The Vital Signs Project: Green on the Grand Case Study

Green on the Grand

Kitchener, Ontario, Canada

Hypothesis 2: Daylighting

• low heat loss
• high transmission of daylight
• low solar heat gain.
• triple glazing (a feature now becoming common in Canadian construction) with two low-e coatings.
• Argon gas in the two cavities between the panes
• silicone edge-spacers are used throughout

This produces a total U-value that is under 1.0 W/m²C. In addition, the outer pane of glass is spectrally-selective, maintaining a high visible light transmission (listed at 0.53) and significantly minimizes solar heat gain (solar heat gain coefficient, SHGC, of 0.28). Ultimately, the glazing luminous efficacy, or visible transmission-to-SHGC ratio, is 1.9 - almost the highest attainable value.

The window frames are constructed from pultruded fiberglass lineals and filled with polystyrene insulation. The frames, constructed of fiberglass, are environmentally advantageous since there is a low embodied energy, provide maximum insulating factors and their manufacture results in few noxious emissions.

To touch briefly upon glazed areas such as entrances, they have been thermally broken with structural aluminum frames, providing maximum strength with a minimum of framing. The thermal break has a 50mm thickness, ten times that found in conventional commercial aluminum windows.

Design intentions claim that, window sizing was decided upon by balancing between the need for light and the need to keep hot/cold air outside, as necessary. It is stated from designer (Enermodal) computer simulations that a window-to-wall ratio of 30% was most optimum and regardless of siting and orientation, windows are distributed evenly on each side of the building to provide light to all perimeter rooms. An issue of contention does arise, in the fact that for reasons of energy efficiency, most windows are fixed. Indeed, only ten percent of the windows are operable and the justification for their existence is for the provision of air in the event of a power failure. Through the tenant survey, it was found that this was one of the drawbacks to the building, but in general, was found to be justifiable.

Lighting

One of the design objectives stated that the Green on the Grand project wished to demonstrate that offices could be effectively lit while consuming only a fraction of normal electrical requirement. Daylighting, energy-efficient light fixtures and task lighting were three methods used to meet this demand. Daylighting is the most efficient source of building lighting, but at the same time it proposes several design problems. Among them is the fact that with the number of windows necessary to accomplish a significant amount of daylighting, perimeter spaces may become overlit while conversely, spaces without windows are too dim and uncomfortable.

A solution seems to have been arrived at with the placement of windows in relation to the office space. Windows are placed high on the wall, allowing natural light to penetrate deep into the office space. At the same time, two methods of interior shading are employed, dependent upon the tenant: translucent fabric roller-blinds that admit diffuse light and horizontal blinds that have upside-down slats (concave up), thus directing light up into the back of the room.

There are also several issues that must be discussed in relation to the whole decision of equal distribution of windows and the use of interior light shading rather than exterior solar shading. First, both the architect and the consulting engineers (Enermodal Engineering, the tenant) decided that the windows were of such high quality and allowed so little radiant heat transmission, that the necessity of exterior solar shading was deemed unnecessary. Enermodal specializes in window design but were surprised that computer test runs revealed the high quality of the window. There was also the economic fact that the combination of conventional window and exterior solar shading would have been more expensive than the windows that were used. The superior performance of the windows, according to the architect, seems to have also justified the equal distribution of the windows, even though it was admitted by the architect as well as observed that currently, there is a problem with excessive light penetration from the West facade. However, natural exterior shading will eventually come into being through the growth of a row of trees set in front of that facade and there is currently an open colonnade that provides very marginal shading to only the first floor. Ultimately, the even distribution allows for flexible design of the perimeter spaces and therefore, it becomes an issue of light control from within the building as opposed to exterior control.

Large dormer windows located on the steeply pitched roof allow a great amount of ambient light to enter into interior spaces. However, due to their positions on the roof, determined by the overall exterior appearance of the building, they create difficult spaces within because rooflines and walls must be greatly manipulated in order to allow the light to enter into the space (Figures 9 & 10). This is particularly apparent in the case of the Enermodal office. This is, however, just an example of how exterior design dictates over interior space, or rather, form following function.

In those areas that are artificially lit, energy efficient fixtures are used. Most fixtures have electronic dimmable ballasts and while providing the same level of light as a 40W fluorescent tube with magnetic ballast, they use 35% less electricity. A modulating dimming system controls electric light according to natural light intensity and motion sensors activate lights only when necessary. Task lighting is accomplished through the use of compact fluorescent and parabollically reflected halogen bulb, thus illuminating only small areas when necessary.

Through all these modifications, a 70% savings has been calculated by the owners. The predicted annual utility cost derived from lighting was taken from $6534CAN for a typical new office to $1978CAN for the Green on the Grand. These savings, we can safely say, will offset the initial increase in expenditure of the efficient fixtures over their life cycle.

Discussion

At the beginning of this case study, the main points of initial question focused around the even distribution of windows, the lack of exterior solar shading and the inoperable nature of the majority of the windows. It is thought that the first of these questions was completely answered through the research and interviews conducted and even the second question was satisfactorily answered because solutions to the initial problem had already been considered. From survey results, it was noted that less than 20% of tenants found daylight to be the cause of significant glare. It is thought that this result could in large part be due to the still to be resolved west façade. In addition to the use of the survey, several HOBOs were placed in the study area. These light reading indicate a significant rise in ambient light during the sunny hours of a day. To further this study, a light model was constructed and placed on the heliodon. The model strongly illustrates the concentrated daylighting on the south façade during working hours.

However, the issue of operable windows, in our opinion, still remains questionable. Ten percent is a low number, and though the C-2000 program bases its system around a sealed structure that is mechanically supplied with fresh air, it is still desirable for one to have the option of opening a window, if not for comfort, for safety. In the event of a power failure, it is not known whether one in ten operable windows will be sufficient for adequate air exchange. However; it must be stated that even though this was a concern for several tenants, there were other concerns that ranked higher in priority, such as noise propagation. Nonetheless, their overall attitude towards the building was very positive (80% satisfaction with overall lighting and just under 80% satisfaction with window size), possibly deeming this issue an acceptable drawback.

The Vital Signs Curriculum Materials Project


Last Modified: April 23rd, 1998