Building heating systems
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Heating in buildings may be necessary to:
- Create comfortable conditions for occupants.
- To prevent condensation.
- For activities such as drying and cooking.
- For industrial processes.
 Heat sources
Examples of fuels and heat sources include:
- Solid fuel – timber, coal, peat, biomass.
- Liquid – oil, liquid petroleum gas (LPG).
- Gas - natural gas, biogas.
- Electricity - grid, wind turbines, hydroelectricity, photovoltaics.
- Water – solar thermal, geothermal, ground source, water source.
- Air source.
- Heat recovery.
- Passive – solar gain, thermal mass.
- Internal heat loads - heat generated by people and equipment.
Heat sources and fuels can be used to generate heat by:
- Solid fuel burners.
- Combined heat and power (CHP) plant.
- Electrical heaters.
- Gas heaters.
- Heat pumps.
 Heat distribution
Heat generators can be local to the demand for heat, or can be centralised and distributed, either within a single building or on a wider basis as part of a district heating network. Heat distribution can be by:
- Air blown through ducts, plenums or occupied spaces.
- Water pumped through pipework.
- Steam distributed through pipework.
- Passive air movement.
- Passive diffusion of heat through thermal mass.
 Heat delivery
Distributed heat can be delivered within a space by:
Heat transfer mechanisms include:
The amount of heat delivered to a space can be controlled:
- Locally by manual or automated thermostats, switches or dampers.
- Centrally by manual or automated thermostats, switches or dampers.
- Building management systems.
Heating control systems often require re-evaluation once buildings are completed and occupied. Systems may require fine-tuning as internal heat loads and occupant behaviour do not always conform with design expectations. Occupant training can be helpful to optimise the performance of heating systems, and occupants can be appreciative of a degree of local control.
 Optimum temperatures
The human thermal environment is not straight forward and cannot be expressed in degrees. Nor can it be satisfactorily defined by acceptable temperature ranges. It is a personal experience dependent on a great number of criteria and can be different from one person to another within the same space.
- Metabolic heat.
For more information see thermal comfort.
There is no legal requirement to achieve a minimum or maximum temperature within a building. The building regulations Part J, Part L and Part F set out requirements for safety, the provision of information, the consumption of energy, standards of construction, carbon emissions and ventilation requirements, but they do not prescribe temperatures.
The Health and Safety Executive suggest that an environment can be said to achieve ‘reasonable comfort’ when at least 80% of its occupants are thermally comfortable. This means that thermal comfort can be assessed by surveying occupants to find out whether they are dissatisfied with their thermal environment.
The Workplace (Health, Safety and Welfare) Regulations simply state that, ‘During working hours, the temperature in all workplaces inside buildings shall be reasonable’, however, the associated approved code of practice Workplace health, safety and welfare. Workplace (Health, Safety and Welfare) Regulations 1992. Approved Code of Practicesuggests:
'The temperature in workrooms should normally be at least 16 degrees Celsius unless much of the work involves severe physical effort in which case the temperature should be at least 13 degrees Celsius. These temperatures may not, however, ensure reasonable comfort, depending on other factors such as air movement and relative humidity.’
There are no legal restrictions to maximum temperatures, however there is strict regulation of heat stress. Previous guidance by the HSE suggested that thermal comfort might be achieved between 13 and 30 degrees Celsius depending on the activity of occupants.
 Related articles on Designing Buildings Wiki
- Air handling unit.
- Approved documents.
- Building services.
- Building services engineer.
- Building regulations.
- Co-heating test.
- Cold stress.
- Corrosion in heating and cooling systems.
- Fan coil unit.
- Heat pump.
- Heat recovery.
- Heat stress.
- Heat transfer.
- Low carbon heating and cooling.
- Mechanical, electrical and plumbing MEP.
- Radiant heating.
- Thermal comfort.
- Underfloor heating.
 External references
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