Green building

Selfbuild Your way to a great eco-home

Self builder, Sarah Villers, has recently completed a spacious detached, 3-bed eco-home. It took three weeks to erect the timber panel frame, including the windows and roof membrane, so making it almost weatherproof. It then took a further three months to complete the rest of the project. It was a fast build. Being fast, it reduced labour costs, though work was pretty intensive and was achieved through plenty of goodwill and very positive cooperation…

applying lime render

From the outset the design of my new ecohome was intended to achieve certain goals:

  • build an ecologically sustainable home
  • use a simple cost-effective design
  • incorporate locally sourced materials where possible (and appropriate) to reduce C02 transport emissions
  • work with local professionals and advice centres as much as possible
  • provide a modest residential example to stimulate the spread of building for a sustainable future
  • incorporate recycled materials where possible.

I chose to use a lightweight timber structure to reduce embodied energy of materials used, with extra insulation to reduce energy use and to lower living-costs. I also wanted to reduce my reliance on imported water so I chose to include rainwater collection to use for toilets and washing machine.

Techniques

To achieve these gains, I used a quick timber frame and partly timber-clad construction. This also had the benefit of minimising the inconvenience time to neighbours. Externally, larch cladding was used on the upper storey and horse-haired lime render on traditional oak lath (see left) on the external of the ground floor walls. The roof was clad with dark grey roof tiles made from recycled car tyres. To reduce energy needs, high levels of recycled cellulose (Warmcel) insulation was used. Also large areas of south-facing double-glazed windows for passive solar heating were incorporated. An integrated solar panel and wood pellet boiler produces hot water and underfloor heating.

The building land is a south-facing, rear 'brown' infill plot which was found with existing outline planning permission (previous use: two nissen huts for cycle and car maintenance). The site is located at the edge of the village boundary, overlooking a meadow and orchards. My plan was to build a simple, single-ridge, rectangular footprint home (12m x 7m) divided into three equal bays (4m x 7m) (north-south) to maximize passive solar gain.

Layout

View showing upper living room
The upper living room with wood burner

As you might expect the layout of rooms in a passive solar home is quite important, so here are the details.
Downstairs: (centre bay) entrance hall; utility; (west) full-depth kitchen-diner and (east) study at the front, guestbed plus ensuite at the rear.
Upstairs: (central) stair-well and bathroom; (west) open living-area rising into the roof void with rear balcony effect gallery continuing over central first floor landing which leads to two bedrooms front and rear (east).

Support

The South Somerset District planning department was very supportive from the start. Before I bought the land, I approached the officer for the area with my design and was encouraged by the positive reaction. However, despite not being a conservation area, it was clear that support was dependent on the plot not fronting onto the road which was mostly lined by stone houses.

Support also came from The ECOS Trust (formerly the Somerset Trust for Sustainable Development), which gave plenty of helpful advice on materials, techniques and sources. The Trust also suggested a number of local architects, one of whom, Mark Orme Architects of Street, agreed to take on the project. They, in turn, suggested the building partnership Thomas and Thomas of Glastonbury who took on the task of main contractor. This was a very lucky break for me as without their initiative and drive the whole build would have been so much less successful - and much less enjoyable.

There is plenty of information around from a multitude of organisations and loads of product websites. The difficulty was more in keeping up with all the new products and weighing the possibilities rather than finding things in the first place.

The building

The finished house showing
the larch cladding
and lime render

The structure of the building is an open timber-frame built off -site and hoisted into place on prepared foundations.
External walls: beneath the shiplap larch boards laid horizontally and the render is Bitrock boards (warm and 'breathable'). The inside face of the wall is covered with oriented strand board (OSB) for structural racking and strength, then plasterboard.
Internal walls: covered with just plasterboard.
Insulation: the walls and roof are insulated with Warmcel recycled newspaper (contains borax salts as fire retardant), 140mm external walls and 90mm in internal walls, all wet blown. The roof is dry-blown 220mm between joists, held in place by OSB (also anti-racking).
Floors: the ground floor is dpm laid on a concrete raft/125mm insulation/ underfloor heating pipes/85mm screed/14.5mm ceramic tiles for additional heat-retaining mass. The first floor is 50mm Warmcel within floor joists/22mm chipboard/rubber matting (recycled car tyres) for acoustic purposes (Part E)/layer of reflective heating mat/underfloor heating pipes between 2 x 1 battens (landing and bathroom only)/18mm chipboard/birchwood veneer click-and-fix flooring. No heating thought necessary, floors covered with cork tiles.
Roof: is a breather membrane/2x2 battens/'Ardesia' tiles made from recycled rubber and crushed limestone. The garage roof is fl at, covered with a metal profile sheet (water and root proof), covered with a mixture of peastones, peat substitute and soil for sedum planting.

Renewable energy

Heating: the underfloor heating system is heated by an Extra Flame Luxrezia Idro pellet-burning boiler which can provide up to 22kW of heat output to the central heating system. Hot water production is assisted by a roof-mounted solar panel. The upstairs living-room has a wood-burning log stove.
Electricity: a 2.5kW (11-metre high) wind turbine had been intended, (with excess electricity to be sold to grid) but was suspended (see later) because of neighbours' petition.
Water: a rainwater harvesting system was installed to reuse water for toilets and for the washing machine. Rainwater is collected in two 1520 litre above-ground tanks which are reclaimed orange juice tanks.
Windows: double-glazed windows with 26mm argon filled units and side vents.
Kitchen: 'A'-rated appliances - oven, cooker hood and fridge
Bathroom: nothing special here. I just got it from a national distributor.

U values

External temperature: -3 Deg C
Internal temperature: +18 Deg C – 21 Deg C

Walls and floors 0.2
Roof 0.15
Windows 2.0
Solid wood doors 3.0

The build team

Everything went remarkably smoothly because of plenty of goodwill, good networking and good organization. I was on-site, living in a tent, so I could participate as much as my low level of skills allowed. It also meant that I was on hand to discuss issues as and when they arose. Timing and dovetailing of the different stages was slick which kept up the momentum and allowed a fast finish. The flexibility and adaptability of everyone on site made the whole process very enjoyable.

Livability

Internal view of house

Last autumn was extremely mild. It was hardly a test of the effectiveness of the heating systems or the pellet boiler! However, the solar panel is doing a great job by heating plenty of hot water for showers. It is, however, a good test of the high levels of insulation which is keeping the house remarkably consistent in temperature without the boiler being needed. Most rooms are between 18 Deg C at night and 21DegC by day, and that is with the special ventilation slits in the window frames set at open during the night and often windows opened by day.

When the cold winter spells came I found I was burning a bag of pellets each day (£2.75 per bag) to maintain an indoor temperature of 18-20 Deg C with the boiler operating at a low setting for most of the day. The slightest bit of sun made a noticeable difference to room temperatures because of the large south facing windows.

So far, family visitors have all found the spaciousness and 'feel' of the home to be welcoming and have also liked the effect created by the interior wood in the doors, upstairs birch floor, staircases, gallery and balcony. This is dramatically increased by the tree feature standing 'straight and true' at the corner of the staircase which soars into the void and supports the roof beam.

Problems Problem one: wind turbine

Some of the immediate neighbouring households were against the wind turbine and organised fierce local opposition. The parish council meeting was heated and the turbine firmly rejected. The planning office received many letters (at best wanting more information and at worst raising many ill-founded notions). At the district meeting it was difficult in my allotted three minutes to address all the points raised by a seven person delegation of opponents. The district council therefore rejected it. So, the wind turbine has been shelved.

There are important lessons to be learned from this about how to introduce new ideas to a sceptical community? Unfortunately, not, being a resident at that time, there seemed little I could do to counter the rumours and misleading information. Despite my architect giving clear facts at the parish council meeting and myself trying to do the same at the district council meeting it was difficult to take effective rearguard action to counter rumours once they have been spread.

I should have taken note of the tactics adopted by a primary school in Seaton, Dorset. The school held open meetings where local experts could give a presentation, any member of the public could ask questions and issues become resolved to such an extent that, in a built-up residential area, within the primary school boundary, a turbine has been successfully installed with no enormous fuss or fears. Hence we learn the importance of giving accurate information before mis-information is spread about innovations of which people are naturally anxious.

Problem two: the foundations

We hit a problem at the start. It turned out that the ground had been quarried and back-filled with compacted sticky clay. My intention had been to use the Walter Segal method of pad and beam foundations. However, the structural engineer and building inspector both agreed that the foundations would need to be a raft of reinforced concrete. This seemed to me anything but 'sustainable', but regulations are regulations and we had to concur.

Conclusions

I believe that homes built in this way are fast and no more expensive than traditional builds (in some respects cheaper) and a great deal more sustainable. Such 'breathing' homes create a positive ambiance and a healthy environment. If more planners supported eco-selfbuilders and more individuals and organisations networked, it would be possible to show the industry a way forward. Government grants help, but a stronger line needs to be taken with the mainstream industry to require more of these known technologies to be incorporated in larger scale, multi house projects.

Sarah Villers


This article has been reproduced with the kind permission of the Green Building Press. It first appeared in the Green Building Magazine (formerly Building for a Future). The Green Building Press is dedicated to promoting sustainable and environmentally responsible construction. Copyright © Green Building Press