An innovative eco-building that uses geothermal heating and energy saving extraction fans could offer a low cost, healthy living, social housing solution. John Davison of Airtech Environmental Systems examines the potential.

Most tenants want greater comfort, more space and less noise along with lower running costs for their home – demands that are not easily met in their entirety. However, ‘Earthdome’, a new eco building founded on the latest ecological design principles and using advanced building materials, insulation technology and energy saving environmental control systems, signals a significant shift towards meeting these ideals.

The property comprises four apartments that use ground source heat pump technology to return water from six bore holes, the deepest at 40m, at the local earth temperature of 10 to 12°C and this raises the temperature in the dwellings to 18 to 20°C. The property is claimed to be the first domestic building in London to tap into the limitless energy resource beneath the earth’s crust.

Bob Harris, the owner, designer and builder of Earthdome says the dwellings create a healthy living environment which should help to alleviate the effects of allergies. Air quality within the building is critical and additional ventilation and environmental control has been incorporated by using two different products from Airtech Environmental Systems who were appointed ventilation consultants at the start of the project in Norbury, in the London Borough of Merton, some three years ago. Airtech’s Energysaver Sensamatic bathroom fans and Energysaver Datamatic kitchen fans combine to ensure Earthdome is free from condensation, damp and mould at all times.

Sensamatic fans have been used to control humidification in social housing for over 15 years. Developed for use in kitchens and bathrooms, these fans incorporate contamination proof microprocessor controlled ceramic sensors that automatically monitor RH and switch on to reduce humidity to preset levels. The fans offer low energy costs for tenants in accordance with the Government’s Directive regarding energy efficient electrical appliances in social housing.

In addition to these benefits Energysaver Datamatic fans have the capability to record, in ‘real time’, environmental data including: RH, temperature, RH set point, vapour pressure, dew point, power interrupts and every instance when they have run. This important data is captured and held for a rolling period of 60 weeks and can be downloaded at anytime to a hand-held reader. Data can subsequently be viewed immediately or be copied to a PC for analysis and printing. Essentially the information reveals how effective an extraction system is at controlling condensation. As such it has the potential to deliver significant energy savings in social housing.

All the fans conform to IEE 16th Edition SELV circuit and offer extraction rates of either 90 m3 per hr (25 ltrs/sec) or 230 m3 per hr (64 ltrs/sec).

Impact of air quality
The automatic evacuation of humid air helps to prevent mould growth and, significantly, dry air is a more efficient medium for heating. Additionally the ventilation system also helps to remove the harmful effects of various off-gassing that occurs from sources such as cooking, perfumes, cleaning products etc. Similarly carbon monoxide can occur in buildings and the Airtech products remove this to allow for a more oxygen-rich environment.

Energy consumption
Earthdome is electrically powered, no domestic gas supplies used. Neither are there solar photo voltaic (PV) panels or wind generators. Instead the property uses thermal heat pumps. These operate on the principle that there is a heat difference that can be exploited through a heat exchanger system and they run at an efficiency rating of approximately 1:4 (1KW electricity input = 4KW heat and hot water output). These systems provide hot water for the under floor heating system and the domestic hot water supply.

Earthdome represents a move towards an environmentally sensitive way of building that can be both practical and economical. It aims to show that it is possible to create a comfortable living or working environment without the need for continuous energy consumption. This is simply achieved because the building itself acts as a thermal barrier between the occupants and the environment outside. The key to creating such a building is thermal mass – a construction technique that uses heavyweight materials that are very good at storing radiant heat during the day while it is warm and then releasing that heat into the interior of the building as night approaches and the air cools.

Another vital concept here is radiant heat – a process where the body is warmed directly by the heat source and not by exposure to air that is warmed up and circulated. A natural fire generates radiant heat, so does the sun, but a radiator does not. Radiators simply warm the air that is trapped with them within a sealed environment.

Earthdome also features reactive lighting that automatically switches lights on or off depending on whether or not a room is occupied. This means that the occupants always have light wherever they happen to be, but don’t have to worry about forgetting to turn lights off when they are no longer needed. Just leaving a single 60 watt light bulb on for six hours per day consumes 2520 Watts per week. Roll that up for a whole year and that same bulb burns its way through 131.4 KW and the energy generation process required may produce up to 197lb (89.4kg) of CO2 emissions as a result.

Note to Editor: Bob Harris comes from a family line of builders and is an MCIOB Chartered Builder, professional teacher and a founder member of the Ecological Design Association. He has been building the Earthdome development over the past two and a half years, and in 2005 he was voted by the National Federation of Master Builders as FMB Master Builder of the Year in the Energy Efficiency category.