HERS Energy Modeling and Analysis 3

Question 1

What is the RESNET-defined default internal gains assumption used in HERS energy modeling for occupancy?

Accepted Answer

Standard occupancy is set at 0.5 + (CFA/100)^0.43 persons as defined in ANSI/RESNET/ICC 301

Answer

ANSI/RESNET/ICC 301 specifies occupancy as 0.5 + (CFA/100)^0.43, ensuring larger homes have proportionally more occupants in the reference calculation.

Question 2

Which climate zone designation system is used by RESNET's ANSI/RESNET/ICC 301 standard for HERS energy modeling inputs?

Accepted Answer

IECC climate zones (1-8 with moisture designations A, B, C)

Answer

HERS ratings use IECC climate zones 1–8 with moisture designations (A=moist, B=dry, C=marine) as defined in the IECC and referenced by ANSI/RESNET/ICC 301.

Question 3

A home has a cathedral ceiling with R-30 insulation between rafters. How should this be entered differently from a standard attic assembly in most energy modeling software?

Accepted Answer

Cathedral ceilings are entered as a roof/ceiling assembly without an attic air space, using the assembly R-value directly

Answer

Cathedral ceilings lack an attic buffer zone, so they are entered as a direct roof/ceiling assembly with the actual installed R-value and no attic air space node.

Question 4

In HERS modeling, how is a home with a walkout basement partially below grade typically handled for foundation inputs?

Accepted Answer

Above-grade portions are modeled as walls and below-grade portions as basement walls with appropriate soil contact fractions

Answer

Software requires separate modeling of above-grade and below-grade wall fractions because heat loss rates differ significantly based on soil contact depth.

Question 5

What effect does increasing the number of bedrooms have on the Reference Home's water heating energy in HERS calculations?

Accepted Answer

More bedrooms increase the assumed number of occupants, which increases hot water consumption in the Reference Home

Answer

ANSI/RESNET/ICC 301 ties hot water usage to bedroom count as a proxy for occupancy, so the Reference Home's water heating load increases with bedroom count.

(HERS) Certified Home Energy Rating System Rater Practice Test

(HERS) Certified Home Energy Rating System Rater Practice Test

HERS Energy Modeling and Analysis 3