Eco House Design for a Self Build Project

This project is for a simple self build eco house. In the spirit of collaboration, which was sustained throughout the project, the client, project manager and architects share their perspectives below in the hope others may find encouragement to follow their dreams too.

Client Perspective

We have just swapped several of our spare pallets for manure from our neighbour, a smallholder. At last the potential of turning our clay mud patch into a lush permaculture plot seems to hold practical promise. We have lived in our new eco-house for 11 months now and at time progress has been very slow – we are still working on our drains. We had long held a dream to build somewhere that not only reduced our environmental impact and facilitated a more environmentally-friendly lifestyle, but would also dramatically reduce our running costs and increase our resilience to climatic uncertainty.

Deciding to build an eco-house with my mother generated a surprisingly number of shocked responses from friends and family. They variously thought Maggie to be too old (she was only in her late 50’s) for such a challenge, and that she would cramp my life choices. Few understood how our skills, ideas and dreams complemented each other. Maggie had explored the idea of living in existing communities and we met with others interested in establishing new eco-co-housing schemes. But we realised we did not want to wait for the slowness of collaborative enterprises and that living together would provide enough challenges, and entail new ways of working together as it was.

Wymondham Eco House in Leicestershire
eco house build
super insulation

We have taken a very pragmatic approach to the build. Inspired by the Centre for Alternative Technology and the Autonomous House we started with a utopian vision which was quickly scaled down. Our choices have been very much shaped by financial and practical limitations and a desire to complete the project so that we could get on with living the way we wanted to. We were determined to prove that older people and those with full-time jobs could still self-build and be eco. Although we had a sizeable budget it was also only slightly more than the average house price (which stood at £219,262 at the time) and we had no back-up plan.

This budget bought us a small (10th of an acre) triangle plot in rural Leicesterhire, near Melton Mowbray. By facing south the house makes the most of passive solar heating through large A rated timber-framed windows, with thick dense block walls (made from 100% recycled aggregate) creating a high thermal mass (with sheepswool insulation in the roof) and reducing noise and vibrations from the abutting railway line. We wanted to build a house that was cheap to run and simple to maintain, only using technology we could understand and if necessary learn how to fix. The house remains at around 17 C without heating, even in winter, though we do have a Clearview wood stove as a back-up. Our solar thermal evacuated tube arrays also work all year round, and when the sun is not shining we heat water either by the wood stove or an efficient electric immersion. Our rainwater harvester feeds the toilets (low-flush IFO CERA from the Green Building Store) and washing machine, and we have low-flow showers to reduce water use. Energy use is much reduced by an induction cooker, A+ appliances, low-energy lighting and the bright aspect reduces the need for lights to be on.

We tried, wherever possible, to source reclaimed, local, and untreated material. Our reclaimed pitch-pine floors came from an old Liverpool factory via the local salvage yard, our reclaimed-pine kitchen units and internals doors were made in Lincolnshire, our Douglas Fir deck has been left untreated, our jute and wool carpets were ordered from the local shop. We, of course, carried on using existing furniture, rescued some pieces from a tip, made some new pieces with help from my father, and added colour by painting tiles ourselves.

We developed some golden rules during the build: we would choose environmentally-friendly products over visual looks; we could not buy anything for the house without mutual agreement; we would worry more about cost than time taken to complete things; local suppliers and workforce were best; just because it was not the conventional way of doing things did not mean it would not work.

 self build eco house
low energy eco house
eco house self build

We struggled, at times, to communicate to others what we meant by eco: it took a while for my dad to understand reclaimed, native, or FSC wood and eco-varnish; the plumbers questioned what our washing would turn out like if we used rainwater; and the painters objected to using Osmo and ECOS paint. Early on we met plenty of patronising builders who advised us to ‘forget all that eco-stuff’ and raised eyebrows when they understood we were two women building a house. But with a highly supportive eco-architect (Andrew Yeats of EcoArc) and a knowledgeable project manager willing to engage with eco-ideas we eventually found suppliers and stockists of the things we needed. My partner, friends and family were invaluable in helping us complete the build – with seemingly endless shelving to put up, a woodshed to build, furniture to strip, and gardens paths to lay. Since moving in a local carpenter has agreed to drop off his off-cuts which we use to supplement our homemade newspaper logs and purchased logs for the wood stove, and a neighbour has offered us free seedlings for our garden. Our house has started all sorts of conversations and we have often invited in passers by who have stopped to ask us questions.

At times we have to remind ourselves why we made certain compromises (often due to a lack of money or plot space) and get frustrated that we do not yet generate our own electricity. Now the project is almost complete we have the confidence in our choices to wonder if we couldn’t have been bolder in some of our earlier decisions. Externally the house has a big visual impact on the landscape (ironically a result of the planning permission which stipulated that it replicate the look of the previous house demolished by Network Rail). We have tried to mitigate this impact by covering the lower external walls with red cedar cladding and choosing a dark slate-effect roof (using Ardesia recycled tyre roofing), but we could have been more radical in our design. We now have the confidence to follow our gut instincts and compromise less in our search for environmental solutions. We only hope that our house will inspire others to follow their dreams too.

Project Managers Perspective

Taking on the project management of an eco build was of real interest to our company, we have managed projects of all types and size, the learning curve was much steeper than we thought as sourcing eco materials seemed to be an excuse for increasing the costs, whether it was fsc timber, sheeps wool insulation or recycled aggregate blocks, we had to work hard to get the prices as low as possible and meet delivery schedules. The one aspect that we would do differently would be the selection of and the management of the sub contractors with relation to eco builds and their time schedules as we lost about 9weeks arguing over the floor and roof timbers and this put the rest of the project under pressure. We think that the end result achieved what Maggie and Jenny and Andrew and Eric from Eco Arc wanted and we are proud of the overall achievement.

Architects Perspective: Building Fabric

The client’s aspirations for a low energy house were primarily addressed by designing a relatively compact, well-insulated and air-tight building fabric. The chart below gives an overview of the fabric U-values and air permeability goal for the Gate House compared with the AECB Silver Standard and the 2006 Part L Building Regulations requirements.

Building Element Gate House Design Values AECB Silver Standard UK Building Regs 2006 Part ADL1
Ground Floor 0.23 Wm2K 0.20 Wm2K 0.25 Wm2K
External Walls 0.23 Wm2K 0.25 Wm2K 0.35 Wm2K
Roof 0.18 Wm2K 0.15 Wm2K 0.20 Wm2K
Windows ≤1.4 Wm2K (uninstalled) ≤1.4 Wm2K (uninstalled) ≤ 2.0-2.2 Wm2K
Doors 1.5 Wm2K ≤1.0 Wm2K ≤ 2.0 Wm2K
Air Permeability 3m3/ m2hr @ 50 Pa 3m3/ m2hr @ 50 Pa 10m3/ m2hr @ 50 Pa

The strip foundation footings support a perimeter blockwork cavity wall with 200mm of mineral wool insulation. The ground floor slab was overlaid with 100mm EPS insulation and a screed (with 25mm of perimeter EPS insulation to minimise thermal bridging along the edge of the screed) was laid on top of this to provide the substrate for the timber boarding on the ground floor. The intermediate floor and traditionally cut roof are both timber framed and the roof is insulated with 250mm of sheep’s wool insulation. The solid external doors were insulated and the windows were low-e, argon-filled double glazed units.

Heating and Ventilation Systems

The brief from Maggie and Jenny was to design a house that was cheap to run and simple to maintain and only use technology that they could understand and maintain. These key principles influenced the choice of the heating and ventilation systems.

Mechanical extract ventilation using low-watt fans was chosen over a passive ventilation system primarily to keep the ‘fear factor’ for both builder and client low. Passive ventilation was considered but was dropped as it would have been more difficult to integrate into the blockwork partition walls without visible ducting in several areas.

Maggie and Jenny are both ‘hands-on’ and were happy to use a (12kW Clearview 650) woodburning stove with a back boiler as their main heating source. Approximately 4m2 of evacuated tube solar hot water panels also assist in heating the hot water in a twin-coil cylinder.

Energy and Water Use

Maggie and Jenny are nearing their first full year of living in the Gatehouse and have undertaken some very basic monitoring of their energy use and intend to continue doing so in more detail in the coming year. The following assessment is based on a combination of information provided by Maggie and Jenny and some educated predictions based on the information currently available.

Water

Up until February of this year, the Gatehouse didn’t have a water meter and at the time of writing this article the first water bill hadn’t arrived. The main water saving features in use at the Gatehouse are a rainwater harvester (feeding the toilets and washing machine); low-flush Ifo Cera toilets; low-flow shower heads.

Fuel 

The main fuel source for the Gatehouse is timber. Maggie and Jenny paid £100 for two deliveries of logs plus used left-over timber construction waste (say £50 worth) for a total of £150 worth of wood. At 2p/kWh this would equal 7500 kWh for space (and some water) heating.

Electricity 

The electricity use for the first 9 months of occupation at the Gatehouse was 4000 kWh. This is an average of 444 kWh per month or approximately 5333 kWh per year.   This figure translates to 48 kWh/m2yr. This figure is above the average and the client is aware of several issues that have possibly contributed to this: use of electric induction cooker; occasional use of an electric immersion heater; washing machine is cold fill only and requires occasional electric heating. It is also likely that a fair amount of this extra usage has been due to the drying out of the building during its first year of occupation.

User Feedback and Project Summary

Now that we have analysed the predicted energy performance how does the house fare for the clients? The passive solar design combined with the higher levels of insulation have created an internal environment that, according to Maggie and Jenny remains at around 17° C, even without heating in the winter months according to the clients. The use of rooflights ensures high levels of daylighting which has significantly reduced the need for lighting during most times of the day.

The build has been challenging for Maggie and Jenny from the beginning meeting resistance and scoffing from some of the patronising’ builders who advised them to ‘forget all that eco-stuff’ and raised eyebrows when they understood they were two women building a house. Later on during the project, Maggie and Jenny were questioned by the project plumbers on the use of rainwater to wash their clothes and the decorators were equally sceptical of the (Osmo and ECOs) low-voc and water based paints and wood treatments.

Even though Maggie and Jenny encountered resistance from various points throughout the project, one area where there was the risk was using a project manager instead of a main contractor. As with any separate trades approach, that the potential lack of quality control would create real difficulties in achieving the client’s high ecological aims. In the end, Oliver Hemlsey, the project manager and main blockworker, Nick Walling were more enthusiastic and eager to learn and provide proactive advice when required. In the end, having a project manager with not much of a track record of ‘eco-builds’ was not really an issue on this project. In summary, the most important keys for the successes in this project are:

  • Client commitment and enthusiasm.
  • Simple and effective design.
  • The project manager was committed and had an open, proactive attitude.
  • Construction methods that were straight forward.
  • The key site workers produced work of high quality and were eager to understand and learn about the alternative approach.
  • Early and consistent setting of standards to be achieved and clear explanation of why the quality matters / what is important to the performance and aims.

Text by Jenny Pickerill, Oliver Hemsley & Eco Arc