Prescriptive Checklist for the
2018 Washington State Energy Code
Chapter 51-11R WAC
State Building Code Adoption and Amendment of the 2018 Edition
of the International Energy Conservation Code, Residential Provisions
Washington State Energy Code – Residential Provisions
Updated December 2020
© 2020 Washington State University Energy Program
This publication contains material written and produced for public distribution. Permission to copy or
disseminate all or part of this material is granted, provided that the copies are not made or distributed
for commercial advantage and that they are referenced by title with credit to the
Washington State University Energy Program.
WSUEEP13-060 • revised December 2020
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This prescriptive checklist cites 2018 Washington State Energy Code - Residential (WSEC-R) items
that apply to most residential new construction projects. This checklist is not a substitute for the
energy code itself, nor is it a list of comprehensive energy code requirements. More resources
about the energy code are available on the Washington State University Energy Program website.
☐ R103.2 Information on Construction Documents
Include details in construction documents regarding insulation materials and their R-values;
fenestration U-factors and SHGCs; area-weighted U-factor and SHGC calculations; mechanical
system design criteria; mechanical and service water heating system and equipment types, sizes
and efficiencies; equipment and systems controls; duct sealing, duct and pipe insulation and
location; and air sealing details.
☐ R103.3.1 Approval of Construction Documents
One set of construction documents so reviewed shall be retained by the code official. The other
set shall be returned to the applicant, kept at the site of work and shall be open to inspection by
the code official or a duly authorized representative.
☐ R104.1 General
Construction or work for which a permit is required shall be subject to inspection by the code
official or his or her designated agent, and such construction or work shall remain visible and able
to be accessed for inspection purposes until approved. It shall be the duty of the permit applicant
to cause the work to remain visible and able to be accessed for inspection purposes. Neither the
code official nor the jurisdiction shall be liable for expense entailed in the removal or replacement
of any material, product, system or building component required to allow inspection to validate
compliance with this code.
☐ R104.2.2.1 Wall Insulation Inspection
The building official, upon notification, shall make a wall insulation inspection in addition to those
inspections required in Section R109 of the International Residential Code. This inspection shall be
made after all wall and cavity insulation is in place and prior to cover.
☐ R302.2 Design Conditions for Sizing HVAC
The heating or cooling outdoor design temperatures shall be selected from Appendix C, RE-95.
Useful Links: Air Conditioning Contractors of America
NEEA HVAC Sizing Tool
☐ R303.1.1 Insulation Certification
The insulation installers shall provide a certification listing the type, manufacturer and R-value of
insulation installed in each element of the building thermal envelope. For blown or sprayed
insulation (fiberglass and cellulose), the initial installed thickness, settled thickness, settled R-value,
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installed density, coverage area and number of bags installed shall be listed on the certification. For
sprayed polyurethane foam (SPF) insulation, the installed thickness of the areas covered and R-value
of installed thickness shall be listed on the certification. For insulated siding, the R-value shall be
labeled on the product’s package and shall be listed on the certification. The insulation installer shall
sign, date and post the certification in a conspicuous location on the job site.
Exception: For roof insulation installed above the deck, the R-value shall be labeled as
required by the material standards specified in Table 1508.2 of the International Building
Code or Table R906.2 of the International Residential Code.
Insulation Certificate for Residential New Construction
Useful Links: North American Insulation Manufacturers Association
Spray Polyurethane Foam Alliance
Foam Sheathing Coalition
☐ R303.1.1.1 Insulation Markers
The thickness of blown-in or sprayed roof/ceiling insulation
(fiberglass or cellulose) shall be written in inches (mm) on
markers that are installed at least one for every 300 square
feet (28 m
2
) throughout the attic space. The markers shall be
affixed to the trusses or joists and marked with the minimum
initial installed thickness with numbers a minimum of 1 inch
(25 mm) in height.
☐ R303.2.1 Protection of Exposed Foundation Insulation -
above grade and 6” below grade
Insulation applied to the exterior of basement walls,
crawlspace walls and the perimeter of slab-on-grade floors
shall have a rigid, opaque and weather-resistant protective
covering to prevent the degradation of the insulation’s
thermal performance.
☐ R401.3 Certificate
A permanent certificate shall be completed by the builder or
other approved party and posted on a wall in the space
where the furnace is located, a utility room, or an approved location inside the building.
2018 Compliance Certificate
2018 Compliance Certificate Instructions
R303.1.3 Insulation Markers
Insulation marker installed in attic. Make
sure the marker is applicable to the type
of insulation installed (fiberglass,
cellulose, etc.)
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☐ Table 402.1.1 Footnote “d” Slab R-Value
R-10 continuous insulation (CI) is required under
heated slab on grade floors. See R402.2.9.1.
☐ Table 402.1.1 Footnote “e” Ceiling R-Value
For single rafter or joist-vaulted ceilings, the
insulation may be reduced to R-38 if the full
insulation depth extends over the top plate of
the exterior wall.
Table R402.1.1 Footnote “d” Slab R-Value
R-10 fully insulated slab for heated slab-on-grade floors
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☐ Table 402.1.1 Footnote “f” Existing Slab R-
Value
R-7.5 CI installed over an existing slab is
deemed equivalent to the required perimeter
slab insulation when applied to existing slabs
complying with Section R503.1.1. If foam
plastic is used, it shall meet requirements for
thermal barriers protecting foam plastics.
☐ Table 402.1.1 Footnote “h” Intermediate
Framing
Intermediate framing denotes framing and
insulation as described in Section A103.2.2
including standard framing 16 inches on center,
78% of wall cavity insulated and headers
insulated with a minimum of R-10 insulation.
☐ R402.2.1 Ceilings with Attic Spaces
Where Section R402.1.1 would require R-49 in
the ceiling, installing R-38 over 100% of the
ceiling area requiring insulation shall be
deemed to satisfy the requirement for R-49
wherever the full height of uncompressed R-38
insulation extends over the wall top plate at the
eaves. This reduction shall not apply to the U-
factor alternative approach in Section R402.1.3
and total UA alternative in Section R402.1.4.
R402.2.1 Ceilings with Attic Spaces
You can reduce ceiling insulation R-value to 38 if you
have R-38 extending to the exterior wall line
Table 402.1.1 Footnote “h” Intermediate Framing
“INT” walls require R-10 insulated headers
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☐ R402.2.1.1 Loose Fill Insulation in Attic Spaces
Open-blown or poured loose fill insulation may be used in attic
spaces where the slope of the ceiling is not more than 3 feet in
12 and there is at least 30 inches of clear distance from the top
of the bottom chord of the truss or ceiling joist to the
underside of the sheathing at the roof ridge.
☐ R402.2.3 Eave Baffle
For air permeable insulation in vented attics, a baffle shall be
installed adjacent to soffit and eave vents.
☐ R402.2.4 Access Hatches and Doors
Access doors from conditioned spaces to unconditioned spaces
(e.g., attics and crawl spaces) shall be weather stripped and
insulated to a level equivalent to the insulation on the
surrounding surfaces.
☐ R402.2.7 Floors
Floor framing cavity insulation shall be installed to maintain
permanent contact with the underside of the subfloor decking.
Insulation supports shall be installed so spacing is no more than
24 inches on center. Foundation vents shall be placed so that the
top of the vent is below the lower surface of the floor insulation.
☐ R402.2.7 Floors Exception
The floor framing cavity insulation shall be permitted to be in
contact with the topside of sheathing or CI installed on the bottom side of floor framing where
combined with insulation that meets or exceeds the minimum Wood Frame R-value in Table
R402.1.1 and extends from the bottom to the top of all perimeter floor framing members.
☐ R402.2.7 Floors Exception
When foundation vents are not placed so that the top of the vent is below the lower surface of the
floor insulation, a permanently attached baffle shall be installed at an angle of 30° from horizontal,
to divert air flow below the lower surface of the floor insulation.
☐ R402.2.7 Floors Exception
Substantial contact with the surface being insulated is not required in enclosed floor/ceiling
assemblies containing ducts where full R value insulation is installed between the duct and the
exterior surface.
R402.2.3 Eave Baffle
Baffle at eave vent. Minimum 1”
unobstructed air space required
R402.2.4 Access Hatches and Doors
Insulated crawl space access. The same
method applies to attic access hatches
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R402.2.7 Floors
Floor insulation installed with contact to the underside of the floor decking. Note the inset stapled twine.
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R402.2.7 Floors Exception
Baffle at rim joist vent. The same application is needed for joists hung from the
mudsill at a foundation vent location.
R402.2.7 Floors Exception
Exception for substantial contact with the surface being insulated in a floor/ceiling assembly. It is imperative
that the rim joist be caulked and sealed to minimize air infiltration.
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☐ R402.2.8 Basement Walls
Below-grade exterior wall insulation used on the exterior (cold) side of the wall shall extend from
the top of the below-grade wall to the top of the footing and shall be approved for below-grade
use. Above-grade insulation shall be protected. Insulation used on the interior (warm) side of the
wall shall extend from the top of the below-grade wall to the below-grade floor level and shall
include R-5 rigid board providing a thermal break between the concrete wall and the slab.
☐ R402.2.9 Slab-on-Grade Floors
The minimum thermal resistance (R-value)
of the insulation around the perimeter of
unheated or heated slab-on-grade floors
shall be as specified in Table R402.1.1. The
insulation shall be placed on the outside of
the foundation or on the inside of the
foundation wall. The insulation shall extend
downward from the top of the slab for a
minimum distance as shown in the table or
to the top of the footing, whichever is less,
or downward to at least the bottom of the
slab and then horizontally to the interior or
exterior for the total distance shown in the table. A 2-inch by 2-inch (maximum) pressure treated
nailer may be placed at the finished floor elevation for attachment of interior finish materials.
Insulation extending away from the building shall be protected by pavement or by a minimum of
10 inches (254 mm) of soil.
R402.2.9 Slab-on-Grade Floors
Exterior applied foundation insulation on a monolithic slab
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R402.2.8 Basement Walls
Exterior insulation R-10 continuous
Interior insulation R-15 continuous
Recommended wall assembly. R-13 batt applied over R-5 foam.
This is equivalent to an R-21 wall.
R-21 cavity allowed but not recommended
due to potential moisture problems
Do not install vapor retarders in below-grade walls
2012 International Residential Code
R702.7 Vapor retarders. Class I
or II vapor retarders are required
on the interior side of frame
walls in Climate Zones 5, 6, 7, 8
and Marine 4.
Exceptions:
1. Basement walls.
2. Below grade portion of any
wall.
3. Construction where
moisture or its freezing will
not damage the materials.
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☐ R402.3.1 U-factor
An area-weighted average of fenestration products shall
be permitted to satisfy the U-factor requirements.
Example of Area Weighted U-Value Calculation:
Window #1 area 10 sf U = .34 U x A = 3.4
Window #2 area 15 sf U = .28 U x A = 4.2
Total area 25 sf Total U x A = 7.6
Area weighted average 7.6/25 = 0.30
The Glazing Schedule can help with this computation.
☐ R402.3.3 Glazed Fenestration Exemption
Up to 15 square feet (1.4 m
2
) of glazed fenestration per
dwelling unit shall be permitted to be exempt from U-
factor and SHGC requirements in Section R402.1.1. This
exemption shall not apply to the U-factor alternative
approach in Section R402.1.3 and the total UA alternative
in Section R402.1.4.
☐ R402.3.4 Opaque Door Exemption
One side-hinged opaque door assembly up to 24 square
feet (2.22 m
2
) in area is exempted from the U-factor
requirement in Section 402.1.1. This exemption shall not
apply to the U-factor alternative approach in Section
R402.1.3 and the total UA alternative in Section R402.1.4.
☐ Table 402.4.1.1 Air Barrier and Insulation Installation
Requirements
Air barriers and insulation must be installed in accordance
with Table 402.4.1.1, below.
☐ R402.4.1.2 Testing
The building or dwelling unit shall be tested and verified as having an air leakage rate of not
exceeding 5 air changes per hour.
Air Leakage Testing Specifications
Glazed Fenestration Exemption
Up to 15 sf of glazing are exempt from U-
factor requirements. This does not apply if
you are doing a UA tradeoff approach.
R402.3.4 Opaque Door Exemption
One door assembly, up to 24 sf, is exempt
from U-factor requirements
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☐ R402.4.2 Fireplaces
New wood-burning fireplaces shall have tight-fitting flue dampers or doors and outdoor
combustion air.
☐ R402.4.2.1 Gas Fireplace Efficiency
All gas fireplace heaters rated to ANSI Z21.88 shall be listed and labeled with a fireplace efficiency
(FE) rating of 50% or greater in accordance with CSA P.4.1. Vented gas fireplaces (decorative
appliances) certified to ANSI Z21.50 shall be listed and labeled, including their FE ratings, in
accordance with CSA P.4.1.
☐ R402.4.4 Combustion Air Openings
Where open combustion air ducts provide combustion air to open combustion, space conditioning
fuel burning appliances, the appliances and combustion air openings shall be located outside of
the building thermal envelope, or enclosed in a room isolated from inside the thermal envelope.
Such rooms shall be sealed and insulated in accordance with the envelope requirements of Table
R402.1.1, where the walls, floors and ceilings shall meet the minimum of the below-grade wall R-
value requirement. The door into the room shall be fully gasketed and any water lines and ducts in
the room insulated in accordance with Section R403. The combustion air duct shall be insulated
where it passes through conditioned space to a minimum of R-8.
Exceptions:
1. Direct vent appliances with both intake and exhaust pipes installed continuous to the outside.
2. Fireplaces and stoves complying with Section R402.4.2 and Section R1006 of the International
Residential Code.
☐ R402.4.5 Recessed Lighting
Recessed luminaires installed in the building thermal
envelope shall be sealed to limit air leakage between
conditioned and unconditioned spaces. All recessed
luminaires shall be Type IC-rated and labeled certified
under ASTM E283 and shall have a label attached showing
compliance with this test method. All recessed luminaires
shall be sealed with a gasket or caulk between the housing
and the interior wall or ceiling covering.
☐ R403.1.1 Programmable Thermostats for Forced Air Furnaces
Where the primary heating system is a forced-air furnace, at least one thermostat per dwelling
unit shall be capable of controlling the heating and cooling system on a daily schedule to maintain
different temperature set points at different times of the day. The thermostat shall allow for, at a
minimum, a 5-2 programmable schedule (weekdays/weekends) and be capable of providing at
least two programmable setback periods per day.
R402.4.4 Recessed Lighting
Labeled and sealed recessed light
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☐ R403.1.2 Heat Pump
Supplementary Heat
Unitary air cooled heat
pumps shall include controls
that minimize supplemental
heat usage during start-up,
set-up, and defrost
conditions. See R403.1.2 for
control and set-up
requirements.
☐ R403.3.1 Insulation
Ducts outside the building
thermal envelope shall be
insulated to a minimum of
R-8. Ducts within a concrete
slab or in the ground shall
be insulated to R-10 with insulation designed to be used below grade.
☐ R403.3.2 Sealing
Ducts, air handlers, and filter boxes shall be sealed. Joints and seams shall comply with either the
International Mechanical Code or International Residential Code, as applicable.
Exceptions:
1. Air-impermeable spray foam products shall be permitted to be applied without additional joint
seals.
2. For ducts having a static pressure classification of less than 2 inches of water column (500 Pa),
additional closure systems shall not be required for continuously welded joints and seams, and
locking-type joints and seams of other than the snap-lock and button-lock types.
☐ R403.3.3 Duct Testing
Ducts shall be leak tested in accordance with WSU RS-33, using the maximum duct leakage rates
specified.
RS-33 Duct Testing Standards
Exceptions:
1. The total leakage test or leakage to the outdoors is not required for ducts and air handlers
located entirely within the building thermal envelope. For forced air ducts, a maximum of 10
linear feet of return ducts and 5 linear feet of supply ducts may be located outside the
conditioned space. All metallic ducts located outside the conditioned space must have both
transverse and longitudinal joints sealed with mastic. If flex ducts are used, they cannot
R403.1.2 Heat Pump Supplementary Heat
Heat pumps with supplemental heat shall have lockout controls. Maximum
setting of 40° F, set to 35° F or less.
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contain splices. Flex duct connections must be made with nylon straps and installed using a
plastic strapping tensioning tool. Ducts located in crawl spaces do not qualify for this
exception.
2. A duct air leakage test shall not be required for ducts serving heat or energy recovery
ventilators that are not integrated with ducts serving heating or cooling systems.
A written report of results shall be signed by the party conducting the test and provided to the
code official.
☐ R403.3.4 Duct Leakage
The total leakage of ducts, where measured in accordance with Section R403.3.3, shall be as follows:
1. Rough-in test: Total leakage shall be less than or equal to 4 cfm (113.3 L/min) per 100 square
feet (9.29 m
2
) of conditioned floor area when tested at a pressure differential of 0.1 inches
w.g. (25 Pa) across the system, including the manufacturer's air handler enclosure. All registers
shall be taped or otherwise sealed during the test. If the air handler is not installed at the time
of the test, total leakage shall be less than or equal to 3 cfm (85 L/min) per 100 square feet
(9.29 m
2
) of conditioned floor area.
2. Postconstruction test: Leakage to outdoors shall be less than or equal to4 cfm (113.3 L/min)
per 100 square feet (9.29 m
2
) of conditioned floor area or total leakage shall be less than or
equal to 4 cfm (113.3 L/min) per 100 square feet (9.29 m
2
) of conditioned floor area when
tested at a pressure differential of 0.1 inches w.g. (25 Pa) across the entire system, including
the manufacturer's air handler enclosure. All register boots shall be taped or otherwise sealed
during the test.
☐ R403.3.5 Building Cavities
Building framing cavities shall not be used as ducts or plenums. Installation of ducts in exterior
walls, floors or ceilings shall not displace required envelope insulation.
☐ R403.3.6 Ducts Buried within Ceiling Insulation
Where supply and return air ducts are partially or completely buried in ceiling insulation, such
ducts shall comply with all of the following:
1. The supply and return ducts shall have an insulation R-value not less than R-8.
2. At all points along each duct, the sum of the ceiling insulation R-value against and above the
top of the duct, and against and below the bottom of the duct, shall be not less than R-19,
excluding the R-value of the duct insulation.
Exception: Sections of the supply duct that are less than 3 feet (914 mm) from the supply
outlet shall not be required to comply with these requirements.
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☐ R403.3.7 Ducts Located in Conditioned Space
For ducts to be considered as inside a conditioned space, such ducts shall comply with either of
the following:
1. All duct systems shall be located completely within the continuous air barrier and within the
building thermal envelope.
2. All heating, cooling and ventilation system components shall be installed inside the
conditioned space including, but not limited to, forced air ducts, hydronic piping, hydronic
floor heating loops, convectors and radiators. Combustion equipment shall be direct vent or
sealed combustion.
3. For forced air ducts, a maximum of 10 linear feet of return ducts and 5 linear feet of supply
ducts is permitted to be located outside the conditioned space, provided they are insulated to
a minimum of R-8.
3.1. Metallic ducts located outside the conditioned space must have both transverse and
longitudinal joints sealed with mastic.
3.2. If flex ducts are used, they cannot contain splices. Flex duct connections must be made
with nylon straps and installed using a plastic strapping tensioning tool.
☐ R403.5.3 Hot Water Pipe Insulation
Insulation for hot water pipe shall have a minimum thermal resistance of R-3. An SBCC
interpretation states that insulation can be discontinuous where passing through framing
members or where necessary to pass another pipe in a stud space.
☐ R403.5.5 Electric Water Heater Insulation
All electric water heaters in unheated spaces or on concrete floors shall be placed on an
incompressible, insulated surface with a minimum thermal resistance of R-10.
☐ R403.6.1 Mechanical Ventilation
A mechanical ventilation system is required to be installed in accordance with the
Washington State amendments to the 2019 International Residential Code. ASHRAE Standard 62.2
is an acceptable alternative for a single-family and townhouses, but is not an acceptable
equivalent for IMC low-rise multifamily.
☐ R404.1 Lighting Equipment
A minimum of 90% of permanently installed lamps in lighting fixtures shall be high-efficacy lamps.
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Section R406 Additional Energy Efficiency Requirements
These tools are available to assist in determining energy and fuel neutrality credits (right-click the form
name and save it to your computer so you can use the form's automated functions):
Single-Family Prescriptive Worksheet
Multifamily Prescriptive Worksheet
Code Compliance Calculator
☐ R406.1 Scope
This section establishes additional energy efficiency requirements for all new construction covered
by this code, including additions subject to Section R502 and change of occupancy or use subject
to Section R505 unless specifically exempted in Section R406. Credit from both Sections R406.2
and R406.3 are required.
☐ R406.2 Carbon Emission Equalization
This section establishes a base equalization between fuels used to define the equivalent carbon
emissions of the options specified. The permit shall define the base fuel selection to be used and
the points specified in Table R406.2 shall be used to modify the requirements in Section R406.3.
The sum of credits from Tables R406.2 and R406.3 shall meet the requirements of Section R406.3.
☐ R406.3 Additional Energy Efficiency Requirements
Each dwelling unit in a residential building shall comply with sufficient options from Table R406.2
so as to achieve the following minimum number of credits:
1. Small Dwelling Unit: 3.0 credits
Dwelling units less than 1,500 sf in conditioned floor area with less than 300 sf of fenestration
area. Additions to existing building greater than 500 sf of heated floor area but less than 1,500 sf.
2. Medium Dwelling Unit: 6.0 credits
All dwelling units that are not included in #1, #3 or #4.
3. Large Dwelling Unit: 7.0 credits
Dwelling units exceeding 5,000 sf of conditioned floor area.
4. Dwelling units serving R-2 occupancies: 4.5 credits
5. Additions less than 500 square feet: 1.5 credits
The drawings included with the building permit application shall identify which options have been
selected and the point value of each option, regardless of whether separate mechanical, plumbing,
electrical, or other permits are utilized for the project.
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Examples of how to obtain 6.0 credits for single-family residences:
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Examples of how to obtain 6.0 credits for multifamily residences:
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