Our highest priority in designing the city must be to make places that will resonate with human sense experience, and support social functioning. Yet, that will require a shift away from the Modern planning paradigm to the longstanding urban tradition that shapes cities according to physical, social and ecological human needs.
In Vancouver, when we speak about ‘urban design’. For example, when a project goes to the Urban Design Panel for review. However, what we are dealing with is Modern urbanism, rather than the longstanding tradition of urban design. We have argued here that Modern urbanism is bereft in one all important area: it has failed to produce any places of lasting value.
Focusing on just one aspect of ‘good’ urbanism, we list here several characteristics in the built form that are fundamental in shaping the human experience of place.
- Perimeter Block Massing
- Continuity of the streetwall
- Human scale
- Street aspect ratio
- Solar penetration
- Environmental performance of the street
Perimeter Block Massing
Perimeter block massing on city blocks presents a hard edge to the street side, and a soft middle to the block interior. Perimeter block massing aligns built form along the edge of the urban block resulting in the continuity of the street wall. By keeping the centre of the urban block free of buildings, and green, it creates an open block middle that we experience as a green space.
Continuity of the Streetwall
In order to achieve ‘the sense of place’—or definition of the street space—pairs of urban blocks must present a continuous streetwall along the full length of street. Provided that the streetwall breaks at regular intervals (measured as the scale of the urban block), and is not too high (measured as the street aspect ratio), the human experience of the street is greatly enhanced by the enclosing gesture of the continuity of the streetwall. In Vancouver, Water Street is the only street that meets this condition along its full length.
The Human Scale Principle
In order to achieve human scale in the experience of the street the height of the streetwall must be set in proportion to the width of the fronting street (below we will discuss this condition in relation to the urban room). We term this relationship the Street Aspect Ratio.
Street Aspect Ratio
Human sense perception is heightened in spaces with proportions that can be described by small, whole-number ratios such as: 1 : 1, 1 : 2, and 1 : 3. We experience spaces that present these ratios as having a high sense of enclosure. If aspect ratios in public spaces reach 1 : 6, or higher, then the “sense of place” is lost for the observer. Other considerations for aspect ratio include:
- Close to the equator, aspect ratios of 2 : 1 are common achieving passive cooling in shadowed streets.
- A row of closely spaced trees (about 20-feet apart) approximates the streetwall effect of a continuous row of buildings.
- As the street aspect ratio decreases, the dispersal of particulates, and emissions increases.
In Vancouver, between December and January, the angle of the sun in the sky at noon dips below 27° above the horizon. Thus, a street aspect ratio of 1 : 2 (tan 27°) will permit solar penetration to the sidewalk opposite 10 months of the year. A street aspect ratio of 1 : 3 (tan 18°) will allow full solar penetration year-round. Therefore, we recommend that street aspects ratios in Vancouver should fall within the following criteria:
- 1 : 3 (minimum streetwall height: 33% of fronting street width); and
- 1 : 2 (maximum streetwall height: 50% of fronting street width).
- 1 : 4 (on residential streets: balancing density, with a reduced sense of enclosure).
© Lewis N. Villegas, Vancouver, February 2012.