In the last month I have had condensation starting to occur in my loft space. It has happened twice, on both days the weather was very cold but the sky was cloudless and the sunshine warm.
My property was built in the 1980’s and had 50mm of fibreglass insulation between the joists. The loft space has no eaves ventilation but each of the 3 gable ends has 2 large air blocks at rafter level. I have just added 200mm of Knauf space blanket insulation (wrapped in silver foil) perpendicular to the rafters leaving ample space around the air blocks.
I have no cold water tanks in the loft. The bathroom and shower room both have extractor fans that are piped via the loft to the outside but there is no sign of leakage. No leaks in the roof itself are apparent. I have dried the loft out once with a dehumidifier and it stayed dry for a couple of weeks until the day with bright sunshine. I am tempted to remove all the insulation as there has never been condensation in the loft before I installed the space blanket.
Could it be the case that the loft gets very cold as it is well insulated and when the sunshine heats the external roof the temperature difference creates the condensation even though the ventilation was sufficient before topping up the insulation? Should I add more ventilation at rafter level or ridge?
Any advice gratefully received.
My property was built in the 1980’s and had 50mm of fibreglass insulation between the joists. The loft space has no eaves ventilation but each of the 3 gable ends has 2 large air blocks at rafter level. I have just added 200mm of Knauf space blanket insulation (wrapped in silver foil) perpendicular to the rafters leaving ample space around the air blocks.
I have no cold water tanks in the loft. The bathroom and shower room both have extractor fans that are piped via the loft to the outside but there is no sign of leakage. No leaks in the roof itself are apparent. I have dried the loft out once with a dehumidifier and it stayed dry for a couple of weeks until the day with bright sunshine. I am tempted to remove all the insulation as there has never been condensation in the loft before I installed the space blanket.
Could it be the case that the loft gets very cold as it is well insulated and when the sunshine heats the external roof the temperature difference creates the condensation even though the ventilation was sufficient before topping up the insulation? Should I add more ventilation at rafter level or ridge?
Any advice gratefully received.
