This section establishes criteria for compliance using simulated energy performance analysis. Such analysis shall include heating, cooling and service water heating energy only.
Compliance with this section requires that the mandatory provisions identified in Section R401.2 be met. All supply and return ducts not completely inside the building thermal envelope shall be insulated to a minimum of R-6.
Compliance based on simulated energy performance requires that a proposed residence (proposed design) be shown to have an annual energy cost that is less than or equal to the annual energy cost of the standard reference design. Energy prices shall be taken from a source approved by the code official, such as the Department of Energy, Energy Information Administration's State Energy Price and Expenditure Report. Code officials shall be permitted to require time-of-use pricing in energy cost calculations.
Exception: The energy use based on source energy expressed in Btu or Btu per square foot of conditioned floor area shall be permitted to be substituted for the energy cost. The source energy multiplier for electricity shall be 3.16. The source energy multiplier for fuels other than electricity shall be 1.1.
Exception: The energy use based on source energy expressed in Btu or Btu per square foot of conditioned floor area shall be permitted to be substituted for the energy cost. The source energy multiplier for electricity shall be 3.16. The source energy multiplier for fuels other than electricity shall be 1.1.
Documentation verifying that the methods and accuracy of the compliance software tools conform to the provisions of this section shall be provided to the code official.
Compliance software tools shall generate a report that documents that the proposed design complies with Section R405.3. A compliance report on the proposed design shall be submitted with the application for the building permit. Upon completion of the building, a compliance report based on the as-built condition of the building shall be submitted to the code official before a certificate of occupancy is issued. Batch sampling of buildings to determine energy code compliance for all buildings in the batch shall be prohibited.
Compliance reports shall include information in accordance with Sections R405.4.2.1 and R405.4.2.2. Where the proposed design of a building could be built on different sites where the cardinal orientation of the building on each site is different, compliance of the proposed design for the purposes of the application for the building permit shall be based on the worst-case orientation, worst-case configuration, worst-case building air leakage and worst-case duct leakage. Such worst-case parameters shall be used as inputs to the compliance software for energy analysis.
Compliance reports shall include information in accordance with Sections R405.4.2.1 and R405.4.2.2. Where the proposed design of a building could be built on different sites where the cardinal orientation of the building on each site is different, compliance of the proposed design for the purposes of the application for the building permit shall be based on the worst-case orientation, worst-case configuration, worst-case building air leakage and worst-case duct leakage. Such worst-case parameters shall be used as inputs to the compliance software for energy analysis.
A compliance report submitted with the application for building permit shall include the following:
1. Building street address, or other building site identification.
2. A statement indicating that the proposed design complies with Section R405.3.
3. An inspection checklist documenting the building component characteristics of the proposed design as indicated in Table R405.5.2(1). The inspection checklist shall show results for both the standard reference design and the proposed design with user inputs to the compliance software to generate the results.
4. A site-specific energy analysis report that is in compliance with Section R405.3.
5. The name of the individual performing the analysis and generating the report.
6. The name and version of the compliance software tool.
1. Building street address, or other building site identification.
2. A statement indicating that the proposed design complies with Section R405.3.
3. An inspection checklist documenting the building component characteristics of the proposed design as indicated in Table R405.5.2(1). The inspection checklist shall show results for both the standard reference design and the proposed design with user inputs to the compliance software to generate the results.
4. A site-specific energy analysis report that is in compliance with Section R405.3.
5. The name of the individual performing the analysis and generating the report.
6. The name and version of the compliance software tool.
A compliance report submitted for obtaining the certificate of occupancy shall include the following:
1. Building street address, or other building site identification.
2. A statement indicating that the as-built building complies with Section R405.3.
3. A certificate indicating that the building passes the performance matrix for code compliance and listing the energy saving features of the buildings.
4. A site-specific energy analysis report that is in compliance with Section R405.3.
5. The name of the individual performing the analysis and generating the report.
6. The name and version of the compliance software tool.
1. Building street address, or other building site identification.
2. A statement indicating that the as-built building complies with Section R405.3.
3. A certificate indicating that the building passes the performance matrix for code compliance and listing the energy saving features of the buildings.
4. A site-specific energy analysis report that is in compliance with Section R405.3.
5. The name of the individual performing the analysis and generating the report.
6. The name and version of the compliance software tool.
The code official shall be permitted to require the following documents:
1. Documentation of the building component characteristics of the standard reference design.
2. A certification signed by the builder providing the building component characteristics of the proposed design as given in Table R405.5.2(1).
3. Documentation of the actual values used in the software calculations for the proposed design.
1. Documentation of the building component characteristics of the standard reference design.
2. A certification signed by the builder providing the building component characteristics of the proposed design as given in Table R405.5.2(1).
3. Documentation of the actual values used in the software calculations for the proposed design.
Calculations of the performance design shall be in accordance with Sections R405.5.1 and R405.5.2.
Except as specified by this section, the standard reference design and proposed design shall be configured and analyzed using identical methods and techniques.
The standard reference design and proposed design shall be configured and analyzed as specified by Table R405.5.2(1). Table R405.5.2(1) shall include, by reference, all notes contained in Table R402.1.2.
TABLE R405.5.2(1) SPECIFICATIONS FOR THE STANDARD REFERENCE AND PROPOSED DESIGNS
TABLE R405.5.2(1)‒continued SPECIFICATIONS FOR THE STANDARD REFERENCE AND PROPOSED DESIGNS
For SI: 1 square foot = 0.93 m2, 1 British thermal unit = 1055 J, 1 pound per square foot = 4.88 kg/m2, 1 gallon (US) = 3.785 L, °C = (°F-32)/1.8, 1 degree = 0.79 rad.
TABLE R405.5.2(2) DEFAULT DISTRIBUTION SYSTEM EFFICIENCIES FOR PROPOSED DESIGNSa
For SI: 1 cubic foot per minute = 0.47 L/s, 1 square foot = 0.093 m2, 1 pound per square inch = 6895 Pa, 1 inch water gauge = 1250 Pa.
TABLE R405.5.2(1) SPECIFICATIONS FOR THE STANDARD REFERENCE AND PROPOSED DESIGNS
| BUILDING COMPONENT | STANDARD REFERENCE DESIGN | PROPOSED DESIGN |
| Above-grade walls | Type: mass wall if proposed wall is mass; otherwise wood frame. | As proposed |
| Gross area: same as proposed | As proposed | |
| U-factor: as specified in Table R402.1.4 | As proposed | |
| Solar absorptance = 0.75 | As proposed | |
| Emittance = 0.90 | As proposed | |
| Basement and crawl space walls | Type: same as proposed | As proposed |
| Gross area: same as proposed | As proposed | |
| U-factor: from Table R402.1.4, with insulation layer on interior side of walls | As proposed | |
| Above-grade floors | Type: wood frame | As proposed |
| Gross area: same as proposed | As proposed | |
| U-factor: as specified in Table R402.1.4 | As proposed | |
| Ceilings | Type: wood frame | As proposed |
| Gross area: same as proposed | As proposed | |
| U-factor: as specified in Table R402.1.4 | As proposed | |
| Roofs | Type: composition shingle on wood sheathing | As proposed |
| Gross area: same as proposed | As proposed | |
| Solar absorptance = 0.75 | As proposed | |
| Emittance = 0.90 | As proposed | |
| Attics | Type: vented with aperture = 1 ft2 per 300 ft2 ceiling area | As proposed |
| Foundations | Type: same as proposed | As proposed |
| Foundation wall area above and below grade and soil characteristics: same as proposed | As proposed | |
| Opaque doors | Area: 40 ft2 | As proposed |
| Orientation: North | As proposed | |
| U-factor: same as fenestration from Table R402.1.4 | As proposed | |
| Vertical fenestration other than opaque doors | Total areah = (a)The proposed glazing area, where the proposed glazing area is less than 15 percent of the conditioned floor area (b)15 percent of the conditioned floor area, where the proposed glazing area is 15 percent or more of the conditioned floor area | As proposed |
| Orientation: equally distributed to four cardinal compass orientations (N, E, S & W). | As proposed | |
| U-factor: as specified in Table R402.1.4 | As proposed | |
| SHGC: as specified in Table R402.1.2 except that for climates with no requirement (NR) SHGC = 0.40 shall be used. | As proposed | |
| Interior shade fraction: 0.92-(0.21 × SHGC for the standard reference design) | 0.92-(0.21 × SHGC as proposed) | |
| External shading: none | As proposed | |
| Skylights | None | As proposed |
| Thermally isolated sunrooms | None | As proposed |
| Air exchange rate | Air leakage rate of 5 air changes per hour in climate zones 1 and 2, and 3 air changes per hour in climate zones 3 through 8 at a pressure of 0.2 inches w.g (50 Pa). The mechanical ventilation rate shall be in addition to the air leakage rate and the same as in the proposed design, but no greater than 0.01 × CFA + 7.5 × (Nbr + 1) where: CFA = conditioned floor area Nbr = number of bedrooms Energy recovery shall not be assumed for mechanical ventilation. | For residences that are not tested, the same air leakage rate as the standard reference design. For tested residences, the measured air exchange ratea. The mechanical ventilation rateb shall be in addition to the air leakage rate and shall be as proposed. |
TABLE R405.5.2(1)‒continued SPECIFICATIONS FOR THE STANDARD REFERENCE AND PROPOSED DESIGNS
| BUILDING COMPONENT | STANDARD REFERENCE DESIGN | PROPOSED DESIGN |
| Mechanical ventilation | None, except where mechanical ventilation is specified by the proposed design, in which case: Annual vent fan energy use: kWh/yr = 0.03942 × CFA + 29.565 × (Nbr + 1) where: CFA = conditioned floor area Nbr = number of bedrooms | As proposed |
| Internal gains | IGain = 17,900 + 23.8 × CFA + 4104 × Nbr (Btu/day per dwelling unit) | Same as standard reference design. |
| Internal mass | An internal mass for furniture and contents of 8 pounds per square foot of floor area. | Same as standard reference design, plus any additional mass specifically designed as a thermal storage elementc but not integral to the building envelope or structure. |
| Structural mass | For masonry floor slabs, 80 percent of floor area covered by R-2 carpet and pad, and 20 percent of floor directly exposed to room air. | As proposed |
| For masonry basement walls, as proposed, but with insulation required by Table R402.1.4 located on the interior side of the walls | As proposed | |
| For other walls, for ceilings, floors, and interior walls, wood frame construction | As proposed | |
| Heating systemsd, e | As proposed for other than electric heating without a heat pump, where the proposed design utilizes electric heating without a heat pump the standard reference design shall be an air source heat pump meeting the requirements of Section C403 of the IECC-Commercial Provisions. Capacity: sized in accordance with Section R403.7 | As proposed |
| Cooling systemsd, f | As proposed Capacity: sized in accordance with Section R403.7. | As proposed |
| Service water heatingd, e, f, g | As proposed Use: same as proposed design | As proposed gal/day = 30 + (10 × Nbr) |
| Thermal distribution systems | Duct insulation: From Section R403.2.1 A thermal distribution system efficiency (DSE) of 0.88 shall be applied to both the heating and cooling system efficiencies for all systems other than tested duct systems. For tested duct systems, the leakage rate shall be 4 cfm (113.3 L/min) per 100 ft2 (9.29 m2) of conditioned floor area at a pressure of differential of 0.1 inches w.g. (25 Pa). | As tested or as specified in Table R405.5.2(2) if not tested. Duct insulation shall be as proposed. |
| Thermostat | Type: Manual, cooling temperature setpoint = 75°F; Heating temperature setpoint = 72°F | Same as standard reference |
For SI: 1 square foot = 0.93 m2, 1 British thermal unit = 1055 J, 1 pound per square foot = 4.88 kg/m2, 1 gallon (US) = 3.785 L, °C = (°F-32)/1.8, 1 degree = 0.79 rad.
- Where required by the code official, testing shall be conducted by an approved party. Hourly calculations as specified in the ASHRAE Handbook of Fundamentals, or the equivalent shall be used to determine the energy loads resulting from infiltration.
- The combined air exchange rate for infiltration and mechanical ventilation shall be determined in accordance with Equation 43 of 2001 ASHRAE Handbook of Fundamentals, page 26.24 and the "Whole-house Ventilation" provisions of 2001 ASHRAE Handbook of Fundamentals, page 26.19 for intermittent mechanical ventilation.
- Thermal storage element shall mean a component not part of the floors, walls or ceilings that is part of a passive solar system, and that provides thermal storage such as enclosed water columns, rock beds, or phase-change containers. A thermal storage element must be in the same room as fenestration that faces within 15 degrees (0.26 rad) of true south, or must be connected to such a room with pipes or ducts that allow the element to be actively charged.
- For a proposed design with multiple heating, cooling or water heating systems using different fuel types, the applicable standard reference design system capacities and fuel types shall be weighted in accordance with their respective loads as calculated by accepted engineering practice for each equipment and fuel type present.
- For a proposed design without a proposed heating system, a heating system with the prevailing federal minimum efficiency shall be assumed for both the standard reference design and proposed design.
- For a proposed design home without a proposed cooling system, an electric air conditioner with the prevailing federal minimum efficiency shall be assumed for both the standard reference design and the proposed design.
- For a proposed design with a nonstorage-type water heater, a 40-gallon storage-type water heater with the prevailing federal minimum energy factor for the same fuel as the predominant heating fuel type shall be assumed. For the case of a proposed design without a proposed water heater, a 40-gallon storage-type water heater with the prevailing federal minimum efficiency for the same fuel as the predominant heating fuel type shall be assumed for both the proposed design and standard reference design.
- For residences with conditioned basements, R-2 and R-4 residences and townhouses, the following formula shall be
used to determine glazing area:
AF = As × FA × F
where:
and where:AF = Total glazing area As = Standard reference design total glazing area. FA = (Above-grade thermal boundary gross wall area)/(above-grade boundary wall area + 0.5 × below-grade boundary wall area). F = (Above-grade thermal boundary wall area)/(above-grade thermal boundary wall area + common wall area) or 0.56, whichever is greater. Thermal boundary wall is any wall that separates conditioned space from unconditioned space or ambient conditions.Above-grade thermal boundary wall is any thermal boundary wall component not in contact with soil.Below-grade boundary wall is any thermal boundary wall in soil contact.Common wall area is the area of walls shared with an adjoining dwelling unit.L and CFA are in the same units.
TABLE R405.5.2(2) DEFAULT DISTRIBUTION SYSTEM EFFICIENCIES FOR PROPOSED DESIGNSa
| DISTRIBUTION SYSTEM CONFIGURATION AND CONDITION | FORCED AIR SYSTEMS | HYDRONIC SYSTEMSb |
| Distribution system components located in unconditioned space | ‒ | 0.95 |
| Untested distribution systems entirely located in conditioned spacec | 0.88 | 1 |
| "Ductless" systemsd | 1 | ‒ |
For SI: 1 cubic foot per minute = 0.47 L/s, 1 square foot = 0.093 m2, 1 pound per square inch = 6895 Pa, 1 inch water gauge = 1250 Pa.
- Default values given by this table are for untested distribution systems, which must still meet minimum requirements for duct system insulation.
- Hydronic systems shall mean those systems that distribute heating and cooling energy directly to individual spaces using liquids pumped through closed-loop piping and that do not depend on ducted, forced airflow to maintain space temperatures.
- Entire system in conditioned space shall mean that no component of the distribution system, including the air-handler unit, is located outside of the conditioned space.
- Ductless systems shall be allowed to have forced airflow across a coil but shall not have any ducted airflow external to the manufacturer's air-handler enclosure.
Calculation procedures used to comply with this section shall be software tools capable of calculating the annual energy consumption of all building elements that differ between the standard reference design and the proposed design and shall include the following capabilities:
1. Computer generation of the standard reference design using only the input for the proposed design. The calculation procedure shall not allow the user to directly modify the building component characteristics of the standard reference design.
2. Calculation of whole-building (as a single zone) sizing for the heating and cooling equipment in the standard reference design residence in accordance with Section R403.6.
3. Calculations that account for the effects of indoor and outdoor temperatures and part-load ratios on the performance of heating, ventilating and air-conditioning equipment based on climate and equipment sizing.
4. Printed code official inspection checklist listing each of the proposed design component characteristics from Table R405.5.2(1) determined by the analysis to provide compliance, along with their respective performance ratings (R-value, U-factor, SHGC, HSPF, AFUE, SEER, EF are some examples).
1. Computer generation of the standard reference design using only the input for the proposed design. The calculation procedure shall not allow the user to directly modify the building component characteristics of the standard reference design.
2. Calculation of whole-building (as a single zone) sizing for the heating and cooling equipment in the standard reference design residence in accordance with Section R403.6.
3. Calculations that account for the effects of indoor and outdoor temperatures and part-load ratios on the performance of heating, ventilating and air-conditioning equipment based on climate and equipment sizing.
4. Printed code official inspection checklist listing each of the proposed design component characteristics from Table R405.5.2(1) determined by the analysis to provide compliance, along with their respective performance ratings (R-value, U-factor, SHGC, HSPF, AFUE, SEER, EF are some examples).
Performance analysis tools meeting the applicable provisions of Section R405 shall be permitted to be approved. Tools are permitted to be approved based on meeting a specified threshold for a jurisdiction. The code official shall be permitted to approve tools for a specified application or limited scope.