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Light Research @ MMU

The Grumble Point

Perusing the 1945 City of Manchester Plan, which sets out the post-war reconstruction of the city, I came across a detailed appendix outlining a daylighting masterplan for the city. Daylighting is the practice of controlling the admission of natural light, such as direct sunlight and diffuse skylight—into a building, through the positioning of apertures and materials to redirect natural light into interior space.  In the 21st century, daylighting has been rediscovered following concerns about sustainability and energy efficiency.  Clearly if we can light buildings naturally it will reduce the need for artifical light sources (Ander, 2012).  It is interesting, therefore, to find that that daylighting was also rediscovered in 1945.

Manchester’s daylighting plans draws on the technical expertise of  T.Smith of the National Physical Laboratory Light Division and contains detailed calculations and daylight graphs for commercial buildings, assessing the amount of natural light penetrating building interiors using a formula based on building length, depth and height.

Light Factors

The Plan draws on The Ministry of Works (1944) guidance on lighting,defining the daylight factor as:

a percentage of total light available outdoors under the unobstructed sky.  Thus a daylight factor of one per cent signifies that at the point in question in which illumination is one per cent of that which would be obtained if from that point the whole hemisphere of the sky could be seen (247)

In the Manchester plan, for example, the following guidance is explained:

In living-rooms and rooms where activities such as reading, writing and sewing are carried on … 1.0 per cent

In kitchens, or rooms where cleanliness of utensils and subtle differences of colour have to be judged … 2.0 per cent

In bedrooms … 0.5 per cent

The plan adopts 1.0 per cent as the norm. This overt concern with daylight penetration masks a deep underlying planning philosophy which underpins The City of Manchester Plan.  Throughout this document is an uncritical appreciation of Le Corbusian principles of modernist planning. Le Corbusier writes:

Light and illumination are inseparable components of form, space and light. These are the things that create ambiance and feel of a place, as well as the expression of a structure that houses the functions within it and around it. Light renders texture, illuminates surface, and provides sparkle and life.

A great example of these ideas in practice is his design for The Chapel of Notre Dame at Ronchamps.  Le Corbusier’s broader intention, however, was to both metaphorically and literally bring the masses into the light, arguing that bodily and spiritual health were connected to exposure to natural light, ideas perhaps expressed in The Radiant City in which he calls for greater use glass walls and facades, together with the spacing apart of tall buildings as practical ways in which to maximise daylight peneratation. Through “slum” clearance and mass redevelopment, Manchester therefore, attempted to put these ideas into practice.

 Grumble Point

According to the Manchester plan the Grumble Point is a level “at which complaints are that visibility is difficult … reached when the light factor sinks to 0.2 per cent”. This exact scientific rationalisation of the availability of lighting is perhaps only to be expected from modernist urban planning.  The document doesn’t mention the qualities of light nor the affordances of darkness and gloom.  The assumption that the more light, the better, is perhaps challenged by contemporary understandings of lighting and architectural design.


Bullock, N (2002) Building the Postwar. Routledge, London

Chynoweth, P 2005, ‘Progressing the Rights to Light Debate Part 2: The Grumble Point Revisited ‘ , Structural Survey, 23 (4) , pp. 251-264

The Ministryof Works (1944) The Lighting of Buildings Post-war Building Studies No.12. HMSO.


April 19th, 2013 - 10:56am

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