The wider the acceptable temperature range, the smaller the demand for heating and cooling will be. Investigations into the impact of adjusting the


thermostat settings on CO2 emissions for a medium-sized retail building have produced informative data. The temperature ranges considered, along with the


associated CO2 emissions, are given in the table below.


Heating set point oC


Heat to 21°C Heat to 17°C


Set back to 12°C Cool to 23°C Cool to 21°C


19 21 17 19 19 19


Heating set back oC*


16 16 16 12 16 16


of condensation or frost damage to the building’s contents by low temperatures.


A low set-back temperature may require a higher capacity heating plant to raise the temperature quickly to the desired daytime level each morning.


Ventilation Our research shows that it is really important to consider


Figure 5. Effects of adjusting the thermostat settings Case


Cooling set point oC


Base case


25 25 25 25 23 21


A change in the heating or cooling set point by only 2°C results in a


change in the CO2 emissions by 3-4%. The CO2 savings relating to the cooling and heating are


independent of each other, since they occur at different times of the year. Changing both set points could therefore reduce emissions by as much as 8% over the whole year.


The most significant change of the cases modelled happened with the reduction of the set back from 16-12°C. This is the temperature of the building outside occupied hours and has minimal effect on the operating conditions. There is a practical lower limit to the set- back temperature, due to the risk


Kg CO2/m2


36.1 37.7 35.0 31.2 37.7 40.3


* Temperature to which the building is heated during unoccupied hours (18.00 to 08.00).


ventilation requirements when designing buildings with very good air-tightness.


The standard measure of ventilation is the air change rate. This is expressed in ‘air changes per hour’ (ACH). Guideline values for typical environments are given by CIBSE guide A.


Mechanical ventilation is driven by electric power, so increasing the design ventilation rate


increases the building’s CO2 emissions. In many cases, particularly for large industrial and warehouse buildings, sufficient ventilation can be achieved through natural air movement and leakage.


/yr Change from base


+4.4% -3.1%


-13.5% +4.4%


+11.7%


Working in collaboration with designers, we have established that good practice means creating a very air-tight building envelope with controlled ventilation.


Where ventilation is controlled, heat ‘lost’ through ventilation may be returned to the building, notably reducing energy demand


and CO2 emissions. Heat recovery systems can be up to 80% efficient, allowing relatively high air-change rates without excessive CO2 emissions.


Tata Steel’s renewable energy system, Colorcoat Renew SC® provides a pre-heat function for gas-fired warm air heating systems. Using renewable solar radiation, the system provides fresh ventilation air that can be easily controlled to enhance occupant comfort in the most sustainable way possible.


Humidity Humidity in a building affects occupants’ comfort and their perception of temperature, which can result in appreciable cost and carbon efficiencies.


Studies by our technical team show that optimising humidity can save energy by making occupants feel more comfortable, which reduces demand for heating and/or cooling.


In order to maximise benefits, the temperature range and ventilation should be assessed by a building services engineer at the design stage.


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