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BUILDING (SCOTLAND) ACT 2003 CONSULTATION ON BUILDING REGULATIONS
AND GUIDANCE DOCUMENT: NON DOMESTIC
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Annex 6.J Heat Loss Method example and worksheet
6.J.4
6.J.0 Introduction
6.J.1 Proposed building
6.J.2 Notional building
6.J.3 Comparison
6.J.4 Worksheet 6.J.4
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annex 6.J
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Heat Loss Method example and worksheet 6.J.4
[Appendix
H J8.5dts]
6.J.0 Introduction
A detached, four storey office building 45 metres x 13 metres
in plan and height of 15 metres is to be constructed with glazing
occupying 42.5% of the external wall area, using plastic framed windows
with a measured U-value of 2.2 W/m2K. The personnel doors
are of the same construction and U-value. No rooflight glazing is proposed.
The exposed walls and the roof are to have U-values of 0.30 W/m2K
and 0.20 W/m2K respectively, with the ground floor being
insulated with 65 mm expanded polystyrene with thermal resistance
of all-over floor insulation 1.76 m2KW, giving a U-value
of 0.20 W/m2K (Annex 6.C).
The loading bay doors do not remain in the open position when the building
is in use and they have a U-value of 0.70 W/m2K
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6.J.1 Proposed building
First calculate the areas of each building element:
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area of roof (45 x 13)
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= 585 m2
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area of elevations (45 + 45 + 13 + 13) x 15
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= 1740 m2
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area of windows (42.5% of 1740 m2)
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= 739.5 m2
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area of personnel doors
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= 14 m2
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area of vehicle loading bay doors
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= 27 m2
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area of exposed wall (1740 — 739.5 - 14 - 27)
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= 959.5 m2
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area of floor (45 x 13)
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= 585 m2
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Then calculate the rate of heat loss from the proposed
building as follows:
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Building element
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Area (m2)
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U-value (W/m2K)
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Rate of heat loss (W/K)
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Roof
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585
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0.20
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117.0
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Exposed walls
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959.5
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0.30
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287.85
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Windows
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739.5
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2.2
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1626.9
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Personnel doors
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14
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2.2
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30.8
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Vehicle loading bay doors
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27
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0.70
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18.9
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Ground floor
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585
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0.20
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117.0
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Total rate of heat loss
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2198.45
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6.J.2 Notional building
The basic area allowance of 40% of exposed wall area
for windows and 20% of roof area for roof windows should be assumed for
the notional building.
First calculate the areas of each building element:
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area of rooflights (20% of 585 m2)
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= 117 m2
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area of roof (45 x 13) -117
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= 468 m2
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area of elevations (45 + 45 + 13 + 13) x 15
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= 1740 m2
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area of windows and personnel doors (40% of 1740 m2)
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= 696 m2
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area of vehicle loading bay doors
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= 27 m2
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area of exposed wall (1740 - 696 - 27)
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= 1017 m2
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area of floor (45 x 13)
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= 585 m2
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Then calculate the rate of heat loss from the notional
building as follows:
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Building element
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Area (m2)
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U-value (w/m2k)
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Rate of heat loss (w/k)
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Rooflights
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117
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2.0
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234.0
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Roof
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468
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0.25
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117.0
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Exposed walls
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1017
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0.30
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305.1
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Windows and personnel doors
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696
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2.0
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1392.0
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Vehicle loading bay doors
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27
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0.7
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18.9
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Ground floor
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585
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0.25
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146.25
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Total rate of heat loss
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2213.25
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6.J.3 The comparison
The rate of heat loss from the proposed building is less
than that from the notional building and therefore the guidance in 6.2.2
has been followed.
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6.J.4 Worksheet [J8.5]
The following worksheet may be photocopied and used to assist with the Heat
Loss Method calculation.
Calculated total rate of heat loss through the insulation envelope
Proposed/Notional building
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Element
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Gross Area in m2
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Openings in m2
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Net Area in m2
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U-value (W/m_K)
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Area x U-value
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Pitched roofs — With insulation between rafters
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-
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=
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x
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=
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Pitched roofs — With insulation between ceiling ties or collars
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-
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=
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x
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=
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Flat roofs or roofs with integral insulation
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-
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=
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x
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=
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Exposed wall, external wall or wall referred to in
6.0.5
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-
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=
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x
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=
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Exposed floor or floor referred to in 6.0.5
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-
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=
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x
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=
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Total A |
= |
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| Windows, personnel doors and rooflights,
glazing in metal frames. (Including glazing and personnel doors located
in walls referred to in 6.0.5) |
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x |
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= |
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| Windows, personnel doors and rooflights,
glazing in wood or plastic frames. (Including glazing and personnel doors
located in walls referred to in 6.0.5) |
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x |
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= |
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| Vehicle and similar large access
doors |
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x |
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= |
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Vehicle access/similar large doors which for operational
reasons, have to be left open when the building is in use and
also shop entrances and shop display windows at an access level
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x
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=
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Total B
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=
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| Total rate of heat
loss (Total A + Total B) |
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= |
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