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

Occupancy is calculated as 1 person per 300 square feet of conditioned floor area

Answer

Internal gains are fixed at 2,400 BTU/hr regardless of home size

Answer

Occupancy defaults to 4 persons for all homes under 3,000 square feet

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

ASHRAE 169 climate zones

Answer

EPA Energy Star climate zones (North/South/Marine)

Answer

DOE Building America climate zones

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 are modeled identically to attic ceilings and require no special entry

Answer

Cathedral ceilings must use the total R-value plus an automatic 10% thermal bridging penalty

Answer

Cathedral ceiling insulation is always entered as R-0 because rafters create full thermal bridging

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

The entire basement is modeled as a slab-on-grade foundation

Answer

Walkout basements default to the same U-factor as conditioned crawlspaces

Answer

The basement is always excluded from conditioned floor area calculations

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

Bedrooms have no effect on water heating; only bathroom count matters

Answer

More bedrooms decrease water heating energy because of assumed efficiency improvements

Answer

Water heating energy is fixed at a national average regardless of bedroom count

Question 6

A rater is modeling a home with a ground-source heat pump. Which COP value should be used in the energy model?

Accepted Answer

The site-specific COP determined by ground loop entering water temperature and manufacturer performance data

Answer

The manufacturer's rated COP at standard ARI test conditions

Answer

The EER rating converted to COP using the formula EER/3.412

Answer

A default COP of 3.0 as specified in ANSI/RESNET/ICC 301 for all ground-source systems

Question 7

Which metric does energy modeling software use to quantify thermal bridging through wood-framed walls?

Accepted Answer

Framing fraction combined with stud and cavity R-values to calculate an assembly U-factor

Answer

A fixed 10% penalty applied to the nominal insulation R-value

Answer

The steel stud correction factor from ASHRAE Fundamentals

Answer

The ratio of wood volume to total wall volume