The inside temperature of public transport buses is typically controlled to ensure the comfort of passengers. On warmer days this temperature can spiral from solar heat energy transmitted through windows and bodywork which is then trapped inside. Engine heating and passenger metabolism can have an even greater impact. Modern buses are equipped with HVAC (Heating, Ventilation and Air Conditioning) units which heat or cool the inside of the bus to maintain a target temperature. However, additional fuel is consumed to power the HVAC units and there is leakage of refrigerant gasses which are much more harmful to the greenhouse effect than CO2.
A Contra Vision bus wrap helps to reduce solar heat transmittance through windows because the printed area acts as a barrier which reflects or absorbs heat before it reaches the glass. The impact of Contra Vision on side bus windows was tested using a simulation model developed by Theseus-FE, a German engineering company based in Munich. A background report which benchmarks the simulation model can be found on the company’s website, including key assumptions such as the make of bus (MAN Bus A37), average bus velocity (20 km/h), target inside temperature (25oC), average number of passengers (33 each with 87W metabolism) and engine heating (35oC wall temperature). The model simulates a full day of activity from 6am to 8pm, calculating the power requirement of the HVAC unit at each point of the day to maintain the target temperature and the corresponding demand on energy.