About our Charity
Energy Efficiency in the Integrated Greenhouse
The aim of the Integrated Greenhouse design is to at least halve The Living Rainforest’s current energy requirements. If planned insulation levels are met, the biomass boiler and Vertical Soil Heat Exchanger combination will then be sufficient to meet The Living Rainforest’s total heat needs.
Energy efficiency is, therefore, central to the Integrated Greenhouse design, with energy requirements being minimised by selection of materials according to their insulation properties and embodied energy, and construction methods according to the amount of energy they use and their ability to reduce energy needs once buildings are in operation.
The energy efficiency of different materials is measured as a U value. The lower the U value the less the material conducts heat and, therefore, the better it is at insulating a building and keeping energy needs down. Currently, glazing in The Living Rainforest’s glasshouses is almost entirely single pane. These single glazed units have a U value higher than 5, although the U value for the glasshouses overall is actually higher than you would expect from these materials because of leakage, due in part to the greenhouses’ age. In practical terms, the heat is being quickly and easily transferred from within the greenhouse to the outside air, increasing the amount of energy required to heat the greenhouses, even with the use of thermal screens.
Energy needs could be almost halved by building a new greenhouse with a U value of around 4 but we plan to go further than this. Building a greenhouse with an average U value of at least 3 could be achieved by glazing with three layer polycarbonate sheets. A value of less than 2 could be accomplished by using double glazing with low emission coatings. Double glazing units with specialist coverings to manage light penetration and emissivity are currently being explored, taking into account the effect of UV light filtering on the behaviour of butterflies, a key issue for The Living Rainforest.
Insulation of non-glazed buildings and areas is also important. Roof, wall and floor voids are being filled with cellulose fibre (100% recycled newspaper), giving a high level of thermal insulation, and insulated panel designs are being considered for greenhouse side walls.
Energy needs have also been reduced by installing passive ventilation (natural ventilation), rather than mechanical, in the Human Impact Building. This involves the use of automatically controlled roof ventilators through which air changes are driven by the movement of warm air inside the building. Office space within the Green Greenhouse (phase 2) will be fitted with a similar balanced ventilation arrangement but will go one step further, incorporating heat recovery. This system will vent clean air into the building and extract stale air, while also recovering heat from the stale air to warm the incoming ventilation. In addition, the air inlet will be provided with a cold water-to-air heat exchanger for summer cooling and the ventilation system will be manually controllable to adjust to differing ventilation demands, depending on population and personal preferences.
The Living Rainforest’s entrance walkway constructed (during phase 1) between the glasshouses and Human Impact Building also reduces energy requirements by acting as a thermal buffer, reducing heat loss from each.
Subscribe to our newsletters
Enter your email address in the box provided to sign up for free email updates
About our charity
Learn more about the work done by The Trust for Sustainable Living... Read more