Evidence quality & categorisation


  • Green claims made about products are only as good as the evidence they are based upon.
  • Just as in matters of safety, building product specifiers need to have confidence in the claims.
  • Different degrees of confidence are induced by corresponding qualities of evidence


GreenSpec system based upon medical evidence rating 

 Guided by initiatives used in medical practice to grade the quality of evidence supporting medical guidelines, we have developed a system for grading the quality of evidence from and therefore the strength of the claims made by manufacturers of building products.


GreenSpec labelling and the quality of evidence

 The GreenSpec PASS system assesses the quality of evidence as in the following categories:


*** 3 star rating:


The assessment is strongly supported by evidence data. It can be used with confidence.

A third party verifies all environmental impact data. In-use data is expert reviewed.

In practice acceptable data will include third party validated Life Cycle Assessments (LCAs) or preferably Environmental Product Declarations to ISO 14025- this gets as close as is possible with environmental studies to a scientific standard of proof. Expert reviews will be reported by building construction experts. Other evidence will include third party certifications, labels and endorsements from other organisations. Overall, there are few or no 'gaps' in the supporting evidence.


** 2 star rating:


The assessment is moderately supported by evidence data.

Some or all of the environmental impact data will be self-certified. Other evidence includes expert-reviewed in-use data as well as third party certifications, labels and other endorsements.

In practice self-certified data will originate directly from the manufacturer without third party validation. Data might include headline quantities such as 'embodied energy', use of recycled materials, waste output, use of water and factory emissions etc.

'Expert review' of the product in-use context will usually be in the form of a report by a third party construction expert. The review will involve consideration of a number of parameters that relate to the contribution made by the product to the overall environmental performance of the building. Overall, gaps in the supporting evidence can be completed using reasonable inferences from other more generic information.


* 1 star rating:

The assessment is weakly supported by evidence data. It should be used with care.
Expert judgement in this category of evidence will be used to determine the balance of probability. In practice there will be an incomplete data set, although sufficient degree of performance can be inferred from validated data provided as well as other generic data. There is no or there is incomplete information regarding the 'in use' aspect of the product.