Hygrothermal assessment of north facing, cold attic spaces under the eaves with varying single sided passive ventilation strategies and infiltration scenarios, in a cool, temperate climate

Relative humidity and temperature were measured in cold attic spaces under the eaves with diffusion-open roofing underlay to investigate different ventilation strategies, the influence of infiltration, and exterior insulated roofing underlay. The project was carried out as a full-scale experimental setup in the cool, temperate climate in Lyngby, Denmark. The objective was to test if the best practice recommendations concerning design of the cold attic space will prevent damaging moisture levels in the attics. Measurements do however indicate that complying with recommendations will not ensure satisfactory moisture levels in the attic spaces. A comparison of the passive ventilation strategies in combination with varying infiltration rates, for attic spaces fitted with diffusion-open roofing underlay, indicate that attic ventilation increases moisture levels. The exterior insulation of the attic space improved the hygrothermal performance.