Massing Study
Macdonald Hotel Development
Jasper Avenue And 100th Street
Edmonton, Alberta
Submitted To:
I.B.I. Group
Edmonton. Alberta.
Morrison, Hershfield, Theakston & Rowan, Limited was retained by I.B.I. Group to conduct a pedestrian level wind massing study on the proposed Macdonald Hotel Development.
The conclusions reached in this report are based on data obtained from tests conducted on a 1:500 scale model of the Macdonald Hotel Development and the surrounding structures located within a 575 m radius of the proposed site. The model of the study building was constructed according to drawings received March 22nd, 1982. An orientation plan of the study site and surrounding area can be viewed in Figure 1.
During the course of the study, a visit was made to the laboratory by Mr. David Thom and Mr. David Kraatz of I.B.I. Group, along with Mr. Mike LaBrier and Mr. Jim Jenkins of NuWest Developments on April 26th, 1982.
The objective of this study was to determine the effect of the study building on the local wind environment and, where necessary, to make recommendations for improving wind conditions.
During the study, the scale model of the Macdonald Hotel Development was placed in our open channel waterflume/wind simulator and dye was injected into the water to make visible the wind flows around the study buildings. The study provided an analysis of the wind environment surrounding the proposed development. The model was also tested in our boundary layer wind tunnel in order to verify our qualitative evaluation of the wind environment as observed in the waterflume.
The waterflume/wind simulator was also used to assess the effect of remedial solutions developed to reduce the level of wind activity within areas identified as experiencing uncomfortable pedestrian level wind conditions. Buildings included in the testing procedure, either proposed or under construction, included the Fidelity Building on Jasper Avenue at the intersection of 100A Street, and the Bowlen Carma Building on Jasper Avenue east of the proposed development. The pedestrian level wind study concentrated on the seven most prevalent wind directions in Edmonton. These directions in decreasing order of frequency are: south, west-northwest, northwest, north-northwest, south-southeast, west and north.
The following conditions were examined during the testing procedure:
1) Existing site conditions,
2) Proposed development on-site.
The results of the pedestrian level wind massing study can be summarized as follows.
2.1 Existing Wind Environment
The Macdonald Hotel site is on the southeast corner of Jasper Avenue and 100th Street.
The existing on-site wind environment was generally found to be comfortable for pedestrian traffic during the summer. However, on-site conditions were found to be uncomfortable for pedestrian traffic at least once per week during the winter.
With the hotel in its present configuration, three areas of high pedestrian level wind activity were identified. These areas included along 100th Street from Jasper Avenue to the main entrance of the hotel, the southwest corner of the property along the river valley, and the eastern edge of the property near the One Thornton Court Building.
An uncomfortable level of wind activity along 100th Street was caused by winds which approached the site from the north-northwest. These winds were channelled along Jasper Avenue upwind of the site, and upon reaching the site met the face of the existing office tower and were forced down to street level thus creating high levels of wind activity. Prevailing winds from the south-southeast were also responsible for uncomfortable wind conditions along 100th Street. These winds approached the site from over the river valley where there is an absence of significantly tall buildings which could provide a barrier to the prevailing winds. During the winter months, uncomfortable wind conditions caused by strong winds from the northwest quadrant (north through west directions) were also found to exist around the main entrance to the Macdonald Hotel.
A high level of wind activity was also noted at the southwest corner of the property. Uncomfortable pedestrian level winds were identified when prevailing winds approached the site unobstructed from the south-southeast.
Along the eastern edge of the property, near the One Thornton Court Building, uncomfortable levels of winds were noted when the prevailing winds were from the south or south-southeast. These winds flowed over the river valley and were then channelled between the existing parkade and the One Thornton Court Building creating a high level of wind activity.
2.2 Wind Environment with Proposed Development On-Site
The addition of two office towers to the site as well as an extension to the hotel complete with an atrium between the old and new wings of the hotel had a number of effects on the wind environment. The configuration of the proposed development can be seen in Figure 2. High levels of wind activity were noted in the proposed pedestrian mews between the 40 storey office tower and the existing parkade. The addition of the proposed development to the site increased wind activity at three locations on the site as described in the following paragraphs.
A significant wind speed increase was noted along Jasper Avenue, immediately north of the proposed 40 storey office tower. The increase in wind activity was due to winds approaching from the north through northwest directions meeting the north face of the tower and being forced to flow vertically down the face of the tower. The winds flowing in a vertical plane joined with winds flowing in a horizontal plane along Jasper Avenue making conditions uncomfortable for pedestrian traffic.
An increase in wind activity was noted between the existing hotel and the 40 storey office tower to the north. Prevailing winds from the west through northwest directions were channelled between the hotel and the office tower creating an uncomfortable pedestrian level wind environment. This area is of concern as it will support a high level of pedestrian traffic which will flow from 100th Street to the Heritage Trail Lookout at the southeast corner of the development.
Increased levels of wind activity were found to exist between the hotel addition and the proposed 35 storey tower to the east. Prevailing south-southeast winds will flow unobstructed over the river valley and be channelled between the hotel and the 35 storey tower. These winds will combine with winds from the north channelled between the 40 storey office tower and the existing parkade to create an area of uncomfortable wind activity. The southern edge of this area is the location of the Heritage Trail Lookout.
The pedestrian mews between the parkade and the 40 storey office tower to the west was subject to uncomfortable levels of wind activity during the summer and winter. Winds from the northwest through north directions were channelled between the parkade and the proposed tower creating accelerated flows and high winds.
The area south of the proposed extension to the hotel experienced lower levels of wind activity when the proposed development was on-site. The Heritage Trail was protected from the prevailing winds from the north through west directions by the presence of the 40 storey office tower and the hotel extension. The planned garden on the west side of the development also experienced comfortable levels of wind activity on a year round basis.
2.3 Effect of Remedial Solutions
During the massing study, a number of remedial solutions were examined in order to reduce the level of wind activity around the 40 storey office tower.
Minor massing changes such as increasing or decreasing the size of arcade spaces at grade level had no significant effect.
A significant improvement in the ground level wind activity was noted when the parking levels were opened to the outside by surrounding them with a porous barrier rather than solid walls. The parking garage which extends from the second level 6 m above grade to the sixth level 17 m above grade was tested with both 30% and 50% porous barriers. The porous barriers allowed the vertical downwashed flows from the faces of the tower to flow through at the parking levels before reaching pedestrian level. This reduced wind activity to the north and west of the tower. The use of a semi-porous barrier around the parking structure of the 40 storey office tower also reduced wind activity in both the pedestrian mews east of the tower and in the area south of the tower.
Both a 30% and 50% porous barrier were tested. The 50% porous barrier was effective at reducing the wind activity in most areas to acceptable levels. The 30% barrier provided some improvement, but wind activity remained high in several areas. If the 30% barrier is used, more extensive use of landscaping will be required to reduce wind activity to acceptable levels.
The existing wind environment on the site was generally found to be comfortable for pedestrian activity during the summer months. A number of locations, however, were subject to uncomfortable wind conditions during the winter months.
The introduction of the proposed Macdonald Hotel Development to the site raised the level of wind activity at several locations on-site. An effective massing change was found to alleviate the presence of uncomfortable wind conditions around the base of the proposed 40 storey tower. The four levels of above grade parking in the 40 storey tower were exposed to the external flow by surrounding them with a 50% porous barrier. The presence of the porous barrier on the tower also reduced the level of wind activity between the proposed hotel and the 35 storey tower to the east. A 30% porous barrier was also tested, but was not as effective.
The level of wind activity to the south of the development on Heritage Trail will be low with the proposed development in placed.
Local areas of high wind activity still existed with the proposed changes in place and the development should be examined with a detailed pedestrian level wind study when the design has been finalized. At that stage, ground level landscaping and minor architectural changes such as the addition of canopies would be used to further improve the wind environment.