The floor construction type you select for your home can play a bigger role on its thermal performance than you may think. Heat gain and losses through the floor can typically vary from 10-20% of a house’s total heat flow in a temperate climate.
One of the key functions of floors from a thermal performance perspective is ideally to act as a body of thermal mass. Thermal mass is the ability of material to store heat and slowly dispense it over time (i.e. thermal lag), moderating the temperature of your home both during the day and night.
In winter, thermal mass absorbs solar gains during the day and radiates it back into the home during the night.
In summer, thermal mass will absorb the heat inside the home, with breezes and adequate shading helping to keep the house cool and discharge the excess heat.
With this in mind, we can then look at the floor construction types and think about the design that’s right for us.
There are generally two types of floor constructions in Australia – concrete slabs and timber floors.
Concrete slab floors
A concrete slab floor, with sufficient solar radiation during the winter months, can provide the thermal mass your home needs in colder climates. In hotter climates, it can also act as a heat sink and help to cool your home down. In both cases though, you will want to make sure that there is adequate protection in place to prevent unwanted solar gains or losses during summer and winter, depending on your climate type.
Concrete slabs connected to the ground usually have an advantage over suspended slabs. When slabs are connected to the ground, the temperature from the ground is more moderate than the ambient air temperature, which tends to fluctuate more with the seasons.
Timber floors do not tend to provide much thermal mass. With a timber floor, the subfloor ventilation has a greater impact on the thermal performance instead. In hotter climates, a more open/ventilated subfloor can help to alleviate cooling energy demand, while in colder climates an enclosed subfloor should be the main priority in order to restrict unnecessary airflow.
If you’re in a cold (or even temperate) climate, you may want to seriously consider adding insulation to minimise heat loss through the timber floor. After all, you’re letting all that heating that you’re paying for simply slip through the floorboards.
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