The renewable-energy revolution

I would like to start by looking at how Passive House can help to deliver a renewable-energy revolution.

Passive House makes it possible to reduce energy demand by up to 90% compared to ordinary buildings. Reducing energy use, mainly in the building and transport sectors, is a key component of the energy revolution that is happening in Germany and Austria – both countries appear to be on target to run their economies on 100% renewable energy by 2050. Renewable energy can meet the summer energy needs of buildings in most climates but without closing the “winter gap” between demand and supply, the energy revolution can only be a dream. As Wolfgang Feist explained in his plenary speech at the 2013 International Passive House Conference in Frankfurt, renewable energy from 41m² of solar PV panels is enough to supply a Passive House with renewable energy throughout the year in a temperate climate. So Passive House and on-site or local renewable energy systems are perfectly matched to support the 21st-century energy revolution.

Energy independence is potentially a huge benefit to a nation’s security and to its economy – and the evidence from Germany and Austria is that this can probably can be achieved without the environmental damage of extracting and burning fossil fuel.

Most UK buildings are draughty, have only single glazing and very little insulation. The Marmot report of 2011, The Health Impacts of Cold Homes and Fuel Poverty, is a vivid portrayal of the health impacts of living in cold, damp homes. The Passfield Drive Retrofit for the Future project used thermal imaging to illustrate the improved comfort and likely health benefits derived from using a range of Passive House methods on an old building including external insulation, triple-glazed windows, heat-recovery ventilation and the elimination of cold draughts (bere:architects, 2011)

Comfort and health

Because Passive House buildings are so cheap to run, they offer affordable comfort. They provide warm and dry spaces in winter, without any condensation at all, and are always full of fresh air. Recent research compared the level of PM10 and PM2.5 particulates in the air of a Passive House and in the air of a neighbouring conventional house (see page 36). It was found that the air inside a Passive House is likely to provide significant health benefits for its users, especially helpful for asthma sufferers and those who have heart or lung conditions.

Harriet McKerrow of Arup used a Building Use Studies (BUS) occupant satisfaction survey to analyse the new Passive House at Ranulf Road in Camden (see page 39), and the house was found to perform well above the usual benchmarks in many respects including overall user satisfaction. Evidence of people’s enjoyment of living in Passive House buildings, and evidence of the health benefits that they are experiencing, can also be seen in a number of interviews of residents in passive house buildings on the Films page of the bere:architects website.

As late as December 2012, the Mayville Centre Passive House retrofit in London required no heating whatsoever, yet indoor temperatures were still around 22°C. At the same time monitoring was undertaken of two small, un-improved solid-wall apartments adjacent to the centre and it was found that, even with some heating (which the residents said they could barely afford) the un-insulated flats both had dreadful condensation problems and were struggling to maintain temperatures of 16 or 17°C.

By contrast, people who visit Passive House buildings always seem to be struck by how simple and normal, and how quiet and calm they seem – and how warm they feel in the winter months. Occupants often say how they never feel too warm or too cold, and say how they appreciate the quality of the air in Passive House buildings.

Affordability

The German government offers a Passive House low interest loan

Assuming that the additional cost of building a Passive House home compared with an ordinary home is around 8%, let’s also assume that the additional investment is financed through a higher mortgage loan, resulting in slightly higher repayment costs. It is estimated that for a house of approximately 150m², and an interest rate of 4.7% and 1.6% repayment rate, there might be an additional annual repayment rate of €945 euros. However, in Germany the house builder or owner can apply for the Development Loan Corporation’s “Energy-efficient construction ESH50/Passivhaus low-interest loan”, which reduces the annual cost burden in the first few years to almost compensate for the additional investment. Additionally, due to the lower annual energy costs of a Passive House compared to an ordinary building, the annual cost burden of a Passive House is lower than that of a normal house. After 30 years, when the cost of the mortgage has been completely repaid, the family will profit from the extremely low energy consumption. Moreover the occupants no longer have to worry about increasing energy prices and such low energy demand can be supplied with renewable energy (Ref: Active for more comfort – The Passive House. PHI/International Passive House Association).

Those in the developed world who question the “affordability” of Passive House should consider the whole-life cost benefits of reduced energy demand. The available options come down to choices between short-termism (buying an energy-inefficient house and then having large energy bills each month) and long-termism (spending more per square metre on the house, but saving money through low bills). As the German government loan system shows, policy can help individuals take a long-term view.

Short-termism has caused us to extract and burn the earth’s coal and oil reserves with massively damaging environmental consequences over a period of just a few generations. With hindsight, that was unaffordable.

A sustainable, long-term approach

In Pathways to 2050: Three Possible UK Energy Strategies, a report published in February 2013 by the thinktank British Pugwash of the Pugwash Conferences on Science and World Affairs, it is stated that during the next 40 years the UK will have to rebuild its energy-supply infrastructure and it is calculated that if low-energy retrofit can be reduced to £20,000 per dwelling by scaling-up our ambitions, this is less than one sixth of the cost of building a low-carbon electricity supply by 2050.

The Passive House approach can be applied to such a programme and would enable us to maintain or achieve high levels of comfort affordably while reducing our consumption of irreplaceable resources.

It seems obvious which path we should follow in an objective, ethical world. Even if we aren’t convinced by ethics or moral principles, we should be worried by the risk of the “perfect storm” of challenges that we are frequently warned about, should we continue with “business as usual”. As Richard Branson says on the cover of his latest book, “Screw business as usual.” If we are warned about the risks ahead but choose to ignore them, then we participate in a huge gamble for the opportunities available to future generations. Building Passive Houses or refurbishing buildings to the Passive House standard will not solve all these problems at once, but they are very positive first steps in trying to avoid them.

Embodied energy

The Passive House methodology requires the use of the Passive House Planning Package to accurately measure energy flows in a building. PHPP is primarily an energy modelling tool. It does not measure embodied energy or whole-life costs, but it does not preclude these important aspects of design either.

The Passive House methodology is complementary and compatable with low embodied energy. Pages 30–33 are devoted to the synergy between Passive House and concepts of local construction and low embodied energy.

Saving money – whole-life costs

When considering the cost of purchasing any product, it surely makes sense to take into account the lasting financial impact of its operation and maintenance.

In spite of this, the main deterrent for constructing low-energy buildings is the associated increase in build costs (Schnieders and Hermelink, 2006; Kansal and Kadambari, 2010; McManus et al., 2010). However, increased upfront costs in a low-energy building are likely to be offset by reduced energy bills during the building’s life. This can be defined numerically using the concept of Whole Life Costs.

Whole Life Costs (WLC) is defined as follows:

In the first UK study to try to quantify these savings using the concept of “Net Present Value” (Passivhaus buildings: Case study evidence for reduced whole life costs, Caroline Johnstone and Nick Newman, bere:architects, 2011, available on the bere:architects Research pages) the authors applied a wide variety of scenarios of gas prices, electricity prices and interest rates to the whole-life costs of a real Passive House building. The conclusions indicated that Passive House buildings were financially viable in all of the scenarios except for when there were continued very high interest rates, and they clearly show that strong benefits are derived even if one excludes the presumed increase of energy prices. So current research is showing that Passive House is the most cost-efficient standard unless energy prices are half of what they are in 2013 (Ref: W. Feist in: International Passive House Conference 2013, Proceedings, PHI 2013. Research Group on Cost Efficient Passive Houses 42, PHI, Darmstadt 2013). Interest rates are unlikely to alter this since the consensus is that they will not rise dramatically for the foreseeable future.

Overcoming the performance gap

The fact that UK buildings have such a poor record of achieving their performance targets is well documented by research from British universities and other research organisations such as the Building Services Research and Information Association (BSRIA) and the Usable Buildings Trust. Further information can be found on the www.usablebuildings.co.uk events resource page. Research carried out by the Carbon Trust’s Low Carbon Buildings Programme 2006, and latterly research being carried out by the Technology Strategy Board, regularly finds energy consumption two to three times higher than design intentions, and in the worst cases actual energy consumption is missing design targets by a factor of five. There are many reasons for this, some of which are out of the control of designers. For example, design-and-build contracts in the UK may enable contractors to change the architect’s design and substitute poorer-quality products.

However, procurement methods apart, the graphs on page 15 show that designers can take action to reduce the performance gap. While some of the variance from design will always be due to “unregulated loads” that were not predictable, much of it is not. According to Roderic Bunn (BSRIA), research has consistently found that building designers have not calculated very well because the tools they were using to predict energy consumption were not very suitable for the job. In light of these results, I think it is reasonable to suggest that if your design methodology does not work for the average user, don’t blame the user, instead change your design method.

Accurate calculation is exactly what the Passive House Planning Package facilitates, and evidence of this has been found in practice both in new and retrofitted UK Passive House buildings as a result of research projects carried out with UK Technology Strategy Board funding. Early results indicate that the use of Passive House methods has a strong tendency to create buildings that are performing as well as, or even better than, the design model predicted – and the Passive House design targets were much more ambitious than the current UK Building Regulations, and even exceed the UK government’s 2016 “zero-carbon” standard.

The publication of such results leaves little ambiguity over how to narrow the gap between design and performance. Passive House can reduce a new or refurbished building’s energy consumption in the hands of an average user by between 50% and 90% in actual use.

Carbon-emission reductions

In proportion to their energy efficiency, Passive House buildings achieve significant in-use carbon-emission reductions compared to the carbon emissions of ordinary buildings. The difference widens when it is understood that ordinary buildings commonly strongly underperform against their design ambitions, whereas Passive House buildings tend to perform close to design ambitions.

Comparison of carbon emissions for a small 3-bedroom house built to four different environmental standards, based on Larch House Ebbw Vale (source bere:architects)

Designed for United Welsh Housing Association as a prototype for social housing, the Larch House at Ebbw Vale, Wales (2010) demonstrated how Passive House can achieve “zero carbon” status according to Code Level 6 of the UK Code for Sustainable Homes, using only on-site renewables

Political incentives – lessons from Austria

Like Germany, Vorarlberg has the serious 21st-century goal of becoming self-sufficient in energy by 2050. In the past few decades, this region of Austria has managed to reinvent itself, bringing concepts of sustainability, efficiency and self-sufficiency to the forefront of public consciousness. Strong political signals have given people the confidence to invest in new, sustainable business enterprises and redevelop older ones. Very high regional prosperity, strong sustainable manufacturing output and low levels of unemployment are all indicators of success in the region, and Vorarlberg has become one of the wealthiest areas in the world with an average regional productivity per inhabitant of €31,000.

So what does this mean at the scale of an individual construction project in Vorarlberg? To illustrate this, let me introduce the drivers behind the Ludesch Community Centre, a case-study featured project.

In response to a request from the local authority, the Ludesch Community Centre project by Hermann Kaufmann was included in the Building for Tomorrow programme, which was established in 1999 as part of a research and development programme titled Technologies for Sustainable Development, funded by the Austrian government. Based upon the Passive House concept, the programme is aimed at promoting energy efficiency and the use of renewable energy sources, as well as the adoption of renewable and “green” building materials. Furthermore, it seeks to develop methods for comparing usage patterns and price structures between energy-efficient and conventional construction methods.

The selection of building materials at the Ludesch centre supported regional economic activity; the use of native timber; the protection of exterior timber surfaces by roof overhangs rather than the use of wood coatings; the use of insulation made from renewable resources; and the avoidance of PVC, solvents and other harmful substances.

Such visionary, politically led incentive programmes are intended to address the perceived environmental imperatives whilst also encouraging investment in research and education. As well as being good for the environment, the foresight of Vorarlberg politicians and public has also succeeded in creating a massive growth in 21st-century, sustainable jobs in skilled manufacturing and in sustainable-energy consulting. There is now a strong market for exporting the products of their “green” industry, and this has brought inward investment for their green products and inventions.

Vorarlberg is now home to numerous manufacturing companies producing goods that are consciously aimed at making the region entirely self-sufficient in everything that it needs, from food to homes. Even manufacturing will be run on 100% renewable energy by 2050, and will source locally grown raw materials wherever possible. At the same time, Vorarlberg is providing excellent education and healthcare for everyone, high salaries and reasonable working hours and a high quality of life in a caring, sharing community. Many of the prosperous Vorarlberg companies remain compact and family owned, but most seem to be competing on the world stage as well as supplying their services locally. The result of such holistic political planning is that relatively little needs to be imported to this increasingly wealthy region.

Many other countries, including the UK, seem to be on a less promising trajectory. Even so, there remains an opportunity for change to reduce the UK’s demand for energy to a sustainable level for a green energy-supply system, and I believe that the German and Austrian energy transition plans could be replicated in the UK and a green economy could deliver a transformation of the UK’s economic prospects.

Why aren’t all buildings built like this?

The main benefits are:

• High levels of comfort, no cold draughts, no cold feet.
• Healthy indoor conditions with no mildew
• Plenty of fresh air and less indoor air pollution
• Reduced environmental impact
• Local economic benefits
• Freedom from energy imports

Passive House is sometimes perceived by those who haven’t used the technology as being too restrictive, but the aesthetics of a Passive House are not prescribed by the Passive House software. An inefficient shape or other factor can be compensated for by additional measures – and this can be established at the earliest stages of design, enabling a capital-cost and operational-cost assessment to be made of the implications of any advantageous or disadvantageous design decisions. Used wisely, the Passive House software provides a fundamentally careful and caring approach to building that underpins an architect’s personal approach to design.

What the Passive House software does not do, however, is tick off a list of tenets or a set of necessary “ingredients”. There are no fixed design features. Instead there are carefully measured quality-control requirements like the prevention of cold bridging and draughts, the recovery of heat from ventilation and the intelligent use of the free energy of the sun. There is little or no restriction to designing beautiful buildings as long as they are designed and built very well – like a machine, or a natural organism. Why aren’t all buildings built like this?

Capital and whole-life costs

The whole-life financial costs of “affordable” Passive House new-build dwellings in the UK context has been investigated and compared with the whole-life costs of similar houses that are built only to the current Building Regulations statutory minimum standard. A study produced by bere:architects in 2010 (after the completion of the Welsh social-housing prototypes) attempted to illustrate the expected running costs of a Passive House compared to a minimum standard Building Regulations house. The quantity surveyor Richard Whidborne contributed to the research.

Comparing calculated energy costs of houses built to UK Building Regulations/Code for Sustainable Homes and Passive House

The graph shows what it theoretically costs to fuel a Passive House compared to three other design specifications. While PHPP was the tool used to make these calculations, it should be noted that the in-use difference between an ordinary building and a Passive House may be even larger than the graph shows due to the greater “performance gap” likely between design and actual use of the ordinary buildings (see pages 15, 26, 27).

The social-housing prototypes at Ebbw Vale were used to model a comparison of the cost of building an affordable Passive House home in the UK compared to a standard Building Regulations house type. The research showed that after 19 years the sum of the build cost and running costs of a Building Regulations house will have exceeded that for a Passive House, and that is without factoring in any increase in energy prices.

Subsequently a case study led by by Caroline Johnstone with bere:architects investigated evidence for reduced whole-life costs. Using the definition

the research concluded: “The study clearly shows that Passive House buildings are financially viable in all situations except in a scenario where very high bank interest rates negate the substantial energy savings.”

Larch and Lime House social-housing prototypes, Ebbw Vale, Wales, used to model the cost of building affordable Passive House homes

In 2012, research was carried out into the capital cost of the Passive House refurbishment of the Mayville Centre It was found that the cost of a basic Passive House refurbishment with a gas boiler was just 3% more than if the building had been built to the minimum Building Regulations standard. Yet this small additional cost had achieved 95% total energy saving over the first winter of operation, whilst at the same time raising indoor winter temperatures to a very comfortable and steady 20–22°C.

Large energy savings achieved at such small extra cost suggest, where fuel has to be imported, that strong national balance-of-payment benefits will accrue in the medium term, and explains why Germany and Austria provide a mixture of financial incentives and statutory requirements to deliver longer-term national benefits.

An example of succesful state inventive is the German Federal State Bank’s “Energiepashaushalt 40/Passivhaus credit which provides a 50,000 Euro loan, a 100% disbursement and 2.1% interest rate for each unit built to the Passive House standard”.

For further information, refer to: Feist, W. Is it profitable to build a Passive House?, Passive House Institute, 2007, http://www.passivhaustagung.de/Passive_House_E/economy_passivehouse.htm

Calculated additional cost of retrofitting the Mayville Community Centre to the Passive House standard compared to UK Building Regulations

Localised Passive House construction
by Thomas Stoney Bryans

Since the Industrial Revolution, construction has been increasingly emancipated from the constraints of the natural world, as we have transitioned from an era of building with labour and materials that were close at hand, to building with whatever we desired from a global marketplace. The inevitable consequence has been a detachment of both architects and society at large from the physical impacts of our buildings on the planet. In specifying steel from China, stone from Italy or tropical hardwoods from South America, we are blind to the impact of their extraction, and to the emissions that result from their production and transportation. If we choose to ignore these environmental costs, we may wish to consider that these processes also have social and economic impacts on the region in which construction is happening. In other words, both jobs and capital – which would once have stayed in the local area – are exported elsewhere.

These challenges may seem distant from the practice of architecture, but they are fundamentally architectural ones – for the potential of the profession to effect change lies in its ability to leverage the act of construction to benefit not just the end user but also the environment and the communities in which construction and extraction occurs. For this to happen, architects need to conceive of buildings not as isolated entities but rather as organisms that are fundamentally integrated into the ecosystems in which they operate. This requires a comprehensive approach to design, one that considers a building’s connections to the environmental and human ecosystems around it: the energy and nutrient flows of the environment, and the social and financial capital flows of human creation.

While the Passive House methodology addresses only operational energy and not embedded energy, it nonetheless provides one of the strongest foundations that we have to develop more comprehensively sustainable architectural strategies. By building upon it – firstly by assessing whole-life energy flows, then whole-life nutrient flows (such as construction materials, water cycles and green roofs), and finally by considering a project’s impacts on the social and financial capital flows of which it is part – Passive House can act as the core of a more holistic approach to design.

Two houses constructed in Ebbw Vale in Wales – bere:architects’ Larch house and Lime house – demonstrate the potential of exactly such an approach. The designs are the culmination of a vision that saw them as a seed for a regional, low-carbon construction industry, utilising local materials and creating local employment. With the specification of Welsh-grown timber, Welsh-made slates, and local stone, for example, the project not only minimises the embodied energy of its construction but also ensures that those materials, as biological nutrients, can remain local when the houses reach the end of their lives.

Such a localised focus is at the core of the international Transition Town movement: a network of communities, from towns to cities, each working to develop resilience in the face of peak oil, climate change and economic instability. As Rob Hopkins, founder of the Transition Network, has written, “The Holy Grail … from a Transition perspective, would be a building that is built to Passive House standards yet uses mostly local building materials”. It is an approach that embodies the “Heavy-Near, Light-Far” paradigm of Jason McLennan, where anything heavy – such as building material – is local, whereas things that are “light” – ideas, images, information – can travel great distances. It is a significant shift from today’s “Heavy-Far, Light-Far” globalised market and has profound implications for architecture, demanding both local adaptation and design intelligence in materials specification.

While the Passive House standard does not demand any particular construction system, an analysis of both embodied energy and nutrient flows will often favour biological materials such as timber, largely due to inherent carbon sequestration and local availability. Both the quality and quantity of available timber, however, varies enormously from region to region. Within Europe for example, some countries, such as Finland and Sweden, have 75% forestry coverage or more, while the UK by contrast has just under 12%. Such variation in timber availability has a significant impact on the potential of localised supply chains and the products that can be produced. The use of solid-core timber panels for instance has grown considerably across Austria, Germany and Scandinavia since its emergence in the mid-1990s, but due to the enormous volume of material it requires it would clearly be ill suited to wide scale use in a British context.

Comparing percentage forest cover in four European countries

For many regions, low-grade timber or restricted supply will demand greater innovation in detailing and construction. The framing system for the Ebbw Vale houses, for instance, was guided by the availability of only small-section low-density Sitka spruce, which had a maximum section size of 215mm. With a requirement for 400mm of insulation, due to the cold and exposed site, a traditional stud frame would have been impossible and the timber-frame manufacturer was not equipped to make the frame from engineered ladder-frame components. A solution was therefore devised with a 215mm stud filled with Welsh Rockwool, with 100mm of wood-fibre insulation on each side.

United Welsh Housing Association’s Larch and Lime House Passive Houses by bere:architects at Ebbw Vale in Wales demonstrated a holistic approach to design.

A greater challenge for the Ebbw Vale project, however, was that of getting Passive House certified windows locally made, and from local materials. To do so required bringing together a consortium of Welsh timber industry bodies, joinery firms, a window designer and a German window manufacturer, along with the architects, to collectively develop a certified product within two-and-a-half months. Made from thermally modified Welsh larch, the windows of the Vale Passive Window Partnership are today one of the only fully UK-made (as opposed to UK-assembled) Passive House windows available. Such a proactive procurement process may be unusual, but in doing so bere:architects were fully engaged with both the social and financial flows of the human ecosystem of which the project was part, using the act of construction – and the investment that it was bringing – to provide the opportunity for long-term benefits for the wider community.

As a collaboration between a number of different manufacturers, all producing the same product but with locally available materials, the window partnership demonstrates the potential of what Pooran Desai and Sue Riddlestone describe as a “bioregional network”:

Desai and Riddlestone’s BioRegional charity (best known for its “One Planet Living” framework) has developed a number of commercial enterprises, including paper mills and charcoal manufacturers, all based on this decentralised model. With a central coordination system enabling them to operate as a single supplier, small producers are able to access large-scale retailers and markets that would otherwise be unattainable. The potential environmental, social and economic benefits that such networks and regional supply chains can produce are profound. They reduce transportation distances and emissions, create more sustainable nutrient flows through the use of locally available materials, create new jobs, develop stronger communities and enable money to stay in local economies for longer.

Through the act of specification, architects, consciously or not, play an active role in the design of supply chains and in the sites of material extraction. As Bernard Planterose, an expert on Scottish forestry, has written, “We specify the timber and we specify the forest together”. For local and regional-scale supply chains to be adopted across the construction industry will therefore require a step change in the way that architects design and specify buildings. It demands that all conceivable impacts of a project on the human and environmental ecosystems around it be considered and actively calibrated, rather than left to chance. Such a comprehensive approach to design is not easy, but projects such as the Larch and Lime Houses demonstrate the potential wide-ranging positive impacts that it can bring. For, regardless of how large or small a project may be, every piece of architecture is an organism that is connected by flows of energy, nutrients and social and financial capital to its surrounding ecosystems. If each project is to give back more than it takes from those ecosystems, localised Passive House construction is a good place to start.

The Nirvana of Zero-Zero – energy efficiency and low embodied energy
by Gareth Roberts of Sturgis Carbon Profiling

Buildings by their very nature always consume resources and energy in their construction, and whilst in recent years progress has been made in reducing the operational emissions of buildings, progress on the materials front appears to have been much slower.

The “embodied” carbon emissions that come from the making and maintenance of buildings are significant enough that for many high-performance, low-energy new homes being built today, a greater proportion of their emissions will be put into the atmosphere through their construction than will be consumed over the lifetime of their use.

Experience of assisting architects with reducing the embodied carbon of their projects shows that the task is relatively simple if the designer includes the following five important considerations in the design of a building:

1: Do more for less – Using less material is one of the simplest ways to improve a building’s carbon footprint, as this avoids excess waste as well as reducing transport emissions.

2: Select alternative materials – Many materials have similar performance and aesthetic properties but have very different carbon impacts. Designers should select the best material for the job with regard to the lowest carbon impact.

3: Use low-carbon industrial processes – Even the same material can have a very different carbon impact depending on the source of energy used to make it; so, where possible designers should source materials manufactured using renewable energy or from countries with low-carbon grids.

4: Use materials that absorb carbon – Materials such as timber effectively lock away carbon from the atmosphere, which helps a designer to reduce a building’s footprint. However, care should be taken to give timber products long-term uses in order to lock the carbon out of the atmosphere for as long as possible.

5: Use locally produced materials – This reduces carbon emissions that arise due to transportation.

In the projects that SCP have worked on over the past four years, it has been possible to reduce the whole-life footprint of most buildings by 30% without adding anything to the construction costs. These savings are achieved by working on the procurement of the materials sympathetically, without affecting the nature of a building’s design.

Taking a whole-life view of the emissions associated with a building also helps to clarify other important carbon issues such as: What is the relative impact of transport, waste and site equipment? Is a long-life material better to specify rather than a short-life one that has lower carbon impacts? This approach also puts into perspective the importance of being able to recycle a building’s components at the end of its service life.

Architects should give serious consideration to minimising the embodied energy of their buildings’ fabric as well as the energy consumption of those buildings, in order to maximise the whole-life benefits of the energy-saving measures deployed in them.

Whole-life design assessment of bere:architects’ BRE Watford Passive House Project

SCP collaborated with bere:architects on the 2012 Building Research Establishment (BRE) Passive House competition to build a new house prototype suitable for widespread adoption by both the private and rented social landlord sectors, at the BRE Watford Innovation Park. The competition-winning design shows our latest thinking in reducing the operational and embodied carbon impacts of new housing. The aim was to deliver an affordable and easily maintained, easy-to-operate building to what the team refer to as a “Zero-Zero Whole Life Standard”.

Life-cycle carbon emission of building components

In the table, each main building component is analysed to give an idea of the contribution it makes to the overall carbon footprint of the building.

Elements which are negative are those which have the net effect of taking carbon from the atmosphere rather than emitting carbon into it. Most of these beneficial components are made from timber or from natural insulation, where the absorption of carbon occurs during the growth of the natural material.

Modelling the carbon-emission stream of a building

The graph above shows the modelled emission stream that belongs to the winning design. The model spans a period of 60 years and identifies opportunities for minimising whole-life carbon emissions due to maintenance operations, as well as the interdependencies of different components and the identification and elimination of “weakest links”. Weakest links are defined as small components of a design which, if they fail, require the wholesale replacement of other building parts to be undertaken. An example of this might be buried mechanical or electrical services that would require the removal of building plasterboard finishes in order to allow a repair to be carried out.

As the design develops for this project, SCP and bere:architects will develop the specification such that for every one of these houses built in the future, the net result will be to reduce the total amount of carbon being put into the atmosphere to the absolute minimum possible, taking into account both embodied and operational energy seen as a whole.

Performance data and user feedback – comfort, health and energy efficiency
by Sarah Lewis

Since the completion of Dr Feist’s pilot project in 1991, performance monitoring has been carried out on hundreds of Passive House projects around Europe, and the finding is that Passive House techniques consistently result in buildings that are performing to, and often even better than, design targets. This section looks in detail at some of the techniques used to assess the performance of low-energy buildings. It presents some analysis of the results obtained from three of the first batch of Passive House projects to be built and monitored in the UK: the Ranulf Road Passive House, the Mayville Centre and the Princedale Road social-housing retrofit; all London projects.

The main techniques are grouped into two basic categories: (1) fabric performance and (2) in-use performance (the latter heading includes both energy consumption and user surveys).

Fabric-performance measurements

Fabric performance is typically measured by the following methods:

5. Infrared thermography

Thermography surveys provide an opportunity to check for defects in the thermal performance of the as-built fabric. They can be used to find any areas of concentrated heat loss resulting from thermal bridges or air leakage. Analysis can be done externally and internally. A temperature differential is required between the internal and external environments, so it is ideal if the thermography survey can be completed in conjunction with the co-heating test.

Clockwise from above: typical equipment required for a coheating test; example of a roof-mounted weather station; carrying out a blower door test; carrying out heat flux measurements

Princedale Road – Passive House primary-energy demand compared to a typical building. (Primary-energy demand accounts for transmission losses. For example, primary-electricity demand in the UK, on average, amounts to 2.7 times the metered electricity.) Graph produced by Eight Associates for Paul Davis and Partners

Thermal imaging at the Mayville Community Centre. Note the glass is reflecting heat from uninsulated flats behind the camera

In-use performance measurements

For the in-use monitoring of projects, sub-metering is required for electricity, gas, and hot- and cold-water utilities. Sub-metering enables design teams to provide a very good level of analytical aftercare for their clients. More advanced in-use monitoring can also be used to measure the efficiency of heat-recovery ventilation units and any air heating or traditional heating systems, as applicable. Internal temperatures, relative humidity and CO₂ levels can also be recorded to assess user comfort and health conditions. These can be analysed in conjunction with occupant surveys. Weather stations accurately record the external conditions – an important component of any in-depth monitoring.

Monitored results – air quality (CO₂ & relative humidity)

In the Passive House at Ranulf Road, the first year of monitored data provided the following information on CO₂:

• The maximum CO₂ level in the master bedroom reached an occasional peak of <1,500 parts per million (ppm), keeping within the maximum indoor CO₂ concentration of 1,600ppm quoted by CIBSE Guide A, and 1,500ppm cited by the German DIN 1946 standard.
• In the living room, there were occasional peaks around 1,000ppm, well within recommended levels.
• The average CO₂ levels were excellent; 733ppm in the bedroom and 679ppm in the living room over the full year from October 2011 to September 2012.

In the same building, the average relative humidity (RH) range was 41.9–53.5%, indicating excellent internal conditions. The RH results that were measured in the house are optimal for human health because scientific research shows that RH of 40–60 supports the minimum of airborne fungal, bacterial and virus concentrations and a minimum of dust-mite particles, which are often blamed for causing asthma symptoms.

Optimal RH and CO₂ levels have been found in all of bere:architects’ six different buildings that are being monitored with funding from the UK Technology Strategy Board. Even when special tests were conducted to measure the effect of daily indoor clothes drying, it was found that the Passive Houses avoided the moisture and mildew problems that occur in ordinary buildings. It was found that moisture is quickly removed in a Passive House building, in spite of long showers and clothes drying.

Monitored results – air quality (PM10 & PM2.5 particulates)

An independent air-quality report by Cranfield University (2013), funded by the UK Technology Strategy Board, comprehensively examined the air quality in the Passive House at Ranulf Road, London, and compared this with the air quality in a conventional house, also in Ranulf Road.

The report provides a comparison between the average level of harmful PM10 and PM2.5 particulates in the certified Passive House in London and the average level of PM10 and PM 2.5 particulates in the conventional house 100 metres along the same road. The average level of harmful PM 2.5 particulates inside the Passive House is half that of the conventional house.

It is also worth noting that the Passive House at Ranulf Road was found to have lower average indoor levels of harmful PM10 and PM2.5 particulates by a factor of three compared to the average level of particulates in the outside air.

Indirect health effects of relative humidity in indoor environments from Environmental Health Perspectives, Vol. 65, p358. Sterling et al. 1986 (note optimum range extended into ranges of 30–40 and 60–70 to conform with general consensus)

Mayville Community Centre. Psychrometric charts for a typical summer month and period Dec 2012–Feb 2013. Conditions were optimal throughout winter. The average temperature of the main hall was 21.3°C. The basement has no heating and the average temperature in the coldest March for 40 years was 21.6°C, with the coldest Monday morning being 19.7°C.

Ranulf Road Passive House. Psychrometric charts for Jun 2012 and Jan 2012. The higher summer living-room temperatures are due to the occupants’ personal preference for enjoying the free warmth and their decision to override the blind controls, a point made by the occupants in the building user survey. The bedroom has perfect humidity and temperature in summer and winter months.

Passfield Drive retrofit (designed towards the Passive House standard). Psychrometric charts for May°Oct 2011 and Nov 2011°Feb 2012. The occupants enjoy winter warmth and choose temperatures that, in the living room, exceed 24°C, yet the overall energy saving in the first year of operation was over 50% compared to the pre-retrofit house.

Lime House Nov-Dec 2012 Graph of interior relative humidity (%RH). RH remained within optimum levels in all living spaces, rising briefly only in the two bathrooms after showers had been taken. Twice-daily clothes washing and drying had no discernible adverse effect on indoor humidity levels.

Overall energy use in Ranulf Road

According to Ian Ridley, UCL Energy Institute and RMIT University, Australia, the Passive House at Ranulf Road is one of the lowest-energy dwellings ever monitored in the UK, with a total gas and electricity consumption of 65kWh/m² per annum, noting that so far only the terraced Passive House at Princedale Road by Paul Davis and Partners has been found to have a lower overall energy demand.

One of the Passive House requirements is that the specific space-heat demand of a building must not exceed 15kWh/m²/yr. At Ranulf Road, the measured specific space-heat demand in use during the first fully monitored 12-month period, July 2011 to July 2012, was even better than designed at 12.2kWh/m²/yr. This is all the more remarkable because it was found that the occupants do not always interact with the building as expected or planned; for example the external solar blinds are often left down in the winter, reducing the useful solar gains, and also the indoor temperatures are set quite high in winter.

The results support the hypothesis that a Passive House building can accommodate varying types of user behaviour without seriously affecting building performance, which was, according to Dr. Feist, the intention during the development of the standard.

Ranulf Road Passive House specific space-heat demand compared with the UK existing housing stock and future best practice

Ranulf Road Passive House, breakdown of electricity consumption by end use, February–July 2012

Overall energy use in the Mayville Centre

At the end of its first winter (2011), monitoring results found that the Mayville Centre made over 90% total energy savings compared to its pre-retrofit total energy use.

The Mayville Centre achieved over 90% reduction in overall energy consumption during its first winter of operation.

Analysis over the first year of occupation also shows that the centre performed significantly better than designed with regard to its specific heat load. This was due to higher occupancy than expected. In spite of the higher than expected occupancy, the overall primary-energy consumption was found to remain as designed.

The results show that PHPP is a robust tool for predicting in-use performance both for new-build and retrofit projects in the UK. We hope that these results will help convince sceptics that it is within their power to design buildings that can meaningfully, and reasonably robustly, contribute to increased energy efficiency and reduced CO₂ emissions – building efficiency that we are told by most scientists is essential and now urgently overdue.

Mayville Community Centre Passive House retrofit – monitoring found that there is a good correlation between design expectations and performance.

Measuring occupant feedback

As a “reality check”, Building Use Studies (BUS) were developed by the social scientist Adrian Leaman and the Usable Building Trust to give a quick but thorough way of obtaining professional-level feedback data on building performance, primarily from the occupants. Arup hold the licence to use the method, enabling them to authoritatively benchmark buildings against others on the BUS database. Ranulf Road, when subjected to a BUS, was found to have the highest user-satisfaction rating of any individual domestic building previously tested. Since only one occupant was surveyed, the result is clearly of limited significance; however, it should be noted that the occupant who was surveyed did not commission the dwelling or have any interest in low-energy buildings beyond the comfort and health benefits that she, as an asthma sufferer, would enjoy.

Overall energy use in social housing development at Wimbish

Monitoring work carried out for the Technology Strategy Board by the Adapt Low Carbon Group at the University of East Anglia has found that Parsons + Whittley’s social housing at Wimbish for Hastoe Housing Association has achieved excellent comfort and energy performance results. Independent monitoring by the Adapt Low Carbon Group at the University of East Anglia has reported that the 6 flats and 8 houses at Wimbish have delivered over 80% reduction in gas use compared to the average domestic UK gas bill. One six-person household set aside £50/month for gas payments but their actual bill for 6 months (July – January) was £30.

Residents love their new homes and all residents have agreed that they would not want to go back to living in an ordinary house, reporting:

BUS sample user comments

The owners of Ranulf Road have provided feedback that attests to the success of the underlying aim of the Passive House standard: to provide comfortable, healthy Passive House standard: to provide comfortable, healthy homes in an environmentally responsible manner for future generations.

Similar feedback has been provided at the Mayville Centre, the facility having been transformed from a cold building running with condensation and blighted by mould growth, draughts and other substandard indoor conditions, to a building that has optimal indoor comfort and optimal health conditions in winter and summer.

This sample data from the Building Use Survey (BUS) for the Passive House at Ranulf Road shows exceptionally high satisfaction with the air quality against benchmarks

Air quality and health

The DIN1946 regulation in Germany recommends that workstations should not exceed a CO₂ level of 1,500ppm, whereas regulations in England and Wales allow mean concentrations in schools of 1,500ppm averaged over the school day (DfES, 2006).

Research published by the City of Frankfurt in 2007 found that winter CO₂ levels in the air of classrooms in ordinary naturally ventilated schools in Frankfurt were for most of the time above 1,000ppm and a significant proportion of the time above 1,500ppm. These classrooms failed the German standard DIN1946.

The Frankfurt study also investigated the performance of a pilot Passive House school in the Riedberg area of the city. By contrast, the CO₂ levels in the pilot Passive House school always remained below 1,500ppm.

The Frankfurt study found that air quality in ordinary schools was poor because people were reluctant to open windows to obtain fresh air in winter due to cold draughts. So classroom CO₂ levels reached 1,800–2,500ppm before window opening occurred.

A Passive House building maintains healthy CO₂ levels, even during the winter, due to the heat-recovery ventilation system with carefully balanced supply and extract air flows. This “breathes” a constant stream of fresh air that is warmed by heat taken from air before it is vented from the building. In the warmer months windows are opened in a Passive House building without affecting its performance, just as in an ordinary building.

Graph compares CO2 concentration in a mechanically ventilated classroom (max spikes of 1,200ppm) with CO2 concentration in a naturally ventilated class room (max spikes 2,300ppm). Research published by the City of Frankfurt, 2007

In the UK, Dr Tim Sharpe and others have highlighted the consequences of poor-quality ventilation in some low-energy buildings. There is plenty of evidence that certified Passive House buildings are not affected. Pages 36–37 add to this evidence, showing that perfect humidity levels are maintained even after indoor clothes drying. There is also some evidence that airborne concentrations of harmful particulates, which may cause lung cancer and asthma, may be reduced in Passive Houses.

Passive House buildings have a series of important design and commissioning requirements for ventilation systems that are missing from the UK Building Regulations. For example, the current Building Regulations make no requirement to design for pressure loss inside ducting. Ducting with high resistance will cause increased energy consumption and potentially inadequate air supply in some rooms while over-ventilating others, and poorly designed systems with high duct resistance create unnecessary noise pollution which may lead users to turn off systems. Furthermore, the UK regulations allow primitive “trickle ventilation” gaps in window frames and they permit crude bathroom extractor fans that waste heat and create cold draughts.

Passive House design and commissioning techniques for ventilation systems offer an excellent model for improvement of the UK Building Regulations.

The importance of skills

This is where the main challenge to Passive House delivery lies – and the main opportunity. The nurturing of skills is synonymous with investment in them, which in turn is synonymous with investment in people.