At last: the affordable solar house that makes a profit for residents

Glen Peters is a man with a mission to show how truly sustainable and affordable housing can be a solution to the housing crisis. Having made a good profit from a solar farm in his field (seen behind the house in the picture above) he's putting it to good use and demonstrating a new model for sustainable housing.

Working with a team of architects and designers he has produced a prototype two-storey detached three bedroomed house with a radical new take on passive house principles. Called Ty Solar (Solar House in Welsh) it is of timber frame construction and insulated with blown cellulose; and is potentially able to export more electricity to the grid than it consumes itself in a given year.

The larch used for the frame and cladding is sourced locally and assembled to specifications that are beyond those required by Building Regulations, giving it a Code for Sustainable Homes 5 rating (out of a maximum of 6). But this doesn't tell the whole story by any means.

By using recycled newsprint (the blown cellulose) as the only insulant around the entire building envelope and local timber, the house is locking up atmospheric carbon in its structure for an indefinite period, unlike buildings that use fossil fuel-based insulants that have emitted carbon during their manufacture.



The embodied energy of the house is therefore already very low, an important factor given that for normal buildings between 10 and 20% of their life-cycle energy consumption is used during the phase of extraction of raw materials and construction.

The final purchase price has been set at a maximum of £75,000. The principal watchword throughout the design process that has enabled this to be possible has been simplicity.

Almost heretically for passive house construction it eschews ventilation and heat recovery, and the only source of energy is solar: both passive solar through the abundance of south-facing windows and active through reliance on solar photovoltaic panels for electricity and top-up space and domestic water heating.

The demonstration house includes lithium iron batteries to store 12 kWh of power but is also grid connected to enable the export of unused electricity and the use of the grid as a backup at other times.

The battery bank is optional and really only for stand-alone houses. Glen says: “A group of 10 or more houses generating in tandem with a local smart grid could form a miniature power station and generate a considerable income, perhaps £1000 per year, for each of the households, or the power could be used to charge electric vehicles which could be shared between them."

Research commissioned by the Welsh Government estimates that over 14,000 new homes are needed every year in Wales for the next 15 years.

The hunger for affordable housing is reflected in lengthy waiting lists and increasing official homelessness figures. Wales' Minister for sustainable development has made the provision of affordable housing a high priority during his tenure.

All of this highlights the urgent need for houses of this nature. As Glen Peters says: "The bulk housing providers in the construction industry are ignoring affordable housing. They say that it doesn't work for them. I say they are missing a trick. We've proved it is perfectly possible to build low carbon housing that is truly affordable and that gives occupants zero energy bills."

With energy bills so high on the public agenda it is hard to see how local authorities and housing associations can ignore the potential that this house demonstrates.

Low embodied energy

This successful and attractive-looking house goes against the grain in terms of many of the current developments in sustainable housing.

Compared to the Mark Group's demonstration house in Nottingham, BRE’s ‘Smart Home’, in Watford, and Velux’ CarbonLight demonstration home in Rothwell near Kettering, it scores very favorably on local sourcing, embodied energy, embodied carbon and simplicity of use. Above all it compares well on price.

All of these three supposedly cutting-edge demonstration homes contain extreme amounts of technology and sophisticated materials.

They represent corporate attempts to capture a high-end market in low or zero carbon housing.

The first utilizes an incredibly energy intensive over specified steel frame.

The second uses occupation sensors to control heating, lighting, ventilation, water and security, as well as heat pumps, solar thermal and PV.

The third is designed to be iconic in its extremely unusual shape and therefore expensive to reproduce. All of them make heavy use of smart electronics. And this is what puts up their price.

But although they may score highly on low operational energy use this does not make them necessarily sustainable.

The real target of sustainable housing should be overall life-cycle impact. This means that in fact small homes that are zero carbon in operation, whose materials are sourced locally and are of low embodied energy, preferably built in bulk and perhaps in a compact urban terrace or block, will be inherently more sustainable than stand-alone large homes packed with different technologies and comprising a high embodied energy.

This makes Ty Solar's closest antecedent perhaps the ecological evolution of Walter Segal Method timber frame construction, as pioneered at the Centre for Alternative Technology. The Segal Method was, pointedly, devised by its architect to produce affordable homes.

Even the low pitch of the roof is designed to minimize the heated but unnecessary interior loft space and increased requirement for materials that are result of higher pitched roofs, while still permitting the solar panels which the roof supports to take advantage of solar radiation.

The larch cladding will protect the building for years to come with minimum need for maintenance. The fact that it is screwed on in panels also makes it easier to access the interior of the walls if needed.

The Passivhaus certified windows and doors are even made locally rather than in Germany.

The house sits on footings raised slightly above the ground to remove the need for unnecessary concrete in foundations.

“Gareth, Jens and I come from very different worlds but we're united in our goal to be a disruptive influence of traditional thinking about building homes. In this, manufacturing becomes a key component and we see ourselves as manufacturers rather than builders,” says Glen. “We have created a lot of goodwill in our community and hope to continue to do so as we expand, creating local jobs, sourcing locally and above all keeping things small."

The test is whether day-to-day the homes do result in their occupants reducing their energy use and bills. This depends on their habits.

To this end simple controls will be easier to manage (see picture above right).

Some developers seem to believe that the occupants need a degree in energy management in order to keep down their running energy and carbon costs. Utility rooms contain a bank of sails and buttons worthy of the cockpit of the Star Ship Enterprise.

Ty Solar, by contrast, scores highly on ease of use since ventilation is controlled just by opening windows when required, and space and water heating is controlled in the traditional way, with thermostats. There are no other controls.

The house has not been formally tested for Passivhaus criteria, nor does it mean to be. It has also yet to be independently pressure tested.

It is a trial house that will be monitored for one year. However, with two floors each of 44.16 square meters and a volume of 254 m³ it has achieved a SAP rated figure of 0.12 air changes per hour.

This compares very favorably to the Passivhaus standard of 0.6 a change as per hour or a permeability rate of 3.0 m³/m²h. Over a 200-day heating period, a typical British house with eight air changes per hour and a 100m2 floor area, heated to 20°C, will cost thirty times more to heat than an equivalent house with 0.3 air changes per hour, according to an energy calculator (SIGA). The SAP-rated space heating requirement of this house is just 32.39kWh/m²/year.

This high performance is shown by the U-values, which are as follows:

Element	Average / Highest W/m2K	Maximum permitted W/m2K	Passivhaus standard
External wall	0.13	0.30	0.25–0.16
Floor	0.13	0.25	0.18–0.12
Roof	0.14	0.20	0.13–0.09
Openings	0.90	2.00	0.85

It can therefore be seen that the house, according to the SAP ratings, compares favourably with Passivhaus.

LED lights are fitted throughout, making the annual lighting consumption just 371.49kWh. With no pumps or fans, there are no further electricity requirements over and above that which is used in day-to-day living by a family in any home – for appliances and gadgets. It is therefore predicted by the SAP rating to have a negative energy use of -3253.56kWh (minus appliance use) and negative carbon dioxide emissions of -596.92 kg/year.

All of this means that the Energy Efficiency Rating on the EPC goes off the scale at 107, with an Environmental Impact (CO²) rating of 108. In the Code for Sustainable Homes assessment it reaches Level 5. The SAP Assessment also predicts that there will be only a medium likelihood of a high internal temperature, or overheating, in July and August, which can easily be catered for by opening the windows.

"We've just bought a 400m² cow shed to convert into our factory so we intend to minimize the impact on the land. We turned down offers of a brand new shed on a business park,” adds Glen.

Future houses could be semi-detached or terraced, and have one, two or three bedrooms, as demand dictates and housing associations or local authorities wish.

Clearly, Glen Peters is a man with an eye on the future - a sustainable future.