9.36.2. Building Envelope
Module 2
BCBC 9.36.
2014
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Richard Kadulski Architect
9.36.2. Building Envelope
• Focus is on total building performance, not
just thermal insulation
• Heat transfer and air leakage between
conditioned space and unconditioned space
• Reference to many requirements already in
Sections 9.7. and 9.25.
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9.36.2. Building Envelope
Scope and Application
• The walls in skylight shafts are treated like
exterior walls. 9.36.2.1.(3)
• Walls less than 60˚ from horizontal are
considered as roof assemblies
• Windows must conform to section 9.7
• Properties of insulation, location and
installation of air barriers, and vapour
barriers must conform to section 9.25.
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Scope and Application
• Any assembly that separates conditioned
space from an adjoining storage garage,
even if the garage is intended to be heated,
must be insulated to the requirements for
exterior assemblies. 9.36.2.1. (2)
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9.36.2.2. Determination of Thermal
Characteristics
• The thermal resistance of opaque assemblies uses
effective thermal resistance – this is a change from
nominal R-values that has been relied on up to now
• This takes into account all material layers in an
assembly, and the thermal bridging of high
conductivity materials – such as framing.
• Look-up tables are provided for most common
assemblies, and information on how to calculate
others (9.36.2.4.)
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Richard Kadulski Architect
9.36.2.2. Determination of Thermal
Characteristics
• Where a component of the building
envelope is enclosed by unconditioned
space, the effective R-value of the
component can be reduced by 0.16 RSI
• 9.36.2.4.(4)
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9.36.2.2. Determination of Thermal
Characteristics
• Thermal characteristics of materials are determined
in accordance with listed product standards
• In absence of product standards, assemblies can be
tested to ASTM-C1363 as an alternative using an
indoor temperature of 21 ± 1 ˚ C and an outdoor air
temperature of - 3 5 ± 1 ˚ C
• Log wall RSI-values must be determined by
calculation in accordance with Section 305 of ICC
400, “Design and Construction of Log Structures.”
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Richard Kadulski Architect
9.36.2.2. Determination of Thermal
Characteristics
• Product standards for many insulation materials are
listed in the code
• New products not listed are acceptable, but must be
tested in accordance with ASTM-C177 or ASTM- C518
• Calculations and tests at an average temperature of
24±2˚C and a temperature differential of 22±2˚C
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Richard Kadulski Architect
9.36.2.4. Calculation of Effective Thermal
Resistance of Assemblies
• Heat transfer depends on the heat flow through
a given area with a temperature difference
across the element
• The NECB requires all building envelope
assemblies and components to comply with the
maximum U-values (overall thermal
transmittance).
• Requirements in 9.36.2. are stated in RSI
values which are the reciprocal of U-values.
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Richard Kadulski Architect
9.36.2.4. Calculation of Effective Thermal
Resistance of Assemblies
• The same nominal insulation can produce
different effective thermal resistance values
depending framing type and material
configurations
• To calculate effective thermal resistance,
contributions from all portions of an
assembly, including heat flow through studs
and insulation are taken into account.
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Richard Kadulski Architect
Difference Between Nominal and Effective
Thermal Resistance of Assemblies
Assembly
Nominal
R-value
Effective
R-value
Conventional 2x6 wood stud @ 16” o/c; R-20
batt insul; gyp bd interior; ply sheathing;
wood siding
20
(RSI 3.52)
17.2
(RSI 3.02)
Advanced 2x6 framing, studs @ 24” o/c, R20 batt insul; gyp bd interior; ply sheathing;
wood siding
20
(RSI 3.52)
18.2
(RSI 3.20)
2x4 wood studs @ 16” o/c; R12 batt insul;
plus R-10 XPS, gyp bd interior; ply sheathing;
wood siding
22
(3.87)
22.4
(RSI 3.94)
2x6 steel studs @ 16” o/c, ; R-20 batt insul.;
gyp bd interior; ply sheathing; wood siding
20
(RSI 3.52)
11.35
(RSI 1.99)
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Richard Kadulski Architect
9.36.2.6. Thermal Characteristics of Above
Ground Opaque Assemblies
• Prescriptive path: Requirements vary
whether or not an HRV is installed
• Table with minimum effective RSI-values
• Look-up tables for most common assemblies, and
information on how to calculate others provided in the
Appendix
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Richard Kadulski Architect
9.36.2.6. Thermal Characteristics of Above
Ground Opaque Assemblies
Table 9.36.2.6.A
Effective RSI-values – without HRV
Assembly
Ceilings
Cathedral
ceilings
Walls (2x6 @
16”)
Floors over
unheated
space
Climate Zone (Heating Degree Days ˚C)
Zone 4
< 3,000
Zone 5
3,001 to
3,999
Zone 6
4,000 to
4,999
Zone 7A
5,000 to
5,999
Zone 7B
6,000 to
6,999
6.91
8.67
(39.23)
(49.2)
8.67
(49.2)
10.43
(59.2)
10.43
(59.2)
4.67
4.67
4.67
(26.5)
(26.5)
(26.5)
5.02
(28.5)
5.02
(28.5)
2.78
3.08
3.08
3.08
3.85
(15.78)
(17.48)
(17.48)
(17.48)
(21.86)
4.67
4.67
4.67
(26.5)
(26.5)
(26.5)
5.02
(28.5)
5.02
(28.5)
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Richard Kadulski Architect
9.36.2.6. Thermal Characteristics of Above
Ground Opaque Assemblies
Table 9.36.2.6.B
Effective RSI-values – with HRV
Assembly
Ceilings
Cathedral
ceilings
Walls (2x6
@ 16”)
Floors over
unheated
space
Climate Zone (Heating Degree Days ˚C)
Zone 4
< 3,000
Zone 5
3,001 to
3,999
Zone 6
4,000 to
4,999
Zone 7A
5,000 to
5,999
Zone 7B
6,000 to
6,999
6.91
(39.23)
6.91
(39.23)
8.67
(49.2)
8.67
(49.2)
10.43
(59.2)
4.67
4.67
4.67
(26.5)
(26.5)
(26.5)
5.02
(28.5)
5.02
(28.5)
2.78
2.97
(15.78)
(16.86)
2.97
(16.86)
2.97
(16.86)
3.08
(17.48)
4.67
4.67
4.67
(26.5)
(26.5)
(26.5)
5.02
(28.5)
5.02
(28.5)
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Richard Kadulski Architect
9.36.2.6. Thermal Characteristics of Above
Ground Opaque Assemblies
• Effective R-value can be reduced at the heel
of sloped roofs for no more than 1200 mm
in from the exterior to allow for framing; and
attic venting
• The minimum nominal R-value directly over
the outside wall must be no less than RSI
3.52 (R-20)
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Richard Kadulski Architect
9.36.2.4. Calculation of Effective Thermal
Resistance of Assemblies
• Major structural penetrations through
assemblies are permitted – but total area
must not exceed 2%
• Allowable penetrations include balcony slabs,
beams, columns, and minor structural or
ornamental elements.
• Pipes, ducts, through-wall equipment vents are
considered minor penetrations and are not
considered.
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Parallel-Path Flow Method
Differing rates of heat loss thru various components
of Building Assembly
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Richard Kadulski Architect
Parallel-Path Flow Method
Need to determine cross sectional areas of the
various components of Building Assembly
Af
A
c
Af
Af
A
c
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Richard Kadulski Architect
Calculating Assembly RSI values
• Continuous layers of insulation
• Isothermal planes method – add RSI values of each layer
• Framed assemblies
• Isothermal planes method – add RSI values of each
Continuous layer PLUS
• Parallel-path flow method – need to determine Effective
Thermal Resistance (ETR) of Non-continuous layers
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Effect of Thermal Bridging
• Where there is thermal bridging:
• Effective R < Nominal
• Where there is NO thermal bridging:
• Effective R = Nominal
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Richard Kadulski Architect
9.36.2.4. Calculation of Effective Thermal
Resistance of Assemblies
RSIeffective vs. RSInominal
Include in
calculation
RSIeff ≠ RSInom
Exclude from Calculations
Repetitive
structural
members
- Studs
- Joists, lintels
- Sills, plates
Minor penetrations
- pipes, ducts
- Packaged air conditioners
- Shelf angles, anchors, fasteners
Credit for adjoining
unconditioned
spaces
Major structural penetrations
- Balcony slabs, beams, columns, ornamentation,
Provided: insulation is tight to penetrating element
- Total area of all major structural penetration is
limited to max 2% of wall area
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Richard Kadulski Architect
Insulating Effect of the Surface Air Films
RSI outside air film = 0.03
RSI inside air film = 0.11
Heat flow Up
RSI outside air film =
0.03
RSI inside air film =
0.12
Heat flow Horizontal
RSI inside air film =
0.12
Heat flow Horizontal
RSI outside air film =
0.03
RSI inside air film = 0.16
Heat flow Down
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Richard Kadulski Architect
Calculating Effective R-value:
Walls above Grade
Structure
0.12
insulation
0.12
1/2” gypsum board
0.08
0.08
Polyethylene barrier
0.00
0.00
2”x6” stud @ 16”o/c
1.19
3.52
7/16 OSB sheathing
0.11
0.11
Hollow backed vinyl siding 0.11
0.11
Air film (exterior)
0.03
Air film (interior)
0.03
Effective Thermal Resistance
2.89 (R-16.37)
New Code Requirement zone 4 (less than 3,000 DDC):
Eff. R 2.78 (R 15.78)
R 20 batt Insulation
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Richard Kadulski Architect
Parallel-Path Flow Method
RSIparallel =
100
% area of framing (Af) +%area of cavity (Ac)
RSIf
RSIc
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Richard Kadulski Architect
Calculating Effective R-value:
Walls above Grade
Structure
Air film (interior)
0.12
1/2” gypsum board
0.08
Polyethylene barrier
0.00
2”x6” stud @ 16” o/c
1.19
7/16 OSB sheathing
0.11
Hollow backed vinyl siding 0.11
Air film (exterior)
0.03
insulation
0.12
0.08
0.00
3.52
0.11
0.11
0.03
Effective Thermal Resistance
2.89 (R-16.37)
Code Requirement zone 4 (less than 3,000 DDC):
Eff. R 2.78 (R 15.78)
Code Requirement zone 5 (3,000 to 4,000 DDC):
Eff. R 2.97 (R 16.86) – with HRV
Eff. R 3.08 (R 17.48) – without HRV
R 20 batt Insulation
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Richard Kadulski Architect
Walls above Grade
Code Requirement zone 5 & 6 (3,000 to 4,999 DDC):
Eff. R 2.97 (R 16.86) – with HRV
Eff. R 3.08 (R 17.48) – without HRV
RSI effective
Reffective
2x6 @ 16” R-22 batt
insulation
3.11
17.63
2x4 @ 16” R14 batt insul
+ R-5 rigid insulation
3.19
18.09
2x4 @ 16” R14 batt insul
+ R-7.5 rigid insulation
3.66
20.78
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✔
✔
✔
Richard Kadulski Architect
Calculating Effective R-value:
Ceilings with Attic Space
R 40 Blown Cellulose
Raised Heel
Air film (interior)
0.11
1/2” gypsum board
Polyethylene barrier
2”x4” bottom chord cavity
Continuous layer of cellulose
Air film (exterior)
0.08
0.00
1.96
4.82
0.03
3 ½” cellulose
3 ½” wood
Effective Thermal Resistance 7.00
Code Requirement zone 4 (less than 3,000 HDD):
Eff. R 6.91 (R 39.23)
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Richard Kadulski Architect
Calculating Effective R-value:
Ceilings with Attic Space
Raised Heel
Air film (interior)
1/2” gypsum board
Polyethylene barrier
2”x4” bottom chord cavity
Continuous layer of cellulose
Air film (exterior)
0.11
0.08
0.00
1.96
4.82
0.03
New Code Requirement zone 5
(3,000-3,999 HDD):
Eff. RSI 6.91 (R-39.23) with HRV
Effective Thermal Resistance 7.00 Eff. RSI 8.67 (R-49.2) without HRV
R 40 Blown Cellulose
(requires R-50 cellulose)
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Richard Kadulski Architect
Calculating Effective R-value:
Ceilings with Attic Space
Raised Heel
Air film (interior)
1/2” gypsum board
Polyethylene barrier
2”x4” bottom chord cavity
Continuous layer of cellulose
Air film (exterior)
0.11
0.08
0.00
1.96
6.59
0.03
Effective Thermal Resistance 8.77
New Code Requirement zone 6
(4,000-4,999 HDD):
Eff. RSI 8.67 (R-49.2) with HRV
Eff. RSI 8.67 (R-49.2) without HRV
(requires R-50 cellulose)
R 50 Blown Cellulose
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Richard Kadulski Architect
9.36.2.4. Calculation of Effective Thermal
Resistance of Assemblies
• Appendix provides examples of calculations
and data tables:
• Framing & cavity percentages for typical wood
frame assemblies [Table A-9.36.2.4.(1)A]
• Factors for steel framing to address higher
thermal bridging through steel studs [Table A9.36.2.4.(1)B]
• Thermal resistance values for common materials
[Table A-9.36.2.4.(1)D]
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Richard Kadulski Architect
9.36.2.4. Calculation of Effective Thermal
Resistance of Assemblies
Table A- 9.36.2.6.(1)A. presents the minimum nominal thermal resistance to
be made up in a given wall assembly for it to achieve the applicable RSI value
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Richard Kadulski Architect
9.36.2.4. Calculation of Effective Thermal
Resistance of Assemblies
• Example using Table A-9.36.2.6.(1)A.
• Required effective RSI-value is 2.78
• 38 x 140 mm studs @ 406 mm o.c. with R-19 batt insulation.
• RSI value of structural assembly is 2.36.
• Minimum additional required is 0.42
•
Other components in wall assembly:
•
•
•
•
•
•
•
Interior air film:
12.7 mm gyp board
12.7 mm ply sheathing
Rain screen cavity
stucco
Exterior air film
Total RSI of other components
0.12
0.08
0.10
0.15
0.013
0.03
0.49
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Richard Kadulski Architect
• Insulation must be continuous across the
entire envelope – but this does not mean
continuous insulation across face.
• This applies to building components such
as partitions, chimneys, fireplaces, and
columns and beams that are embedded
along exterior walls, but not to stud
framing and ends of joists.
HPO Illustrated Guide: Energy Efficiency
Requirements for Houses in British Columbia
9.36.2.5. Continuity of Insulation
• Studs and joists in frame construction
are dealt with by the calculation method
for determining effective R-values.
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Richard Kadulski Architect
9.36.2.5. Continuity of Insulation
• Article 9.36.2.5. (2) to (8) introduces
relaxations for various details
• Article 9.36.2.5. (9) allows complete
exemption to sentence (1) for three specific
details:
• At junction between foundation wall and floor slab
• The perimeter of a floating slab-on-grade
• Foundation wall portion that supports masonry
veneer
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Richard Kadulski Architect
9.36.2.5. Continuity of Insulation
• Allowable exemptions:
• Required fire safety clearances
• Major structural components that penetrate the
envelope (e.g. structural beams, balcony & canopy
slabs) provided
• total area is not more than 2% of gross wall area
• Insulation is installed tight against the penetration
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Richard Kadulski Architect
9.36.2.5. Continuity of Insulation
• 9.36.2.5.(2) minimizing thermal bridging
• Where a wall or structural element
penetrates exterior envelope, it must be
insulated.
• Note that continuity of air barrier must also
be maintained at these details.
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Richard Kadulski Architect
9.36.2.5. Continuity of Insulation
• 9.36.2.5.(2)(a)
• Minimizing thermal bridging
where a wall or structural
element penetrates exterior
envelope, it must be
insulated on interior (or
exterior if element projects
outward).
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Richard Kadulski Architect
9.36.2.5. Continuity of Insulation
• 9.36.2.5.(2)(b)
• Minimizing thermal
bridging of a wall or
structural element at
exterior envelope, where
insulation is within plane of
wall.
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Richard Kadulski Architect
9.36.2.5. Continuity of Insulation
• 9.36.2.5.(2)(c)
• Minimizing thermal
bridging of a wall or
structural element at
exterior envelope, where
insulation is within plane of
wall.
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Richard Kadulski Architect
9.36.2.5. Continuity of Insulation
9.36.2.5.3. A masonry fireplace or flue on an
exterior wall must be insulated to an effective Rvalue not less than 55% of that required for the
exterior wall
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Richard Kadulski Architect
9.36.2.5. Continuity of Insulation
• Insulation placement can be
inside or outside; if there is a
cross-over, the over lap must
be 4 times the thickness of
the wall
• i.e. for 8” wall, the minimum
overlap will be 32”
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Richard Kadulski Architect
9.36.2.5. Continuity of Insulation
• 9.36.2.5. (6) mechanical,
plumbing or electrical system
components (such as pipes,
ducts, conduits, cabinets, chases,
panels or recessed heaters) within
or parallel to wall assembly must
be insulated to the same effective
insulation level as required for the
wall
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Richard Kadulski Architect
9.36.2.5. Continuity of Insulation
• 9.36.2.5. (7) ducts, plumbing pipes,
electrical or communication conduits placed
within the insulated portion of a floor or
ceiling assembly must have an effective
insulation level not less than RSI 2.78 (R15.78)
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Richard Kadulski Architect
9.36.2.5. Continuity of Insulation
• Ducts outside the heated
envelope must be insulated
to the same effective
insulation level as required
for walls above grade
✖
✖
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Richard Kadulski Architect
9.36.2.5. Continuity of Insulation
• EXCEPTION: does not apply
where cladding is masonry and
foundation wall is insulated on
the exterior [9.36.2.5.(9)c]
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Richard Kadulski Architect
9.36.2.5. Continuity of Insulation
• 9.36.2.5.(8) Joints and
junctions between walls
and other building envelope
components shall be
insulated in a manner that
provides an effective
thermal resistance that is
no less than the lower of
the minimum values
required for the respective
adjoining components.
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Richard Kadulski Architect
9.36.2.7. Fenestration, Doors &
Skylights
• Fenestration and doors must have a U-value no
greater than that in table 9.36.2.7.A, and skylights
as in table 9.36.2.7B
Climate Zone (Heating Degree Days ˚C)
Zone 4
<
3,000
Zone 5
Zone 6 Zone 7A Zone 7B
3,001 to 4,000 to 5,000 to 6,000 to
3,999
4,999
5,999
6,999
Zone 8
>7,000
Windows
& doors
1.80
1.80
1.60
1.60
1.40
1.40
skylights
2.90
2.90
2.70
2.70
2.40
2.40
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Richard Kadulski Architect
9.36.2.7. Fenestration, Doors &
Skylights
• Site assembled, or site glazed factory-made
products, curtain walls, and site built windows must
be tested or calculated
• Garage vehicular doors must have nominal RSI 1.1.
• Access hatches to unconditioned space: the U-value
not to exceed 2.6
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Richard Kadulski Architect
9.36.2.7. Fenestration, Doors & Skylights
Exceptions
• An exemption to requirements in table 9.36.2.7.A was
made for site-built windows and glazed doors, but they
must comply with properties laid out in Table 9.36.2.7.C
• Max U-value for glass block in an exterior wall must be
not more than 2.9, and total area of glass block must
not exceed 1.85 m (19.9 sq.ft.)
• One exterior door is permitted to have U-value of 2.6
• (this allows for a feature entry door)
• Storm windows are exempt form these requirements
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Richard Kadulski Architect
9.36.2.8. Assemblies In Contact With
Ground
• Full height basement wall insulation
required
• Top of foundation wall - up to 600 mm above
grade is insulated as a foundation wall.
• Appendix table lists typical assemblies
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Richard Kadulski Architect
9.36.2.8. Assemblies In Contact With
Ground
• Effective R-values requirements vary whether HRV is
installed or not
•
Table 9.36.2.8.A. or 9.36.2.8.B
• Example – [required RSI effective is 1.99]:
• Concrete foundation wall, 38x89 (2x4) furring, RSI-2.11 (R12) insulation.
• From table A-9.36.2.8 (1)A the effective R-value of assembly
is 1.79. Minimum additional required is 0.20
• This can be made up by installing 12.7 mm gyp board
(0.0775) plus interior air film (0.12)
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Richard Kadulski Architect
9.36.2.8. Assemblies In Contact With
Ground
• Heated floor slabs must be insulated under
entire area, including the edges
• Floating slabs must be insulated under
entire floor slab, but not under integral
perimeter footing, but skirt insulation is
required to same value as under the slab
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Richard Kadulski Architect
9.36.2.8. Assemblies In Contact With
Ground
• Floor slab insulation depends whether or not
it is a heated slab, and above or below frost
line
• If entire floor fits into two categories, the
more restrictive applies.
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Richard Kadulski Architect
9.36.2.8. Assemblies In Contact
With Ground
• Unheated floor slabs must
be insulated min. 1.2m
horizontally or vertically
down from its perimeter,
with a thermal break along
edge of slab a min. 50% of
required insulation
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Richard Kadulski Architect
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