I had heard of Passivhaus prior to attending the conference, but not many details in what it was and how it affected structural engineering. Put simply Passivhaus is design focussed on minimising energy use during it’s lifetime. (This links quite nicely with Peter Head’s talk focussing on performance focussed, rather than financially focussed tenders written about here.) Passivhaus, as a basis, tends to ensure the following in its design:
- good levels of insulation with minimal thermal bridges
- passive solar gains and internal heat sources
- excellent level of airtightness
- good indoor air quality, provided by a whole house mechanical ventilation system with highly efficient heat recovery (more info)
There is also a very similar set of standards for retrofitting properties called EnerPHit, since we obviously can’t solve poor building design by simply starting again. The EnerPHit standard is a slightly more relaxed version to Passivhaus due to the difficulties in renovating properties and because there needs to be an element of value for money. I live in a draughty, Victorian terrace, solid wall construction. Making it anywhere close to Passivhaus standards would be incredibly difficult.
Why follow Passivhaus design?
In an average building there is a 60-80% increase on heating costs compared to its design expectations.
78% of homes do not achieve the required air change rate rising high humidity levels, condensation, mould growth and associated health issues.
How does it affect structural engineering?
Thermal bridging: Make sure the structural framework of a building is enveloped within a thermal, insulating layer (and preferably a thick one). In professional work ensure a masonry column supporting a steel beam doesn’t penetrate through the cavity, ensure appropriate construction notes ensure all displace insulation is re-inserted.
Airtightness: During construction a building should have continuous plastic sheeting within the external structure. How do you fix this without using nails or staples? How do you ensure a building’s structure doesn’t penetrate through this?
Communication: Both of the above topics cannot be resolved without considerable communication between architects and engineers. Personally I have a great interest in sustainable design. Unusually I also have a degree in Architecture, as well as currently studying in Civil / Structural engineering. I hope in the future I am able to work on projects that combine both my personal interests, and also combine my skill sets.