Passive houses, explained
Posted by: electime 20th September 2023
Alan Siggins, indoor ventilation expert and Managing Director of Airflow, says:
“According to the World Green Building Council, buildings account for 39 per cent of global energy-related carbon emissions. Passive house aims to change this scenario. It’s a concept in construction and a standard for energy efficiency in buildings. Because of its origins at the Passivhaus Institut (PHI) in Darmstadt, Germany, it’s also known as Passivhaus.”
What is a Passive House?
“Passive houses are ultra-low energy buildings that require minimal energy for heating or cooling. They use clever design and engineering to both generate heat and avoid losing it. Common features include triple-glazed windows, high-quality insulation and a near-perfect level of airtightness.
“A passive house is a house that meets the Passive House Standard. These standards prioritise energy efficiency and aim to minimise a building’s impact on the environment. The minimal ecological impact of these houses is where the term passive comes in. The idea is that the building is almost just part of the natural background, rather than actively affecting the environment as traditional houses do.
“Energy costs in passive houses can be up to 90 per cent less than in traditional houses. And they can even be 75 per cent less than in new-build homes. Passive house designs consider every little detail and take advantage of every single opportunity to save energy.”
Can you retrofit a Passive House?
“It’s easier to apply passive house or equivalent principles to a new-build property, where key passive house features can be planned in from day one.
“In some cases with new-builds, you might even be able to choose the orientation of the property – to attract less sun in summer and more during the winter. Controlling the amount of sunlight in new-builds is also simpler because you can decide where windows go and how big they are, right from the blueprint stage.
“Another important factor is how much easier it is to install ventilation systems like MVHR in new-build properties.When retrofitting MVHR and related systems into an existing property, it’s especially vital to have a thorough site survey first. Then the ductwork can be carefully planned to minimise the complexity of its route, which will, in turn, minimise pressure resistance. The result will be a more efficient ventilation system, with a smaller price tag.
“All told, a passive house retrofit won’t usually reach the same levels of insulation as can be achieved with a newly built property. Nonetheless, it’s always worthwhile to adapt older properties to incorporate passive house principles. Even if it becomes quite a complicated project, the energy savings of a passive house retrofit will soon justify the initial outlay.”
What are the benefits of passive houses?
“Whether focusing on a new-build project or an existing property, the benefits of passive house design are compelling and long-lasting. Some of the benefits include energy and cost savings, eco-friendly design, comfort and noise reduction and the longevity of the house due to the high-quality materials. There is also a positive effect on air quality and mental well-being due to improved sunlight and air flow.”
How is Scotland leading the way on Passive House legislation?
“Scotland has great interest in protecting the natural environment. And when it comes to passive house, Scotland is certainly doing that. The Scottish government announced that by the end of 2024, all new residential buildings constructed in Scotland must adhere to the Passive House Standard – or a similar Scottish standard that is currently being designed.
“Following a proposal by Alex Rowley, Labour Member of Scottish Parliament (MSP) for Mid Scotland and Fife, the Scottish Parliament has fast-tracked the necessary legislation. The move is part of Scotland’s efforts to reach net zero for greenhouse gases by 2045.”
Are passive houses expensive?
“Because of the many variables involved in passive house construction/retrofitting, it’s difficult to calculate an average cost. However, Checkatrade estimates that for certified retrofitting in the UK, the average cost per square metre is around £2,150. For a 150m2 house, the cost would be about £322,500. Once the work is all finished, the cost of passive house UK certification is an additional £1,500.
“That sais, as passive house principles become more widely adopted in response to energy efficiency drives, the costs of passive house projects are coming down.
“According to Passivhaus Trust analysis from 2018, building to the Passive House Standard was 8% more expensive than building a new property without incorporating passive house features. However, once the build is finished, the energy savings soon come into effect. Homeowners will notice the difference from their very first gas or electricity bill, particularly if it comes during the winter, when usage is obviously higher. Plus, they’ll always be more self-sufficient when it comes to energy usage, leaving them almost entirely unaffected bvy future price hikes.”
Is Passive House the future?
“Governments around the world are rightly focusing their energies on energy efficiency and carbon reduction. According to the UN, more than 70 countries have set net-zero targets.
“All kinds of businesses, local councils and property developers now – or will soon – have to construct buildings in a more environmentally-friendly manner. The support for counteracting climate change will also lead countless individual homeowners to desire a greener home.”
