3.1.1.5. Thermal Characteristics of Building Assemblies

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Nov 25, 2013 (3 years and 6 months ago)

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NECB


Division B, Part 3



excerpt of calculation procedures

Division B, Part 3
-
1


3.1.1.5
.
Thermal Characteristics of Building Assemblies

(See
Appendix A
.)

1)

Except as provided in Sentence (2), t
he thermal characteristics of materials shall be
determined in accordance with the relevant product standards listed in the National Building
Code or, in the absence of such a standard or where such a standard does not address
determination of thermal char
acteristics, in accordance with ASTM Standard C

518, “Standard
Test Method for Steady
-
State Heat Flux Measurements and Thermal Transmission Properties by
Means of the Heat Flow Meter Apparatus,” or ASTM Standard C 177, “Standard Test Method for
Steady
-
Stat
e Heat Flux Measurements and Thermal Transmission Properties by Means of the
Guarded
-
Hot
-
Plate Apparatus.”

2)

Calculations and tests performed according to Sentence (1) shall be carried out at an
average temperature of
(24


2
)

C
and under a temperature difference of
(22


2
)

C
.

3)

The
overall thermal transmittance

of
fenestration

and
doors
shall be determined for the
reference sizes listed in accordance with
CSA Standard A440.2, “Fenestration Energy
Performance” or NFRC Standard 100, “Procedure for Determining Fenestration Product U
-
factors”
.

4)

The
overall thermal

transmittance

of
fenestration

and doors

that are not within the

scope
of CSA Standard A440.2, “Fenestration Energy Performance”, or NFRC Standard 100, “Procedure
for determining Fenestration Product U
-
factors”,

sha
ll be determined from

a)

calculations carried out using
procedure
s

described in the ASHRAE Handbook


Fundamentals, or

b)

laboratory tests performed in accordance with ASTM C
1363
, “Standard Test Method
for
Thermal Performance of Buildi
ng
Materials and Envelope
Assemblies by Means of a
Hot Box

Apparatus
.”

5
)

Tests conducted according to Clause (4)(b) shall be carried out with an indoor air
temperature of
(
21


1)

C
and an outdoor air temperature of
(
-
18


1)

C
measured at the
mid
-
height of the window.

6
)

The thermal characteristics of other building assemblies shall be determined from

a)

calculations
,
or

b)

laboratory tests performed in accordance with ASTM Standard C
1363,
“Standard Test
Method for
Thermal Performance of Building
Materials and Envelope
Assemblies by
Means of a
Hot Box
Apparatus
”. (See
Appendix A
.)

7
)

Tests conducted
in accordance with
Clause (
6
)(b) shall be carried out at an average
temperature of
(24


1)

C
and under a temperature difference of
(22


1)

C
.



NECB


Division B, Part 3



excerpt of calculation procedures

Division B, Part 3
-
2


3.1.1.6.

Areas of
Fenestration and
Doors

1)

In the calculation of area,

fenestration

and doors
shall be considered to include all related
frame and sash members
and their areas shall be measured to the rough opening in the wall (see
Appendix A
).

2)

The

area of fenestration made of
flat panes that are not all in the same plane or
curved
p
anes
shall be measured along the glass surface (see
Appendix A
).

3)

In the calculation of allowable areas of
fenestration

and doors, the gross wall area is the
sum of the areas of all above
-
ground wall assem
blies including
fenestration

and doors, but not
including parapets, projected fins, ornamentation and appendages.
(see
Appendix A
).

4)

In the calculation

of allowable areas of skylights, the gross roof area is the sum of the
areas of insulated roof area including skylights.

5)

For the purpose of
calculating allowable areas of
fenestration

and doors
, the compliance
of additions shall be based upon either

a)

the
additi
on
being considered by itself, or

b)

the
addition
being considered together with the existing
building

provided that the
combined addition and existing buildings
overall
thermal transmittance
meets the
prescriptive or trade off
requirements.

3.1.1.
7
. Calculation

Procedure
s

1)

In calculating the
overall thermal transmittance
of assemblies for purposes of comparison
with the
provis
ions

in Section
3.2.
,
the thermal bridging effect of closely
-
spaced, repetitive
structural members such as studs and joists, and of ancillary members such as lintels, sills and
plates, shall be accounted for as described in
S
ub
s
ection
1.1.4.

2)

In calculating the
overall thermal transmittance
of assemblies for purposes of comparison
with the
provisions

in Section
3.2
.
,
the thermal bridging effect of major structural members, such
as columns and spandrel beams, that a
re parallel to the plane of the
building envelope
and partly
penetrate that
building envelope
assembly need not be taken into account provided they do not
increase the
overall thermal transmittance
at the projected area of the member to more than twice
tha
t permitted in Section
3.
2
.

(see
Appendix A
).

3)

In calculating the
overall thermal transmittance
of assemblies for purposes of comparison
with the
provisions

in Section
3.
2
.,

pipes, ducts, equipment with through
-
the
-
wall venting,
packaged terminal air
-
conditioners or heat pumps, shelf angles, anchors and ties and associated
fasteners, and other minor structural members that must
partially or
completely penetrate the
building en
velope
to perform their intended function need not be taken into account
.


(see
Appendix A
)

4)

In calculating the
overall thermal transmittance
of assemblies for purposes of comparison
with the
provisions

in Section
3.
2
.
, major structural penetrations, such as
balcony slabs, beams,
girders, columns and
ornamentation or
appendages

that must completely penetrate the
building
envelope
to perform their intended function need not be taken into account, provided that


the sum of the cross
-
sectio
nal areas at such major structural penetrations is limited to a
maximum of 2% of the above
-
ground
building envelope
area.

(see
Appendix A
)

5)

Where a component of the
building envelope
is protected by an enclosed unconditioned
space, such as a sun porch, enclosed veranda or vestibule, the unconditioned enclosure may be
considered to
have
an
overall

thermal
transmittance

of
6.25 W/m
2

K

or the equivalent of one layer
of glass (see
Appendix A
).

NECB


Division B, Part 3



excerpt of calculation procedures

Division B, Part 3
-
3


6)

Roof assemblies shall be considered to include all related structural framing

for the
purposes of determining the
overall thermal transmittance.

7
)

Wall
assemblies inclined less than 60


from horizontal are considered to be roof
assemblies, and roof assemblies inclined 60


or more from horizontal are considered to be wall
assemblies

for the purposes
of determining the
overall thermal transmittance
.

8)
Wall assemblies shall be considered to include all related structural framing and perimeter
areas of intersecting interior

walls for purposes of determining the
overall thermal transmittance
,
but shall not include the perimeter areas where floor or roof slabs interrupt the wall construction
(see
Appendix A
).

9)

Floor assemblies shall be considered to include all related structural framing for the
purposes of determining the
overall thermal transmittance
.