The number of existing buildings far outweigh the amount currently under construction. Many of these buildings are energy inefficient, and limit the benefit of sustainable development within the UK. BREEAM In-Use is an environmental assessment methodology and independent certification process which provides an opportunity to substantially improve the environmental performance of existing buildings, as well as reducing the running costs. It improves the efficiency of a building by highlighting underperforming elements which require readdressing. As well as reducing the energy costs of a building, and therefore its environmental impact, BREEAM In-Use certification can be utilised to promote a company’s green credentials and social responsibility, as well as gain a higher property value.
BREEAM In-Use covers the same nine environmental issues as the 2011 BREEAM New Construction. Fire and security are also assessed, but these are of limited relevance to green roofs so are not discussed here. The BREEAM classifications used are also the same as 2011 BREEAM, and the certification level is revised on an annual basis, in order to allow for continual improvements to be made, and for these improvements to be verified by an independent and internationally known third party.
Whilst the inherent performance characteristics of a property are taken into context at the start of the assessment process, it can be extremely difficult for a building to retrospectively gain accreditation due to the limited number of building features which can be improved. Roof space is predominantly wasted within properties. The extreme thermal fluctuations experienced across conventional roof surfaces make traditional roofs extremely hostile to wildlife. These roofs also place a stress upon the systems that support urban environments, especially the urban hydrological cycle.
Green roofs present a relatively simple approach to provide a range of aforementioned benefits, and gain recognition within the BREEAM In-Use system.
There is also some potential for retrofit.
These roofs have the potential to retrospectively gain BREEAM credits for developments and buildings in two contexts:
1. When a new development falls short of its predicted accreditation.
2. Gaining credits within BREEAM In-Use for existing buildings.
The Interim BREEAM certification stage within 2011 BREEAM New Construction predicts the amount of credits a project can gain, and therefore the BREEAM certification level the development should achieve. However, projects can easily fall short of the predicted number of credits, despite the recommended 5% accreditation buffer recommended by BRE, as specifications change throughout the construction process. A relatively simple approach would be to compensate through the retrospective installation of green roofs. Similarly, green roofs can hold great potential to benefit buildings undertaking BREEAM In-Use assessments.
The exact magnitude of benefit is restricted by the type of green roof utilised, and this is often determined by the weight bearing capacity of the building in question. If designed correctly, green roofs can aid in retrospectively gaining the credits outlined earlier.
– The conceptual basis for BREEAM assumes linearity in product performance, yet green roofs behaviour changes according to construction and climate. Green roofs are therefore underused within BREEAM due to lack of acceptance.
– The roofs can currently gain up to 5 credits independently within Hea05, LE03 and LE04.
– They can help towards attaining up to 30 credits within Man04, Ene01, Ene04, Mat03, Mat04, Wst01, Wst02, LE05, Pol03 and Pol05.
Green roofs can be used to retrospectively gain credits in two contexts:
1 – When a development doesn’t achieve the number of credits predicted
2 – For BREEAM In-Use for existing buildings