Sustainability is generally accepted as being the movement towards energy efficiency, use of renewable energy sources and recycling.  In broad terms this means buildings need to minimise both the amount of energy used to operate and the amount of waste produced.

Given the high cost of energy and waste removal, this is a good idea from an economic standpoint, irrespective of ecological issues. So, becoming sustainable is one of those win – win situations, saving the planet and money!

If only things were that simple. Looking purely at the energy issues, a fully sustainable building would be described as carbon neutral, ie: the net energy used by the building is zero.  In order to achieve this, a building needs to capture energy from the environment to offset that used from the grid.

Whilst this is technically possible, especially on new buildings, applying this idea to existing properties is very difficult. Consider the average small office block in an average town centre. It is probably surrounded by other properties on three sides, fronts directly onto a main street and has a mix of occupiers.  It was probably built in the late 1960’s and although maintained, it could now do with a full refurbishment.

The question is, how could a property such as this be made sustainable? The biggest cost of running any building relates to maintaining a stable temperature. To do this the building must first be protected from temperature variations outside as far as possible.  To do this, the walls, floor and roof will need to receive additional insulation, the glazing will likewise need replacing with more thermally efficient units and draughts will need to be eliminated.  The effect of these changes will be to minimise the amount of energy needed to heat or cool the building.

The next stage will involve the replacement of heating and cooling plant with more efficient units.  This is the point where the building can start to extract energy from the surrounding environment.  Modern air conditioning systems are actually heat pumps which can move energy from one place to another. So, in the winter energy is taken from outside the building and put inside, and in summer the reverse occurs. When heating, these systems are often able to transfer three times the energy they use into the building: ie; for every 1kW used by the system, 3kW is transferred into the building.

Whilst these systems are efficient,  power is still used to run them.  Also, when cooling, the system has to remove heat gained from the environment (sun etc) plus remove the energy produced by people and office equipment.

The building must therefore generate power to run the air-conditioning plant.  The choices available for power generation from renewable sources are limited, especially within a town centre. Given our scenario, wind turbines are unlikely to work due to the shading effects of nearby structures. Also, to generate the power required, either the building would become festooned with turbines (1 small turbine for every 6 square metres) or one very large unit would need to be installed. Clearly neither option is viable.

The alternative is photovoltaic cells converting sunlight directly into electricity. The problem with this solution, and putting the weather aside, is that the roof of the property is simply too small to install sufficient cells to generate the amount of power required.

So, is becoming sustainable impossible?

On an individual building basis, this is true, however all buildings need to lower their energy requirements to enable the gap between the amount of non-carbon dioxide generating power produced, and the country’s energy requirements to be closed as far as possible.

Whether this is enough of a driver to persuade landlords and tenants to contribute to the costs of the works required is questionable. What may persuade landlords is recent evidence that energy efficient buildings are beginning to attract higher rents. While the percentage uplifts are small at present, this effect is bound to grow as energy costs increase and tenants seek lower operating costs.