The metabolic rate of a person depends on his/her level of activity. Metabolism can be classified as the sum of all chemical reactions that go in the human body for producing energy by means of converting consumed food. The metabolic rate and the heat created by a person increases as the rate of expenditure of physical energy increases. Therefore, he/she will be comfortable at a slightly lower resultant temperature. Sedentary people lose body heat at a rate of about 120 W at a temperature of 21 °C. The rate of body heat loss will increase to about 240 W on taking up light physical activity. The room temperature may be reduced slightly to maintain the thermal comfort.
Clothing
Clothes provide thermal insulation due to the low thermal conductivity of the clothing material and the air layer trapped between the clothing and the skin. The thermal resistance of clothing is expressed in terms of a unit known as the clo-value; 1 clo being the insulation provided by men's business suit. In winter people wear thicker and heavier clothing to get better insulation and hence more comfort. In summer people need to lose more heat from their bodies, therefore, lightweight clothing like shirt/blouse and trousers/skirt may provide the necessary comfort. Women, generally, wear lighter clothing as compared to men and hence prefer slightly higher temperatures.
Air movement
Air movement in a building is usually due to ventilation and draughts. The draughts could be due to gaps around openable parts of doors and single-glazed windows. Air movement creates freshness in a building and is more desirable in summer than in winter. Air movement increases heat loss from human body and causes chilliness and discomfort in winter. In domestic buildings, an air velocity of 0.1 - 0.2 m/s is considered to be reasonable. As draught increases and air velocity of 0.2 m/s or more is achieved, an increase in the dry resultant temperature is required to compensate for the cooling effect produced by air movement.
Humidity
The effect of humidity on human comfort is studied by considering the relative humidity (RH) of air. Its effect is considered to be very small when the resultant temperature is close to the recommended value. At temperatures above 25 °C (approx.) and higher activity level, heat is lost from the body by sweating. If the RH of the air is high, i.e. > 70%, the evaporation of sweat is very slow and people feel uncomfortable. The comfortable range of relative humidity is about 40 - 70%. If the RH of air is below 40%, some people may suffer from dry throat and dryness of skin and eyes.
Ventilation
Ventilation is the process by which clean air is brought into a building to remove the stale air. It is essential in buildings to remove carbon dioxide gas, body odours, bacteria, cooking smells and humidity. In crowded rooms the humidity may increase due to respiration and perspiration of the occupants, and there will also be an increase in the air temperature. Adequate ventilation will bring in fresh air to maintain the supply of oxygen for breathing, remove smells and excess water vapour, and lower the air temperature. See below table 'Extract ventilation rates' for a selection of ventilation requirements.
Extract ventilation rates
Room
Extract rate
Rooms containing printers and photocopiers in substantial use (greater than 30 minutes per hour)
Air extract rate of 20 l/s per machine during use. Note that, if the operators are in the room continuously, use the greater of the extract and whole building ventilation rates
Office sanitary accommodation and washrooms
Intermittent air extract rate of:
15 l/s per shower/bath
6 l/s per WC/urinal
Food and beverage preparation areas (not commercial kitchens)
Intermittent air extract rate of:
15 l/s with microwave and beverages only
30 l/s adjacent to the hob with cooker(s)
60 l/s elsewhere with cooker(s)
All to operate while food and beverage preparation is in progress
Whole building ventilation rate for air supply to offices
Air supply rate
Total outdoor air supply rate for offices (no smoking and no significant pollutant sources)
10 l/s per person
Noise
Noise can be defined as unwanted sound. Noise in a building may be produced by a multitude of sources like printers, photocopiers, air-conditioning systems, people in a room and people in adjoining rooms. Whatever the source, noise may interfere with our hearing of speech, distract us from what we are trying to do or it may just be annoying. Various criteria have been developed to analyse noise and hence minimise or avoid disturbance and speech interference. Two of these criteria are:
speech interference criteria
noise criteria curves
b) State the acceptable values of each factor.
Recommended comfort criteria for specific applications
Building/room type
Winter operative temp. range for stated activity and clothing levels
Summer operative temp. range (air conditioned buildings) for stated activity and clothing levels
Suggested air supply rate / (L.s-1 per person) unless stated otherwise
Filtration grade
Maintained illuminance
/lux
Noise rating
(NR)
Temp
/°C
Activity
/met
Clothing
/clo
Temp
/°C
Activity
/met
Clothing
/clo
Conference/board rooms
22-23
1.1
1.0
23-25
1.1
0.65
10
F6-F7
300/500
25-30
Source: (CIBSE, 2006, p.16)
Temperature
The acceptable value for temperature in the conference room can be broken down in to winter and summer:
Winter ideal range is 22-23°C.
Summer ideal range is 23-25°C.
Activity
The acceptable value for activity in the conference room is 1.1 met.
Clothing
The acceptable value for clothing in the conference room can be broken down in to winter and summer:
Winter ideal range is 1 clo.
Summer ideal range is 0.65 clo.
Air supply rate
The acceptable value for air supply rate in the conference room is 10 L.s-1 per person.
Illuminance
The acceptable value for illuminance in the conference room is 300-500 lux.
Noise
The acceptable value for noise in the conference room is 25-30 NR.
Task 2 (Assessment Criteria 3.2)
Explain the provision of services for the building and for the safe disposal of waste products. Discuss how you would expect the services to be incorporated into the overall design of the building.
The Offices, Shops and Railway Premises Act require buildings in use to have suitably located accommodation for sanitary appliances.
In general, the following minimum necessities apply:
Sufficient ventilation
Regular cleaning plan
Cold and hot running water, or mixed warm water
Way for cleaning (soap) and drying (warm air or towels)
Shower, if the type of work gives good reason for it
Toilet paper and coat hook in the WC cubicle
Privacy, if possible with separate male and female accommodation unless each facility is separated with a lockable door for use by one person at a time
Ease of access - not necessarily in the workplace but within the vicinity
Minimum facilities:
Mixed use or female use only -
Persons
WCs
Washbasins
1-5
1
1
6-25
2
2
Source: (Hall, F and Greeno, R, 2011, p.391)
Thereafter, 1 additional WC and 1 additional washbasin per 25 persons
Male use only -
Persons
WCs
Urinals
Washbasins
1-15
1
1
As above
16-30
2
1
As above
31-45
2
2
As above
46-60
3
2
As above
61-75
3
3
As above
76-90
4
3
As above
Source: (Hall, F and Greeno, R, 2011, p.391)
Thereafter, allocated on the same proportional basis
Sanitary accommodation design
It is estimated that the conference room will have capacity for up to 100 persons. For the purpose of sanitary accommodation design is has been assumed that 50% of the capacity will be male and the remaining 50% will be female.
Both female and male use only WCs should be provided and include for the following sanitary accommodation:-
Male WC (see sketch SK01)
Three WCs
Two urinals
Three washbasins
Female WC (see sketch SK02)
Three WCs
Three washbasins
Male WC.bmp
Female WC.bmp
Task 3 (Assessment Criteria 3.3)
a) Calculate the coefficient of thermal transmission (U-value) of the external wall. Refer to the data sheet for the ð€-values. If you need additional information, reference should be made to text books on construction science.
Thermal conductivity of some building materials
Material
Thermal conductivity (ð€) W/m K
Brickwork (external)
0.84
Aerated concrete blocks
0.11
Mineral wool batt
0.038
Plaster - lightweight
0.16
Source: (Virdi, 2012, p.101)
Standard thermal resistances
Type of resistance
Construction element
Heat flow
Surface emissivity
Standard resistances (m2 K/W)
Inside surfaces
Walls
Horizontal
High
0.12
Outside surfaces
Walls
Horizontal
High
0.06
Source: (McMullan, 2007, p.23)
Total thermal resistance
For a cavity wall consisting of 12 mm thick lightweight plaster, 100mm thick aerated concrete blocks (inner leaf), 100mm wide cavity filled with 100mm thick mineral wool insulation, 103mm thick brickwork (outer leaf), the total thermal resistance is given by:
Where
is the total thermal resistance of an element
is the resistance of the inside surface
is the material resistance
is the material resistance
is the material resistance
is the material resistance
is the resistance of the outside surface
Alternatively, in tabular format
Total thermal resistance
Layer
Thermal conductivity (ð€) W/m K
Thickness d (m)
Thermal resistance R (m2K/W)
Inside surface
n/a
n/a
Standard
0.12
Plaster - lightweight
0.16
0.012
0.012/0.16
0.075
Aerated concrete blocks
0.11
0.100
0.100/0.11
0.909
Mineral wool batt
0.038
0.100
0.100/0.038
2.632
Brickwork (external)
0.84
0.103
0.103/0.84
0.123
Outside surface
n/a
n/a
Standard
0.06
Total thermal resistance, Rtotal
3.918
Calculation of U-values
The U-value is calculated as the reciprocal of the total thermal resistance using the following formula.
Where
U-value (W/m2 K)
sum of the thermal resistances (R-values) of all the components in the
element
Task 3 (Assessment Criteria 3.3)
b) Calculate the heat loss from the building and the heat gain over a heating season of 33 weeks.
Heat loss from the building over a heating season of 33 weeks
Fabric heat loss
Limiting fabric parameters
Windows, roof windows, rooflights, curtain walling and pedestrian doors
2.2 W/m2 K
Source: (HM Government, 2010, p.18)
The inside measurements should be used in this question:
Walls:
Door(s):
Window(s):
The rate of heat loss through the fabric of the building may be calculated by using the following table:
Total rate of fabric heat loss
Element
U-value, U
(W/m2 K)
Area, A
(m2)
Temperature difference, T
(K)
Rate of heat loss,
U x A x T
(W)
Windows
2.2
3.1.5
19
1316.70
Door
2.2
2.0
19
83.60
Walls
0.26
221.65
19
1094.951
Roof
0.45
284.94
19
2436.237
Floor
0.25
284.94
16
1139.76
Total rate of fabric heat loss
6071.248
Heat loss due to ventilation
The rate of heat loss due to ventilation is given by the formula:
Where
is the volumetric specific heat capacity of air (J/m2 K)
is the volume of room (m3)
is the number of complete air changes per hour (each)
is the difference between the inside and outside air temperature (K)
Seconds in 1 hour = 3600
The total rate of heat loss from a building is determined by adding the fabric heat loss and the ventilation heat loss.
Or
Heat gains over a heating season of 33 weeks
Solar heat gains from the sun
Seasonal solar gain through windows
Type of window
(vertical unobstructed)
Average solar flux
Seasonal total heat gain
South-facing windows
72 W/m2
680 MJ/m2 glass
East and west-facing windows
48 W/m2
410 MJ/m2 glass
North facing windows
29 W/m2
250 MJ/m2 glass
Source: (McMullan, 2007, p.58)
Casual heat gains from occupants and equipment in the building
Heat emissions from casual sources
Type of source
Typical heat emission
Adult person (for 20°C surroundings)
Seated at rest
90 W
Lighting
Fluorescent system giving 400 lux (e.g. classroom)
20 W/m2 floor area
Source: (McMullan, 2007, p.59)
Or
Or
Find the number of radiators required
Heat output of compact radiators
Output based on a mean radiator water temperature of 70°C and a room temperature of 20°C
Nominal
Length
Single convector
Double panel plus
Double convector
height
mm
btu/h
watts
btu/h
watts
btu/h
watts
400 mm
500 mm
1244
365
1066
521
2372
695
Source: (Virdi, 2012, p.129)
Try 500 x 400mm double panel plus radiators.
Provide FOURTEEN 500 x 400 high double panel plus radiators (see sketch SK03).
Drawing1.bmp
Reference list
Hall, F. and Greeno, R. (2011) Building Services Handbook. 6th Ed. Oxford: Elsevier Butterworth-Heinemann.
HM Government. (2010) The Building Regulations 2010: Approved Document L2A: Conservation of fuel and power in new buildings other than dwellings. London: NBS.
HM Government. (2010) The Building Regulations 2010: Approved Document F1: Means of ventilation. London: NBS.
McMullan, R. (2007) Environmental Science in Building. 6th Ed. Basingstoke: Palgrave Macmillan.
The Chartered Institution of Building Services Engineers. (2006) CIBSE Guide A: Environmental design. 7th Ed. London: CIBSE Publications.
Virdi, S. (2012) Construction Science and Materials. Chichester: Wiley-Blackwell.
