Washington Administrative Code › Title 51 - Enterprise Services, Department of (Building Code Council) › Chapter 51-11R - State Building Code adoption and amendment of the 2021 edition of the International Energy Conservation Code, Residential › Section 51-11R-40551 - Table R405.4.2(1)-Specifications for the standard reference and proposed designs

Current through Register Vol. 24-14, July 15, 2024
TABLE R405.4.2(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.
Gross area: Same as proposed
U
-factor: From Table R402.1.2
Solar absorptance = 0.75
Emittance = 0.90
As proposed
As proposed
As proposed
As proposed
As proposed
Below-grade walls
Type: Same as proposed
Gross area: Same as proposed
U
-factor: From Table R402.1.2, with
						  insulation layer on interior side of walls.
As proposed
As proposed
As proposed
Above-grade floors
Type: Wood frame
Gross area: Same as proposed
U
-factor: From Table R402.1.2
As proposed
As proposed
As proposed
Ceilings
Type: Wood frame
Gross area: Same as proposed
U
-factor: From Table R402.1.2
As proposed
As proposed
As proposed
Roofs
Type: Composition shingle on wood sheathing Gross area:
						  Same as proposed Solar absorptance = 0.75 Emittance = 0.90
As proposed
As proposed
As proposed
As proposed
Attics
Type: Vented with aperture = 1
						  ft2 per 300 ft2 ceiling
						  area
As proposed
Foundations
Type: Same as proposed foundation wall area above and
						  below-grade
Soil characteristics: Same as proposed.
As proposed
As proposed
Opaque doors
Area: 40 ft2
Orientation: North
U
-factor: Same as fenestration from
						  Table R402.1.2.
As proposed
As proposed
As proposed
Vertical fenestration other than opaque
						  doorsa
Total areah =
(a) The proposed glazing area; where proposed glazing
						  area is less than 15% of the conditioned floor area.
(b) 15% of the conditioned floor area; where the
						  proposed glazing area is 15% 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: From Table R402.1.2
As proposed
SHGC: From Table R402.1.1 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)
External shading: None
0.92 - (0.21 × SHGC as proposed)
As proposed
Skylights
None
As proposed
Air exchange rate
Air leakage rate of 4 air changes per hour 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
N
br = number of
						  bedrooms
- The mechanical ventilation system type shall be the
						  same as in the proposed design. Energy recovery shall not be assumed for
						  mechanical ventilation.
As proposeda. The mechanical
						  ventilation rateb shall be in addition to the air
						  leakage rate and shall be as proposed.
Mechanical ventilation
None, except where mechanical ventilation is specified
						  by the proposed design, in which case:
Annual vent fan energy use:
kWh/yr = (1ef) × (0.0876
						  ×
CFA
+ 65.7 × (
Nbr
+ 1)
where:
ef = the minimum fan efficacy
						  from Table R403.6.1
corresponding to the system type at a flow rate of 0.01
						  ×
CFA
+ 7.5 ×
						  (
Nbr
+ 1)
CFA
= conditioned floor area
N
br = 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% of floor area covered by
						  R-2 carpet and pad, and 20% of floor directly exposed to room air.
As proposed
For masonry basement walls, as proposed, but with
						  insulation required by Table R402.1.2 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
The standard reference design shall be an air source
						  heat pump meeting the requirements of Section C403 of the
WSEC-Commercial Provisions.
Capacity: Sized in accordance with Section
						  R403.7
As proposed
Cooling systemsd, f
Same system type as proposed. Same system efficiency as
						  required by prevailing minimum federal standard. Capacity: Sized in accordance
						  with Section R403.7
As proposed
Service water heatingd, e, f,
							 g
The standard reference design shall be a heat pump
						  water heater meeting the efficiency standards of Table C404.2.
Use, in units of gal/day = 25.5 + (8.5 x
						  Nbr) Where Nbr = number of
						  bedrooms
As proposed
Use, in units of gal/day = 25.5 + (8.5 x
						  Nbr) x (1 - HWDS)
Where:
Nbr= number of bedrooms
HWDS = factor for the compactness of the hot water
						  distribution system
Click here to view
						  image
Thermal distribution systems
Duct insulation: From Section R403.3.3.
Duct location: Same as proposed design.
A thermal distribution system efficiency (DSE) of 0.93
						  shall be applied to both the heating and cooling system efficiencies for all
						  systems.
Exception:
For nonducted heating and
						  cooling systems that do not have a fan, the standard reference design
						  distribution system efficiency (DSE) shall be 1.
Duct insulation: As proposed.
Duct location: As proposed.
As specified in Table R405.5.2(2).
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 (U.S.) = 3.785 L, °C =
				(°F-3)/1.8, 1 degree = 0.79 rad
a 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.
b 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.
c 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.
d 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.
e 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.
f 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.
g 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.
h For residences with conditioned
				basements, R-2 and R-4 residences and townhouses, the following formula shall
				be used to determine fenestration area:
Click
				here to view image
and where:
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.
i The factor for the compactness of
				the hot water distribution system is the ratio of the area of the rectangle
				that bounds the source of hot water and the fixtures that it serves (the "hot
				water rectangle") divided by the floor area of the dwelling.
1. Sources of hot water include water
			 heaters, or in multifamily buildings with central water heating systems,
			 circulation loops, or electric heat traced pipes.
2. The hot water rectangle shall include the
			 source of hot water and the points of termination of all hot water fixture
			 supply piping.
3. The hot water
			 rectangle shall be shown on the floor plans and the area shall be computed to
			 the nearest square foot.
4. Where
			 there is more than one water heater and each water heater serves different
			 plumbing fixtures and appliances, it is permissible to establish a separate hot
			 water rectangle for each hot water distribution system and add the area of
			 these rectangles together to determine the compactness ratio.
5. The basement or attic shall be counted as
			 a story when it contains the water heater.
6. Compliance shall be demonstrated by
			 providing a drawing on the plans that shows the hot water distribution system
			 rectangle(s), comparing the area of the rectangle(s) to the area of the
			 dwelling and identifying the appropriate compactness ratio and HWDS
			 factor.
Statutory Authority:
				  RCW
				    19.27A.020,
				  19.27A.045 and
				  chapters
				  19.27 and
				  34.05 RCW. 13-04-055, §
				  51-11R-40551, filed 2/1/13, effective
				  7/1/13.