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Preventing mould & condensation in energy efficient homes

Question: We live in a 1930s house which has had cavity wall insulation installed and has a good level of insulation in the loft. We also have uPVC double glazed windows which don’t need replacing anytime soon. We’ve started getting mould on the walls on our first floor (where the walls meet the ceiling). What would you advise?

Answer: It sounds like you have made some good steps towards improving the energy efficiency of your home. The only problem is that as insulation and airtightness levels increase in a home (as they must do to reduce energy consumption and keep you warmer) you also need to develop a ventilation strategy to avoid mould and condensation issues. At the level of insulation and airtightness you describe, the ventilation strategies you need may simply be installation of effective fans in the bathrooms and kitchen and use of trickle vents on windows (these can be installed retrospectively in uPVC windows, though it is tricky). We look at ventilation strategies in more depth in our Warmer Homes resources.

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