[Code of Federal Regulations]
[Title 10, Volume 3]
[Revised as of January 1, 2005]
From the U.S. Government Printing Office via GPO Access
[CITE: 10CFR434.402]
[Page 373-380]
TITLE 10--ENERGY
CHAPTER II--DEPARTMENT OF ENERGY
PART 434_ENERGY CODE FOR NEW FEDERAL COMMERCIAL AND MULTI-FAMILY HIGH
RISE RESIDENTIAL BUILDINGS--Table of Contents
Subpart D_Building Design Requirements_Electric Systems and Equipment
Sec. 434.402 Building envelope assemblies and materials.
The building envelope and its associated assemblies and materials
shall meet the provisions of this section.
402.1 Calculations and Supporting Information.
402.1.1 Material Properties. Information on thermal properties,
building envelope system performance, and component heat transfer shall
be obtained from RS-4. When the information is not available from RS-4,
(incorporated by reference, see Sec. 434.701) the data shall be
obtained from manufacturer's information or laboratory or field test
measurements using RS-5, RS-6, RS-7, or RS-8 (incorporated by reference,
see Sec. 434.701).
402.1.1.1 The shading coefficient (SC) for fenestration shall be
obtained from RS-4 (incorporated by reference, see Sec. 434.701) or
from manufacturer's test data. The shading coefficient of the
fenestration, including both internal and external shading devices, is
SCX and excludes the effect of external shading projections,
which are calculated separately. The shading coefficient used for
louvered shade screens shall be determined using a profile angle of 30
degrees as found in Table 41, Chapter 27 of RS-4 (incorporated by
reference, see Sec. 434.701).
402.1.2 Thermal Performance Calculations. The overall thermal
transmittance of the building envelope shall be calculated in accordance
with Equation 402.1.2:
[GRAPHIC] [TIFF OMITTED] TR06OC00.022
Where:
Uo = the area-weighted average thermal transmittance of the
gross area of the building envelope; i.e., the exterior wall assembly
including fenestration and doors, the roof and ceiling assembly, and the
floor assembly, Btu/(h[middot]ft\2\[middot][deg]F)
Ao = the gross area of the building envelope, ft\2\
Ui = the thermal transmittance of each individual path of the
building envelope, i.e., the opaque portion or the fenestration, Btu/
(h[middot]ft\2\[middot][deg]F)
Ui = 1/Ri (where Ri is the total
resistance to heat flow of an individual path through the building
envelope)
Ai = the area of each individual element of the building
envelope, ft\2\
The thermal transmittance of each component of the building envelope
shall be determined with due consideration of all major series and
parallel heat flow paths through the elements of the component and film
coefficients and shall account for any compression of insulation. The
thermal transmittance of opaque elements of assemblies
[[Page 374]]
shall be determined using a series path procedure with corrections for
the presence of parallel paths within an element of the envelope
assembly (such as wall cavities with parallel paths through insulation
and studs). The thermal performance of adjacent ground in below-grade
applications shall be excluded from all thermal calculations.
402.1.2.1 Envelope Assemblies Containing Metal Framing. The thermal
transmittance of the envelope assembly containing metal framing shall be
determined from one of three methods:
(a) Laboratory or field test measurements based on RS-5, RS-6, RS-7,
or RS-8 (incorporated by reference, see Sec. 434.701).
(b) The zone method described in Chapter 22 of RS-4 (incorporated by
reference, see Sec. 434.701) and the formulas on page 22.10.
(c) For metal roof trusses or metal studs covered by Tables
402.1.2.1a and b, the total resistance of the series path shall be
calculated in accordance with the following Equations:
[GRAPHIC] [TIFF OMITTED] TR06OC00.023
Where:
Rt = the total resistance of the envelope assembly
Ri = the resistance of the series elements (for i = 1 to n)
excluding the parallel path element(s)
Re = the equivalent resistance of the element containing the
parallel path (R-value of insulation x Fc). Values for
Fc and equivalent resistances shall be taken from Tables
402.1.2.1a or b.
Table 402.1.2.1a--Parallel Path Correction Factors--Metal Roof Trusses
Spaced 4 ft. o.c. or Greater That Penetrate the Insulation
------------------------------------------------------------------------
Equivalent
Effective framing cavity R-values Correction resistance
factor Fc Re \1\
------------------------------------------------------------------------
R-0......................................... 1.00 R-0
R-5......................................... 0.96 R-4.8
R-10........................................ 0.92 R-9.2
R-15........................................ 0.88 R-13.2
R-20........................................ 0.85 R-17.0
R-25........................................ 0.81 R-20.3
R-30........................................ 0.79 R-23.7
R-35........................................ 0.76 R-26.6
R-40........................................ 0.73 R-29.2
R-45........................................ 0.71 R-32.0
R-50........................................ 0.69 R-34.5
R-55........................................ 0.67 R-36.0
------------------------------------------------------------------------
1 Based on 0.66-inch-diameter cross members every one foot.
Table 402.1.2.1b--Parallel Path Correction Factors--Metal Framed Walls With Studs 16 Ga. or Lighter
----------------------------------------------------------------------------------------------------------------
Equivalent
Size of members Spacing of framing, Cavity insulation R- Correction resistance
in. Value factor Fc Re
----------------------------------------------------------------------------------------------------------------
2 x 4............................... 16 O.C. R-11 0.50 R-5.5
R-13 0.46 R-6.0
R-15 0.43 R-6.4
2 x 4............................... 24 O.C. R-11 0.60 R-6.6
R-13 0.55 R-7.2
R-15 0.52 R-7.8
2 x 6............................... 16 O.C. R-19 0.37 R-7.1
R-21 0.35 R-7.4
2 x 6............................... 24 O.C. R-19 0.45 R-8.6
R-21 0.43 R-9.0
2 x 8............................... 16 O.C. R-25 0.31 R-7.8
2 x 8............................... 24 O.C. R-25 0.38 R-9.6
----------------------------------------------------------------------------------------------------------------
402.1.2.2 Envelope Assemblies Containing Nonmetal Framing. The
thermal transmittance of the envelope assembly shall be determined from
laboratory or field test measurements based on RS-5, RS-6, RS-7, or RS-8
(incorporated by reference, see Sec. 434.701) or from the series-
parallel (isothermal planes) method provided in page 23.2 of Chapter 23
of RS-4 (incorporated be reference, see Sec. 434.701).
402.1.2.3 Metal Buildings. For elements with internal metallic
structures bonded on one or both sides to a metal skin or covering, the
calculation
[[Page 375]]
procedure specified in RS-9 (incorporated by reference, see Sec.
434.701) shall be used.
402.1.2.4 Fenestration Assemblies. Determine the overall thermal
transmittance of fenestration assemblies in accordance with RS-18 and
RS-19 (incorporated by reference, see Sec. 434.701) or by calculation.
Calculation of the overall thermal transmittance of fenestration
assemblies shall consider the center-of-glass, edge-of-glass, and frame
components.
(a) The following equation 402.1.2.4a shall be used.
[GRAPHIC] [TIFF OMITTED] TR06OC00.024
Where:
Uof = the overall thermal transmittance of the fenestration
assemblies, including the center-of-glass, edge-of-glass, and frame
components, Btu/(h[middot]ft2[middot][deg]F)
i = numerical subscript (1, 2, . . .n) refers to each of the various
fenestration types present in the wall
n = the number of fenestration assemblies in the wall assembly
Ucg = the thermal transmittance of the center-of-glass area,
Btu/(h[middot]ft2[middot][deg]F)
Acg = the center of glass area, that is the overall visible
glass area minus the edge-of-glass area, ft2
Ueg = the thermal transmittance of the edge of the visible
glass area including the effects of spacers in multiple glazed units,
Btu/(h[middot]ft2[middot][deg]F)
Aeg = the edge of the visible glass area, that is the 2.5 in.
perimeter band adjacent to the frame, ft2
Uf = the thermal transmittance of the frame area, Btu/
(h[middot]ft2[middot][deg]F)
Af = the frame area that is the overall area of the entire
glazing product minus the center-of-glass area and minus the edge-of-
glass area, ft\2\
(b) Values of Uof shall be based on one of the following
methods:
(1) Results from laboratory test of center-of-glass, edge-of-glass,
and frame assemblies tested as a unit at winter conditions. One of the
procedures in Section 8.3.2 of RS-1 (incorporated by reference, see
Sec. 434.701) shall be used.
(2) Overall generic product C (commercial) in Table 13, Chapter 27,
of the RS-4 (incorporated by reference, see Sec. 434.701). The generic
product C in Table 13, Chapter 27, is based on a product of 24 ft\2\.
Larger units will produce lower U-values and thus it is recommended to
use the calculation procedure detailed in Equation 402.1.2.4a.
(3) Calculations based on the actual area for center-of-glass, edge-
of-glass, and frame assemblies and on the thermal transmittance of
components derived from 402.1.2.4a, 402.1.2.4b or a combination of the
two.
402.1.3 Gross Areas of Envelope Components.
402.1.3.1 Roof Assembly. The gross area of a roof assembly shall
consist of the total surface of the roof assembly exposed to outside air
or unconditioned spaces and is measured from the exterior faces of
exterior walls and centerline of walls separating buildings. The roof
assembly includes all roof or ceiling components through which heat may
flow between indoor and outdoor environments, including skylight
surfaces but excluding service openings. For thermal transmittance
purposes when return air ceiling plenums are employed, the roof or
ceiling assembly
[[Page 376]]
shall not include the resistance of the ceiling or the plenum space as
part of the total resistance of the assembly.
402.1.3.2 Floor Assembly. The gross area of a floor assembly over
outside or unconditioned spaces shall consist of the total surface of
the floor assembly exposed to outside air or unconditioned space and is
measured from the exterior face of exterior walls and centerline of
walls separating buildings. The floor assembly shall include all floor
components through which heat may flow between indoor and outdoor or
unconditioned space environments.
402.1.3.3 Wall Assembly. The gross area of exterior walls enclosing
a heated or cooled space is measured on the exterior and consists of the
opaque walls, including between-floor spandrels, peripheral edges of
flooring, window areas (including sash), and door areas but excluding
vents, grilles, and pipes.
402.2 Air Leakage and Moisture Mitigation. The requirements of this
section shall apply only to those building components that separate
interior building conditioned space from the outdoors or from
unconditioned space or crawl spaces. Compliance with the criteria for
air leakage through building components shall be determined by tests
conducted in accordance with RS-10 (incorporated by reference, see Sec.
434.701).
402.2.1 Air Barrier System. A barrier against leakage shall be
installed to prevent the leakage of air through the building envelope
according to the following requirements:
(a) The air barrier shall be continuous at all plumbing and heating
penetrations of the building opaque wall.
(b) The air barrier shall be sealed at all penetrations of the
opaque building wall for electrical and telecommunications equipment.
Table 402.2.1--Air Leakage for Fenestration and Doors Maximum Allowable Infiltration Rate
----------------------------------------------------------------------------------------------------------------
cfm/lin ft Sash crack or cfm/
Component Reference standard ft2 of area
----------------------------------------------------------------------------------------------------------------
Fenestration
Aluminum:
Operable............................. RS-11* 0.37 cfm/lin ft.
Jalousie............................. RS-11* 1.50 cfm/ft2.
Fixed................................ RS-11* 0.15 cfm/ft2.
Poly Vinyl Chloride (PVC):
Prime Windows........................ RS-12* 0.37 cfm/ft2.
Wood:
Residential.......................... RS-13* 0.37 cfm/ft2.
Light Commercial..................... RS-13* 0.25 cfm/ft2.
Heavy Commercial..................... RS-13* 0.15 cfm/ft2.
Sliding Glass Doors:
Aluminum............................. RS-11* 0.37 cfm/ft2.
PVC.................................. RS-12* 0.37 cfm/lin ft.
Doors--Wood:
Residential.......................... RS-14* 0.34 cfm/ft2.
Light Commercial..................... RS-14* 0.25 cfm/ft2.
Heavy Commercial..................... RS-14* 0.10 cfm/ft2.
Commercial Entrance Doors................ RS-10* 1.25 cfm/ft2.
Residential Swinging Doors............... RS-10* 0.50 cfm/ft2.
Wall Sections Aluminum................... RS-10* 0.06 cfm/ft2.
----------------------------------------------------------------------------------------------------------------
Note:
[The ``Maximum Allowable Infiltration Rates'' are from current standards to allow the use of available
products.]
* Incorporated by reference, see Sec. 434.701.
402.2.2 Building Envelope. The following areas of the building
envelope shall be sealed, caulked, gasketed, or weatherstripped to limit
air leakage:
(a) Intersections of the fenestration and door frames with the
opaque wall sections.
(b) Openings between walls and foundations, between walls and roof
and wall panels.
(c) Openings at penetrations of utility service through, roofs,
walls, and floors.
(d) Site built fenestration and doors.
[[Page 377]]
(e) All other openings in the building envelope.
Exceptions are as follows: Outside air intakes, exhaust outlets,
relief outlets, stair shaft, elevator shaft smoke relief openings, and
other similar elements shall comply with subsection 403.
402.2.2.1 Fenestration and Doors Fenestration and doors shall meet
the requirements of Table 402.2.1.
402.2.2.2 Building Assemblies Used as Ducts or Plenums. Building
assemblies used as ducts or plenums shall be sealed, caulked, and
gasketed to limit air leakage.
402.2.2.3 Vestibules. A door that separates conditioned space from
the exterior shall be equipped with an enclosed vestibule with all doors
opening into and out of the vestibule equipped with self-closing
devices. Vestibules shall be designed so that in passing through the
vestibule, it is not necessary for the interior and exterior doors to
open at the same time. Exceptions are as follows: Exterior doors need
not be protected with a vestibule where:
(a) The door is a revolving door.
(b) The door is used primarily to facilitate vehicular movement or
material handling.
(c) The door is not intended to be used as a general entrance door.
(d) The door opens directly from a dwelling unit.
(e) The door opens directly from a retail space less than 2,000
ft\2\ in area, or from a space less than 1,500 ft\2\ for other uses.
(f) In buildings less than three stories in building height in
regions that have less than 6,300 heating degree days base 65[deg]F.
402.2.2.4 Compliance Testing. All buildings shall be tested after
completion using the methodology in RS-11, (incorporated by reference,
see Sec. 434.701) or an equivalent approved method to determine the
envelope air leakage. A standard blower door test is an acceptable
technique to pressurize the building if the building is 5,000 ft\2\ or
less in area. The buildings's air handling system can be used to
pressurize the building if the building is larger than 5,000 ft\2\. The
following test conditions shall be:
(a) The measured envelope air leakage shall not exceed 1.57 pounds
per square foot of wall area at a pressure difference of 0.3 inches
water.
(b) At the time of testing, all windows and outside doors shall be
installed and closed, all interior doors shall be open, and all air
handlers and dampers shall be operable. The building shall be
unoccupied.
(c) During the testing period, the average wind speed during the
test shall be less than 6.6 feet per second, the average outside
temperature greater than 59[deg]F, and the average inside-outside
temperature difference is less than 41[deg]F.
402.2.2.5 Moisture Migration. The building envelope shall be
designed to limit moisture migration that leads to deterioration in
insulation or equipment performance as determined by the following
construction practices:
(a) A vapor retarder shall be installed to retard, or slow down the
rate of water vapor diffusion through the building envelope. The
position of the vapor retarder shall be determined taking into account
local climate and indoor humidity levels. The methodologies presented in
Chapter 20 of RS-4 (incorporated by reference, see Sec. 434.701) shall
be used to determine temperature and water vapor profiles through the
envelope systems to assess the potential for condensation within the
envelope and to determine the position of the vapor retarder within the
envelope system.
(b) The vapor retarder shall be installed over the entire building
envelope.
(c) The perm rating requirements of the vapor retarder shall be
determined using the methodologies contained in Chapter 20 of RS-4,
(incorporated by reference, see Sec. 434.701) and shall take into
account local climate and indoor humidity level. The vapor retarder
shall have a performance rating of 1 perm or less.
402.3 Thermal Performance Criteria.
402.3.1 Roofs; Floors and Walls Adjacent to Unconditioned Spaces.
The area weighted average thermal transmittance of roofs and also of
floors and walls adjacent to unconditioned spaces shall not exceed the
criteria in Table 402.3.1a. Exceptions are as follows: Skylights for
which daylight credit is
[[Page 378]]
taken may be excluded from the calculations of the roof assembly
Uor if all of the following conditions are met:
(a) The opaque roof thermal transmittance is less than the criteria
in Table 402.3.1b.
(b) Skylight areas, including framing, as a percentage of the roof
area do not exceed the values specified in Table 402.3.1b. The maximum
skylight area from Table 402.3.1b may be increased by 50% if a shading
device is used that blocks over 50% of the solar gain during the peak
cooling design condition. For shell buildings, the permitted skylight
area shall be based on a light level of 30 foot candles and a lighting
power density (LPD) of less than 1.0 w/ft \2\. For speculative
buildings, the permitted skylight area shall be based on the unit
lighting power allowance from Table 401.3.2a and an illuminance level as
follows: for LPD < 1.0, use 30 footcandles; for 1.0 < LPD < 2.5, use 50
footcandles; and for LPD = 2.5, use 70 footcandles.
(c) All electric lighting fixtures within daylighted zones under
skylights are controlled by automatic daylighting controls.
(d) The Uo of the skylight assembly including framing
does not exceed------------Btu/(h[middot]ft \2\[middot][deg]F) [Use 0.70
for <= 8000 HDD65 and 0.45 for 8000 HDD65 or both if the
jurisdiction includes cities that are both below and above 8000 HDD65.]
(e) Skylight curb U-value does not exceed 0.21 Btu/(h[middot]ft
\2\[middot][deg]F).
(f) The infiltration coefficient of the skylights does not exceed
0.05 cfm/ft \2\.
402.3.2 Below-Grade Walls and Slabs-on-Grade. The thermal resistance
(R-value) of insulation for slabs-on-grade, or the overall thermal
resistance of walls in contact with the earth, shall be equal to or
greater than the values in Table 402.3.2.
402.4 Exterior Walls. Exterior walls shall comply with either
402.4.1 or 402.4.2.
402.4.1 Prescriptive Criteria. (a) The exterior wall shall be
designed in accordance with subsections 402.4.1.1 and 402.4.1.2. When
the internal load density range is not known, the 0-1.50 W/ft \2\ range
shall be used for residential, hotel/motel guest rooms, or warehouse
occupancies; the 3.01-3.50 w/ft \2\ range shall be used for retail
stores smaller than 2,000 ft \2\ and technical and vocational schools
smaller than 10,000 ft \2\; and the 1.51-3.00 W/ft \2\ range shall be
used for all other occupancies and building sizes. When the building
envelope is designed or constructed prior to knowing the building
occupancy type, an internal load density of ------ W/ft \2\ shall be
used. [Use 3.0 W/ft \2\ for HDD65 <3000, 2.25 W/ft \2\ for 3000 < HDD65
< 6000, and 1.5 W/ft \2\ for HDD65 6000.]
(b) When more than one condition exists, area weighted averages
shall be used. This requirement shall apply to all thermal
transmittances, shading coefficients, projection factors, and internal
load densities rounded to the same number of decimal places as shown in
the respective table.
402.4.1.1 Opaque Walls. The weighted average thermal transmittance
(U-value) of opaque wall elements shall be less than the values in Table
402.4.1.1. For mass walls (HC = 5), criteria are presented
for low and high window/wall ratios and the criteria shall be determined
by interpolating between these values for the window/wall ratio of the
building.
402.4.1.2 Fenestration. The design of the fenestration shall meet
the criteria of Table 402.4.1.2. When the fenestration columns labeled
``Perimeter Daylighting'' are used, automatic daylighting controls shall
be installed in the perimeter daylighted zones of the building. These
daylighting controls shall be capable of reducing electric lighting
power to at least 50% of full power. Only those shading or lighting
controls for perimeter daylighting that are shown on the plans shall be
considered. The column labeled ``VLT = SC'' shall be used
only when the shading coefficient of the glass is less than its visible
light transmittance.
Appendix A
The example Alternate Component Package tables illustrate the
requirements of subsections 434.301.1, 434.402.3.1, 434.402.3.2,
434.402.4.1.1 and 434.402.4.1.2. Copies of specific tables contained in
this Appendix A can be obtained from the Energy Code for Federal
Commercial Buildings, Docket No. EE-RM-79-112-C, EE-43, Office of
Building Research and Standards, U.S. Department of Energy, Room 1J-018,
1000 Independence Avenue, SW., Washington, DC 20585, (202) 586-9127.
[[Page 379]]
[GRAPHIC] [TIFF OMITTED] TR06OC00.011
402.4.2 System Performance Criteria. The cumulative annual energy
flux attributable to thermal transmittance and solar gains shall be less
than the criteria determined using the ENVSTD24 computer program in
Standard 90.1-1989, or the equations in RS-1, (incorporated by
reference, see Sec. 434.701) Attachment 8-B. The cumulative annual
energy flux shall be calculated using the ENVSTD24 computer program or
the equations in RS-1, (incorporated by reference, see Sec. 434.701)
Attachment 8-B.
[[Page 380]]
Table 402.4.2--EQUIP Default Values for ENVSTD24
----------------------------------------------------------------------------------------------------------------
Default Default
equipment Default adjusted
Occupancy power density occupant load equipment
1 adjustment 1 power density
----------------------------------------------------------------------------------------------------------------
Assembly........................................................ 0.25 0.75 1.00
Health/Institutional............................................ 1.00 -0.26 0.74
Hotel/Motel..................................................... 0.25 -0.33 0.00
Warehouse/Storage............................................... 0.10 -0.60 0.00
Multi-Family High Rise.......................................... 0.75 N/A 0.00
Office.......................................................... 0.75 -0.35 0.40
Restaurant...................................................... 0.10 0.07 0.17
Retail.......................................................... 0.25 -0.38 0.00
School.......................................................... 0.50 0.30 0.80
----------------------------------------------------------------------------------------------------------------
1 Defaults as defined in Section 8.6.10.5, Table 8-4, and Sections 8.6.10.6 and 13.7.2.1, Table 13-2 from RS-1
(incorporated by reference, see Sec. 434.701).
402.4.2.1 Equipment Power Density (EQUIP). The equipment power
density used in the ENVSTD24 computer program shall use the actual
equipment power density from the building plans and specifications or be
taken from Table 402.4.2 using the column titled ``Default Adjusted
Equipment Power Density'' or calculated for the building using the
procedures of RS-1. (incorporated by reference, see Sec. 434.701). The
program limits consideration of the equipment power density to a maximum
of 1 W/ft 2.
402.4.2.2 Lighting Power Density (LIGHTS). The lighting power
density used in the ENVSTD24 computer program shall use the actual
lighting power density from the building plans and specifications or the
appropriate value from Tables 401.3.2a, b, c, or d.
402.4.2.3 Daylighting Control Credit Fraction (DLCF). When the
daylighting control credit fraction is other than zero, automatic
daylighting controls shall be installed in the appropriate perimeter
zones(s) of the building to justify the credit.