Insulative Comparisons of Residentials Walls

The performance of an insulation material is measured by its 'Thermal Resistance' otherwise known as its 'R-value'. All walls or roofs  have an R-value even if they are not insulated. Simply put the greater the R-value, the more effective is the wall or roof at resisting heat flow both coming in and going out.

It is believed by most people that that "double brick is better" from the point of view of thermal comfort than compared to a timber frame or other form of construction. People are surprised when the find out the facts.

The R- values of the common wall types m are quite similar. For example uninsulated double brick (RO.50); uninsulated brick veneer (RO.46); and, uninsulated weatherboard (0.46). So whilst double brick is better than timber framed - it is so just marginally.

The difference in thermal comfort between these building materials can be explained by the difference in the thermal response of the materials. Under changing conditions, the rate of heat flow through a building section is determined by both the R-value and the thermal response of the building materials.

The outside or ambient temperature may easily vary by as much as 7 to 25ºC during a night and day cycle. As the outside temperature cools down or heats up, so does the building structure, and it is this behaviour which we call the "Thermal Response'. A building of heavy material (ie brick or mud brick) responds slower than a building of lighter material (ie timber). This is known as 'thermal lag'.

This indicates a building of more stable thermal conditions which does not require as much heating or cooling to maintain comfort conditions. It is for this reason, 'brick is better', but brick walls still need to be insulated as the outside temperatures in winter are mostly lower than the inside temperatures. So if the walls are not insulated then the heat is effectively lost through the wall during winter.

There are now some very cost effective ways of insulating existing double brick homes today that greatly improve the performance of the home.