Passivhaus Cost Optimisations explored in June Tutorial
Earlier this month, the Tutorial, Passivhaus Cost Optimisation, focused upon designing cost effective Passivhaus buildings, highlighting key steps to reduce costs, budget constraints, and common mistakes & misconceptions. The event had a strong turnout of approximately 25 delegates from a wide range of backgrounds with 50% architects, and surveyors, contractors and other construction professionals making up the remainder. The Tutorial was delivered by experts Chris Parsons of Parsons + Whittley Architects and Nick Grant of Elemental Solutions.
Chris Parsons began the day by advising delegates to be critical of cost comparisons and to be clear on what you are comparing. Costs may not take into consideration comfort and performance.
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How can you compare a building that performs so well, and efficiently compared to standard construction, to one that just simply doesn’t."
Chris Parsons, Parsons + Whittley
A clearly defined base cost would be beneficial, and cost/comfort ratios even more so, however, we are all faced with clients that ask the question – How much more does Passivhaus cost? The course highlighted some key cost drivers and Passivhaus savings.
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Better quality components
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Airtightness products
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Ventilation system
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High quality construction and care
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Compact forms
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Simpler systems, particularly heating
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Simpler controls
A great group exercise highlighted some really interesting topic discussions by posing the following question:
If you can’t seemingly afford Passivhaus – What is going to give? How much does it cost to go the extra mile?
The group explored a few options including relaxing the airtightness, reducing the levels of insulation, downgrading the MVHR system and not persuing Certification. It was soon realised that all the various components were intrinsically linked. The same question was revisted at the end of the tutorial.
The course was filled with nuggets of good practice to minimise & reduce costs from modelling in PHPP through to construction:
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The most cost effective solutions are taken at early sketch & design stages. |
Using £/m2 comparisons without a clearly defined base is unhelpful. |
Keep details, services and controls are Simple. |
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Remember that price is not the same as cost. |
Embrace project constraints rather than working against them. |
Beware of the Form Factor double whammy. Bigger buildings and complicated shapes = more walls, roofs, technical details = greater costs. |
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Avoid unnecessary transforms and mullions with clever window design. |
Don’t over compensate with south facing glazing. Analyse the impacts of floor to ceiling glazing. |
Design out mechanical shading (UK Climate) |
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Finalise the design before you finalise prices |
Enshrine collaboration into contracts and procurement that work. |
Try to retain skills and contractors/ professionals with Passivhaus experience. |
The group exercise examining how to reduce costs in a Passivhaus if it were seemingly unaffordable, was revisited. It looked at drawings of an exisiting pioneering social housing scheme, Wimbish Passivhaus, to determine cost savings.
Results
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Reduce south windows – don’t extend glazing all the way to the floor.
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Reduce the floor insulation under the slab – looks over estimated and results in increased price of insulation and excavation.
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Party walls – remove and certify as one large block.
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Emit internal walls and make it open plan to increase the TFA. (Not a viable solution for Wimbish Passivhaus as it is not favoured upon in social housing.)
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Form – make a more compact box to create a better form factor.
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Wet plaster as the airtightness layer was a struggle. An appointed airtightness tester was a good idea.
Watch this space for upcoming Masterclasses and Tutorials. We are planning an International Masterclass comparing EU - UK Passivhaus approaches and techniques in autumn. Also in the pipeline is a Tutorial on the new Passivhaus Standards later this year. Sign up to our monthly newsletter and follow us on twitter to keep up to date with UK Passivhaus events and activities.
29th June 2015
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