In the first of a new series of NLA Technical Explainers, Gwilym Still - Director, Passivhaus Leader and Partner at Max Fordham - takes us through an explanation of Passivhaus, featuring exemplar projects and useful insights.
1. What is Passivhaus?
Passivhaus is many things: a voluntary standard, a set of tools and processes, an international community, and more. At its core, it focuses on designing and delivering high-comfort, low-energy-use buildings that close the performance gap. The energy targets it sets are consistent with designing the built environment for the climate emergency, and are aligned with both the RIBA 2030 Challenge and the LETI Climate Emergency Design Guide. In some senses, it’s a sneak preview of where UK building regulations need to be in 2030!
2. What does it achieve/deliver?
Passivhaus delivers low operational energy high comfort buildings. Common features of them include:
- Excellent levels of airtightness
- Good air quality, delivered through reliable and low energy mechanical ventilation with heat recovery
- Well installed and well performing insulation, with limited thermal bridging
- High-performance triple glazing
3. What does it involve for a client/developer/design team?
Projects generally work best where the design considers Passivhaus from early on, so it’s a good idea to involve a Passivhaus consultant/designer from the outset, even if certification is only being considered as an option. This helps incorporate the principles in an efficient and cost-effective way, and modelling from the Passivhaus energy tool (Passivhaus Planning Package – PHPP) can be used to inform the design.
It’s sensible to have involvement and feedback from a certifier, including at key points during the project, like pre-planning, pre-tender, and pre-construction.
Construction needs to be evidenced, so this should be set out for the main contractor as part of their role, and they then work through this during the build phase of the project. All being well, the building is certified at, or around, practical completion.
4. How much does it cost?
The question of cost is a tricky one. There are some very cost-effective Passivhaus projects around, with the Goldsmith Street project reported at around £1,900m², and still managing to win the Stirling Prize
. Research by the Passivhaus Trust puts the figure at around 8%
, and the Passivhaus Institute says around 4%. Exeter report delivering Passivhaus figures at industry standard benchmark costs.
It’s also worth bearing in mind that this is talking about up-front cost, compared to business-as-usual, and doesn’t include operational energy and cost savings. The building regulations are gradually improving, and as Passivhaus targets are equivalent to other climate emergency frameworks like the LETI CEDG, and the RIBA 2030 challenge, it’s worth being clear on the baseline for comparison. Is the baseline the worst-performing building it’s legally possible to erect, or a building which is responsible given the climate emergency?