Whilst insulation is great for making top floor rooms warmer, it comes at the cost of making your loft or roof space cooler.
Condensation in lofts occurs when humid air makes its way through insulation or other gaps into the loft space and hits a cooler surface leading to beads of moisture on timbers, lintels and on the underside of the roof.
Causes of condensation in loft and roof spaces
As with other rooms in the house, condensation in the loft is caused by excess moisture in the air and a lack of adequate air ventilation.
Ensure ventilation slots in the roof space are unobstructed.
If possible remove storage or boxes from the space in order to improve air flow.
You may have to install additional roof vents.
Secondly, you should attempt to address the amount of humid and damp air you release into the property. Warm air always rises so it is natural that excess condensation will make its way up to the loft space where it will condense in the cold atmosphere.
Inform your builder immediately