Standards Table 140.3-D
Reference Nonresidential Appendix NA4
Public school building design is defined by two prescriptive requirements ('listed in Tables 140.3-B and 140.3-D of the Standards). Table 140.3-B covers prescriptive requirements for climate-specific relocatable public school buildings; Table 140.3-D covers prescriptive requirements for relocatable public school buildings that can be installed in any climate. Building envelopes must meet the prescriptive requirements in §140.3. For additional design requirements, refer to §140.3 and Reference Nonresidential Appendix NA4. Manufacturers must certify compliance and provide documentation according to the chosen method of compliance. Performance compliance calculations must be performed for multiple orientations, each model using the same proposed design energy features rotated through 12 different orientations and different climate zones (Reference Nonresidential Appendix NA4). Also see §140.3(a)8 and §141.0(b)2.
§140.1
Performance
Reference Nonresidential Appendix
NA4
When the manufacturer/builder certifies a relocatable public school building for use in any climate zone, the building must be designed and built to meet the energy budget for the most severe climate zones (as specified in the Reference Nonresidential Appendix NA4), assuming the prescriptive envelope criteria in Table 140.3-D.
When the manufacturer/builder certifies that the relocatable building is manufactured for use in specific climate zones and that the relocatable building cannot be lawfully used in other climate zones, the energy budget must be met for each climate zone that the manufacturer/building certifies, assuming the prescriptive envelope criteria in Table 140.3-B, including the non-north window RSHG and skylight SHGC requirements for each climate zone. The energy budget and the energy use of the proposed building must be determined using the multiple orientation approach specified in the Reference Nonresidential Appendix NA4. The manufacturer/builder shall meet the requirements for identification labels specified in §140.3(a)8.
Manufacturers may certify the relocatable classrooms for multiple orientations or for compliance for all climate zones statewide. Since relocatable public school buildings could be positioned in any orientation, it is necessary to perform compliance calculations for multiple orientations. Each model with the same proposed design energy features shall be rotated through 12 different orientations: either in climate zones 14, 15 and 16 for relocatables showing statewide compliance; or, in the specific climate zones that the manufacturer proposes for the relocatable be allowed to be installed (i.e., the building with the same proposed design energy features), the relocatable model is rotated in 30 degree increments. The relocatable model shall comply in each case. Approved compliance software programs shall automate the rotation of the building and reporting of the compliance results to insure it is done correctly and uniformly and to avoid unnecessary documentation.
Under the performance approach, energy use of the building is modeled by compliance software approved by the Energy Commission. The compliance software does an hourly simulation of the proposed building, including a detailed accounting of envelope heat transfers using the assemblies and fenestration input, and including the precise geometry of exterior overhangs or side fins. The most accurate tradeoffs between different envelope components – and between the envelope, the space-conditioning system and the installed lighting design – are therefore accounted for and compared with the standard design version of the building. The proposed design has to have TDV energy less than or equal to the standard design. This section presents some basic details on the modeling of building envelope components. Program users and those checking for enforcement should consult the most current version of the user’s manuals and associated compliance supplements for specific instructions on the operation of the program. All compliance software, however, are required to have the same basic modeling capabilities. A discussion on the performance approach, and fixed and restricted inputs, is included in Chapter 9.
The following modeling capabilities are required by all approved nonresidential compliance software. These modeling features affect the thermal loads seen by the HVAC system model.
Heat absorption, retention and thermal transfer characteristics associated with the heat capacity of exterior opaque mass surfaces such as walls, roofs and floors are modeled. Typical inputs are spacing, thickness, Standard U-factor, JA4 Table references, Framed Cavity R-value and Proposed Assembly U-factor. The heat capacity of concrete masonry unit walls and solid concrete walls is provided in Tables 4.3.5 and 4.3.6 of Reference Joint Appendix JA4. Effective R-values for interior and exterior insulation are provided in Table 4.3.13 of Reference Joint Appendix JA4.
Heat gains and heat losses are modeled through opaque surfaces of the building envelope. The following inputs or acceptable alternative inputs are used by this modeling capability:
A. Surface areas by opaque surface type.
B. Surface orientation and slope.
C. Thermal conductance of the surface. The construction assembly U-factor is chosen from tabulated values in Reference Joint Appendix JA4.
D. Surface absorptance. Surface absorptance is a restricted input (except for roofs).
Note, for roofs, surface absorptance and emittance are variable inputs in the proposed design for roofs to provide a ‘cool roof credit’ in climate zones where a cool roof is not required. The roof reference design is set with a cool roof surface absorptance for nonresidential buildings in all climate zones. The difference in surface absorptance creates a credit that can be used with the whole building performance method. Cool roofs have both a high reflectance and a high emittance. The high reflectance keeps much of the sun’s energy from being absorbed and becoming a component of heat transfer. The high emittance ensures that when the roof does warm up, its heat can escape through radiation to the sky. To model the proposed design as a cool roof, the roofing product must be 'listed in the Rated Product Directory of the Cool Roof Rating Council. If the roof is not rated, a default aged reflectance of 0.08 is used for asphalt or composition shingles and 0.10 for other roofing products. If the proposed design does not have a cool roof, the performance method may be used to trade off with other measures, such as increased insulation or HVAC equipment efficiency, so that the TDV energy of the proposed design does not exceed that of the standard design.
Heat transfer through all fenestration surfaces of the building envelope are modeled using the following inputs:
A. Fenestration areas. The glazing width and height dimensions are those of the rough-out opening for the window or fenestration product. Window area of the standard design is limited to the prescriptive limit of 40 percent of the gross wall area or 6 times the display perimeter, whichever is greater. If the proposed design window area exceeds this limit, a trade-off may be made with measures such as increased envelope insulation or increased equipment efficiency to offset the energy penalty from fenestration.
B. Fenestration orientation and slope. Vertical windows installed in a building located in any of the four cardinal orientation; North, South West, and East. Skylights are considered less than 60o from the horizontal and all windows and skylights provide solar gain that can have an effect on the overall energy of the building unless they are insulated glass.
C. Fenestration thermal conductance. The overall U-factor shall be taken from NFRC rating information, default values in Table 110.6-A of the Standards or from the Alternative Default Fenestration, Reference Nonresidential Appendix NA6, if less than 1,000 ft².
D. Fenestration solar heat gain coefficient. The SHGC shall be taken from NFRC rating information default values in Table 110.6-B of the Standards or from the Alternative Default Fenestration, Reference Nonresidential Appendix NA6 if less than 1,000 ft². The baseline building uses a solar heat gain coefficient equal to the relative solar heat gain value from Table 140.3-B, 140.3-C or 140.3-D. The baseline building has no overhangs, but overhangs can be modeled in the baseline building, as described below.
If the compliance software
requires input of the shading coefficient (SC) instead of the SHGC, the shading
coefficient shall be calculated by the following formula:
SC = SHGC /
0.87
Approved compliance software programs are able to model overhangs and vertical fins. Typical inputs are overhang projection, height above window, window height and the overhang horizontal extension past the edge of the window. If the overhang horizontal extension (past the window jambs) is not an input, then the program must assume that the extension is zero (i.e., overhang width is equal to window width) which results in less benefits from the overhang.
Vertical fins are modeled with inputs of horizontal and vertical position relative to the window, the vertical height of the fin and the fin depth (projection outward perpendicular to the wall).
Heat transfer modeled through all surfaces separating different space conditioning zones may be modeled with inputs such as surface area, surface tilt and thermal conductance. Thermal mass characteristics may be modeled using the thickness, specific heat, density and types of layers that comprise the construction assembly. Demising partitions separating a conditioned space from an unconditioned space that are insulated with R-13 cavity insulation or with a U-factor less than 0.218 are modeled as adiabatic partitions (no heat transfer). Walls that separate directly conditioned zones from other conditioned zones are modeled as “air walls” with no heat capacity and an overall U-factor of 1.0 Btu/h-ft²-˚F.
Heat transfer through slab-on-grade floors and basement floors is modeled by calculating perimeter heat losses and interior slab heat losses. The heat lossees from the presimeter and the interior are modeled by the use of an F-factor that accounts for the rate of heat transfer from the slab to the soil. Reference Appendix JA4 contains F-factors for common insulation conditions (vertical insulation outside or a combination of the two. The user must select from the list of insulation conditions in Reference Appendix JA4. The insulation depth and insulation R-value affect heat loss through basement floors.
§100.0(a), Exception 1, states that qualified historic buildings, as defined in the California Historical Building Code (Title 24, Part 8 or California Building Code, Title 24, Part 2, Volume I, Chapter 34, Division II) are not covered by the Standards. However, non-historical components of the buildings, such as new or replaced space-conditioning, plumbing, and electrical (including lighting) equipment, additions and alterations to historic buildings, and new appliances in historic buildings must comply with Building Energy Efficiency Standards and Appliance Efficiency Regulations, as well as other codes. Additions and alterations to historic buildings must also meet applicable requirements of the Standards. For more information about energy compliance requirements for Historic Buildings, see Section 1.7.1, Building Types Covered, in Chapter 1, the Overview of this 'manual.