A unique combination of eco-building principles, radiant heating, energy saving construction materials and the latest environmental control products could solve the problem of condensation and change the way social housing is designed and built. John Davison of Airtech Environmental Systems explains.

Condensation, damp and mould in social housing are major headaches for both tenants and local authority surveyors. While tenants blame health problems on damp living conditions some abuse the corrective measures installed to address the problem. The best solution is to tackle the problem at source and prevent any build up of warm moist air. Combine this with a healthy heating system, extensive use of natural materials and low running costs and you are approaching the ultimate living environment.

Four new build award winning eco-homes in the London Borough of Merton offer a unique an innovative expression of these ideals. Called Earth dome the property, comprising four apartments, taps into the limitless energy resource beneath the earth’s crust. It presents a benchmark in eco living and a sound commercial proposition for the use of ground source heat technology. Pumps return water from six bore holes, drilled up to 40m deep into the London clay, at the local earth temperature of 10 to 12°C. Working in conjunction with a radiant heating system the ambient temperature in the dwellings is raised to an average of 18 to 20°C, a comfortable level for radiantly heated homes. In summer the temperature of the underground water source is used to cool the property.

Radiant heat is widely regarded as the most comfortable, healthiest and natural heating form available. Its key benefit over warm-air heating is that it warms people and objects in the building, as well as the building fabric — not simply the air in the building. For normal comfort the air temperature can be substantially lower and this reduces heat losses.

Around 3-400 geothermal heat source technology systems are believed to be installed in the UK but Earthdome is the first in London.

The building comprises downstairs one-bedroom dwellings with a living room/kitchen area and a bedroom at the rear with a small bathroom leading off it. French windows open onto a small patio garden with rainwater recycling facilities. Designed for single occupancy the accommodation is compact and yet comfortable.

Upstairs are two, two-bedroom apartments that include living areas, kitchen and sleeping quarters via a stylish recyclable staircase. The bedrooms are designed to flood with light and are designated ‘light therapy’ areas by Bob Harris, the owner and designer of Earthdome.

Central to the specification of all the materials in the building are the principles of health and energy efficiency. The building has been designed to use the thermal mass – in this case blockwork – with a dense internal render to absorb heat or coolness and store it for a long period of time. These materials react slowly to temperature variations and are important aspects of any passive heating or cooling system.

The building’s thermal mass is critical to the success of the heating systems. It uses energy efficient solid wall thin-bed aircrete blockwork, supplied by Tarmac, and with the internal face rendered using a dense sand and lime mix to provide a thermal mass element. This absorbs and releases healthy radiant heat into the building. Heating bills for residents could be as low as £60 per year.

This type of construction can dramatically increase thermal efficiency. Also it also prevents cold bridging and as there are no void areas it inhibits the growth of moulds, many of which are known to cause significant health problems.

Environmental control As Earthdome is designed to be ‘airtight’ the quality of the air within it must be strictly controlled and this is achieved by using the latest Energysaver data-logging monitoring and ventilation equipment from Airtech Environmental Systems.

Bob Harris engaged Airtech as ventilation consultants at the outset of the project. “Airtech were immediately responsive to my ideas” says Harris. “They fulfilled their task of ensuring that the environmental conditions within the properties matched the superior standards and integrity of the building’s pioneering eco credentials.”

Two different Airtech ventilation products are installed – Energysaver Sensamatic bathroom fans and Energysaver Datamatic kitchen fans – which combine to ensure each dwelling is free from condensation, damp and mould at all times.

For many years Sensamatic fans have been the benchmark extractor fan installed in social housing to control humidity. Designed and manufactured for long term use in kitchens and bathrooms they offer low energy costs for tenants in accordance with the Government’s Directive regarding energy efficient electrical appliances in social housing. Every fan incorporates a contamination-proof microprocessor controlled ceramic sensor that automatically monitors relative humidity (RH) and switches on to reduce humidity to preset levels.

Datamatic fans feature all the benefits of the Sensamatic range plus the capability to record, in ‘real time’, important environmental data including: RH, temperature, RH set point, vapour pressure, dew point, power interrupts and every instance when the fan has run. Data is held for a rolling period of 60 weeks and can be downloaded on demand at anytime via either a cable or infrared link to a hand-held reader. Data can subsequently be read on screen immediately or be transferred to a PC for analysis and printing. The information captured ultimately reveals exactly how effective an extraction system is at controlling condensation and has the potential to deliver substantial energy savings in social housing installations.

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

Earthdome includes many innovative features including three-phase electricity to optimise the efficiency of the electric motors used to move the water around. Moreover, electrical systems are ‘shielded’ and ‘smoothed’ to minimise the impact of electrical waves as well as offering cost savings.

A lecturer in eco building at Richmond-upon-Thames tertiary college and a founding member of the Ecological Design Association, Bob Harris firmly believes that the relationship between the building and its natural environment plays a crucial role in its success and the well-being of its inhabitants. “People should find sanctuary in their home and be rejuvenated by their environment,” he says. At a practical level he is convinced that the advance of climate change will impact building design so much so that keeping a home cool will be as important as heating it.

“This building is a testing ground and a commercial approach to eco building,” concludes Harris. “We are at a tipping point right now in eco building and the design principles that are going into Earthdome can be replicated in refurbishment projects as well as new-builds.”