Innovative eco-social housing neighbourhood reaches completion in Wales

A version of this article was published on The Fifth Estate on 17 May.

Glen Peters standing outside one of the two-bedroomed semi-detached houses.

The first tenants have moved into Pentre Solar, an eco-social housing neighbourhood being constructed in Glanrhyd, Wales. ('Pentre' means village in Welsh.)


Dr Glen Peters, chief executive of Western Solar, has an ambition for his company to supply 1000 homes and to work with housing associations and local authorities to provide social housing.

The South-facing front of a three bedroomed house with plenty of glazing to capture the sun's heat. Inside it falls onto a black, melamine-covered concrete floor to absorb the heat.

The North-facing rear of a three bedroomed house. The homes are clad in local larch. This is projected to last at least 25 years before it needs replacing. Much care in the detailing of the design should extend the cladding life well beyond this point.

Peters estimates the build cost is about £120 per square foot (AU$19 a square metre). This has led him to set a rental cost of the two-bedroom houses of £480 a month (AU$836), a level in line with the local 106 planning condition of no more than 80 per cent of local market rents. The three-bedroom houses are set at £620 a month (AU$1080). For the developer, this gives a 3.5-4 per cent return on investment.

A pair of two-bedroomed semi-detached houses. All the homes have solar roofs.

Local materials and labour

Costs have been kept low and as much as possible of the houses manufactured locally from local materials. In total 80 per cent of the building is manufactured locally out of local timber and 40 per cent – the airtight frames – are manufactured in a nearby factory – a converted cowshed – to be assembled on site.

Peters says the multiplier effect of the benefit to the local community for every £1000 invested is £2200, a factor of 2.2.

The timber frames are kept out of direct contact with the ground to prevent damp from rising:

A footing protected from damp on the patio.

The homes’ design builds upon the developer’s experience of a prototype house, Ty Solar:

The prototype Ty Solar (Ty is Welsh for House so the name means Solar House in English) in West Wales. In the background can be seen the first solar farm in Wales which finance the building of Ty Solar.

Ty Solar was constructed in 2010 using the profit from Peters’ solar farm, the first in Wales. It cost about £75,000 (AU$130,640) to build with a £47,000 (AU$81,870) grant from the Sustainable Development Fund.

The unit costs of the Glanrhyd houses, built on the site of a now-demolished garage, were higher than normal, mainly because of the land reclamation, provision of services and unusual weather-related costs, as well as complying with planning conditions in an area of outstanding natural beauty.

The three-bedroom homes occupy 100 square metres, the two-bed ones slightly less, but still feel spacious.

The company is focused on providing social housing as Peters believes there is a reasonable business in creating good quality affordable housing, as none of the large developers seem to interested in doing so.

While it is economic and technically feasible to build these homes, politically Peters’ route has not been easy.

”Politicians have been unduly influenced by volume building companies, and while they love the houses it has been difficult to persuade local authorities and housing associations of the benefit of backing this design, despite the fact that occupants have virtually zero energy bills. The key performance indicators imposed on housing associations are unduly skewed towards capital costs rather than tenant and community welfare,” he says.

He is hoping that when he has occupancy data to back up his case, more housing associations and councils will be interested in the model.

Zero energy bills

The timber frame houses are built according to passive house principles, though are not validated as such due the cost of doing so, versus the benefits.

Each monopitch roof sports 8kW of integrated photovoltaic panels. Over a year these generate surplus energy, providing an income from a feed-in tariff, as well as giving the occupants free electricity. Total energy demand is about 12 per cent of a conventionally built home. Beneath the solar panels is a galvanised steel sheet that laps over the timber frame.

They sit on a concrete slab, unlike the prototype, which was constructed using the box beam method with a suspended timber floor. Peters says concrete is more durable, with more thermal mass and has a lower maintenance requirement, although with a greater carbon footprint.

The windows are double, not triple-glazed, to keep costs low as Peters believes that the incremental benefit of the extra pane of glazing is cancelled by the cost in the mild local climate.

The insulation is all 27cm of recycled newsprint pumped into the cavity. This type of eco-insulation is in general the most economic and ecological. The paint is clay-based – breathable and with no off-gassing. Although more expensive per litre, it requires fewer coats on bare plaster.

The houses all come fitted out with the most efficient washing machine, condenser drier, kitchen, water-saving bathroom with occupancy sensors in areas such as toilets, internet connection, Wi-Fi and an outside socket for charging an electric vehicle. There are LED lights throughout.

All of these relatively spacious homes are provided with the most energy-efficient appliances and exceptional attention to detail.

Communal electric car

The Nissan Leaf charging outside one of the houses.

The occupants of the estate have been given a Nissan Leaf to use collectively, charged by the solar panels on the roofs.

“It’s a way of getting neighbours to cooperate with each other and eliminate the need for a second car,” Peters says.

Energy storage

The South-facing homes are generous in their space, their form determined by the maximum depth allowed by the passive heating.

The rest of the heating is provided in a surprising manner, using the best of old technology with new: solar electricity and storage heaters.

An installed storage heater; proven, old technology meeting the new.

Storage heaters contain thermally massive blocks that are heated up by an element. They then release that heat gradually over many subsequent hours.

This form of energy storage was introduced to British homes in the 1960s and ’70s on a special tariff called Economy 7. Since nuclear power stations could not be switched off, unlike other forms of electricity generation, these tariffs allowed people to use nuclear electricity at night – at a lower rate when national demand was low – to charge the storage heaters.

The problem was that by the time the heat was needed, the following evening, they were often too cool and many people subsequently removed them and installed central heating instead.

Here, the idea is to let the storage heaters be heated up during the day by the solar panels on the roof, meaning they are able to provide adequate heating through the evening and night provided that there has been average sunshine (50 per cent of a June summer’s day) during the day.

This may not be the case in the depths of winter and so the homes are also grid-connected. They export surplus energy when there is some – after the electric car and storage heaters have been topped up – and purchase it when not enough has been generated.

“Storage heaters are incredibly cheap,” Peters says, “and a well proven technology. Whereas the storage we had to start with in the prototype house – lithium-ion batteries – were designated a fire risk and we had them taken out. They are also much more expensive.”

A pair of two-bedroomed semi-detached passive solar houses.

The prototype house has been monitored and has well exceeded the predicted generation capacity, providing twice the electricity used over the year.

Peters says: “We have spent £2 million (AU$3.5m) researching and developing a sustainable timber building system that is 100 per cent British, powered by solar energy. We hope now to create 1000 homes across Wales and the UK, once the current political uncertainty is out of the way and we have won the argument on the efficacy of timber housing.”

David Thorpe is the author of a number of books on energy efficiency, sustainable building and renewable energy, including:

• The Expert Guide To Energy Management In Buildings
• The Expert Guide to Solar Technology and
• The Earthscan Expert Guide to Retrofitting Homes for Efficiency.

Find out more and buy the books here.

UNEP backs Passivhaus to help meet climate targets

[This post originally appeared on The Fifth Estate website on 9 November.]

As the latest round of global climate talks begins, the UN Environment Programme is calling on nations to ramp up their action to reduce greenhouse gas emissions and is explicitly backing the use of the Passivhaus Standard to reduce emissions from buildings.

Thermal image showing how a Passivhaus refurbishment/makeover of a terraced home (the blue one) means it radiates (loses) no heat compared to its neighbours (red and yellow - meaning they are radiating heat. The more red, the more heat is being lost).

Delegates in Marrakesh for yet another climate conference, the 2016 UN Conference of the Parties (COP22), have been studying a report by UNEP on what the world needs to do to meet the requirements of the Paris Agreement and halt dangerous global warming.

COP22 is about following up the just-ratified Paris Agreement. The agreement marks a turning point in the history of the world, establishing both the commitment and the framework for dealing with climate change. COP22 is about fleshing out the detail, and there is a great deal of detail to be fleshed out.

The Intended Nationally Determined Contributions from COP21 form the basis of the Paris Agreement; they are the pledges that each country laid out at year’s negotiations, showing their contribution to tackling climate. But these presently fall well short of achieving COP21’s “well below 2°C” temperature goal.

The Emissions Gap Report

Just in advance of the conference the UNEP issued its “Emissions Gap Report“, which notes the “troubling paradox at the heart of climate policy”.

Erik Solheim

In the words of Erik Solheim, the head of the program, the paradox is that “on the one hand nobody can doubt the historic success of the Paris Agreement, but on the other hand everybody willing to look can already see the impact of our changing climate”.

(Everybody, that is, apart from the Republicans in the US who elected Donald Trump and his cronies. But that is another story.)

This report estimates that we are actually on track for global warming of up to 3.4°C – way over the target. The current commitments made by nations “will reduce emissions by no more than a third of the levels required by 2030 to avert disaster”, he says.

“So, we must take urgent action. If we don’t, we will mourn the loss of biodiversity and natural resources. We will regret the economic fallout. But most of all we will grieve over the avoidable human tragedy.”

Global greenhouse gas emissions continue to grow. UNEP is calling for accelerated efforts now, prior to 2020, and for nations to increase their ambitions in their INDCs.

“Pathways for staying well below 2°C and 1.5°C require deep emission reductions after, and preferably also before 2020, and lower levels of emissions in 2030 than earlier assessed 2°C pathways,” the report says.

The report does identify where solutions are available that can deliver low-cost emission reductions at scale, including the acceleration of energy efficiency.

Much has been said, including by myself, about the effect on emissions by actors who are not nations, such as cities, regions and companies. It’s possible, the report notes, that these could reduce emissions in 2020 and 2030 by a few additional gigatonnes, but it is difficult to assess the overlap with INDCs because these are not usually detailed enough and non-state actions can overlap or mutually reinforce each other.

The importance of energy efficiency

The report emphasises that ambitious action on energy efficiency is urgent. Well-documented opportunities exist to strengthen national policies on energy efficiency.

Studies based on the Fourth Assessment Report of the Intergovernmental Panel on Climate Change show that for a cost range of between US$20 and $100 per tonne of carbon dioxide, 5.9 gigatonnes of emissions could be saved from buildings, 4.1 for industry and 2.1 for transport by 2030. These estimates are conservative and the real potential in each sector is likely to be bigger.

A more recent analysis by the International Energy Agency indicates that the cumulative direct and indirect emissions estimates to 2035 are 30 gigatonnes for buildings, 22 for industry and 12 for transport.

The two studies are not comparable due to differences in approaches, but together illustrate the significant potential in the three sectors.

Improving energy efficiency also offers many other benefits like reduced air pollution and local employment.

It is an integral part of Sustainable Development Goal 7, which aims to “ensure access to affordable, reliable, sustainable and modern energy for all”.

The energy efficiency target is to double the global rate of improvement in energy efficiency by 2030, from 1.3 per cent per year to 2.6 per cent. Achieving this goal will be important for achieving many of the other goals:

• Building energy efficiency will be increased by ratcheting up the ambition of energy codes, and increasing monitoring and enforcement of building regulations with the use of energy performance certification and with encouragement to create highly efficient buildings.

• Industrial energy efficiency will be helped the more that companies introduce energy management by adopting ISO 50001 an energy performance monitoring. Energy performance standards need to be enforced for all industrial equipment.

• Transport energy efficiency is improved by the adoption of vehicle fuel economy standards and electric mobility for passenger transport. For freight movements sustainable logistics can be deployed.

There is a huge role for energy service companies to offer these services.

All of these efficiency savings can be encouraged by planning policy. For example:

• Successful zoning can reduce the need to travel, and neighbourhood layouts can reduce the need for heating or cooling.

• Spatial planning can help to improve transit options, increase and co-locate employment and residential densities, and increase the amount of green spaces.

• Heating, cooling and electrical energy services can also be more efficiently delivered at a neighbourhood scale than at a building scale, with distributed renewable or low-carbon energy supplied by local energy service companies.

The Passivhaus standard

The report explicitly advocates the adoption of the Passivhaus standard. Passivhaus, originating in Germany, is primarily a tough quality assurance standard, which demands great attention to detail during the design and construction process to achieve certification.

Key to it is a target that annual final energy use for heating and cooling should not exceed 15 kilowatt hours a square metre a year.

The report says that the global floor area covered by Passivhaus buildings has grown from 10 million sq m in 2010 to 46 million sq m in 2016, with most activity occurring in Europe.

And importantly, it says the price for new Passivhaus buildings in several countries is comparable to standard construction costs.

Initially developed for mid and northern European climates, Passivhaus has been proven to work extremely well in hot climates too. High levels of airtightness and insulation work equally well in protecting buildings from overheating provided there is adequate solar shading.

Controlled mechanical ventilation allows options to pre-cool or pre-heat the supply air and also to humidify or dehumidify the ambient air depending on the relative humidity. In combination these strategies are capable of significantly buffering the daytime temperature swing.

Conventional cross ventilation through open windows and night purge ventilation strategies may also be used as part of the Passivhaus cooling concept when appropriate, such as during the cooler evening of a hot day.

In order to achieve the Passivehaus standard in hot countries, the outer wall must have a U-value between 0.20-0.45 W/m2K.

Depending on the heat-insulating properties of the loadbearing outer walls and on the thermal conductivity of the insulation material used, it may be necessary to install an external thermal insulation system of up to 30cm thickness.

Modern external thermal insulation composite systems based on mineral raw materials combine the best insulating properties with ease of handling. Compared to conventional insulation systems, the additional expense pays off after only a few years.

In climatic regions where the daytime temperature does not drop low enough to purge the accumulated heat gains from the building at night there will be a residual cooling load.

In such cases the Passivhaus standard permits 15 kWh/m2.yr of cooling energy to be used. A small cooling load has proven to be sufficient in almost all cases because the Passivhaus concept is highly effective in reducing unwanted heat gains.

The blower door test is used to detect leaks in the building envelope. The smaller the measured value, the higher the airtightness. Passive houses in hot countries require a value =< 1.0. This means that during the measurement at most 100 per cent of the indoor air volume is allowed to escape through leaky spots within one hour. Experience has shown that values between 0.3 and 0.4 are attainable.

Passivhaus principles can also be applied to refurbishment of existing buildings and achieve impressive results. In the UK there are many examples of ultra-low energy, low carbon retrofits.

At the same time, the Passivhaus Institut has launched a Passivhaus standard for refurbishment projects, known as “EnerPHit”, covering a range of property types, including tower blocks, terraced houses and community centres.

Given that costs are around the same as for conventional buildings but energy costs of using the building are drastically reduced, why are they not more widely adopted?

The main reasons are the lack of ambition in building codes, the lack of awareness, trained construction workers and appropriate monitoring. For the aims of the Paris Agreement to be realised this is just one opportunity that needs to be grasped.

Since the US election, the need to grasp these opportunities has become even more urgent.

David Thorpe is the author of:

• Best Practices and Case Studies for Industrial Energy Efficiency Improvement (with Oung, K. and Fawkes, S. UNEP, 2016)
• A London Conversation: Business Briefing on Green Bonds (The Fifth Estate, 2015)
• The One Planet Life (Introduction: Jane Davidson. Routledge, 2015)
• Earthscan Expert Guide to Energy Management in Buildings (Earthscan, 2013)
• Earthscan Expert Guide to Energy Management in Industry (Earthscan, 2013)
• Earthscan Expert Guide to Solar Technology (Earthscan, 2011)
• Earthscan Expert Guide to Sustainable Home Refurbishment (Earthscan, 2010)

It's time to make carbon negative buildings the norm

Climate change has entered into a new phase that could last generations even if governments act to curb human activity that leads to global warming. But the Habitat III New Urban Agenda agreed ten days ago offers a chance for the built environment to become negative carbon. Buildings can now begin to withdraw carbon dioxide from the atmosphere. This article gives a few tips on how.

Globally averaged concentration of carbon dioxide in the atmosphere reached the symbolic and significant milestone of 400 parts per million for the first time in 2015 and surged again to new records in 2016 on the back of the very powerful El Niño event, according to a new bulletin issued last week from the World Meteorological Organization's annual Greenhouse Gas Bulletin.

"The year 2015 ushered in a new era of optimism and climate action with the Paris climate change agreement. But it will also make history as marking a new era of climate change reality with record high greenhouse gas concentrations," WMO Secretary-General Petteri Taalas said in a statement.

The data "predicts that carbon dioxide concentrations will stay above 400 ppm for the whole of 2016 and not dip below that level for many generations," the WMO said. “The El Niño event has disappeared. Climate change has not. Without tackling carbon dioxide emissions, we cannot tackle climate change and keep temperature increases to below 2^oC above the pre-industrial era. It is therefore of the utmost importance that the that the Paris agreement does indeed enter into force well ahead of schedule on 4 November and that we fast-track its implementation.”

The El Niño event triggered droughts in tropical regions and reduced the capacity of “sinks” like forests, vegetation and the oceans to absorb CO₂. Besides this it also led to an increase in CO₂ emissions from forest fires. According to the Global Fire Emission Database, CO₂ emissions in Equatorial Asia – where there were serious forest fires in Indonesia in August-September 2015 - were more than twice as high as the 1997-2015 average.

Habitat III's New Urban Agenda

But there's hope. Habitat III, which took place in Quito last week with around 36,000 people attending from 167 different countries, adopted the New Urban Agenda which, amongst other things, urges cities to tackle climate change.

Joan Clos, the Executive Director of the UN Human Settlements Programme (UN-Habitat), called the Agenda "a common roadmap for the 20 years to come” at the closing plenary of the conference.

Cities are both the source of most of the world’s carbon-dioxide emissions and the place where the most impactful interventions can occur — to reduce automobile driving, improve energy-efficiency in buildings and switch to renewable energy sources, among other opportunities.

“By making the Paris Agreement one of its antecedents and quoting its long-term goal, the New Urban Agenda is acknowledging the climate challenge in cities, and putting climate action at the core of urban policies at national and local levels — and that’s a good thing,” said Mark Watts, executive director of the C40 Cities Climate Leadership Group.

The agenda does not bind Member States or city governments to specific targets or goals, but is rather a “shared vision” that set standards for transforming urban areas into safer, resilient and more sustainable places, based on better planning and development.

The Quito Implementation Plan is now set up to support the outcomes of Habitat III and the New Urban Agenda.

Negative carbon buildings

Amongst the potential strategies to help with the Quito implementation plan is for building specifiers, developers and architects to generate buildings which are at least zero carbon on balance, when totalling the carbon impacts of materials, construction, use and demolition. But what does this mean?

Some features of zero or carbon negative buildings are to:

• minimise the use of fossil fuel energy during the supply chain and process of construction;
• encourage the use of materials which store atmospheric carbon in the fabric of the building;
• construct and manage it in such a way that it minimises the emission of greenhouse gases during its lifetime and eventual demolition;
• encourage the capture, generation and even export of renewable energy;
• make the structure very airtight;
• make the structure breathable;
• make it durable, resilient, low-maintenance, fire- and weather-resistant;
• incorporate a large amount of insulation. 

The ideal features of zero-carbon, solar buildings.

Such a building could, over its lifetime, become zero carbon, or even negative carbon by generating enough power to more than make up for the fossil fuels it has used and storing atmospheric carbon in its structure.

Neighbourhood design

From a planning angle, different neighbourhood layouts for developments are appropriate depending on the regional climate as shown in these figures:

 Hot climates: inappropriate (left) and appropriate (right) spatial layouts for settlements. Organic, non-grid layouts provide shade and can be designed to block winds, preventing issues with wind funnelling. Grid layouts borrowed from other climates, and wide spacing of buildings, do not provide shade or wind shelter.

Higher latitudes: in this housing estate each property has both privacy and an equator-facing aspect and roof to maximise the potential for the use of solar energy. Grey circles are trees, grey lines are hedges (preferably) or walls.

Carbon intensity

On average the carbon impact of the construction of conventional buildings is between 10 and 20% of their use during their lifetime. But it is self-defeating to construct a zero carbon building with materials that cause high carbon emissions in their manufacture.

Conversely it is ideal to use materials which lock up atmospheric carbon, for situations where well-performing and suitable alternatives exist, usually made from natural cellulose-based materials. (Plants absorb atmospheric carbon while growing and 'lock it up' in their mass.)

Steel is a possible exception, despite its high embodied carbon, as it is long-lasting, but many large and high-rise structures are now being made using frames made of timber products.

‘Natural’, ‘green’, ‘bio’ or ‘renewable’ building materials can be classed together as ‘cellulose-based’. Amongst their benefits are that they:

• lock up atmospheric carbon in the building;
• have varying degrees of insulation ability;
• are easy to work with;
• make structures that are breathable.

They are also biodegradable or easily recycled at the end of the building's life and may support local agroforestry.

Wood has a greater tensile strength relative to steel – two times on a strength-to-weight basis – and has a greater compressive resistance strength than concrete.

Sustainably sourced timber and timber products specially designed for structural use must be specified. These include glued laminated timber ('glulam') and Cross-Laminated Timber (CLT).

The tallest building in the world made with timber frame is 14 storeys high and is in Bergen, Norway. It uses metre-thick columns of glulam and CLT, plus two concrete decks above the 5th and 10th floors. See the video below.


Glulam can produce columns, beams and curved, arched shapes and has a much lower embodied energy than reinforced concrete and steel, although higher than solid timber.

CLT is an engineered timber product with good structural properties and low environmental impact able to provide dry, fast onsite construction, with good potential for airtightness and a robust wall and floor structure suitable for most finishes internally and externally. It requires only limited new site skills and can be assembled without the use of adhesives using mechanical fixing. Its low weight means that a high degree of offsite manufacture is possible.

Other useful timber products include:

• Plywood, wood structural panel;
• Oriented strand board (OSB);
• Laminated veneer lumber (LVL);
• Parallel strand lumber (PSL);
• Laminated strand lumber (LSL);
• Finger-jointed lumber;
• I-joists and wood I-beams – "I"-shaped structural members designed for use in floor and roof construction;
• Roof trusses and floor trusses.

Other natural carbon- negative materials currently used in construction include:

Material	Application
Flax	Roofing insulation
Hemp fibres	Insulation
	Medium density fibre board
	Oriented strand board
Hemp shiv	Monolithic construction ofwalls, floors and roofs
	Insulation
	Panel construction
Jute	Carpet
	Plastering mesh
	Scrim
Paper	Recycled and shredded forinsulation
	Mixed with cement to formblocks
Reed	Thatching
Reed mats	Plastering base (like laths)
Sisal	Carpet (mixed with reinforcedcement in some countries)
Straw	Bales as building blocks
	Wall panels
	Thatching

For reporting purposes, it may be useful to report the carbon storage capacity of a building, to add to the carbon saved from using renewable energy to heat and power it. For buildings a web-based calculator like the one on this page may be used.

Phase shifting Phase shifting is another useful tool for building designers. It denotes the time taken for an extreme external temperature to reach the interior, travelling through the building envelope.

The aim of passive cooling in hot, non-humid areas is to have a phase shift of 12 hours, so that the midday heat only reaches the interior in the middle of the night. With good amplitude dampening, its effect will also be very much moderated.

Some of the stored energy in the fabric is thus automatically transferred back outside, ensuring that temperature fluctuations and extremes on the inside are much less than outdoors.

Amplitude dampening and phase shifting should be particularly observed in roof areas. These may get very hot and so require large thicknesses of insulation with low thermal diffusivity. Aim for an amplitude dampening value of 10 (TAV 10%) and a minimum phase shift value of 10 hours.

There is now no excuse for building specifiers and designers not to give us at least zero carbon buildings.

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David Thorpe is the author of:

• Best Practices and Case Studies for Industrial Energy Efficiency Improvement (with Oung, K. and Fawkes, S. UNEP, 2016)
• A London Conversation: Business Briefing on Green Bonds (The Fifth Estate, 2015)
• The One Planet Life (Introduction: Jane Davidson. Routledge, 2015)
• Earthscan Expert Guide to Energy Management in Buildings (Earthscan, 2013)
• Earthscan Expert Guide to Energy Management in Industry (Earthscan, 2013)
• Earthscan Expert Guide to Solar Technology (Earthscan, 2011)
• Earthscan Expert Guide to Sustainable Home Refurbishment (Earthscan, 2010)