How to deliver cost-effective Passivhaus
In a cost of living and inflationary crisis, with material costs spiralling, the UK Passivhaus Conference 2022 grasped the nettle of construction costs.
This year’s UK Passivhaus conference was held in Exeter, reflecting Exeter City Council’s record for developing ultra-low energy Passivhaus buildings over the last decade, including the new St Sidwell’s Point leisure centre and Edward’s Court Extra Care unit, as well as more than 200 new council homes. St Sidwell’s Point is the UK’s first leisure centre built to the Passivhaus standard and puts Exeter on the world map for Passivhaus developments. The conference, which was held over 25-26 October, also included largescale keynote case studies including Hounslow Council’s Masterplan to build 967 homes to the Passivhaus standard and Exeter University’s ambitious Passivhaus student accommodation plans. Plans for the widescale Passivhaus training of architecture students and others were also announced at the conference. The 2-day conference attracted 200+ in-person delegates and over 250 online delegates. Kier Construction, the main contractor on St Sidwell’s Point, was a Gold sponsor of the conference, which enabled public sector attendees to attend for free.
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Cost-effective Passivhaus
Addressing the cost of living crisis and fluctuating construction material costs, the conference session on ‘How to deliver cost-effective Passivhaus’, included the following speakers and panellists:
- Alun Watkins, Kalm Consulting Services
- Sarah Price, QODA Consulting
- Stewart MacLeod, Faithful+Gould
- Emma Osmundsen, Exeter City Living.
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I think the tension we’ve got at the moment is not confusing ‘normal’ construction costs with Passivhaus costs.
Emma Osmundensen, Exeter City Living
The big picture
Stewart MacLeod gave an overview of the situation affecting the wider construction industry because of higher energy prices and escalating inflation, to better understand how Passivhaus projects could fit within this uncertain and unstable wider context.
In the longer term, as energy prices go down or stabilise there was the chance of construction prices settling, but market forecasts are suggesting that 2023 is going to be a bumpy year. Stewart also shared a forecast that costs are unlikely to decrease, with a higher baseline for construction costs going forward. It was emphasised that this is affecting ALL construction projects, not just Passivhaus ones. However, Stewart also pointed out that “For Passivhaus, materials and material selection are of paramount importance, therefore there aren’t any corners that can be cut in reducing the costs.”
Looking at Passivhaus, the reality is that it should be impacted neither more nor less by the cost increases that have appeared in the market. This is on the basis that material selection and design stages are carefully made earlier on.
Stewart MacLeod, Faithful+Gould
Easy wins
The panellists shared some 'easy win' suggestions, which can have a huge impact on Passivhaus project costs:
- Simplifying building form factor, the lower the form factor the greater energy efficiency, reducing the money needed for insulation
- Using careful orientation of the building to optimise passive solar gains
- Building at scale, with repeat building designs
- Building more compactly and doing more with the same site footprint
The financial benefits of simplifying form factor and rationalising design has been a theme of other recent Passivhaus conferences and the Masterclass on the Agar Grove development, and is something the Passivhaus Trust will be expanding upon soon.
Designing out avoidable costs
There are also many potential avoidable costs on a Passivhaus project. Alun Watkins outlined a number of ways that avoidable costs could be reduced by careful planning and value engineering early on in a Passivhaus project:
- Design early, with Passivhaus as the goal from the outset
- Prioritise function over form (whilst strongly maintaining that Passivhaus buildings can be beautiful!)
- Carefully assess window design, which offers great opportunities for value engineering
- Limit ‘first time’ costs by integrating Passivhaus experience within the project team
- Design out thermal bridges and use of airtightness tapes and membranes, as far as possible
- Work closely with contractors and manufacturers from the outset
The usefulness of PHPP (Passive House Planning Package) as a value engineering tool was reinforced and the need for front-loaded early-stage design was reiterated. True value engineering was described as early-stage analysis of the function of every component in the project, as opposed to late-stage cost-cutting to rescue a budget.
We take the approach that 60% of any cost premium for Passivhaus can be designed out.
Emma Osmundsen, Exeter City Living
Unavoidable costs & whole life benefits
Alun Watkins gave a clear and realistic assessment of the potential additional costs relating to Passivhaus, irrespective of the wider construction industry pressures. Passivhaus often requires additional costs for materials, labour and design and certification but this uplift is usually now less than 10%, when factoring in other savings through reduced heating equipment need and economies of scale.
Certainly from our experience, the cost premium has been diminishing the more we build to Passivhaus standard.
Emma Osmundsen, Exeter City Living
The panellists emphasised that this uplift was more than repaid through long-term energy bill savings. In the face of escalating energy bills, the long term lifecycle payback is a powerful business case argument for Passivhaus.
Passivhaus looks far cheaper when whole lifecycle costs are analysed
Alun Watkins, Kalm Consulting Services
Retrofit approaches
Drawing on a case study comparing an EnerPHit project to an affordable retrofit, Sarah Price commented “You get what you pay for” with the EnerPHit project yielding 84% fuel bill reductions, compared to 34% for the Affordable retrofit. Moreover, both the cheaper retrofit and the EnerPHit deep retrofit ended up costing the exact same per tonne of carbon saved
When it comes to delivering cost-effective retrofits, Sarah made the case for ‘retrofit with an essence of EnerPHit’, commenting "The EnerPHit standard is great but is it cost-effective and realistic for all our buildings? Probably not". It was suggested that this cost-effective approach to retrofit involves keeping the key elements of the Passivhaus and EnerPHit methodology, focusing on eliminating the performance gap, and not skimping on the quality. The AECB retrofit standard and PAS 2030/ 2035 were referenced as ways in which Passivhaus approaches were being applied to retrofits.
Cost-effective strategies were outlined that can be achieved for retrofit especially on projects with good form factor, such as blocks of flats, and through careful building physics modelling of detailing. Pragmatic retrofit solutions, which can be undertaken while residents are in situ and without needing wholescale roof replacement or digging down below foundations were exemplified. A case study of external wall insulation retrofit detailing showed that it was not necessary to take insulation right the way down to the foundations to have a positive effect on heat loss Psi values.
Challenging times require smart approaches
The panellists agreed that intelligent value engineering approaches in the early stages of design, using all the tools available, are crucial to making Passivhaus cost-effective, given the current financial and budgetary challenges. As Wolfgang Feist, Founder of the Passivhaus Institut, has said “Investing in value instead of energy consumption requires little financial efforts but rather creativity and intelligent solutions”.
This is about prioritisation. Unless budgets are increasing, designs are going to have to work harder and harder to balance these priorities within the budgets that are available.
Stewart MacLeod, Faithful&Gould
Emma Osmundsen stressed the importance of keeping the Passivhaus standard as the ‘North Star’ throughout projects. There was agreement by the panellists on a need to focus on overall value and not only cost, during the current financial challenges. Energy efficient buildings are starting to see a cost premium when valued for the market, with recent research showing that house buyers willing to pay almost 10% more for energy efficient properties. We leave you with a final quote from Alun Watkins: "Passivhaus may not deliver lowest cost, but it can deliver the best value".
Further information
UK Passivhaus Conference 2022, Olia Kyritsi (pickeverard.co.uk)
9th November 2022
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