How to control heat transfer

There’s many guides out there on designing energy-efficient buildings, both houses and commercial. But what do you know about heat transfer & what can you do when your building is too hot? We’ve come up with a few tips to help you understand overheating & how to control it!

Heat transfer in and out of a building occurs in only three ways:

• Radiation
• Conduction
• Convection

The physical laws and ways to control each form of are different. Heat enters through the roof, external walls, windows, and floor. Generally, in SE Queensland you want less heat going into the building in summer, and more entering the building in winter. Some treatments to the building design can achieve both

How can you reduce Radiation heat transfer?

Remember that it’s from both reflecting direct sunlight and indirect (sky) light:

• Use light colours on the roof and external walls
• Increase wall shading with verandahs, patios, pergolas or carports on North walls (this can also improve sun penetration in winter)
• Reduce window sizes on West facing walls
• Add window shading, awnings or louvres on East, North and West walls
• Curtains & heavy drapes with pelmets reflect more
• Consider window tinting or reflective film

Conduction is the pathways the heat travels though.

• Keep external surfaces cooler in summer, e.g. by shading or using light colours
• Insulation reduces thermal conduction through roof, ceiling and external walls
• Warmth through the ceiling is controlled by ceiling insulation and roof cavity temperature
• Windows conduct much more heat than brick veneer walls
• Window coverings with pelmets add additional isolation spaces from outside temperatures
• Thermal mass (bricks and concrete) in contact with inside air, regulates temperature by absorbing heat, delaying and reducing temperature changes
• Slate or ceramic tiled floors conduct heat better than timber, cork, vinyl or carpet
• Light construction homes don’t have the benefit of thermal mass and therefore require more attention to shading, windows and insulation

Thermal Convection is improved by airflow controls:

• Window size and position, cross ventilation breeze paths and ceiling fans
• Roof ventilation reduces roof cavity temperature
• Controlled infiltration or leakage of external air into the house
• Weather stripping, flue dampers, closeable vents including downlights or skylights