19 Aug 2022

Why More Self-builders Are Considering Passivhaus

As energy bills soar and the climate crisis becomes ever more urgent, a tried-and-tested building design standard is coming into its own. The international Passivhaus standard is an ‘efficiency-first’ approach grounded in building physics. Passivhaus offers additional peace of mind through an independent quality assurance certification.

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Passivhaus works with any construction type, from straw bale to masonry, and any design style, from contemporary to traditional. The Passivhaus Trust’s dedicated self-build campaign page, ‘Passivhaus goes Personal’, features a selection of beautiful and inspirational self-build projects.

What’s more, the methodology can also be applied to existing buildings, with the EnerPHit standard established for Passivhaus retrofits. So, if you’re struggling to find a plot for your self-build, retrofitting your existing home offers a brilliant alternative.

How does Passivhaus work?

A Passivhaus is a building that requires minimal heating because it is built in such a way that it holds onto the heat it already has – in much the same way a thermos flask keeps coffee warm. This contrasts with most UK homes that need regular heating up, like a coffee percolator, for much of the heat to just escape through walls and air gaps.

High levels of airtightness, super insulation, use of triple glazing, and ensuring insulation and airtightness are continuous all contribute to this Passivhaus’ thermos flask’ effect. Passivhaus homes use up to 90% less energy to heat than typical uninsulated UK housing stock and have a space heating target of 15kWh/m2/year.

The magic number

Modelling the house in Passive House Planning Package (PHPP) software is an essential part of the Passivhaus process and is a handy early design decision-making tool. PHPP enables the Passivhaus designer to model and refine their design to achieve the ‘magic’ space heating target of 15kWh/m2/year.

Costs and benefits of Passivhaus

Additional insulation, triple glazing and MVHR ventilation systems do add to the capital costs of building to Passivhaus by around 8%, but this will fall over time to about 4%, with economies of scale and as the industry and supply chains gear up.

It is well established that reduced energy bills in a Passivhaus will quickly pay back the initial financial uplift. Moreover, for this slight uplift in cost, Passivhaus offers so many benefits, including:

•  Warm in winter, cool in summer. Year-round comfort is a key element, and Passivhaus occupants often express high levels of satisfaction. Certified Passivhaus buildings must carefully consider summer comfort and avoid overheating risks through the modelling of glazing and shading strategies.

•  Indoor comfort. Draughts are virtually eliminated, thanks to quality construction and high levels of airtightness. Passivhaus design also ensures no cold radiance or down draughting from cold surfaces internally.

•  Good indoor air quality. A high standard of indoor air quality is delivered by an ingenious - yet simple - piece of technology called MVHR (mechanical ventilation with heat recovery), which ensures that fresh air continually enters the building and is warmed up, through a honeycomb heat exchanger, by heat recovered from the air leaving the building.

•  Minimised energy consumption. Passivhaus helps deliver significant savings in energy bills, likely to be at the forefront of everyone’s mind due to the escalating hikes in the cost of living.

•  Reduced carbon emissions. 35% of global energy consumption comes from the building sector alone, with the largest contributor stemming from heating and cooling demand. The UK has some of the oldest and leakiest building stock in Europe. As we transition away from fossil fuels and electrify everything, energy demand reduction is essential to meet net-zero carbon targets and helps alleviate the peak pressure on the grid.

Read our benefits guide for more.

Quality assurance and peace of mind

Most current new builds suffer a 60% ‘performance gap’ between design ambition and the reality of energy performance in use. The Passivhaus standard has been around for 30+ years now and has been extensively monitored. Data proves that Passivhaus eliminates the performance gap.

Passivhaus has a rigorous quality assurance certification procedure that offers a third-party check of the design and construction by an independent expert, giving confidence and peace of mind that the building will work as designed. Even when working with experienced Passivhaus professionals, certification ensures that no corners are cut during the design process or on site. Certification also offers would-be purchasers third-party verification, which is important for anyone considering selling a Passivhaus building now or in the future.

Tips for a successful - and cost-effective - Passivhaus self-build

•  Incorporate Passivhaus into your initial brief, ideally before your designs are complete and planning approved

•  Work with a team that ‘gets it’ and has a can-do attitude. Ensure you have at least one person experienced with delivering Passivhaus across all project stages, from concept to completion

•  Keep it simple. A simple shape and ‘form factor’ will keep costs down and improve thermal performance

•  Pay close attention to ventilation design, summer comfort and airtightness. Getting those right will help avoid additional costs further down the line.

Next steps

Getting professional support
The Passivhaus Trust has a map of UK Passivhaus professionals to find who may be able to help, or you can search by category.

Free resources
Take advantage of free Passivhaus guidance and training on the Passivhaus Trust website to learn more. Delve into the trust’s project gallery and ‘Passivhaus goes Personal’ pages for more self-build inspiration.

Passivhaus open days
Experience the warmth and comfort of a Passivhaus first hand. Take advantage of the annual International Passivhaus Open Days, held in June and November each year.

NSBRC Passivhaus workshops
The National Self Build & Renovation Centre in Swindon holds Passivhaus workshops twice a year, offering a chance to hear from expert speakers and to explore related products and services.

For more information, visit the Passivhaus goes Personal section of the Passivhaus Trust website.

Further information....

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