Mixed Deck — All HERS Topics Flashcards

What safety device is required by most codes in sleeping areas and on each level of a home to protect against CO poisoning?

Answer: CO alarm

CO alarms are required on each level of a home and outside sleeping areas to provide early warning of dangerous CO concentrations from combustion appliances.

In the context of HERS ratings, what is 'source energy' and how does it differ from 'site energy'?

Answer: Site energy is measured at the home; source energy accounts for generation and transmission losses back at the power plant

Site energy is measured at the meter, while source energy traces consumption back through generation and transmission, using fuel-specific site-to-source multipliers.

A heat pump water heater (HPWH) will operate most efficiently when installed in which location?

Answer: An unconditioned space such as a garage with sufficient air volume

HPWHs need access to a large volume of ambient air to extract heat efficiently; unconditioned spaces like garages provide a heat source without penalizing conditioned space HVAC loads.

What does the term 'thermal bypass' refer to in a HERS field inspection context?

Answer: Air movement around or through insulation that reduces its effective R-value

A thermal bypass is any air movement pathway that allows air to flow around insulation, significantly reducing its effective thermal resistance.

According to RESNET standards, what are the minimum Quality Assurance (QA) requirements that a HERS Rater's Provider must perform annually on the rater's work?

Answer: A 10% file review and a 1% on-site field review of the rater's projects.

RESNET standards require that a Rater's Quality Assurance Provider must conduct a file review on at least 10% of the rater's energy modeling files and an on-site field review for at least 1% of the rater's total rated homes each year to ensure compliance and accuracy.

Which RESNET Standard addresses the energy rating of manufactured and factory-built housing?

Answer: ANSI/RESNET/ACCA 310

ANSI/RESNET/ACCA Standard 310 establishes the methodology for rating manufactured and factory-built housing, which has unique construction characteristics compared to site-built homes.

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

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

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.

A HERS rater finds duct leakage to outside of 8% of system airflow. Under RESNET standards, how is this reported?

Answer: Pass — within the 10% default allowance

RESNET allows a 10% duct leakage to outside default, so 8% passes the verified leakage threshold.

What AFUE rating is the minimum threshold for a gas furnace to be considered high-efficiency under current U.S. energy standards?

Answer: 90%

A gas furnace must have an AFUE of 90% or higher to be classified as high-efficiency under U.S. standards.

Which of the following items is NOT required to be included in a HERS rating file submitted to a RESNET Provider?

Answer: Homeowner occupancy data

Occupancy data is not part of the energy rating inputs; HERS ratings are based on standardized assumptions for occupancy.

Which of the following components is a fixed assumption for BOTH the HERS Reference Home and the Rated Home in an energy model, ensuring a fair comparison of the building envelope and systems?

Answer: Geographic location and climate data

To create an accurate relative comparison, the HERS rating methodology (ANSI/RESNET/ICC 301) specifies that the Rated Home and the HERS Reference Home must be modeled with the exact same location, climate data, orientation, and geometry. The efficiency of components like windows, insulation, and mechanical systems are then compared against the Reference Home's standard specifications.

What is the typical worst-case depressurization threshold (in Pascals) at which natural-draft combustion appliances are considered at high risk for sustained backdrafting?

Answer: -5 Pa

A CAZ pressure at or below -5 Pa relative to outside under worst-case conditions indicates high backdrafting risk for naturally vented appliances.

What does a high static pressure reading in a forced-air HVAC system indicate to a HERS rater?

Answer: There is likely restricted airflow due to undersized ducts or a dirty filter

High static pressure indicates restricted airflow, commonly caused by undersized duct work or a clogged air filter.

A HERS rater finds that recessed can lights are installed in an insulated ceiling. Why is this a concern for energy performance?

Answer: Non-airtight can lights are significant air leakage points that bypass ceiling insulation

Non-airtight recessed lights create direct air leakage pathways through the ceiling, bypassing insulation and significantly increasing infiltration.

A rater is performing total duct leakage testing on a home where all registers cannot be sealed. Which method should be used instead of the standard total leakage test?

Answer: Duct leakage to outside test

When registers cannot all be sealed, the duct leakage to outside (sometimes called duct leakage outside conditioned space) method is used to isolate leakage from the exterior.

What is the purpose of a draft pressure test on a natural-draft appliance flue?

Answer: To verify the flue is creating adequate negative pressure to remove combustion gases

Draft pressure testing verifies that the flue system is generating enough negative pressure (draft) to reliably pull combustion gases upward and out of the building.

In a duct leakage test, what does a very low CFM25 out reading (near zero) with a relatively high CFM25 total reading suggest?

Answer: The duct system has significant leaks, all within the conditioned space

High total leakage with near-zero outside leakage means ducts are leaking significantly but all the leakage goes into conditioned space, not to unconditioned areas.

What is the formula for converting CFM50 to ACH50?

Answer: ACH50 = CFM50 × 60 / conditioned volume (ft³)

ACH50 = (CFM50 × 60 min/hr) ÷ conditioned volume in cubic feet, converting the per-minute flow to an hourly air change rate.

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.

Under RESNET standards, which party is ultimately responsible for the accuracy of a HERS rating?

Answer: The RESNET-accredited Rating Provider

RESNET places ultimate responsibility for rating accuracy on the accredited Rating Provider, which must oversee and quality-assure each rater's work.