Mr Roofer

Rooftherm had an interesting problem and project this week. A developer had built flats and had used steel powered coated sheets for the roof covering, a sort of box profile sheet. The development was in the wind down phase and the new owners had taken residence.

The developer had been in contact with us because, despite putting in ventilation in the form of air bricks to vent the loft void, the roof was suffering from a really excessive amount of condensation. This developer has not been alone with this problem; this has well and truly been the year for condensation, a large number of rainy and overcast days followed by low daytime and very cold night time temperatures being the factors causing the problem.

Condensation forms when water vapour within the air comes into contact with a colder than air surface. The ability of water vapour to remain vapour drops at the surface contact resulting in droplets of water. Scientifically, the average energy of the water vapour molecules drop at the colder surface contact as heat energy gets conducted out; as the average energy level drops around the cold surface the water vapour undergoes a change in phase and becomes liquid, i.e. condensation.

Now the problem was indeed quite bad. The loft void had created its own micro climate. Condensation was occurring on the steel roof sheets and was running and dripping off onto the mineral wool insulation laid at ceiling height within the loft void. The mineral wool was getting saturated, and we mean saturated like a sponge! Water was dripping out of light fittings in the ceiling and the developer had thoughtfully placed buckets under the lights! Needless to say ceiling, walls and decorations were becoming progressively ruined. The new owners of the flats were putting their central heating systems on and, without any insulation in the ceilings since the mineral wool was sodden wet, the warmth of the air was evaporating off the water within the mineral wool and recycling the condensation back again - a sort of mini Amazon rain forest effect. It was described by one of the spray team on the job as like a dripping tap that could not be turned off, as fast as they tried to dry the steel sheets with towels the condensation came straight back.

The solution involved removing all the mineral wool since this was acting as a condensation recycling unit, putting in commercial dehumidifiers and fans to dry the air and evaporate off any remaining condensation, a process that took about 3 days. Once the condensation has been stabilised, Rooftherm sprayed an anti condensation coating of polyurethane spray foam to the underside of the steel sheets. Since the polyurethane has to be bonded to the steel sheet it clearly helps if the sheet is dry before we start spraying. Polyurethane foam is such a good insulator it prevents the water vapour within the air from coming into contact with the colder than air steel sheets thus preventing condensation.

So, condensation problem eventually solved but not before new loft hatches had to be cut into the ceilings due to the size of the equipment needed to be lugged into the loft void to cure the problem. The sprayers became super heroes for the week by the flat owners but I am afraid the developer did not want to come on site and run the gauntlet preferring to give instructions by mobile phone a safe distance away from the development!