By creating a continuous hermetic airtight layer, enclosing the complete envelope of the house, enclosed by the roof, external walls, windows and ground floor. This should be addressed by treating the house like a ‘balloon’ with no leaks or punctures for air to escape out. Warm, vapour-laden air, that’s generated in the inside of the house, under a driving pressure to the outside, should be prevented from seeping out, by providing a continuous membrane or air tight surface, preventing it from convecting and diffusing through the interior, warm side of the insulation, or through multiple small gaps that may occur at joints and junctions.
Archive for July, 2010
Controlling vapour diffusion and dampness from condensation
July 8th, 2010
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During this winter’s cold spell, many householders encountered problems of condensation forming on the inside surface of roofing felts, which collected and dripped down onto the ceiling, causing dampness to rooms below. Many complained of ice forming from this condensation on the underside of the cold roofing felt. When this started to melt, it dripped down and caused puddles of dampness to form.
So where does this condensation come from? Well it is not from the outside environment, or from the cold- water storage tank, even many may be uncovered. Some of this vapour could have been generated by small expansion tank, venting the central heating system, often located in the attic space. But by far, most of this condensation is formed from warm vapour-laden air that drives under pressure from heated habitable rooms into the cold attic to condense on the coldest and least ventilated surfaces, such as roofing felt.
