TIÊU CHUẨN KỸ THUẬT BSRIA

TECHNICAL NOTE TN 15/2001

Rules of Thumb (UK 3rd edition)
Guidelines for assessing building services
Edited by Martin Boushear

Supported by


Contents
Space and weight allowances
TABLE
TABLE
TABLE
TABLE
TABLE
TABLE
TABLE
TABLE

1: Floor space allowance for services
2: Space allowances for plant rooms
3: Miscellaneous services
4: Space allowances for on-floor services
5: Space allowances for service ducts and shafts
6: Space allowances for catering facilities
7: Floor space allowance per occupant
8: Plant weight allowances

Equipment and solar loads
TABLE

TABLE
TABLE
TABLE

14

1: Cooling loads
2: Cooling plant
3: Solar gains
4: Heat loads

Comfort factors
TABLE
TABLE
TABLE
TABLE
TABLE
TABLE

6

16

1: External conditions
2: Ventilation and air conditioning
3: Information technology
4: Room air movement
5: Noise levels
6: Comfort data sheet

System features

20

TABLE 1: Sizing and operating characteristics of plant
TABLE 2: Water treatment

Energy and carbon issues

24

TABLE 1: Energy conversions
TABLE 2: Energy benchmarks (offices)
TABLE 3: Lighting benchmarks

Electrical systems

26

TABLE 1: Electrical supplies and loads

Cost data

27

TABLE 1: Capital and maintenance costs
TABLE 2: Services costs as a percentage of total costs
TABLE 3: System capital and maintenance costs

References

Rules of Thumb BSRIA 2001

32
3


Acknowledgements
The story behind the guide
This publication is the third update of the Technical Note TN 17/95: Rules
of Thumb last issued in 1995. The rules have been collected from various
contemporary sources in the building services industry and can reasonably
be held to reflect current design practices. The sources include major
design offices, individual engineers and public domain information
published by BSRIA and others.
The industry review team for this project comprised: John Louis Auguste
(Bovis Lend-Lease), Dennis Bastow (NHS Estates), Brian Charlesworth
(Troup Bywaters & Anders), Laurie Clark (Cundall Johnston & Partners),
Michelle Field (Buro Happold), Manus Freeman (SVM Partnership),
Nigel Hawkes (Fulcrum Consulting), Glen Irwin (Roberts & Partners),
Bob Keenan and Dr Ian Selby (Sheppard Robson, on behalf of the
British Council for Offices), Nick Mead (ACDP), Richard Tudor (WSP
Group), and Gay Lawrence Race and John Sands (BSRIA). We would
also like to thank AMEC Capital Projects, BAA plc, N G Bailey, Bryan
Franklin, Building Design Partnership, Foggo Associates, Foremans Ltd,
Hoare Lea & Partners, Max Fordham & Partners, Stanhope, and Whitby
Bird & Partners for their help.
Finally, BSRIA would like to make special acknowedgement to the
consulting engineers Foremans Ltd, whose financial support has enabled
BSRIA to extend the print run. BSRIA also acknowledges the editing
help of Nigel Pavey, author of the second edition of Rules of Thumb and

now chief engineer with Foremans Ltd.

All rights reserved. No part of this publication may be reproduced, stored in a retrieval
system, or transmitted in any form or by any means electronic or mechanical including
photocopying, recording or otherwise without prior written permission of the publisher.
BSRIA TN 15/2001 August 2001

4

Rules of Thumb BSRIA 2001

ISBN 086022 587 9

Printed by The Chameleon Press Ltd


How to use this guide
What this guide will do
Rules of Thumb has been written to help engineers in the initial stages of
designing a building and its services. By gathering many of the most
common rules of thumb into one document, BSRIA has provided a
powerful source of inital design data that every engineer should find
indispensable.
Thumb rules (or heuristics as they are more properly known) are
extremely useful values for use at various stages of design, such as project
inception and outline briefing, feasibility planning, the assessment of
global loads and space requirements. They are also useful for getting a
initial grasp of costs. Rules of thumb come in handy for carrying out
"what if" calculations, and for use by senior engineers when checking the
work of junior engineers.

The data have been derived from a wide variety of authoratative sources,
all of which are referenced. All the figures quoted have also been
assessed for usefulness and relevance by a panel of experienced,
practising services engineers.

What this guide will not do
While every effort has been made to establish current practice, the
guide's authors are keen to point out that the rules of thumb are merely
aids to the design process. They must not be used in place of detailed
design data. The responsibility for the safe and appropriate use of this
data therefore rests with the engineer.
Rules of Thumb has been designed to be your own personal reference
document. Use it, add your own data to it, and guard it jealously. And
please let us know how it works and where it can be improved.

Roderic Bunn
Publisher
Rules of Thumb BSRIA 2001

5


6

Space and weight allowances

When to use: During the early stages of design prior to plant selection or system analysis
Where to use: Plant room sizes, riser cupboard locations and plant capacities
Watch out for: Poor information that fails to allow for installation, commissioning or maintenance

TABLE 1: Floor space allowance for services (as a percentage of floor area)

Rules of Thumb BSRIA 2001

Design area

Application

All services

Air conditioning (excluding
boilers & refrigeration)

Other information

Rule of thumb

Ref

Simple factory
Offices and commercial
Hi-tech building

4%
6 – 10%
15 – 30%

26
26
26

Fan coil system
VAV system

1⅐⅐ 5 – 2⅐⅐ 5%
3 – 4⅐⅐ 5%

26
26

0⅐⅐3 – 1⅐⅐5%

26

Electrical services (excluding
sub-stations and standby
generation sets)

0⅐⅐5 – 1⅐⅐ 5%

26

Lift motor rooms

0⅐⅐2 – 0⅐⅐ 5%

26

Central plant

1 – 2%

26

Toilet extract
Supply and extract system
All air low velocity system

0⅐⅐3 – 1%
3 – 5%
4 – 6%

26
26
26

Cooling towers and air-cooled
condensers

Refrigeration (excluding
cooling towers)

Ventilation

For references see page 32

Your notes and comments


TABLE 2: Space allowances for plant rooms (floor area)

Design area

Application

Air cooled condenser and
controls

Air handling units

Other information

Rule of thumb

Ref

space for
installation and
maintenance

25 + kW/200 m2

29

With extract
/recirculation

8 m2 per m3/s

29

Without extract
/recirculation

5 m2 per m3/s

29

Rules of Thumb BSRIA 2001

Boilers
(percentage floor area)

Boiler plant
& calorifiers

Oil tank room

0⅐⅐ 8 – 1⅐⅐ 8%
1 – 2%

26
26

Boilers
(floor area and height)

Boilers, pumps,
piping and space for
installation and
maintenance

Output: 100 kW
Output: 200 kW
Output: 1000 kW
Output: 4000 kW

15 m2 x 3 m
25 m2 x 3 m
80 m2 x 4 m
140 m2 x 5 m

29
29
29
29

Calorifiers
(floor area and height)

Calorifiers, pumps,
pipework, controls
and space for
installation and
maintenance

Vertical
Vertical
Vertical
Vertical

(1 m3)
(5 m3)
(10 m3)
(15 m3)

Horizontal
Horizontal
Horizontal
Horizontal

(1 m3)
(5 m3)
(10 m3)
(15 m3)

10
20
25
60

m2
m2
m2
m2

x
x
x
x

3
4
5
3

m
m
m
m

29
29
29
29

25
30
45
60

m2
m2
m2
m2

x
x
x
x

3
3
3
3

m
m
m
m

29
29
29
29

Your notes and comments

Table 2 continued Ł
7

For references see page 32


8

Space and weight allowances
TABLE 2: Space allowances for plant rooms (floor area)

Rules of Thumb BSRIA 2001

Design area

Application

Other information

Rule of thumb

Ref

Chillers (water cooled)
Floor area times height

With pumps,
pressurisation,
pipework and
control panels

Output: 1000 kW
Output: 2000 kW
Output: 3000 kW
Output: 4000 kW

50 m2 x 3 m
63 m2 x 3 m
83 m2 x 3⅐⅐ 5 m
108 m2 x 4 m

29
29

29
29

Chillers (air cooled)

Located outside.
Includes space for
installation and
maintenance

Output: 200 kW
Output: 400 kW
Output: 600 kW
Output: 800 kW
Output: 1000 kW
Output: 1200 kW

39 m2
53 m2
75 m2
84 m2
98 m2
116 m2

29
29
29
29
29
29

Cold water storage

Single cold water tank
Includes space for
installation and
maintenance but add
space for
pressurisation plant
or circulation pumps

FA: Floor area
V: gross storage m3
1 m high
2 m high
3 m high

FA: 10 + V/0⅐⅐75 m2
FA: 10 + V/1⅐⅐ 6 m2
FA: 10 + V/2⅐⅐ 4 m2

29
29
29

Minimum for
hot and cold
outlets

Offices

10-20 litres/person

4

Cold water storage

Hotels, children’s home,
residential nursery,
convalescent home
135 litres/bed space

Your notes and comments

4

Table 2 continued Ł
For references see page 32


Design area

Application

Other information

Rule of thumb

Ref

Cold water storage
(domestic) continued

Minimum for
hot and cold
outlets

Restaurant
Day school
Hostel

7 litres/meal
15-20 litres/pupil
90 litres/bed space

20
20
20

FA: Floor area
(kW: heat rejection)

FA: 50 + kW/66 m2

29

HV switchgear
HV + LV switchgear

47 m2

14 m2
27 m2

29
29
29

Standby sets and
accessories

FA: Floor area

FA:15 + kVA/30 m2

29

Single module system
(add space for
batteries)

FA: Floor area

FA: (2 + kW/200) x 2 m2

29

Other information

Rule of thumb

Ref

1200 – 1800 mm

18

Tank contents + 10%

19

Cooling towers

Sub-station

Rules of Thumb BSRIA 2001

Standby generation

Uninterruptible power supply

2000 kVA
transformers
Switchgear

Your notes and comments

TABLE 3: Miscellaneous services
Design area

Application

Control panels & distribution
boards

Front panel controls, Fixing height range
wall-mounted or floor (above finished floor
standing
or operating platform
level)

LTHW boiler plant
component criteria for
leakage containment

Oil storage tanks,
distillate & residual
fuel oils

9

For references see page 32

If tank fails, walls and
doors treated to
contain spillage

Your notes and comments


10

Space and weight allowances
TABLE 4: Space allowances for services (depth of clear space in ceiling/floor void)
Design area

Application

Air conditioning

Rules of Thumb BSRIA 2001

Rule of thumb

Ref

VAV
VRV
Recessed chilled beams
Surface chilled beams
Chilled ceilings
Fan coils
Ducted air system

350 – 750 mm
450 mm
350 – 450 mm
250 mm
250 mm
450 mm
450 mm

16
16
16
16
16
27
27

Drainage
Soil and waste

100 mm dia.
150 mm dia.

10 – 25 mm per m run
7 – 16 mm per m run

27
27

Lighting

Fluorescent
Downlighter

100 – 150 mm (‫ ם‬access) 16
150 – 300 mm
16

Power and communications

Multi-core cables and
lighting cables

100 – 200 mm

16

Power and data
(heavy line)

200 – 250 mm

16

Computer rooms

300 mm

16

For references see page 32

Other information

Your notes and comments


TABLE 5: Space allowances for service ducts and shafts

Design area

Application

Air ducting

Lift shafts

Mechanical service
riser

Simple pipework
riser

Rules of Thumb BSRIA 2001

Three-sided riser

11

For references see page 32

Rule of thumb

Ref

Typical ducting size

0⅐⅐2 m2/m3/s

30

3+A(N-4)/250 m2

30

Between 4 – 18 floors Internal shaft area
in office-type buildings A: floor area/
storey (250 m2 min),
N: Floors

Pipework

Service ducts

Other information

Vertical service duct

Depth needed to open
access door/pane when
width of door varies
with size/type of pipe
or depth of service/duct 690 mm

17

Pipe: 20 mm dia.
Pipe: 25 mm dia.
Pipe: 32 mm dia.

100 mm x 100 mm
120 mm x 120 mm
130 mm x 130 mm

30
30
30

Minimum depth
from services to (open)
access door/panel

690 mm

17

Floor space served by
vertical service (radius)

15 – 23 m

30

Aspect ratio of vertical
service duct

2:1 – 4:1

30

Total duct area as %
of gross floor area

2%

30

Your notes and comments


12

Space and weight allowances
TABLE 6: Space allowances for catering facilities

Rules of Thumb BSRIA 2001

Design area

Application

Other information

Rule of thumb

Ref

Kitchen and dining facilities

Kitchens including
preparation and
storage

Min. requirements:
Up to 100 meals
Up to 500 meals

0⅐⅐4 m2/meal
0⅐⅐ 25 m2/meal

31
31

For single sittings

Ratio of kitchen
space to dining space

0⅐⅐33:1 to 0⅐⅐ 5:1

31

Ratio of kitchen space
to dining space

1:1

31

For multiple sittings

Your notes and comments

TABLE 7: Floor space allowance per occupant (net internal area)
Design area

Rule of thumb

Ref

General offices

12 – 17 m2/person

4

Trading desks, call
centre, work stations

4 – 6 m2/person

4

15 m2 (or more)
per person

4

Enclosed offices

For references see page 32

Application

Other information

Your notes and comments


TABLE 8: Plant weight allowances
Design area

Application

Single boiler

Rules of Thumb BSRIA 2001

Rule of thumb

Ref

500 kW
1500 kW
2500 kW

1500 kg
4250 kg
6500 kg

39
39
39

Single storage steel calorifier

4 m3
8 m3
12 m3

1250 kg
2500 kg
3300 kg

39
39
39

Single non-storage mild-steel
heating calorifier

500 kW
1000 kW
1500 kW
2000 kW

150
225
275

325

kg
kg
kg
kg

39
39
39
39

1500 kW
3000 kW
4500 kW

10 000 kg
20 000 kg
30 000 kg

39
39
39

Single air-cooled liquid chiller

500 kW
1000 kW
1500 kW

6 000 kg
11 000 kg
14 000 kg

39
39
39

Single generator

500 kVa
1000 kVa
1500 kVa

5000 kg
8000 kg
11 000 kg

39
39
39

100 kVa
300 kVa
500 kVa

1250 kg
2750 kg
4250 kg

39
39
39

Single water-cooled
liquid chiller

Single UPS system

13

For references see page 32

Other information

Your notes and comments


14

When to use:
How to use:
Watch out for:

Equipment and solar loads

For estimates of thermal loads used to assess plant and terminal equipment sizes
To determine total solar and internal gains, multiply the loads by total floor area
Solar gains depend on glazing and shading, and contribution of thermal mass

TABLE 1: Cooling loads
Design area

Application

Other information

Rules Of Thumb BSRIA 2001

Rule of thumb

Ref

Banks

160 W/m2

34

Computer suites

400 W/m2 approx

34

Hotels

150 – 300 W/m2

34

Offices (general)

125 W/m2

34

75 W/m2

34

120 W/m2
180 W/m2

34
34

Restaurants

220 W/m2

34

Retail buildings

140 W/m2

34

Other information

Rule of thumb

Ref

Central cooling plant

Load/m2 of floor area
Load/m3 of floor vol.

125 W/m2
40 W/m3

36
36

Distributed cooling plant

Load/m2 of floor area
Load/m3 of floor vol.

140 W/m2
45 W/m3

36
36

Central plant
Distributed plant

0⅐⅐5 kW/kW
0⅐⅐ 78 kW/kW

36
36

Interior zones more
than 7 m from windows
Perimeter zones
up to 6 m

60% glazing
65% glazing

Your notes and comments

TABLE 2: Cooling plant
Design area

Electrical power for
refrigeration plant

For references see page 32

Application

kW/kW cooling
capacity

Your notes and comments

TABLE 3: Solar gains (over floor area)

Rules Of Thumb BSRIA 2001

Design area

Application

Other information

Rule of thumb

Ref

Windows with
internal blinds

(June-Sept)
(June-Sept)

South facing
East-West facing

250 W/m2 of glass
150 W/m2 of glass

34
34

Clear double-glazed with
internal blinds

Out-of-town building

All data for 6 m deep,
1500 mm wide module.
U-value 3⅐3 W/m2K.

2650 W instant
2490 W lag (mass)

39
39

As above with flat slab

Plus brise soleil

1860 W instant
1710 W lag (mass)

39
39

As above with coffered slab

Plus brise soleil

1860 W instant
1680 W lag (mass)

39
39

Other information

Rule of thumb

Ref

Floor area

90 W/m2 (30 W/m3)

34

Educational buildings

100 W/m2

34

Industrial buildings

80 W/m2

34

Offices

70 W/m2

34

Residential buildings

60 W/m2

34

Infiltration: air heating load

7⅐⅐ 5 W/m3

34

Retail buildings

110 W/m2

34

10 W/m2
12 W/m2
15 – 25 W/m2

16
16

16

Your notes and comments

TABLE 4: Heat loads
Design area

Application

General buildings

Other heat gains

Offices
General offices

15

For references see page 32

Metabolic
Lighting
Office equipment

Your notes and comments


16

When to use:

Where to use:
Watch out for:

Comfort factors

During the early stages of design
When setting inernal environmental conditons based on known or assumed loads
Specific client requirements, and contexts that allow greater latitude in design settings

TABLE 1: External conditions
Design area

Application

Winter design temperatures
for heating

Without surplus
boiler capacity
With 20% surplus
boiler capacity

Other information

Single-storey building
Other buildings

Rules of Thumb BSRIA 2001

Rate of lowering

outdoor design temp.
with altitude above
sea level

Rule of thumb

Ref

-4ЊЊC

37

-3ЊЊ C
-1ЊЊC

37
37

-0⅐⅐6ЊЊ C/100 m

37

Summer design temperature

Dry bulb temp.

28ЊЊC

37

for air conditioning

Wet bulb temp.

19ЊЊC

37

Your notes and comments

TABLE 2: Ventilation and air conditioning
Design area

Application

Other information

Rule of thumb

Ref

Ventilation: recommended
maximum temperature

Offices

95% operation/year

25ЊЊ C

4

Air conditioning: recommended
maximum temperature

Offices

95% operation/year

24ЊЊC (or lower)

4

IT rooms by classification

Type A IT rooms

Specifically designed
and built for IT equipment
(ideally, isolated from
office areas)
Dedicated IT room
required

For references see page 32

38

Your notes and comments

TABLE 3: Information technology
Design area

Application

Other information

IT rooms by classification
(continued)

Type B IT rooms

Designed for intensive
use of IT equipment at
workstations (where
air-conditioning must
be used)

Type C IT rooms

Rules of Thumb BSRIA 2001

Rule of thumb

Ref

Air-conditioned office,
room or workspace

38

Non air-conditioned
office, room or
workspace

38

Other information

Rule of thumb

Ref

In Winter
In Summer
At 21ЊC
At 22ЊC
At 23ЊC
At 24ЊC
On back of neck

0⅐⅐15 m/s
0⅐⅐ 25 m/s
0⅐⅐ 15 m/s
0⅐⅐ 2 m/s
0⅐⅐ 25 m/s
0⅐⅐ 3 m/s
0⅐⅐ 2 m/s

37
37
37
37
37
37
37

Papers will lift at
velocities in excess of

0⅐⅐8 m/s

37

0⅐⅐2 – 0⅐⅐ 3 m/s

2

Your notes and comments

Room where IT
equipment is used at
workstations (may use
natural or mechanical
ventilation)

TABLE 4: Room air movement
Design area
Maximum recommended

mean air velocities

Application

Television and
broadcasting studios

17

For references see page 32

Your notes and comments


18

Comfort factors
TABLE 5: Noise levels
Design area

Application

Other information

Rule of thumb

Ref

Recommended maximum
background noise levels

Very quiet rooms

Concert halls, sound
studios
Bedrooms, theatres,
churches
Small offices, libraries,
living rooms
General offices,
classrooms, small shops
Reception areas,
restaurants
Kitchens, computer
rooms, large shops
Factories

NR 20

37

NR 25

37

NR 30

37

NR 35

37

NR 40

37

NR 45
NR 50 or above

37
37

Intelligibility of telephone
conversation at background
noise levels

Satisfactory
Slightly difficult
Difficult
Unsatisfactory

Up to NR 50
Up to NR 60
Up to NR 75
Over NR 75

37
37
37

37

External noise level criteria for
new noise (above background noise)

If more than 10 dBA
If less than 5 dBA

Complaints expected
Marginal

37
37

Limiting distances for speech
intelligibility (background noise
level)

Up to NR 40
Up to NR 45
Up to NR 50
Up to NR 55
Over NR 70

7m
4m
2⅐⅐ 2 m
1⅐⅐ 2 m
Too noisy

37
37
37
37
37

Quiet rooms
Private rooms
Public rooms

Rules of Thumb BSRIA 2001

General areas
Work areas
Industrial areas

For references see page 32

Your notes and comments


TABLE 6: Comfort data sheet
Building Type

Internal design temperature
Summer
Winter

Humidity
(% RH)

Infiltration
(ac/h)

Ventilation
fresh air

Ventilation
air change

Lighting level
(Lux)

Noise level
(NR)

Cinemas (sedentary role)

21-23ЊC

19-21ЊC

50‫ע‬10% RH

0⅐5 ac/h

8 l/s/person

6-10 ac/h

300 lux

NR25-NR30

Computer rooms (general)

21-23ЊC

19-21ЊC

50‫ע‬5% RH

1 ac/h

8 l/s/person

4-15 ac/h

300 lux

NR35-NR45

Education (teaching spaces)

21-23ЊC

19-21ЊC

50‫ע‬5% RH

2 ac/h

8 l/s/person

6-10 ac/h

300 lux

NR25-NR35

Exhibition hall/conference facilities

21-23ЊC

19-21ЊC

50-55% RH

0⅐25-0⅐5 ac/h

8 l/s/person

1 ac/h

300 lux

NR40

Factory/warehouse

21-23ЊC

11-21ЊC

50‫ע‬10% RH

0⅐25-2⅐5 ac/h

8 l/s/person

6 ac/h

750-1000 lux

NR45-NR65

Fitness/health clubs (equipment rooms)

>18ЊC

12-18ЊC

40-70% RH

0⅐75 ac/h

8 l/s/person

4 ac/h

300 lux

NR30-NR40

Hospitals (ward and patient areas)

23-25ЊC

22-24ЊC

50-60% RH

2 ac/h

8 l/s/person

3 ac/h

50-100 lux

NR30-NR35

Hotels (bedrooms)

21-23ЊC

19-21ЊC

50‫ע‬10% RH

1 ac/h

8 l/s/person

6-10 ac/h

50-100 lux

NR20-NR30

Rules of Thumb BSRIA 2001

Libraries (reading rooms)

24-25ЊC

22-23ЊC

50‫ע‬5% RH

0⅐25-0⅐75 ac/h

8 l/s/person

3-4 ac/h

300 lux

NR30-NR35

Museums and galleries (display, storage)

21-23ЊC

19-21ЊC

50-55% RH

1 ac/h

8 l/s/person

3-4 ac/h

200 lux

NR30-NR35

Offices (general, BCO data)

24ЊC

22ЊC

35-40% RH

0⅐25-0⅐5 ac/h

8-12 l/s/person

4-6 ac/h

300-500 lux

NR25-NR40

Retail (shops/stores)

21-23ЊC

19-21ЊC

45‫ע‬5% RH

0⅐5-1 ac/h

8 l/s/person

3-8 ac/h

500-750 lux

NR35-NR45

300 lux

NR 40-NR50

19

For references see page 32

Swimming pools (pool halls)
Your notes and comments

23-26ЊC

23-26ЊC

40-70% RH

0⅐5 ac/h

2

0-15 l/s/m (of wetted area)


20

When to use:
Where to use:
Watch out for:

System features

During outline design before the architect has finalised space planning
For determining the spatial and operational characteristics of main plant
The rules for boiler and cooling plant are based on unit floor area or unit volume

TABLE 1: Sizing and operating characteristics of plant
Design area
Air handling units
Air face velocity

Application

Other information

Rules of Thumb BSRIA 2001

Coil water velocity

36
16

Heating mode
Cooling mode

30ЊC (max)
13ЊC (min)

16
16

Air discharge

0⅐⅐6 – 2 m/s

36

10 – 40 kPa
0⅐⅐ 33 – 1⅐⅐ 72 bar

16
36

8m
Not to exceed
50 mm within 1m
of diffuser outlet

36

Maximum height

66% of ceiling height

36

Allowance for grille

Allow 0⅐⅐3 m
width

36

120 W/m2 floor area
40 W/m3 volume

36
36

Water pressure drop
Steam pressure drop

Air distribution
From source

Ceiling diffusers

Non-zoning partitions
Sill diffusers

Boiler plant capacity

Power per unit area

Ref

2⅐⅐5 – 4 m/s
1⅐⅐ 0 – 2⅐⅐ 5 m/s

Heating coil
Cooling coil
Air supply
temperatures

Rule of thumb

Limit of throw
Surface projections

Your notes and comments

36

Table 1 continued Ł
For references see page 32


Design area

Application

Other information

Rule of thumb

Ref

Boiler plant efficiency

Boiler efficiency
Efficiency losses

Typical efficiency
Blowdown (steam)
Casing
Flue

75%
2%
3%
15 – 20 %

36
36
36
36

Condensing boilers

Underfloor or warm
water system

90%

22

Standard size radiators,
variable temp circuit
(weather
compensation)

87%

22

Standard fixedtemperature emitters

(83/72ЊC flow/return)

85%

22

Modern high efficiency
boilers

80 – 82%

22

Good modern boiler
design closely matched
to demand

75%

22

Typical good boiler

70%

22

1 kW/person

36

Volume per kW

40 litres/kW

36

Low velocity systems
High velocity systems

3 – 5 m/s
7⅐⅐ 5 – 15 m/s

36
36

Boiler plant
Typical seasonal
efficiencies

Rules of Thumb BSRIA 2001

Non-condensing
boilers

Chiller plant capacity

Fuel storage

Ductwork

Typical duct velocities

Class D oil

Your notes and comments

Table 1 continued Ł
21

For references see page 32


22

System features
Design area

Application

Other information Rule of thumb

Ductwork

Inlet louvres

(through free area)

Maximum pressure drop
rates (per m run)

Ref

Rules of Thumb BSRIA 2001

2⅐⅐5 m/s

36

Low velocity systems
High velocity systems

1 Pa/m
8 Pa/m

36
36

Typical system resistances
(including air handling plant)

Low velocity supply
Low velocity extract
High velocity supply

900 Pa
400 Pa
1⅐⅐ 5 – 2 kPa

36
36

36

Air leakage system loss (%)

Low pressure systems
Med. pressure systems
High pressure systems

6%
3%
2%

15
15
15

Fans

Electrical input (kW)

1⅐⅐6 x total fan pressure
(kPa) x volume flow
rate (m3/s)

36

1ЊC per kPa

36

Offices
Restaurants
Retail stores, halls, theatres

1⅐⅐4 litres/s per m3
3⅐⅐ 5 litres/s per m3
2⅐⅐ 1 litres/s per m3

23
23
23

Total system volume
(system size, in litres)

Domestic systems
Commercial systems

6 x boiler size (kW)+10% 3
10 x boiler size (kW)+10% 3

Capacity per unit area of
radiator surface

Conventional system

1 litre/m2

36

Capacity per unit of power
produced (boilers, radiators)

Boilers
Aluminium, cast radiator

1⅐⅐5 litres/kW
3 litres/kW

36
36

Temperature rise of air
Fan capacity of ventilated space

Class A
Class B
Class C

Total fan pressure

Your notes and comments

Heating systems
Approx. value
Approx. value

Table 1 continued Ł
For references see page 32

Design area

Pipework
Capacity per unit length of
of steel pipe

Application

Rule of thumb

Ref

E xtruded aluminium
Steel panel radiators

1⅐⅐2 litres/kW
5 litres/kW

36
36

15 mm diameter pipe
20 mm diameter pipe
25 mm diameter pipe
32 mm diameter pipe
40 mm diameter pipe

0⅐⅐25 litres/m
0⅐⅐ 4 litres/m

0⅐⅐ 6 litres/m
1⅐⅐ 2 litres/m
1⅐⅐ 5 litres/m

36
36
36
36
36

15 – 50 mm pipe dia.
Over 50 mm pipe dia.

0⅐⅐75 – 1⅐⅐ 5 m/s
1⅐⅐ 25 – 3 m/s

36
36

Initial pressure
per 100 m pipe run

6%

36

Over 50 mm pipe dia.

100 – 300 Pa/m

16

Corrosive water

1 m/s
1⅐⅐ 2 m/s
2 m/s max

36
36
36

Superheated steam
Saturated steam
Exhaust

40 – 60 m/s
30 – 40 m/s
20 – 30 m/s

36
36
36

4⅐⅐9 litres/m2

36

Pressure (in kPa),
length (m)

0⅐⅐36 x circuit length

36

Copper pipework

With steel pipework

Add 10% to water

36

Frost protection

Glycol concentration

30% of system vol.

16

Water velocity
Conventional systems

Rules of Thumb BSRIA 2001

Steam pressure drop

Water pressure

Conventional systems

Water velocity (system)

Small bore
Microbore

Steam velocity

Capacity per unit of finned area

Finned tube coils

Pumps
Head pressure (pump head)
Water treatment
Additives required

23

For references see page 32

Other information

Your notes and comments


24

When to use:

Where to use:
Watch out for:

Energy and carbon issues

When determining total building energy consumption
From briefing onwards through to design and operation (See also CIBSE TM22)
Change to the carbon conversion ratios which are continually being updated

TABLE 1: Energy conversions
Design area
Carbon dioxide emission
(Kg CO2/kWh delivery) by fuel

Application

Natural Gas
Oil
Electricity
Coal

Other information

Average

CO2 to Carbon

Rule of thumb

Ref

0⅐⅐19
0⅐⅐ 25
0⅐⅐ 46
0⅐⅐ 30

1
1
1
1

kg
kg
kg
kg

CO2/kWh
CO2/kWh
CO2/kWh
CO2/kWh

Divide by 3⅐⅐ 67

1

Your notes and comments

Rules of Thumb BSRIA 2001

TABLE 2: Energy benchmarks (offices)

Design area

Application

Other information

Rule of thumb

Ref

Naturally ventilated (cellular)
Type 1, simple relatively
small building, sometimes
converted residential,
100 – 3000 m2

Energy costs over
treated floor area (tfa)

Good practice
Typical

£3.50 m2 tfa
£6.00 m2 tfa

1
1

Gas or oil
(delivered)

Good practice
Typical

79 kWh/m2
151 kWh/m2

1
1

Electricity
(delivered)

Good practice
Typical

33 kWh/m2
54 kWh/m2

1
1

Good practice
Typical

£4.50 m2 tfa
£7.00 m2 tfa

1
1

Good practice
Typical

79 kWh/m2
151 kWh/m2

1
1

Good practice
Typical

54 kWh/m2
85 kWh/m2

1
1

Naturally ventilated (open plan) Energy costs over
Type 2, purpose-built, sometimes
treated floor area
converted industrial space, 500 m2
– 4000 m2
Gas or oil
(delivered)
Electricity
(delivered)

Your notes and comments

Table 2 continued Ł
For references see page 32


Rules of Thumb BSRIA 2001

Design area

Application

Other information

Rule of thumb

Ref

Air conditioned (standard)
Type 3, purpose-built, speculative
often intensively used,
2000 – 8000 m2

Energy costs

Good practice
Typical

£8.00 m2 tfa
£14.00 m2 tfa

1
1

Gas or oil
(delivered)

Good practice
Typical

97 kWh/m2
178 kWh/m2

1
1

Electricity
(delivered)

Good practice
Typical

128 kWh/m2
226 kWh/m2

1
1

Energy costs

Good practice

Typical

£13.00 m2 tfa
£20.00 m2 tfa

1
1

Gas or oil
(delivered)

Good practice
Typical

114 kWh/m2
210 kWh/m2

1
1

Electricity
(delivered)

Good practice
Typical

234 kWh/m2
358 kWh/m2

1

1

Design area

Application

Other information

Rule of thumb

Ref

Lighting benchmarks

Type 1

Good practice
Typical

12 W/m2
15 W/m2

1
1

Type 2

Good practice
Typical

12 W/m2
18 W/m2

1
1

Type 3

Good practice
Typical

12 W/m2
20 W/m2

1
1

Type 4

Good practice
Typical

12 W/m2
20 W/m2

1
1

Air conditioned (prestige)
Type 4, national or regional

head office, purpose-built to high
standards, intensively used and
extensive storage, parking and
leisure facilities, 4000 – 20 000 m2

Your notes and comments

TABLE 2: Lighting systems

25

For references see page 32

Your notes and comments


26

When to use:
Where to use:
Watch out for:

Electrical systems

To determine electrical supply requirements in buildings
When assessing the connected capacity in terms of unit floor area
Allowances for expansion, particularly for on-floor communications rooms

TABLE 1: Electrical supplies and loads
Design area

Application

Other information

Rule of thumb

Ref

Electrical supply

Electrical motors
Electrical motors

Above 3 kW rating
Up to and including
3 kW rating

3-phase supply

16

Direct on-line
starting

16

Assisted start

16

Lighting

10 – 12 W/m2

16

Small power

15 – 45 W/m2

16

Air conditioning

60 W/m2

35

Passenger lifts

10 W/m2

35

Electrical motors

Rules of Thumb BSRIA 2001

Electrical services load

(per m2 of building floor area)

Total load (kVA)
Design allowance for future
expansion (%)

For references see page 32

Above 4 kW rating

Small computer room

Net area

200 – 400 W/m2

16

Bespoke call centre

Net area

500 – 1000 W/m2

16

Total building load

Total kW/0⅐⅐8

35

% increase in load

Add 25% to
existing capacity

35

Your notes and comments