Thermal Bridging

30th September 2014
Thermal Bridging

I've seen many a roof cavity where either the roof insulation has not been extended to the building edge or part of the insulation has been removed (to get to, for example, electrical cable). If just 10% of your roof is not properly insulated 90% of your unwanted ceiling heat loss can occur through that gap – and in summer there would be some unwanted heat gain.

Another issue is unwanted heat loss/gain conducted by materials connecting the inside of a building to the outside. This is known as ‘thermal bridging’ and the remedy is a ‘thermal block’ using some non-conducting (insulating) material.

 

Justin McGar reports in Sourceable (30/9/14) on the 'New Green Building Guide to Combat Thermal Bridging'

"Thermal bridges are localized areas of high heat flow through walls, roofs and other insulated building envelope components. Thermal bridging is caused by highly conductive elements that penetrate the separation between the interior and exterior planes of a building, allowing heat flow to bypass the insulating layer and reducing its insulation effectiveness. 

"The thermal bridge may go through a wall and its insulation, through the space between the glass and steel of a curtainwall or simply through a leaky roof. The impact, however, can be significant to whole building energy use, the risk of condensation on cold surfaces, and occupant comfort. ...

"Studies have shown that the contribution of details that are typically disregarded [in the building process] can result in the underestimation of 20 per cent to 70 per cent of the total heat flow through walls [caused by thermal bridging]." 

Read more at: http://sourceable.net/new-green-building-guide-combat-thermal-bridging/#...

 

Insulation removed but not replaced

Insulation removed but not replaced

 

Insulation cut away from down light

Insulation cut away from a downlight. We recommend avoiding downlights (in part for this reason) but if you do use them install a guard (which we can supply). Note also the uninsulated metal framework in the ceiling which would act as a thermal bridge. The hotter the room below (in comparison to the ceiling space) the greater the heat loss.

 

Insulation not installed

Insulation not installed properly

 

Insulation not installed properly

Insulation not installed properly

 

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