5.3.3.2.2 For envelope assemblies containing Non-Metal Framing, the U¡ shall be determined from one of the laboratory or field test measurements specified in Section 5.1.5 or from the ASHRAE series-parallel method. Formulas in Chapter 23, page 23.2 of the ASHRAE Handbook, 1985 Fundamentals Volume, shall be used for these calculations.

5.3.3.3 The thermal transmittance of fenestration assemblies shall be corrected to account for the presence of sash, frames, edge effects and spacers in multiple-glazed units.

If thermal transmittances of sash and frames are known, Equation 5.3-1 shall be used, otherwise the thermal

Where:

Equation 5.3-20

A¡-area of ith fenestration assembly i=numerical subscript (1,2,...n) refers to each of the various fenestration assemblies present in the wall

n=the number of fenestration assemblies in the wall assembly.

Uof the overall thermal transmittance of the fenestration assembly, including sash and frames, Btu/h ft2°F. Ug=the thermal transmittance of the central area of the fenestration excluding edge effects, spacers in multiple-glazed units, and the sash and frame, Btu/h ft2°F. Fr=framing adjustment factor for sash, frames, etc.

Aor the area of all fenestration including glazed portions, sash, frames, etc.

5.3.3.3.1 Values for U shall be the winter value obtained from the glazing manufacturer's test data or from Table 13 or Figure 14 of Chapter 27 of the ASHRAE Handbook, 1985 Fundamentals Volume. Values for F, shall be obtained from the frame manufacturer's test data or from the average adjustment factor for a particular product in Table 13, Part C, in Chapter 27 of the ASHRAE Handbook, 1985 Fundamentals Volume. For glass products with a U value of 0.45 or less, use the Fr for triple insulated glazing. Alternatively, values of the Ug°F product may be used from manufacturer's test data for open window and frame assemblies tested as a unit provided that the tests referenced edge-effects and windspeed are accounted for winter tested U-values are used.

5.3.4 Gross Area of Envelope Components

5.3.4.1 The gross area of a roof assembly consists of the total surface of the roof assembly exposed to outside air or unconditioned spaces. The roof assembly shall include all roof/ceiling components through which heat may flow between indoor and outdoor environments including skylight surfaces, but excluding service openings.

5.3.4.1.1 For thermal transmittance purposes, when return air ceiling plenums are employed, the roof/ceiling

assembly shall not include the thermal resistance of the ceiling, or the plenum space, as part of the total thermal resistance of the assembly.

5.3.4.2 The gross area of a floor assembly over outside or unconditioned space consists of the total surface of the floor assembly exposed to the outside air or an unconditioned space. The floor assembly shall include all floor components through which heat may flow between indoor and outdoor or unconditioned space environments.

5.3.4.3 The gross area of exterior walls enclosing a heated or cooled space is measured on the exterior and consists of the opaque wall including between floor spandrels, peripheral edges of flooring, window areas including sash and door areas, but excluding vents, grilles and pipes.

5.3.5 Shading Coefficients

5.3.5.1 The Shading Coefficient (SC) for fenestration shall be obtained from Chapter 27 of the ASHRAE Handbook, 1985 Fundamentals Volume or from manufacturers' test data. For the prescriptive or system performance envelope compliance calculations in sections 5.4 and 5.5, a factor, SCx, is used. SC, is the Shading Coefficient of the fenestration, including internal and external shading devices, but excluding the effect of external shading projections, which is calculated separately. The shading coefficient used for louvered shade screens shall be determined using a profile angle of 30°, as found in Table 41, Chapter 27 of the ASHRAE Handbook, 1985 Fundamentals Volume.

5.3.6 Wall Heat Capacity

5.3.6.1 Heat capacity in Btu/F⚫ft2, shall be determined as the product of the average wall weight in lb/ft2 and the weighted average specific heat of the wall component in Btu/lb•°•.

5.3.6.2 If the wall system is defined as having exterior insulation only the properties of the wall elements inside of the insulation layer shall be used in determining the wall heat capacity.

5.3.6.3 For walls with integral insulation, all of the elements of the entire wall system may be used in the calculation of the wall heat capacity.

5.3.7 Air Leakage and Moisture Migration

5.3.7.1 The requirements of this subsection apply only to those locations

separating the outdoors from interior building conditioned space. Compliance with the criteria for air leakage through building components shall be determined by ASTM E 283-1984, "Standard Method of Test Rate of Air Leakage Through Exterior Windows, Curtain Walls and Doors."

5.3.7.2 Air Leakage Requirements for Fenestration and Doors

5.3.7.2.1 Fenestration meeting the following standards for air leakage is acceptable:

(a) ANSI/AAMA 101-85, "Aluminum Prime Windows."

(b) ASTM D-4099-83, "Specifications for Poly(Vinyl Chloride) (PVC) Prime Windows."

(c) ANSI/NWMA I.S. 2-80, "Wood Window Units (Improved Performance Rating Only)."

5.3.7.2.2 Sliding Doors shall meet one of the following standards for air leakage:

(a) ANSI/AAMA 101-85, "Aluminum Sliding Glass Doors."

(b) NWMA I.S. 3-83, "Wood Sliding Patio Doors."

5.3.7.2.3 Commercial entrance swinging or revolving doors shall limit air leakage to a rate not to exceed 1.25 cfm/ft2 of door area, at standard test conditions.

5.3.7.2.4 Residential swinging doors shall limit air leakage to a rate not to exceed 0.5 cfm/ft2 of door area, at standard test conditions.

5.3.7.2.5 Where spaces have regular high volume traffic through the building envelope, such as retail store entrances and loading bays, estimates of air leakage for HVAC system design shall be based on air exchange by traffic flow.

5.3.7.2.6 To reduce infiltration due to stack-effect draft in multi-story buildings, the use of vestibules or revolving doors on all primary entries and exits shall be considered.

5.3.7.3 Air Leakage Requirements for Exterior Envelope Joints and Penetrations.

5.3.7.3.1 Exterior joints, cracks, and holes in the building envelope, such as those around window or door frames, between wall and foundation, between wall and roof, through wall panels at penetrations of utility services or other service entry through walls,

floors, and roofs, between wall panels, particularly at corners and changes in orientation, between wall and floor, where floor penetrates wall, around penetrations of chimney, flue vents, or attic hatches, shall be caulked, gasketed, weather stripped, or otherwise sealed.

5.3.7.4 Moisture Migration Requirements for Exterior Envelopes

5.3.7.4.1 The building envelope shall be designed to prevent moisture migration that leads to deterioration in insulation performance of the building.

5.3.7.4.2 Vapor retarders shall be considered to prevent moisture from collecting within the envelope. Designs should incorporate the principles of ASHRAE Handbook, 1985 Fundamentals Volume, Chapter 21, "Moisture in Building Construction."

5.3.8.1.2 Fenestration shading devices. Only those shading devices that are part of the design when it is being evaluated for compliance shall be considered when determining compliance.

5.3.8.1.3 Daylighting controls for electric lighting. Only those controls that are part of the design when it is being evaluated for compliance shall be considered when determining compliance.

5.3.9 Buildings Located in Climates With Greater Than 15,000 HDD Base 65 °F.

5.3.9.1 For locations with a heating degree-day base (HDD) 65 °F greater than 15,000, the envelope criteria listed in Table 5.3-5 shall apply, and the window wall ratio (WWR) shall be less than or equal to 0.20.