Green Guide to Specification
The Green Guide to Specification (Green Guide) is an online resource for designers and specifiers to compare the environmental ranking of construction elements as part of an overall environmental or sustainability assessment for a project or development. It is managed by BRE Global Ltd and forms part of the way to score credits in the Materials sections of a BREEAM or Code for Sustainable homes assessment.
Generic descriptions of many construction elements are given a summary ranking E through to A+ for various types of buildings, based on Life Cycle Assessments (LCA) using the BRE’s Environmental profiles methodology.
In addition to the online collection of ratings the BRE offer a Green Guide Calculator for BREEAM assessors to establish a bespoke specification based on the same methodology.
The introduction of Environmental Performance Declarations (EPDs), product specific Environmental profiles on the BRE GreenBook live and the use of the BRE’s IMPACT tool provide alternative means of LCA comparisons with more upto date and specific data.
Concrete in the green guide
There are a range of concrete construction elements in the Green Guide, many of which score well. For instance, concrete block cavity walls score an A or A+ rating for every building type. However the list is far from comprehensive, particularly with regards to options for concrete mixes.
There are a number of design strategies that can be considered when selecting concrete elements, each of which can influence the Green Guide overall rating positively. Examples of these strategies are:
1) Use the most appropriate Green Guide building categories or a bespoke building type
- The rating of a building element can vary considerably depending upon which category of building type is being considered, despite being identical specifications, especially concrete floors
2) Check if the building elements needs to be assessed
- Not every major building element is assessed in each building category. For example there is no Green Guide rating for the ground floor of non-residential buildings, or for any substructure and basements.
3) Adapt the concrete specification or product choice to optimise LCA scores
- This includes use of [low carbon cements] such as ground-granulated blast furnace slag (GGBS) and Fly ash (FA) and recycled or secondary aggregates. Refer to publication [Specifying Sustainable Concrete] for more details on their use in concrete.
- Lighter weight concrete, such as pre-stressed or voided slabs, power floated floors or lightweight aggregates tend to score higher.
- Seek guidance from manufacturers and suppliers about product ratings.
4) Consider using alternative LCA method
- Use of EPD’s and Green book Live provide an uplift in credits in BREEAM 2014 and bespoke LCA rating by a BREEAM assessor could also provide a more accurate, improved rating.
For more guidance on scoring in the Green Guide refer to the Materials chapter in publication Concrete and BREEAM.
It is important to recognise that the holistic benefits of material choice extend beyond a Green Guide rating. Some of the key material benefits for concrete, including material efficiency, thermal mass, long life and flood resilience are not factored into the Green Guide rating. These sustainability benefits may in themselves be a significant factor in the selection of concrete for construction.