Whilst giving an informative overview of Passivhaus, the article notably raises the issue of higher costs (15-20% more than a conventional project) involved to meet the Passivhaus standard, something which can understandably put people off pursuing this highly energy efficient building standard. However this data is from 2015 and it should be mentioned that the Passivhaus Trust updated their best practice costs to expect around an 8% uplift as of 2018.
Significantly, however, we have calculated our build uplift at Anchorage to be only 6% against a comparable design built to Building Regulation (2022) standards. This is a bespoke Passivhaus without compromise of aesthetic design or functionality, but benefiting from experienced Passivhaus designers who have kept Passivhaus at the heart of the project. As such it is a compelling result.
So where was money saved?
Minimal space heating requirement. A real positive of any Passivhaus, the space heating here is provided entirely by a pair of towel radiators and two Neo Trust panel radiators. This avoided an air source heat pump (ASHP) for heating and a central heating system, both of which would have come at significantly greater cost.
Glazing. The triple glazed windows from Ideal Combi and bi fold doors from Lucana were incredible value, and from experience were no more expensive than high-quality double glazed products, avoiding the glazing uplift which typically is to be expected.
Hot water is provided through a Sunamp Thermino which was not only incredibly cost effective to purchase and install, but not dependant on an ASHP or other method of power generation.
Where was extra cost added?
MVHR (mechanical ventilation with heat recovery) is an obvious additional expense although offset against other ventilation which would otherwise have been required. Even considering the requirement for MVHR, building services overhaul are significantly less costly.
Air tightness. Our contractor would say that he didn’t allow enough for all of the air tightness work, so for this comparison we have added a significant extra compensatory sum to make this a truer comparison.
Insulation: unsurprisingly the extra insulation added throughout created additional expenditure.
Superstructure. Building the 300mm Larson truss timber superstructure was comparative to a traditional, higher carbon construction, however the outer leaf could not be stone or rendered onto blockwork and instead required timber battens and a backing board to apply stone slips and render, adding cost.
PHPP and Certification: Although certification isn’t a requirement, it does provide a valuable quality assurance and is a good way to demonstrate that a building meets the standard. Whilst this is an additional cost, it is a very small proportion of the build cost.
We have found that although creating a Certified (pending) Passivhaus came with a construction uplift of approximately 6%, based on the actual space heating demand (7.1 kWh/m2/yr) this should translate into a payback period of less than 8 years.
It is also important to remember that creating and living in a Passivhaus isn’t all about cost. The improved comfort and health benefits along with the reduced emissions all provide significant and very real benefits for the occupants throughout the building’s lifetime.
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