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The Resilience of Passivhaus Homes in Power and Heating Cuts
Read Time: 2 minutes
Author. Clare Booth • Director
Author. Clare Booth • Director
Read Time: 2 minutes
•
Discover how Passivhaus homes stay comfortable for up to a week during power and heating cuts – making them the ultimate solution for a changing climate.
In the winter of 2021, Storm Arwen caused widespread disruption across Great Britain. Nearly one million homes lost power and heating, with 40,000 homes cut off for three days and almost 4,000 having to cope with freezing conditions for more than a week.
Experts warn that climate change will bring “more frequent and extreme weather events”, increasing the risk of prolonged power and heating outages. A study by UK Power revealed cuts are becoming all-too-common, whether caused by severe weather, high energy demand, or faults within the electricity network. These outages disrupt heating, cause emotional strain and significantly impact daily life.
This highlights the urgent need for new homes to be future-ready and designed with resilience as a top priority. Thankfully, the Passivhaus standard provides a tried-and-tested solution.
Why Passivhaus is the solution
Developed in Germany in the 1990s, Passivhaus is accepted as the world’s leading low-energy building standard. Homes built to this standard can remain comfortable for extended periods during power outages or heating system failures. Even in severe cold, they provide a safe, habitable environment for up to a week.
The Heating Failure Study
In 2023, the International Passive House Association conducted a technical study using simulations to compare how homes perform during a heating system failure. This study examined three types of homes under the following scenario: heating is cut for seven days in late January, with outside temperatures plummeting to -13°C. Electrical appliances and the ventilation system remained operational.
The study compared:
- An old home
- A Passivhaus
- A home built to Germany’s low-energy building standard, the Energy Conservation Ordinance (EnEV)
X-Axis: Date, Y-Axis: Temperature ºC • Source: International Passive House Association
What the Results Reveal
The living rooms in all three homes began at a temperature of 22°C. Once the heating was turned off, the following was observed:
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Old Home
Represented by the blue line on the graph, the old home became uncomfortably cold and uninhabitable within hours, even with double glazing. Within a few days, internal temperatures dropped so low (0°C) that water pipes were at risk of freezing.
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EnEV Home
The EnEV home, shown by the orange line, offered better insulation but still became uncomfortably cold (below 15°C) within one to two days.
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Passivhaus
In sharp contrast, the Passivhaus, represented by the green line, maintained an almost comfortable temperature range. It only dropped below 18°C after more than a week without heating.
The Power Cut Study
A similar study in Norway (2021) explored how homes in Oslo coped with a four-day power outage starting on the 14th January – statistically the coldest day of the year. Two types of homes were tested, both with and without solar panels and battery storage:
- A home built to Norway’s TEK17 standard, one of the world’s strictest low-energy building standards
- A Passivhaus
Home built to Norway’s building standard, TEK17 • Source: Shabnam Homaei & Mohamed Hamdy
Home built to the Passivhaus Standard • Source: Shabnam Homaei & Mohamed Hamdy
What the Results Reveal
The living rooms in each home began at a temperature of 21°C. After the power was cut, the following occurred:
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TEK17 Home
The TEK17 home (without PV solar panels or battery storage) dropped below 18°C within a few hours—a cold but still livable temperature. By the following day, however, the temperature fell to an uninhabitable level (below 15°C). Once power was restored, it took 12 hours of heating to bring the indoor temperature back to normal.
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Passivhaus
The Passivhaus (without PV solar panels or battery storage) maintained a comfortable temperature for more than 24 hours. It takes four days for the temperature to fall below 15 °C. The Passivhaus remains habitable for twice as long as a TEK17 home and is considerably faster to return to a normal temperature.
Extra technologies like solar panels and storage batteries further improve both home's resilience during a power cut (see the blue and red dotted lines in the graph). Although they have much better impact in the Passivhaus.
Why does a Passivhaus stay comfortable even in power and heating cuts?
The more insulated a home is, the slower it cools down.
Passivhaus homes are packed with higher quality and far greater levels of insulation than average new builds. The insulation wraps the home like a thermal blanket, reducing heat loss in winter and keeping the interior cool in summer.
Passivhaus homes are airtight, with no gaps for cold draughts to seep in and warm air to leak out. This is achieved through the use of a continuous air barrier that envelopes the entire building – from the walls and roof, to the floors and openings. The design process identifies all potential air leakage paths. During construction, even the smallest of these gaps are sealed using specialist tapes and adhesives. Anywhere an air leak could occur, Passivhaus makes the extra effort to plug it.
High performance triple glazing comes as standard. The spaces between each pane of glass are filled with Argon gas, which functions as an acoustic and thermal insulator. It reduces outdoor noise, prevents cold glass surfaces and eliminates condensation – warding off mould growth and keeping the atmosphere in your home a healthy one.
The bulk of the home’s heat is supplied by ‘passive’ sources, including sunlight, the body heat of occupants and electrical appliances (ie - boiling the kettle, watching tv). These are converted into efficient, usable energy.
Final Thoughts
Passivhaus homes are more than energy-efficient; they are a resilient solution to the challenges of a changing climate, ensuring comfort and safety even in the most extreme conditions.
Author.
Clare Booth
• Director
A trained communicator, Clare co-founded Coldwells Build with the aim of improving consumer experience within the construction process. Working previously as a television director and journalist, she understands more than most, about the power of detail, organisation and timing.
