This is a normative appendix and is part of this standard
The following minimum information shall be specified for the proposed design.
The floor area, broken down by space-conditioning categories and building area type, shall be specified. Each building area type shall be chosen from Table 9.5.1.
The building envelope assembly type, gross area, orientation, tilt, and associated space-conditioning category and building area type shall be specified. The surface shall be designated as exterior or semiexterior. A semiexterior surface separating a conditioned space from a semiheated space shall be specified with two associated space-conditioning categories. A semiexterior surface separating a conditioned space from an unconditioned space shall be specified with an associated space-conditioning category and with an adjacency to an unconditioned space. Exterior surfaces with the same building envelope assembly type and associated space-conditioning category and building area type whose orientations differ by no more than 22.5 degrees and whose tilts differ by no more than 22.5 degrees are allowed to be described as a single surface.
The class of construction, opaque area, U-factor, HC, and insulation position shall be specified. Where three-year-aged test data for the solar reflectance and three-year-aged thermal emittance of the exterior roof surface are available, the three-year-aged solar reflectance and three-year-aged thermal emittance shall be specified.
The class of construction, area, and U-factor shall be specified. Each opaque door shall be associated with a surface as described in Section C1.2 and shall have the orientation of that surface.
The class of construction, area, U-factor, SHGC, VT, and PF shall be specified for fenestration. For skylight wells, the width, depth, and height shall be defined as shown in Figure C1.4. Each fenestration element shall be associated with a surface as defined in Section C1.2 and shall have the orientation of that surface.
Figure C1.4 Skylight well dimensions.
Output reports shall contain the following information.
Name and contact information of the entity executing the simulation, and date of report.
Location of the building, including street address and climate zone.
Location corresponding to the weather data used to perform the simulation.
Simulation program used to perform the simulation.
Tables summarizing the minimum information described in Section C1.
All differences between the proposed envelope performance factor and the base envelope performance factor.
Total conductive heat gain and conductive heat loss through all opaque classes of construction.
Total conductive heat gain, conductive heat loss, and solar heat gain through all fenestration classes of construction.
The simulation program shall be a computer-based software program for the analysis of energy consumption in buildings. The simulation program shall include calculation methodologies for the building components being modeled.
The simulation program shall be approved by the adopting authority and shall, at minimum, have the ability to explicitly model all of the following:
- The base envelope performance factor, using only the input for the proposed envelope performance factor. The calculation procedure shall not allow the user to directly modify the building component characteristics of the base design.
- 8760 hours per year.
- Hourly variations in occupancy, lighting power, miscellaneous equipment power, thermostat set points, and HVAC system operation, defined separately for each day of the week and holidays.
- Thermal mass effects.
- The number of thermal zones in the proposed design or nine thermal zones, whichever is greater.
- Air economizers with integrated control.
- Continuous daylight dimming controls and photosensors.
The simulation program shall have the ability to determine the proposed envelope performance factor and base envelope performance factor by calculating annual energy costs.
The simulation program shall be capable of performing design load calculations to determine required HVAC equipment capacities and airflow rates in accordance with Section 6.4.2 for both the proposed design building envelope and the base design building envelope.
The simulation program shall be tested according to ASHRAE Standard 140, except for Sections 7 and 8, and the results shall be furnished by the software provider.
The simulation program shall perform the simulation using hourly values of climatic data, including temperature, humidity, solar radiation, and wind speed and direction from representative climatic data, for the proposed design building envelope location. For cities or urban regions for which several climatic data sources are available and for locations for which weather data are not available, the designer shall select available weather data that represent the climate at the construction site. Selected weather data shall be approved by the authority having jurisdiction.
Semiexterior surfaces separating conditioned spaces from unconditioned spaces shall be simulated as exterior surfaces with no exposure to wind or solar radiation.
The following rates for purchased energy shall be used to determine the proposed envelope performance factor and the base envelope performance factor:
- Electricity: 0.1032/kWh
- Heating: 0.99/therm
Exception to C3.3
Where approved by the authority having jurisdiction, actual annual rates for purchased energy or state average energy prices published by the Department of Energy's Energy Information Administration shall be permitted. The same rates shall be used for both the proposed envelope performance factor and the base envelope performance factor.
The proposed envelope performance factor and base envelope performance factor shall be calculated using the same
- simulation program,
- climatic data, and
- purchased energy rates.
The simulation model for calculating the proposed envelope performance factor shall be developed in accordance with Sections C3.5.1 through C3.5.11.
All conditioned spaces in the proposed design shall be simulated as being both heated and cooled, even if no cooling or heating system is being installed. Temperature control set points and schedules shall be consistent with those in the building envelope trade-off schedules and loads for the applicable building area type. All semiheated spaces shall be simulated as being heated and not cooled. The heating temperature control set point shall be 50°F for all hours.
The building model shall be divided into thermal zones described as follows:
- Determine the ratio (Rc) of the floor area to the gross wall area for each unique combination of space-conditioning category and building area type. The index "c" refers to a combination of space-conditioning category and building area type as defined for each surface.
- Create a perimeter zone for each unique combination of building area type, above-grade-wall orientation, and space-conditioning category. If there is more than one above-grade-wall assembly for a building area type and orientation, each above-grade-wall assembly shall be placed end-to-end in the order it is defined. The area of each perimeter zone shall be the gross wall area of the zone times Rc or 1.25, whichever is smaller.
- For each unique combination of space-conditioning category and building area type with Rc greater than 1.25, interior zones shall be created and used in the trade-off procedure. The area of the interior zone shall be the total area for the unique combination of space-conditioning category and building area type less the area of the perimeter zones for that combination of space-conditioning category and building area type.
- Create a below-grade zone for each unique combination of space-conditioning category and building area type associated with below-grade walls. If there is more than one below-grade-wall assembly for a building area type, each below- grade-wall assembly shall be placed end-to-end in the order it is defined. The area of each below-grade zone shall be the gross wall area of the zone times Rc or 1.25, whichever is smaller.
- The wall height and the height of each thermal zone shall be 15 ft.
- Roof area and floor area associated with each building area type shall be prorated among all zones of the corresponding building area type in proportion to the zone area of each zone. Roof area and floor area in each zone shall be centered in the horizontal plane of the zone with the same aspect ratio as the horizontal plane of the zone.
- Slab-on-grade floor perimeter associated with each building area type shall be prorated among perimeter zones of the corresponding building area type in proportion to the area of each zone.
- Vertical fenestration area shall be assigned to the associated surface as described in Section C1.4. Vertical fenestration shall be centered on the associated surface with the same aspect ratio as the associated surface. Windows with equivalent U- factor, SHGC, and VT that do not include fins may be combined into a single window on the associated surface.
- Skylight area shall be assigned to the associated surface as described in Section C1.4. prorated among interior zones containing the roof area with which the skylight area is associated, in proportion to the associated roof area. If the total skylight area exceeds the associated roof area in interior zones, the remaining skylight area shall be prorated among perimeter zones containing the roof area with which the skylight area is associated, in proportion to the associated roof area.
- Each zone shall be modeled as being fully enclosed. Zone boundaries not created as described above shall be modeled as adiabatic interior surfaces.
Daylight areas and photosensors shall not be modeled in residential zones. In each non-residential zone, daylight areas and photosensor locations shall be modeled in accordance with the following:
- For each nonresidential zone associated with vertical fenestration, the daylight area shall be modeled as directly adjacent to the vertical fenestration with a width equal to the width of the vertical fenestration and a depth equal to the head height of the vertical fenestration.
- In each nonresidential zone associated with skylights, the daylight area under skylights shall be modeled as bounded, in each direction, by the edge of the skylight area plus 10 ft or the distance to the edge of the zone, whichever is less.
- For each daylight area associated with vertical fenestration, a photosensor shall be modeled as located at the center of the width of the daylight area, at the depth of the daylight area and at a height of 3 ft.
- For each daylight area associated with a skylight, a photosensor shall be modeled as located at the center of the horizontal plane of the skylight and at a height of 5 ft.
The schedule types listed in Section C3.1.1(c) shall be required input. The schedules shall be consistent with those in the building envelope trade-off schedules and loads2 for the applicable building area type.
2. Schedules and internal loads by building area type are found at http://sspc901.ashraepcs.org/documents. php.
The building envelope shall reflect the information specified in Section C1.
Exception to C3.5.5
Where three-year-aged test data for the solar reflectance and three-year-aged thermal emittance of the exterior roof surface are unavailable, the exterior roof surface shall be modeled with a solar reflectance of 0.30 and a thermal emittance of 0.90.
Manually operated interior shades shall be modeled on all vertical fenestration. Shades shall be modeled to be lowered when the transmitted luminous intensity is greater than 200 cd/ft2 or the direct solar transmitted energy exceeds 30 Btu/h•ft2 and then remain lowered for rest of the day. Shades shall be modeled with visible light transmittance of 0.10, visible light reflectance of 0.40, solar transmittance of 0.21, and solar reflectance of 0.23. Permanent shading devices such as fins and overhangs shall be modeled.
Automatically controlled dynamic glazing is allowed to be modeled. Manually controlled dynamic glazing shall use the average of the minimum and maximum values for both SHGC and VT.
The air leakage rate of the building envelope (I75Pa) at a pressure differential of 0.3 in. of water shall be 0.4 cfm/ft2 of building envelope area. The air leakage of the building envelope shall be converted to the appropriate units to describe the air leakage as a function of the area of walls that separate conditioned spaces and semiheated spaces from the exterior as follows:
IAGW = 0.112 × I75Pa × S/AAGW
where
| I75Pa | = | air leakage rate of the building envelope (cfm/ft2) at a fixed building pressure differential of 0.3 in. of water, or 1.57 psf |
| S | = | total area of the building envelope (ft2) including the lowest floor, any below- grade walls or above-grade walls, and roof (including vertical fenestration and skylights) |
| IAGW | = | adjusted air leakage rate of the building envelope (cfm/ft2) at a reference wind speed of 10 mph and relative to the area of the above-grade walls |
| AAGW | = | the total area of above-grade walls that comprise the building envelope, ft2 |
Exception to C3.5.5.3
If the simulation program cannot simulate air leakage as a function of the area of walls that separate conditioned spaces and semiheated spaces from the exterior, the air leakage of the building envelope shall be converted to the appropriate units to describe the air leakage as a function of gross floor area as follows:
IFLR = 0.112 × I75Pa × S/AFLR
where
| IFLR | = | adjusted air leakage rate of the building envelope (cfm/ft2) at a reference wind speed of 10 mph and relative to the gross floor area |
| AFLR | = | gross floor area, ft2 |
Upcodes Diagrams
Infiltration shall be adjusted in accordance with the infiltration schedule in the building envelope trade-off schedules and loads for the applicable building area type.
Interior surfaces shall be modeled with visible light reflectances of 0.80 for ceilings, 0.50 for walls, and 0.20 for floors. Interior surfaces shall be modeled with a thermal emittance of 0.90.
The modeled lighting power shall be determined using the lighting power density allowances in Table 9.5.1 for the applicable building area type. The modeled lighting power shall be adjusted in accordance with the lighting schedule in the building envelope trade-off schedules and loads for the applicable building area type. Fifty percent (50%) of lighting in daylight areas shall be modeled with continuous daylight dimming controls such that when sufficient daylight is available at the corresponding photosensor, lighting power is reduced to maintain a minimum 50 fc for conditioned spaces and 30 fc for semiheated spaces. The minimum light output for the continuous daylight dimming shall be 6% of peak light output. Power input shall be modeled as 20% of lighting power at the minimum light output and scaled linearly to 100% of lighting power at peak light output.
One HVAC system shall be provided for each thermal zone and shall have the following characteristics:
- Constant-volume fan control.
- Electrically-provided cooling with constant COP, excluding the indoor fan power equal to 4.4.
- Gas furnace with constant thermal efficiency equal to the minimum AFUE allowed for gas-fired warm-air furnaces with maximum capacity <225,000 Btu/h, in accordance with Table 6.8.1-5.
- The ventilation rate for each building area type shall be consistent with the ventilation rate in the building envelope trade-off schedules and loads for the applicable building area type.
- Air economizers, except in Climate Zones 0 and 1. The high-limit shutoff shall be "Fixed Dry Bulb" type as described in Table 6.5.1.1.3.
- System design supply air rates shall be based on a supply-air-to-room-air temperature difference of 20°F in cooling.
- System capacities used in the annual simulation shall be 1.5 times the capacities determined by the sizing simulations.
- Fans shall cycle ON whenever the space calls for heating or cooling. The fan power shall be 0.3 W/cfm, and the fan energy shall be modeled explicitly.
Miscellaneous loads shall be modeled as included in the building envelope trade-off schedules and loads for the applicable building area type.
The occupant density shall be modeled according to the peak occupant density and the occupancy rate schedule in the building envelope trade-off schedules and loads for the applicable building area type.
The sensible and latent heat gain due to occupants shall be modeled as included in the building envelope trade-off schedules and loads for the applicable building area type.
The simulation model for calculating the base envelope performance factor shall modify the simulation model for calculating the proposed envelope performance factor as follows:
- All opaque assemblies shall be modeled with the maximum U-factor required in Section 5.5.3 for the appropriate class of construction, space-conditioning category, and climate zone. Mass walls and mass floors shall be modeled with HC equal to 7.2 Btu/ft2•°F. All other opaque assemblies shall be modeled with the same HC as the proposed design. Mass walls shall be modeled with equal mass on each side of the insulation. All other opaque assemblies shall be modeled with insulation on the exterior.
- The exterior roof surfaces shall be modeled with a solar reflectance and thermal emittance as required in Section 5.5.3.1.1(1a). All other roofs, including roofs exempted from the requirements in Section 5.5.3.1.1. shall be modeled the same as in the proposed design.
- Fenestration shall be assumed to be flush with the wall or roof. If the fenestration area for new buildings or additions exceeds the maximum allowed by Section 5.5.4.2. the area shall be reduced proportionally along each exposure until the limit set in Section 5.5.4.2 is met. If the fenestration area facing west or east of the proposed design exceeds the area limit set in Section 5.5.4.5. the baseline building performance shall be generated by simulating the building with its actual orientation and again after rotating the entire building 90, 180, and 270 degrees, then averaging the results of the four simulations. Fenestration U-factor and SHGC shall be the maximum allowed for the appropriate class of construction, space-conditioning category, and climate zone in accordance with Section 5.5.4. Where there is no SHGC requirement, the SHGC shall be equal to 0.40 for all vertical fenestration and 0.55 for skylights. The VT for fenestration in the base envelope design shall be equal to 1.10 times the SHGC.
- Manually operated interior shades shall be modeled on all vertical fenestration as described in Section C3.5.5.1. Permanent shading devices, such as fins and overhangs, shall not be modeled.
- Daylight areas and photosensor locations shall be modeled as described in Section C3.5.3 after reducing the fenestration area as described in Section C3.6(c).