I have previously posted about the Heat Loss from a Slab Floor so how does that compare with a suspended timber, or particle board, floor?

Well its not as bad as you might think because the the space under the floor acts as a Buffer Zone between the room and the external temperature. (Unless you have got a pole house or a Queenslander.)

The main considerations are:

- The amount of external wall compared with the area of the floor, ‘ Perimeter to Area Ratio’ (PAR).
- The height of the floor above the ground (the calculations below are based on this height being 0.5m or less)
- The amount of ventilation expressed as m
^{2}/ m length of perimeter wall.

# Heat loss Calculations

## Perimeter to Area Ratio.

For a 10m x 10m house the PAR = 40/100 = 0.25

For a 20m x 5m house the PAR = 50/100 = 0.5

## Ventilation

Low ventilation = 0.0015m^{2}/ m length of perimeter wall

High ventilation = 0.003m^{2}/ m length of perimeter wall.

The table below provides some values of ‘U’ for the floor .

PAR |
.2 |
3 |
.4 |
.5 |
6 |
7 |
8 |
.9 |

‘U’ low ventilation |
0.4 |
0.51 |
0.59 |
0.66 |
0.72 |
0.77 |
0.82 |
0.86 |

‘U’ high ventilation |
0.42 |
0.53 |
0.62 |
0.7 |
0.76 |
0.81 |
0.86 |
0.9 |

So for a typical single storey house of 20m x 10m

The PAR = 60 / 200 = 0.3

From the table ‘U’ is 0.51 -0.53 depending on ventilation

The heat loss from the slab = Area x ‘U’

= 200 x (0.51 -0.53)

= 102 -106 watts/degree C

The heat loss for this floor is 4 – 8% higher than the same sized slab on ground. The suspended floor will however have a lower thermal mass.

#### See Insulation for similar Posts

#### For Posts about Green Buildings see **Sustainability**

With a suspended beam and Aircrete block floor, ground floor heat loss is reduced by up to 25%, compared to other forms of construction, offering excellent cost savings through secondary insulation. Further thermal improvements can be achieved using Aircrete blocks in the foundations.

Aircrete isn’t available in Australia but Hebel do have have similar products for this application

Brian