Is Roof Ventilation Important?

December 2, 2020

What is ventilation?

Put simply, ventilation is the changing of the air within a space. If we take the example of a loft, if there is no ventilation then the air will be stagnant, it will not change in any dramatic way unless something changes. If we introduce ventilation, for example by adding a vent in the roof, then the air will blow in from the outside and the air inside the loft will cycle out.

Do we need to ventilate a loft?

In many houses, the loft space is simply a place to store possessions we don’t use that often, the Christmas decorations, the suitcases etc. So why would we care if we didn’t ventilate the space? Below is an image of a poorly ventilated loft space:

 

In this image we see the timber roof structure above, the white membrane (with mould growth) above the timber structure and ventilation below. The ends of the timber are very wet and are a dark colour and clearly mould growth is occurring. This is all due to condensation and has been ongoing for long enough that the timber structure of the roof is rotten and requires replacement. This is because the insulation has reduced ventilation to almost nothing and is absorbing the condensation, making the whole area wet. All because the ventilation wasn’t good enough.

How to improve ventilation

The scenario in the image above is as follows:

Air comes in underneath the gutters but cannot get through and past the insulation which is pressed tight to the underside of the roof membrane.

It should look like this:

In this image the insulation is not pressed onto the underside of the roof and air can get through.

Are there products that improve roof ventilation?

There are many products on the market, some provide ventilation around the eaves such as this (https://www.roofingoutlet.co.uk/products/sandtoft-eaves-vent-pack-10mm):

Or there are vents that take the place of tiling like this (https://redland.co.uk/products/components/ventilation-tiles/rapid-roof-vent-tile):

There are also modern breathable membranes as opposed to older non-breathable bituminous or plastic membranes which create problems with condensation.

 

For further information please feel free to call The Hopps Partnership.

 

Posted by:

Robert Hopps

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