Energy Modeling and Analysis Flashcards
7 cards from real HERS practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Energy Modeling and Analysis flashcards as text
During a HERS rating, a rater finds that the installed furnace has a higher AFUE than what the builder specified. How should this be handled in the energy model?
Answer: Enter the actual installed equipment AFUE as verified in the field, since the rating reflects as-built conditions
HERS Confirmed ratings must reflect as-built conditions, so the rater must enter the actual installed equipment efficiency rather than the specification.
What is 'duct leakage to outside' (Qto) and why is it modeled differently from total duct leakage in energy software?
Answer: Qto is leakage to unconditioned space that causes a net energy penalty, whereas leakage within conditioned space recirculates and has less energy impact
Duct leakage to unconditioned space (outside) is a true energy loss, while leakage within conditioned space partially recirculates, so models apply different penalty factors to each.
A home uses a combination boiler that provides both space heating and domestic hot water. How should this system be entered in most HERS modeling software?
Answer: As a combined hydronic system with a single combined efficiency rating (such as Annual Fuel Utilization Efficiency for the integrated unit)
Combination systems are entered as a single integrated unit using the manufacturer's combined efficiency rating, which accounts for thermal interactions between space heating and DHW modes.
In HERS energy modeling, what is the 'orientation adjustment' and when is it applied?
Answer: A correction applied when the rated home's orientation differs from due north, redistributing solar gains across actual window orientations
Software rotates window solar gain calculations to match the home's actual orientation so that modeled solar heat gain accurately reflects the building's real-world sun exposure.
What heating and cooling loads are explicitly NOT included in the HERS Index calculation per ANSI/RESNET/ICC 301?
Answer: Plug loads and process energy from consumer electronics and appliances not listed in the standard
The HERS Index covers regulated end-uses (heating, cooling, DHW, lighting, and approved appliances); miscellaneous plug loads and process energy from unlisted consumer electronics are excluded.
A rater is modeling a spray foam insulated unvented crawlspace. How should this space be designated in the energy model?
Answer: As a semi-conditioned or conditioned space within the thermal boundary, with insulation applied to the foundation walls rather than the floor above
An unvented spray-foam crawlspace brings the crawl inside the thermal envelope; the model must reflect insulation on the foundation walls and treat the space as semi-conditioned rather than outside the building envelope.
How does HERS energy modeling account for the impact of whole-house fans on annual energy use?
Answer: Whole-house fans reduce cooling energy by enabling economizer hours when outdoor air is cooler than indoor air, modeled based on fan airflow and local climate data
Whole-house fans provide cooling by flushing conditioned space with cooler outdoor air during suitable hours; software credits this based on fan capacity, climate data, and eligible economizer hours.