What is a cold flat roof?
A cold flat roof is where the insulation is placed between the joists under the flat roof so that the roof and the roof timbers are cold. Therefore, the cold roof ventilation needs to be provided to create airflow to the front and rear of the roof to prevent condensation.
This is a slightly more expensive flat roof system in comparison to a warm flat roof system as it’s more expensive to build. Also, it’s not as good thermally as the warm roof option due to more exposure.
The advantage of the cold flat roof system is that is no additional height is added to the structure.