Building Services Engineering 5th Edition Handbook

3 Heat loss calculations
Learning objectives
Study of this chapter will enable the reader to:
1. identify and use the thermal conductivity and resistivity of building materials;
2. calculate the thermal resistance of a composite structure;
3. use building exposure categories;
4. use surface and cavity thermal resistance values;
5. identify high- and low-emissivity building materials;
6. calculate, or find, the thermal transmittance of walls, flat and pitched roofs, floors
and windows;
7. use the proportional area method to calculate the average U value of a thermally
bridged wall or other structure;
8. calculate the fabric and ventilation building heat loss components for a building;
9. calculate air and environmental temperatures produced in a room from a specified
resultant temperature;
10. identify the use of admittance Y values;
11. hot-water storage boiler power requirements;
12. calculate total boiler power.
Key terms and concepts
boiler power 71; edge insulation 66; exposure: sheltered, normal and severe 63; hot-water
heat load 71; intermittent heat load 70; proportion area method 64; steady-state heat loss 67;
surface emissivity 63; surface resistance 63; thermal conductivity 61; thermal resistance 61;
thermal storage of structure 67; thermal transmittance 64; U value 64; Y value 70.
Introduction
The terms and techniques for handling thermal properties of building materials are introduced to
enable calculation of the thermal resistance R, thermal transmittance U and use of admittance