Building Services Engineering 5th Edition Handbook

Ventilation and air conditioning 131
The design team of a new building need to develop a method of solving the complex issues
surrounding the task of providing a building which satisfies the:
• basic needs of the owner;
• architectural and local planning design philosophy;
• requirements of legislation;
• access, spatial, visual, aural and thermal comfort needs of the occupants;
• use of energy during the 50-year service period of the building;
• sources of energy that are available for the building and the maintainability of the whole
complex.
Those matters which relate to the need, or otherwise, for air conditioning can be summarized
as follows:
1. the local design weather conditions;
2. the indoor design set points for zone air temperature and relative humidity;
3. the allowable variation in the indoor design air conditions;
4. the number of occasions during each year that divergence from the specified indoor design
conditions are allowable;
5. the time periods when the building will be occupied by the main users and the service
personnel;
6. the sources of primary energy available for the building, their long-term reliability, storage
requirements and safety considerations;
7. whether renewable energy can be used on the site;
8. the building usage;
9. the means by which the building can be heated;
10 the outdoor air ventilation quantity requirements;
11. the peak energy requirements for heating and cooling;
12. the location and sizes of plant and service shaft spaces available;
13. whether natural ventilation or assisted natural ventilation can provide the required air flow
through the building;
14. whether mechanical cooling systems are needed to maintain the specified peak design
conditions;
15. the need to provide accurate indoor environmental conditions for equipment, material
storage and handling, or an industrial process;
16. whether low-cost cooling systems can be used;
17. whether there is a real need to provide a mechanical means of air conditioning;
18. if there is a process requirement for closely conditioned air within the building;
19. energy recovery strategies available;
20. the maintainability of the mechanical services and how replacement plant can be provided
without major structural works becoming necessary.
These considerations all have an impact on the building design team’s decision-making process.
The local weather conditions that create the maximum heating and cooling loads during the
occupied part of the day, or night, will determine the size of the heating and cooling plant that are
required. Occupancy times can sometimes be varied in order to minimize the plant capacity that
is needed, for example, by using the Mediterranean region off-peak working principle, however
unpalatable this may seem to northern European practices. The architectural and engineering
designers have the option to experiment with the thermal insulation value of the exterior envelope