The aim of the design stage assessment is:
- To assess the design specifications (i.e. before construction begins) for each individual dwelling to determine the design stage or interim rating
- To award (subject to quality assurance) a design stage or interim certificate.
The DS assessment is carried out on the detailed design of each dwelling in the period up to the issue of tender documents, sometimes referred to as RIBA Stages A–G. A Code assessment requires a more detailed specification than Building Regulations compliance because the Code covers many more aspects of the performance of the dwelling. For instance, specification details of all the sanitary fittings are required to calculate the score for the Code indoor water issue.
The assessor will also be able to calculate, at this initial design stage assessment, any site-related credits. Therefore, details of final landscaping and ecological enhancement measures will also need to be known.
The assessor should work closely with the design team to:
- Demonstrate that the performance requirements set for each of the three non-creditable mandatory issues of environmental impact are met for each dwelling.
- Demonstrate that the performance requirements set for each of the credited mandatory issues of environmental impact (dwelling emission rate, fabric energy efficiency, indoor water use and Lifetime Homes) are met for the desired rating for each dwelling.
- Choose the remaining tradable issues which are required to achieve the desired overall rating.
- Evaluate the performance of each dwelling against the requirements set for each of the chosen issues to confirm that the required standards are met for the desired overall rating.
- Assemble and check the evidence required for the developer, design team and other consultants to show the intended performance will be met.
When the assessor is satisfied with the performance under the Code, they shall submit the assessment report to the service provider for quality assurance and to receive design stage or interim Code certification. The report must contain references to documentary evidence describing how performance requirements are met, creating a clear audit trail linking the rating awarded to the evidence used to justify it. The service provider may issue a standard report format for the assessor to complete.
(reproduced under crown copyright from Code for Sustainable Homes Technical Guide, November 2010, Department for Communities and Local Government)
