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 Sanitar 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 families consumption from 65,700 litres per year to 20,440 litres per year. All black and grey water are feed 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 hedge rows and fruit trees to retain the valuable nutrients within 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 will be composted and then returned to the land as an invaluable nontoxic 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 within the boundaries of the site.
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. (Davis Langdon Consultancy 1997).
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.
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. The house has a Building Energy Performance Index of 241 and a calculated per annum Carbon Dioxide Emissions of 5.0 tonnes / year and 29.6 kg / sq. m. / yr.
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.