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David Johnson’s Zero CO2 / Autonomous Eco House.
South elevation onto the timber deck and garden
 
We first worked with David to convert a coach house at Lam Rim Monastery into four meditation retreat apartments and then he asked us to design the UK’s first autonomous Masonite framed eco house.
 
David's house is a low embodied energy, super insulated, timber frame construction using 300 mm Masonite I studs, joists and rafters.
The house is conceived as an integrated closed loop system within the boundaries of the site and is self-reliant in terms of renewable electrical supply, space heating, hot and cold water supply, and biologically processes human waste streams to fertilise its edible landscape.
 
It includes green oak structural timbers to the roof, super insulated breathing construction with one foot'' of recycled newspaper cellulose insulation, a 2 storey triple glazed conservatory and a mixture of new and recycled local natural materials finished to a high specification.
 
Electricity comes from a wind turbine and solar photovoltaic panels. Cold water comes from collecting and purifying the rain. Hot water comes from the sun via solar hot water evacuated tubes. All foul water is naturally treated and recycled on site. Organic, non-toxic finishes where used throughout the house to create a healthy interior environment.
 
House view from the woodland garden
 
Passive solar sunspace off the staircase
 

Introduction To A Sustainable Way Forward

 

David's house attempts to create a non-exploitative, symbiotic integrated eco system of human habitat in harmony with the natural world.  The house expresses an awareness of the ecological imbalance of conventional housing based on linear thinking, where resources are taken, used and thrown away as garbage.

 

The autonomous house has adopted the notion of Eco-cycles which attempts to integrate human settlement and nature in a sustainable way, where resources consumed are vigorously considered, and used as efficiently as possible, in such a way that the resource can be reused or recycled again without creating pollution or garbage. This awareness of the cyclical nature of the eco-systems offers a demonstration of  a sustainable way forward in which we can live as a species in harmony with ourselves, our neighbours and the natural world which supports us.

 

Super Insulated Building Fabric

 

The super insulated breathing walls, floors and roof have 300 mm of blown cellulose fibre made from recycled waste news paper between Masonite I beams to give a consistent all over fabric U Value of 0.12 W/m2k.  The windows are Low E Scandinavian triple glazed to give a centre pane U value of 1.1 W/m2k.  Cold bridging is avoided with careful detailing around all reveals.

 
The Masonite I members comprise of solid 47 x 47 mm timber flanges and 8 mm K40 hardboard webs.  This makes more use of a tree than does log conversion for solid timber and can utilise forest thinnings and lower grade faster growing species.  The Masonite I members are guaranteed to be straight, strong, light, (using 65% less raw material than conventional timber) and energy saving giving a K value 15% better than a conventional wooden frame. All other timbers for external cladding, exposed structure and internal floors and wall cladding will be recycled from an existing chalet on the site or sustainable sourced indigenous green oak or Douglas fir from local Welsh woodlands.
 
Green oak arched braced truss to the mezzanine
 

On Site Renewable Electrical Supply

 

The 20 m2 solar electric array of BP Solarex photovoltaic panels produces 2kW peak output. The PV panels are mounted on a simple Douglas fir garden timber trellis which permits optimum solar orientation without compromising the building and provides optimum performance by avoiding excess heat build up. The panels at ground level can be cleaned / maintained and can be easily extended if after the first year's monitoring this appears necessary.

 

Due to the seasonal and day-to-day fluctuations in any solar array output the system is complemented with a matching 2.5 kW Scottish made proven wind turbine. The combined wind and solar provision will give a more consistent and steady supply of renewable energy with the ability to adapt to seasonal variations. To ensure a back up electrical supply, if the sun isn't shining and the wind isn't blowing a 48V, 12 kWh useable battery store is provided.

 

Local Rain Water Harvesting For All Household Requirements

 

All household drinking and washing water requirements are met by collected rain water from the main slate roof via copper gutters and down pipes and stored in a 8m3 integral tank in the storage under croft.  Water is then plumbed through a 5-micron cartridge filter and a UV. steriliser to a 200 ltr holding storage tank in the roof loft.

 

Embodied Energy

 

Cradle to grave embodied energy costs are difficult to determine, but concrete and brick masonry buildings rely on excavating from the earth finite natural resources, which cannot be replaced. In comparison timber is a totally renewable resource if it is carefully and sustainably managed. At David's house ten times the number of trees used to make the house will be planted on the site to ensure that overall there is a net environmental resource gain. This clearly cannot be replicated with heavy weight masonry buildings.

 

For a typical masonry house the embodied energy measured in delivered energy is about 6.5 J/per m2 and only 1.2 J/m2 for a timber frame house, which compares with consumption in use for a mid terrace house predicted as 39.8 GJ/per annum. 
 
Natural timber staircase into glazed sunspace
 

Healthy-Internal Environment
 

The breathing construction where the vapour barrier is removed and the permeability of the layers in the fabric reduces toward the outside creates a vapour hydroscopic envelope without the risk of condensation.  Scatter rugs over waxed timber floors, organic paints and stains to walls, avoidance of formaldehyde and equivalents combined with natural materials and a Passivent natural ventilation system will lead to a healthy internal air quality.

 

Energy Performance

 

The house has a calculated Standard Assessment Procedure rating (SAP) of 100 and a National House Energy Rating (NHER) of 10 both of which are the maximum rating achievable on the scale. The building fabric heat loss at 21 degrees internal temperature and a 0 degree external temperature is 2.55 kW’s.

 

Conclusion

 

The super insulated timber frame construction following Scandinavian and Canadian best practice indicates that it is suited to sustainable autonomous housing in our temperate climate. The improved embodied energy figures and quick thermal response of timber construction can however be offset against the improved thermal mass characteristics of heavy masonry construction.

 

David's house makes a valuable contribution to the sustainable housing debate and demonstrates a successful attempt to create an integrated eco system of human habitat in balance with the natural world. It points to a future possibility where whole community based housing projects could be positive energy producers rather than negative parasitical energy consumers.  The implications if taken at a larger scale could dramatically improve the environmental imbalance of our co-habitation with the earth that sustains us.

 
Lobby space between dining room and staircase
 
We have been honoured to develop our friendship with David and delighted to receive 4 national design awards for the house and have enjoyed been involved in making 3 television programmes about this innovative autonomous home.
 
 
Click on the logos below to visit the websites
 

 
Triple height glazed sunspace viewed from across the reflective Buddha pool
For more detailed information please read on:
Until recently the idea of living in low impact zero rated autonomous housing has been considered impractical within our UK damp temperate climate. However David’s House indicates a viable way forward in which we can live autonomously and sustainably utilising renewable resources sun, wind and bio-fuels available on a given site.
Although this web site is predominantly a practical review of "how to" build more sustainable buildings it seems important to briefly consider the "why" issues to put the technical innovations into a philosophical and environmental context.
Introduction To The Status Quo

It is fair to say that much of our conventional housing in the UK is very poorly designed in terms of energy conservation and ecological awareness.
 
Most houses are poorly insulated and consume unnecessarily high, indeed absurd, levels of energy (usually from non renewable sources) and at the same time produce high levels of waste and pollution.
 
This unbalanced situation can be seen as an expression of our exploitative, consumerist `throw away' culture, which is totally non-sustainable and detrimental to the well being of our precious environment as well as future generations.
 
We in the consumer society make up 1.1 billion people - 20% of 5.5 billion of the world's population, yet we consume 64% of the world's resources, 32 times as much as the poorer populations. The building industry is highly implicated in the levels of consumption.  "The construction industry, together with the building materials industries which supply it, is one of the largest exploiters of natural resources, both mineral and biological.  Its activities cause irreversible transformations of the natural environment, and it contributes significantly to the accumulation of pollutants in the atmosphere and general environmental stress.
 
Buildings are now revealed as sites of parasitic consumption.  Such consumption occurs initially when the building is constructed, continues throughout its life time (through the fossil fuel resource demands of use, repairs and renewals) and extends beyond its removal because its demolition wastes then have to be accommodated elsewhere. 
 
Architects through their role in design decision-making are one of the agents by which an individual, organisation or society may or may not appropriate more than its fair share of the planet's resources.
 
Wind turbine and photo voltaic renewable energy system
 

David's House Introduction

 

David's house differs from previous examples in that it is a low embodied energy, super insulated, timber frame construction using 300 mm Masonite I studs, joists and rafters. The house is conceived as an integrated eco system within the boundaries of the site and aims to be self-sufficient in terms of electrical supply, space heating, hot and cold water supply, and will biologically process human waste streams to fertilise its edible landscape. It is an ecological approach which goes beyond energy to abroad concern with the sum of the resources used to make the house.

 

Central Conservatory Passive Solar Space

 

The conservatory offers a passive solar heart to the house also providing the vertical circulation route and a raised seating platform to enjoy the distant views. It is normally hard to justify an isolated conservatory space in cost and energy terms but if it is an integrated multi function space it becomes not only a net solar gain asset but also a most beautiful place to relax for very little additional cost. 75 mm-insulated internal shutters are provided to reduce heat loss during mid winter and at nighttime.  A 150 mm thick insulated concrete slab provides thermal mass to the glazed space retaining the suns latent heat.

 

Bio- Fuel Heating System

 
The conservatory pre-heat buffer zone and super insulation levels with minimal heat losses combined with thermal mass creates considerable thermal inertia eliminating the need for a full central heating system. A 4/6 kW efficient Scandinavian wood burning stove fuelled from timbers harvested from the 4 acre site provides a social focus to the living room and can compliment the heat gains from the occupants and appliances.
 

Low Energy Appliances

 

All appliances have been carefully considered to eliminate unnecessary electrical demand and to optimise the efficiency of the required essential A* rated items, cooker, fridge, lighting etc. Excess electricity produced from the renewables, which cannot be stored in the battery pack, will be dumped into the hot water cylinder to run in parallel with the hot water coil heated by the solar hot water panels.

 
Renewable energy distribution diagram
 

Non Mechanical Passive Ventilation

 

Mechanical ventilation has been avoided in favour of a healthy breathing wall construction and a Passivent system which naturally draws air through ducts from dry rooms through wet rooms (bathrooms and kitchen) and vents stale moist air through roof ridge vents with out the use of electric consuming mechanical fans.

 

On Site Natural Treatment Of Waste Streams

 

Presently we spend an enormous amount of energy and money collecting and purifying fresh water to a high EEC standard suitable for drinking.  We then urinate in it and defecate in it only to flush it down the loo back to where it came from to begin the entire process again.  In doing so we negate the hard work required to purify the water.  We throw away the potentially valuable nutrients in our urine and faeces and create unmanageable levels of pollution as the sewage is pumped into our rivers and seas.

 

There is something clearly tragic and wrong with this scenario and our collective reluctance to deal with our own waste. David's house uses Ifo Cera dual flush WC’s, which are at present the most water efficient flush toilets available with a minimum flush of 2 litres. This may be compared with a 9-litre flush, which is commonly found in standard UK WC's.

 

Given that flushing the toilet accounts for over 40% of our average water use the low flush Ifo WC's can reduce a typical families consumption from 65,700 litres per year to 20,440 litres per year with a real cost saving of £60.00 on metre charges. All black and grey water are fed to an existing septic tank on the site with a reed bed secondary tertiary system to absorb leaching liquids. Solids after an extensive settlement period will be extracted from the septic tank and distributed among the hedgerows and fruit trees to retain the valuable nutrients with in the boundaries of the site. If an existing septic tank infrastructure was not already present on site a dry composting system would have been more seriously considered. Kitchen wastes and garden debris material are composted and then returned to the land as an invaluable non-toxic fertiliser.

 

The above experiments demonstrate that human wastes do not need to become toxic pollutants of our rivers and seas but can be recycled and reused within an integrated eco system to become an invaluable resource furthering new life with in the boundaries of the site.

 
Looking up through the natural wood and powder coated steel staircase
 
Double height living room space and wood burning stove
         
 
 
 
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