The story of one man’s desire to lift his tenants out of fuel poverty

Why Passivehouses are Energy Efficient Houses, what are Passivehouses and why are they different from ordinary houses.

The UK has a poor record of building well insulated homes. Our first real legislation didn’t appear in The Building Regulations until 1984 and even then, it was acknowledged that we were well behind the standards achieved by our European neighbours in Sweden and Germany. One of the reasons given for not aiming for those higher standards was a fear that it might negatively affect the construction industry. A group think that continues to dog our attempts to drive up standards in this area even today.

Passivhauses are a method of building houses and other buildings and is not a stylistic approach. That is why they are different. It challenges contractors to build in a methodical manner. Controlling potential air leakage and thermal bridging, maintaining high levels of workmanship and observing the materials specification set by the client and the designer. Then crucially subjecting the buildings to thorough testing during and at the end of the build to ensure that the buildings meet the standards set and if the client requires certified Passivhaus status the build is inspected by a third-party inspector throughout the build.

The Passivhaus designer has to work under equally rigorous constraints. Whilst designing, the key features of the design are fed into a computer programme that assesses the performance of the design to see whether it matches the Passivhaus criteria for energy performance. Only when a ‘Pass’ is achieved can the design move forward for construction.

It is unusual for any UK designed house to be submitted to such rigorous scrutiny at the design stage. Most if not all UK houses are designed empirically. The Passivhaus approach represents a complete sea change approach to housing design.

In 2019 Derrick Dyas, Midland Rural Housing Association’s Chairman retired after a lifetime delivering affordable housing across the West Midlands. Derrick wanted before he retired to deliver a housing scheme that could demonstrate that it was possible to build housing that could lift people out of fuel poverty. Fuel poverty is where a household spends more than 10% of its income on fuel to maintain an adequate standard of warmth. In 2024 fuel poverty still affects 19.2% of the West Midlands population according to the government’s annual fuel poverty data.

In Wootton Wawen we had a forward-thinking parish council that had developed a truly ambitious neighbourhood plan embracing the need for affordable housing in their village, but it had to be truly energy efficient.

With an enthusiastic local community and an enlightened client, we saw this as an ideal site to trial a Passivhaus scheme with Warwickshire Rural Housing Association, a branch of Midland Rural. The houses would be the first Passivhauses in Warwickshire. Derrick supported the scheme throughout, helping us to push boundaries and committing to the extra spend required to deliver a Passivhaus scheme which amounts to between 8% to 10% above the cost of the average housing scheme.

The land was provided by a local landowner Allens Caravans within the village. The scheme consisted of 14 Passivhauses. All the houses were carefully orientated North / South to achieve perfect solar gain and arranged around a new access road. The eastern flank of the site faces open countryside and has a 15-metre-wide tree belt along the whole length of the site, which acts naturally as a Sustainable Drainage System for storm water. As the tree mature, they will soak up the storm water off the houses and paving around them providing much needed flood relief to the lower parts of the village.

How do the houses work?

1. They are super insulated with 300mm insulated cavity wall construction and triple glazed windows.

Our approach to the design was to use traditional English building techniques but by going back to first principals we tailored them to the Passivhaus approach.

2. Air tightness achieved by an internal render coat and attention to detail. The insulation and air tightness work together to keep the heat in.

3. Preventing Thermal bridging – ensuring the outside construction is isolated from the inside construction. Again, attention to detail on the part of the MWK design team designing the building.

4. MVHR – all the houses have a mechanical ventilation and heat recovery unit that pushes fresh, filtered air into the houses at a very low rate all day and night.

5. Solar gain – Large south facing windows and the external shading canopies modelled on Georgian canopies found in nearby Leamington Spa. Capturing the sun’s free heat is essential to the design.

The ground-breaking scheme, which was opened by HRH The Princess Royal in September 2018, scooped the Best Green Scheme in the national 24housing Awards 2018. At a prestigious ceremony at Coventry’s Ricoh Arena, WRHA beat off stiff competition from some top names in the housing industry.

Derrick Dyas, Chairman of Warwickshire Rural Housing Association, proudly commented: “We are absolutely delighted that Keyte Gardens has been recognised nationally as an outstanding development. It has been a real partnership project from beginning to end and we are pleased that this community development is already making a big difference to the local people who have made it their home.”

We think that was Derrick being modest. He was over the moon, thrilled that for the first time in his long career, a housing scheme that he had commissioned had won a National Housing Award.

But the real winners as Derrick Dyas had hoped were the new residents. Passivhauses have been proven to maintain a constant 21 deg temperature all year round at very little cost which makes them ideal homes for the elderly.

In 2015 we estimated at the outset of this endeavour that a 2 bed bungalows would use 1390 kWhr of energy per year. That amounted to £60 per year. At 2024 prices for electricity (our Passivhauses have no gas supply) that cost would have risen to £375 per year. The energy demand of the larger 3 Bed houses was 2487 kWhr which was less than £150 in 2015, which in 2024 was now £670 per annum.

Cost constraints at the time prevented us from installing solar panels, but with the fall in the cost of these panels over the past ten years, this would now be a viable option today.

So did Derrick achieve his wish that these houses would lift their residents out of full poverty. Yes, we know he did. The full costs of a pensioner in Keyte Gardens is 6% of their income, compared to Age UK’s research that suggests that the worst off pensioners spend 18% of their income on fuel. More than 10% is the government’s definition of fuel poverty.

The technical bit

Passive house is a voluntary standard for energy efficiency in a building that reduces the building’s carbon footprint. Conforming to these standards results in ultra-low energy buildings that require less energy for space heating or cooling.

The passive house standard originated from a meeting in May 1988 between Bo Adamson of Lund University, in Sweden, and Wolfgang Feist of the Institut für Wohnen und Umwelt (Institute for Housing and Environment), in Darmstadt, Germany. Their concept was developed through a number of research projects with financial assistance from the German state of Hesse.

In September 1996, the Passivhaus-Institut was founded in Darmstadt to promote and control passive house standards. By 2010 more than 25,000 passive house structures were estimated to have been built. Most are located in Germany and Austria, others in various countries worldwide.

Passive Houses are not mandated by law or regulation – they are a voluntarily agreed standard. However, this standard is clearly and unambiguously defined: The Passive House Institute has formulated the criteria for Passive Houses for different building tasks (e.g. residential buildings, office- educational buildings). These are exclusively so-called “functional criteria”, i.e. individual structural or technical details are not prescribed, but an overall coherent planning with a competently executed energy balance, elaboration of the details and documentation of the components is required. This ensures that the designed building can really produce the results expected of it in practice. The measurement results of a large number of examined Passive House projects confirm this.

The International Passive House Standard

The passive house standard requires that the building fulfils the following requirements.

Use up to 15 kWh/m2 (4,755 BTU/sq ft; 5.017 MJ/sq ft) of floor area per year for heating and cooling as calculated by the Passivhaus Planning Package PHPP, or a peak heat load of 10 W/m2 (1.2 hp/1000 sq ft) of floor area based on local climate data.

Use up to 60 kWh/m2 (19,020 BTU/sq ft; 20.07 MJ/sq ft) of floor area per year primary energy (for heating, hot water and electricity).

Air leakage up to 0.6 times the house volume per hour (n50 ≤ 0.6 / hour) at 50 Pa (0.0073 psi) as tested by a blower door; or up to 0.05 cubic feet per minute (1.4 L/min) per square foot of the surface area of the enclosure.

Costs

On average, passive houses are reported to be more expensive upfront than conventional buildings 8% to 10% in UK.

Passivhaus Comfort

Aside from very low energy bills, the houses are very comfortable environments in which to live.

• Filtered fresh air is provided 24/7 throughout the house, ideal for allergy sufferers

• The air is circulated at a very low velocity to prevent drafts and to prevent fan noise

• Windows and doors and all internal surfaces are warm to the touch, including glass (>16.5 degrees) giving better use of space because triple glazing is used

• High surface temperatures avoid or eliminate mould, leading to lower maintenance costs and significant health benefits

• The absence of/or reduction in radiators and heating appliances facilitates the free use of space. Radiators no longer need to be under windows.

• The build quality, including windows and doors, air tightness and insulation provides a very quiet environment and lower maintenance costs