Research published by the Passivhaus Trust reveals that the extra capital cost of building to the Passivhaus standard can be little as 2% in mid-rise flats.
Co-authored by Currie & Brown, Elemental Solutions and the Passivhaus Trust, the research paper draws on previously published modelling of the capital costs of Passivhaus construction compared with current building regulations.
The modelling suggests that the capital cost uplift from current regulations for a semi-detached house is 3–5% (£4,900–£8,500 per house), with mid-rise flats having an uplift of just 2% (£4,100–£5,300 per flat).
The trust said the smaller cost uplift for flats shows how the Passivhaus standard rewards efficient building geometry. Savings also come from simplifying glazing design and building services. The research also finds that early design-led optimisations may bring cost parity between Passivhaus and conventional approaches.
Then there are the cost benefits, principally in heating costs.
Crunching the numbers
Once the efficiency of the heat pump unit in each home is considered, the estimated electricity savings are in the order of 1,000kWh a year for a 93-sq-m semi-detached house and 500kWh a year for a 66-sq-m flat.
Assuming electricity prices at their current capped price of £0.2769 per kWh, the energy saving for a Passivhaus in comparison to a home built to Scottish Section 6 standards is £277 a year for the semi-detached house and £138 a year for the flat.
However, if the typical performance gap of 60% is reached, this increases the projected savings to £442 a year for the house and £220 a year for the flat.
Against these savings are the cost of new MVHR filters, which brings net savings down to around £392 a year for a semi-detached house and £170 a year for the flat.
And, as things heat up …
The paper raises another cost-benefit consideration for owners: the erosion of the value of a home or building that performs less well in the face of rising temperatures, energy and insurance costs.
It says buildings that are highly efficient, well-ventilated and robust “are likely to be more resilient, maintaining desirability, insurability and long-term value”.
“In this context, the question may be less about whether Passivhaus commands a fixed price premium today, and more about the extent to which it protects against future depreciation and obsolescence,” the paper says.
Passivhaus Trust chief executive Jon Bootland said cost was often cited as the chief barrier to Passivhaus homes and buildings, but the research shows the uplift is “negligible”.
“Passivhaus delivers lower running costs and greater confidence in real-world performance, helping close the gap between designed and delivered energy use,” he said. “Wider benefits include comfort, health and indoor air quality, resilience to changing energy prices and climate risks, and improved design coordination and delivery certainty.”
Download the report here.
