Last edited 12 Jun 2019

Environmental performance


[edit] Introduction

Environmental performance comprises an aggregation of various factors that can be measured to give an idea of a building’s environmental impact during construction, use and demolition. The factors usually involved give an indication of the quantity of resource consumed by a building, whether it will consume more resource during demolition and the degree to which materials can be recycled.

Typically, factors that measure environmental performance include:

[edit] Materials

The materials from which a building is constructed are important in determining its overall environmental performance. Materials such as timber are sustainable as timber can be sourced responsibly and regrown relatively easily. Its supply is almost limitless and its use does not deplete the earth’s resources.

Stone, too is relatively sustainable as long as it is not transported to the job site over long distances. Materials such as brick, metal sheeting, concrete and steel may be less sustainable as large amounts of electricity are required for their manufacture, releasing more carbon into the atmosphere. Their use on a building could increase its carbon footprint.

However, it is also important to note the performance of materials in use: for example, brick may have high embodied energy but this is balanced by its relative longevity, minimal maintenance throughout its life and good thermal performance. Furthermore, the ability to recycle certain brick types and other building materials when it comes to demolish or reconfigure a building further increases its green credentials. Brick and other materials will therefore have a more favourable environmental performance when their entire life-cycle is considered, rather than just manufacture. Possibilities for re-use and recycling of materials can boost overall environmental performance and reduce carbon emissions as no new materials have to be produced and there could also be fewer deliveries to site

[edit] Energy efficiency

How much or how little energy a building uses will depend on its design, workmanship, orientation and the materials from which it is built. Generally, thermal performance depends on the materials used for roofs, walls and floors, and the way they are assembled. Increasing the amount of insulation in walls and roofs will reduce heating costs and greenhouse gases as well as saving money. Allied with thicker walls, and good workmanship throughout will produce a building with a good thermal mass: not only will it minimise heat loss, but in summer it will stay cooler for longer and thereby minimise the requirement for air conditioning.

[edit] Thermal efficiency

A thermally efficient building is one that reduces heat losses/gains and so requires minimal heating and cooling. This may be achieved by thicker, better insulated walls and either smaller openings or the inclusion of high-performance glass that has low heat emissivity. A building that has been poorly constructed is likely to have more cracks and gaps through which heat can escape in winter.

[edit] Daylighting

Maximising daylight will help reduce heating and lighting costs, especially in winter. A building that is designed for the best possible orientation allied with intelligent window design can maximise daylighting to reduce electricity reliance and also capitalise on solar heat gain in winter to lower heating costs.

[edit] Indoor air quality

The quality of air inside a building is crucial to the well-being of occupants. It is frequently observed that in some instances, indoor air quality can be worse than outside. Good ventilation with frequent air changes per hour can make buildings far more liveable.

[edit] Flexibility for change of use

When it comes to change of use or ownership, the ease with which a building can be reconfigured or deconstructed will give it a higher sustainability rating and therefore a better environmental score. But this will depend mainly on the design, the way materials have been assembled and the materials themselves.

Timber for example can be easily reused – cut, stripped, planed or reshaped – to give it a new life as long as it has not been excessively fastened in place, say by over nailing or with a very strong adhesive. Bricks too can be reused if they were laid with a soft mortar – such as lime mortar – that is more easily separated allowing the brick to be reused. Specifying materials that can participate in the circular economy will give more sustainable buildings.

[edit] Water recycling

Minimising water usage through greywater recycling and rainwater collection devices, allied with greater efficiency in water usage through plumbing fittings and fixtures, e.g low-flush toilets and water-saving showers, will greatly increase the water efficiency of a building. This is particularly important in housing. Minimising water usage also saves consumers money.

[edit] Building design and geometry

The shape of a building and therefore its contact with the outside air can influence its environmental performance. A minimal surface area will give lower heat loss – and gain – compared to a complex shape with projections and recesses.

Minimising the total glazed area will reduce solar heat gains and losses. This is particularly pertinent when allied with constructions that have a high thermal mass. For example, masonry, when compared to lightweight construction, can regulate the flow of heat far more efficiently. This means interiors that are generally warmer in winter and cooler in summer, resulting in less energy used for heating and air conditioning and so, a better environmental performance.

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