The Home Energy Rating System (HERS) authorizes the use of several computer energy modeling programs.  The most widely used is REM/Rate, created by Architectural Energy Corporation of Boulder, Colorado.  It is used by Energy Raters to arrive at a building’s HERS (Home Energy Rating System) Index Score.

 

The lower the HERS Score, the more energy efficient the building.  A “standard” new home built to today's code would score approximately a 100 HERS score.  A new home built 30% more energy efficient than the standard home would score a 70.  Homes with solar panels supplying all of the home’s energy needs could score a 0.

 

When an Energy Rater rates a home, he/she creates a computer model of the home by measuring it, then entering the data shown below into the energy modeling program.  Once the energy model is created, the energy impact of various changes to the home can be predicted.

 

A partial list of the modeling software entries to REM/Rate, the most popular program, includes ...

 

Site Information

* Electricity rates

* Gas rates

 

General Building Information

* Area of conditioned space

* Volume of conditioned space

* Year built

* Housing type

* Number of floors above grade

* Number of bedrooms

* Foundation type

 

Slab Floor Properties Summary

* Type of slab, its insulation, floor covering inside

* Area

* Depth below grade

* Full perimeter

* Total exposed perimeter

 

Frame Floor Properties Summary

* Area

* Type

          - Floor covering

- Continuous insulation R-value

- Cavity insulation R-value

- Cavity insulation thickness

- Cavity insulation grade

- Joist size

- Joist spacing

- Framing factor

* Location (what is above and below it)

 

Rim and Band Joist Properties Summary

* Area

* Continuous Insulation (R-value)

* Joint cavity Insulation (R-value)

* Joint cavity Insulation thickness

* Joist spacing

* Location (what is on either side of it)

 

Above-Grade Wall Properties Summary

* Type

         - Continuous insulation R-value

          - Cavity insulation R-value

- Cavity insulation thickness

- Cavity insulation grade

- Stud size

- Stud spacing

- Framing factor

* Gross area

* Exterior color

* Location (what is on either side of it)

 

Window and Glass Door Properties Summary

* Type (single or double glazed, metal, vinyl, etc.)

* Area

* Orientation (cardinal compass direction)

* U-value

* SHGC (solar heat gain coefficient)

* Overhang depth

* Ft to top of window (this calculates how much radiant heat comes in)

* Ft to bottom of window (this completes the calculation)

* Shading

          - Winter

          - Summer

* Wall assignment

 

Door Properties Summary

* Opaque area

* Type (material, insulation, u-value)

* Wall assignment

 

Ceiling Properties (Attic) Summary

* Type and U-value

- Continuous insulation R-value

- Cavity insulation R-value

- Cavity insulation thickness

- Cavity insulation grade

- Joist size

- Joist spacing

- Framing factor

* Ceiling area

* Roof area

* Radiant barrier (or not)

* Exterior color

 

Skylight Properties

* Type

* U-value

* SHGC

* Pitch

* Area

Winter shading factor

* Summer shading factor

* Orientation

* Ceiling assignment

 

Mechanical Equipment Properties Summary

* Type

- Water heating

- Space heating

- Space cooling

- Air source heat pump

- Water source heat pump

* Equipment

- Gas furnace – afue, Btu

- Air conditioner – Btu, seer, sensible heat fraction

- Heat pump – Btu, seer, hspf, electrical resistance backup kW, sensible heat fraction

* Number of units

* Location

* Set point temperature (thermostat default is 68º heating and 78º cooling)

* Programmable thermostat (or not)

 

Duct System Properties Summary

* Heating system for ducts

* Cooling system for ducts

* Square feet served

* # Return registers

* Supply duct surface area

* Return duct surface area

* Duct leakage to outside in CFM @ 25 pascals

* Total duct leakage in CFM @ 25 pascals

* Duct location

* R-value of supply

* R-value of return

 

Whole House Infiltration (leakage)

* Heating/Cooling infiltration value in CFM @ 50 pascals, Air Changes /Hr, etc.

* Shelter class (how shielded the building is from wind pressure)

 

Mechanical Ventilation for Indoor Air Quality

*Type

- Balanced

- Exhaust only

- Supply only

- Air cycler

* Rate (cfm)

* Hours/Day (the fan runs)

* Fan watts

 

Use of Operable Windows

* Cooling season strategy (natural ventilation, whole house fan, etc.)

 

Lights & Appliances

* Refrigerator kWh/yr

* Refrigerator efficiency

* Dishwasher efficiency

* Oven/range fuel

* Clothes dryer fuel, efficiency, location, size, Energy Star (or not)

* Percent fluorescent or LED lighting

* Ceiling fan cfm/watt

 

Energy Program Requirements Met By House

* IECC mandatory requirements (2004-2012)

* Energy Star for Homes

* Energy Star products (refrigerators, fans, exhaust fans, dishwashers)

* Indoor airPlus

* DOE Challenge Home

* Optional Home Builder Commitments for Recognition

 

Interior Mass Properties Summary

* Type (concrete, brick, tile, water, adobe)

* Location

* Area

* Thickness

* Drywall Thickness 

 

Active Solar Thermal Summary  (for water heating)

* System type

* Collector loop type

* Collector location

* Collector area

* Collector tilt

* Storage volume

 

Photovoltaic Energy System Properties Summary

* Array orientation

* Array area

* Array peak power

* Array tilt

* Inverter efficiency

 

Sunspace

* Too many entries to enumerate

ENERGY  MODELING  SOFTWARE  ENTRIES

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