a04 - Roof non-ventilated construction

Introduction

From the 1970’s on, the asphalt shingle roof became popular and this roof has a watertight layer without the ventilated cavity. But because of the building physics many mistakes were made, resulting in damaged roofs. So this did not make the asphalt shingle very popular after the first ten years.

 

EPDM rubber

EPDM rubber membranes became first popular for flat roofs and later also for solar roofs. Upscaling BIPV resulted in more and more non-ventilated  tilted roofs with a watertight membrane under the photo-voltaic solar modules. One of the first large scale project was in the City of the Sun Heerhugowaard (NL). To increase the efficiency at the construction site, all roofs were made with EPDM membranes.

 

Building physics

To apply the EPDM membranes, all roofs were constructed in the factory and not on site. The pre-fabricated roofs were manufactured like wooden boxes including a vapour barrier on the inside and 100 to 140 mm of thermal insulation (mostly insulation wool). In most projects aluminium profiles were already mounted on the outside for the PV modules.

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Roof details of the prefabricated roofs before installation (Heerhugowaard NL).

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Roof details of the prefabricated roofs with PV modules (Heerhugowaard NL)

 

Relation with PV-Module

The PV modules are mounted on top of the watertight membrane. So in this way there is no need to make overlapping modules or connections between modules. Actually rain water can flow over and under the modules. In case of frameless modules the rain will most of the time clean the modules as well. There will be enough ventilation because of the open space around the modules.