENERGY STAR Performance Pathway (Correct answer)
ENERGY STAR Prescriptive Pathway
ENERGY STAR Equivalent Pathway
ENERGY STAR Qualified Contractor Pathway

Correct 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.

Question 16: A HERS rater is told a home has an infiltration rate of 3.5 ACH50. How does this value factor into the HERS Index?

It is used to calculate heat loss/gain from air leakage, affecting the energy score (Correct answer)
It is recorded for permitting only and does not influence the index
It only matters if the home lacks mechanical ventilation
ACH50 is converted to CFM25 before entry into HERS software

Correct 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.

Question 17: What is the significance of the HERS Index value of 130?

It is the maximum score a home can receive
It indicates the home uses 30% more energy than the 2006 IECC reference home (Correct answer)
It means the home failed the blower door test
It signifies the home is 30% better than code minimum

Correct 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.

Question 18: In HERS ratings, what is the 'rated home' compared against to generate the index score?

The national average home from the latest census
A computer model of the same home built to the RESNET reference specifications (Correct answer)
The best-performing home in the same climate zone
The local utility's average residential customer energy use

Correct 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.

Question 19: A HERS rater discovers that a home's HVAC ducts are entirely within conditioned space. What is the likely effect on the HERS Index?

The HERS Index increases because duct insulation is still required
The HERS Index may decrease because duct losses to unconditioned space are eliminated (Correct answer)
Duct location has no bearing on the HERS Index
The HERS Index increases because unconditioned duct runs are more efficient

Correct 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.

Question 20: Which software tool is most commonly used by HERS raters to calculate the HERS Index for residential buildings?

EnergyPlus standalone
REM/Rate or equivalent RESNET-approved rating software (Correct answer)
ASHRAE HAP (Hourly Analysis Program)
BEopt design optimization tool

Correct 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.

Question 21: A homeowner wants to improve their HERS rating from 72 to 55. Which measure is most likely to produce the largest single improvement?

Replacing incandescent bulbs with LEDs throughout the home
Air sealing the building envelope to reduce infiltration from 8 ACH50 to 3 ACH50 (Correct answer)
Installing low-flow showerheads
Adding a programmable thermostat

Correct answer: Air sealing the building envelope to reduce infiltration from 8 ACH50 to 3 ACH50

Significantly reducing air infiltration through envelope air sealing typically yields large energy savings and a meaningful drop in the HERS Index.

HERS Index and Ratings

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

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