Guide to Conversion of Traditional Buildings

3.16 Natural lighting

Mandatory Standard

Standard 3.16

Every building must be designed and constructed in such a way that natural lighting is provided to ensure that the health of the occupants is not threatened.

Limitation:

This standard applies only to a dwelling.

3.16.1 Application of standard to conversions

In the case of conversions, as specified in regulation 4, the building as converted must be improved to as close to the requirement of that standard as is reasonably practicable, and in no case worse than before the conversion (regulation 12, schedule 6).

3.16.2 Commentary

This standard applies to dwellings, and only to habitable rooms or apartments within the dwellings. Therefore, a space that is designated as a store or box room does not need to comply with this standard. It is unlikely that the application of this standard to the conversion of a traditional building will present any significant risk to the fabric or character of the building, as the minimum requirements for natural lighting can be readily achieved in most buildings. The exception to this is when new openings for natural lighting are inserted into the existing fabric.

3.16.3 Issues to be considered

Typical risks in the conversion of historic/traditional buildings

1. Natural lighting provision

• New window openings to rooms, whether through walls or in the roof, have the potential to have a significant impact on the cultural significance of a building if they are poorly designed, badly integrated into the envelope or use inappropriate materials.

3.16.4 Recommendations to meet the standard

The daylight requirement of this standard can be achieved by means other than a window. Alternative means of providing natural lighting can be through:

• rooflight,
• glazed roof,
• fan lights above door,
• glazed door, and
• glass bricks.

All the areas of glazing can be aggregated to provide the total area required. The conversion of a traditional building must meet the requirements of the standard to as close as is reasonably practicable and in no case worse than before. However, it is often the case that the windows of an existing building cannot be altered to allow the room to be designated as an apartment. In these cases, it may be possible to redesign the space to reduce its size to ensure compliance or to combine spaces into an open-plan area to permit an aggregation of daylight provision to meet the required standard. These are likely to be exceptional cases as an apartment can be as small as circa 6m², in which case the glazed area need only be 0.4m².

If an area is to be designated as an apartment but does not meet the full natural lighting requirement, a solution may be to introduce a sunpipe to allow transmission of light into the space. Sunpipes are not specifically included within the standards, and the advice of the verifier should be sought.

Consultation with the forthcoming Scottish Accessible Homes Standard should be carried out for all spaces, and consideration given to the outlined requirements for adapting dwellings to accessible use. Section 16 of the standard is relevant for window design and operation and may inform natural lighting strategies for the conversion of a traditional building.