Delivering passivhaus requires integrated design approach to ensure completion of the design
Delivering a Passivhaus requires an integrated design approach; therefore it is unlikely to be possible to commence the construction phase of a project before the vast majority of the design work is complete. Starting before detailed design work and Passivhaus planning has been completed may result in compromises to the building performance that threatens its certification.
For example it is hard to rectify the level of insulation in the ground floor or the design of the floor to wall junction detail, after this has been constructed. Therefore before commencing site work it is important to check that the design work is complete and that all the required drawings are in place; including plans, sections and clearly annotated details for all junctions between building elements (e.g. floor to wall), components (e.g. window to wall) as well as building services layouts.
High quality buildings require high quality materials that are delivered and installed in good condition. Therefore the handling of materials and their protection on site matters to the performance of the completed Passivhaus. Substituting materials during construction is not advisable as the use of inferior or non-certified products could
jeopardize Passivhaus certification. Insulation for example must conform precisely to the specification and can only
be accepted if the packaging is undamaged, correctly labelled and stamped with a ‘CE’ kitemark (UK).
During installation it must be laid in a continuous manner, leaving no gaps between panels or rolls. Even a 5mm gap
between insulation panels will result in ‘thermal bypass’ as warm air moves through the gap significantly increasing the effective U-value of a completed wall. Insulation panels must therefore have square edges to ensure that there are no gaps – and this means protecting the insulation during transportation, storage and handling on site.
The extremely low energy consumption of Passivhaus buildings means that drying out of materials can consume a considerable proportion of the heating energy used during the first year of occupation. Materials should therefore be kept dry on site.
Excerpt from “Passivhaus primer: Contractor’s guide. So you’ve been asked to build a Passivhaus?” by BRE.