The following guidance, found in the Methodology section of BIU USA V6 Commercial, can also be applied to BIU USA V6 Residential assessments:
For assets with identical lighting systems and floor layouts across multiple areas or floors, illuminance levels in a representative sample of areas or floors may be measured, if in the professional opinion of the suitably qualified person, these are likely to give measurements that reflect the performance of the lighting in all relevant spaces within the asset. Illuminance measurements must be taken at least every five years and after any changes to lighting systems. Where the asset is less than five years old and illuminance levels were assessed as part of the design or construction of the asset that demonstrate compliance with the criteria in this assessment issue, then the results of these studies may be used as evidence (assuming there have been no changes to the lighting systems in the intervening period).
