Greening the high-rise office
Pointers from a front-line practitioner
Throughout Canada, as in the rest of the developed world, employers are confronting the looming demographic crisis — the retirement of vast numbers of baby boomers from the workforce — and projected acute shortage of younger skilled workers to replace them. The competition to attract and retain these workers has begun in earnest, and there is a growing consensus in the marketplace that offering a high quality work environment is an essential key to success. The result is a revolution in commercial office building design, the first since the 1960s.By Dermot Sweeny
CONTINUING EDUCATION UNIT ARTICLE
When Mies van der Rohe and the Cadillac Corporation created the Toronto Dominion Centre in 1967, market conditions in Toronto were similar to today with moderate to low vacancy rates. Yet the combination of a central core, high-speed elevators, central HVAC, glass curtain wall and column-based structures was compelling. It represented a new benchmark of environmental quality, advanced technology, improved human comfort and spatial flexibility sufficient to draw major tenants and catalyze a market transformation.
Response to the new RBC Centre and Telus House at 25 York suggests that we may have reached that point again.
So why has the Miesian model run out of steam, and what is different about the new generation of buildings that is coming on stream? The answer to the first question lies in a Harpers Index I read some 15 years ago that addressed the topic of employee satisfaction in office buildings. Complaint number one was “I am too hot,” and complaint number two was “I am too cold.” Clearly HVAC technology was no longer delivering the comfort it had originally promised.
The reasons were simple: space per person in office environments was on a downward slide from the 300–350sf per person in the 1960s, to the 150sf per person or less that is the rule of thumb today; while at the same time the amount of heat-producing equipment in buildings was going up exponentially. Cooling loads are far greater today than they were even five years ago. Exhaust air is increasing in temperature and accumulating more rapidly at ceiling level.
With fresh air also being delivered from above, the only way to combat higher temperatures in the occupied zone was to increase cooling by reducing the temperature and increasing the velocity of incoming supply air. Intake air temperatures of 55° F or lower were not uncommon, nor were all manner of improvised occupant-constructed cardboard and duct tape deflectors to keep the cold drafts off the occupants.
Alternatively, more zones were needed, many more diffusers and VAV boxes to dispense supply air, increasing both capital cost and space requirements. As servicing for communications, power and information technology also increased, so did the desired depth of the suspended ceiling — culminating in Microsoft asking us to allow for a stratified, four-foot deep ceiling in their new headquarters. This had at least two major negative impacts on building environmental quality and building cost: either lowered ceilings to maintain reasonable floor-to-floor heights; or greatly increased envelope costs — or a combination of both.
Add to this literal “pushing of the envelope” the demographic factors mentioned earlier, and you reach a tipping point. The base building response developed in the 60s no longer works, and the design of office buildings must be reconsidered from first principles.
These principles are: human confort, flexibility, green branding and cost saving.
- HUMAN COMFORT
In the face of demographic changes, designing for human comfort in all its aspects is the best way for an organization to future-proof itself against the changing supply and demand equation for skilled workers.
At Sweeny Sterling Finlayson & Co, we begin with the HVAC issue. Working with, rather than against, the natural buoyancy of warm air, we introduce air through a raised-floor plenum allowing it to be warmed by bodies and equipment in the space, then exhaust the stale air at high level.
Introducing air through an under-floor plenum reduces the need for pressurization within the occupied area, greatly reduces air velocities allowing for the supply air to be much warmer [66ºF – 69ºF], and gives each occupant individual control of their temperature and air volume at a work station level by simply opening or closing manual in-floor diffusers.
With air at 68oF rather than 55oF, outside air can be used for cooling much later into the spring, and much earlier in the fall. This amounts to more “free” cooling and greatly reduces energy requirements for air conditioning. The fact that the air is being introduced at close to the desired ambient temperature, makes it more likely those occupants will adjust their individual intakes to allow more fresh air.
Because the delivery plenum rather than the occupied space is pressurized, it is also possible to open windows without upsetting the balance of the ventilation system. Both these factors obviously contribute to improve indoor air quality and occupant comfort.
There is an apparent capital cost premium for using a raised-floor system when compared to a suspended ceiling system but there are several mitigating factors. The depth of the raised-floor plenum is less than that of a suspended ceiling, with consequent savings in building envelope area; and the mechanical system requires fewer motors, and ducting fans making the system less expensive.
There is lots of anecdotal evidence, and some empirical evidence, to support our contention that natural light and views to the outside are critical contributors to stimulation, human comfort and well being. Effective daylight harvesting depends on capitalizing fully on daylight penetration into the space while controlling direct sunlight and glare.
We achieve this by maximizing ceiling heights, arguing successfully with our clients that the best compromise between economy and performance is achieved with a 13ft. floor-to-floor height incorporating 18in. of raised floor, a 10in. slab, and ceiling heights approaching 11ft., with full height glazing for excellent natural light penetration.
ASHRAE has tended to discourage this fully-glazed approach in order to increase insulation levels and reduce solar heat gain or conversely heat loss. This resulted in a reduction of glazed surface from somewhere between 80% and 90% in Mies’ day, to about 40% in the 1990s. What ASHRAE fails to recognize is that over the same period, the relative importance of solar gain through windows has been reduced both by advancements in glazing technology, and by the dramatic increase in internal heat loads noted above.
While it is still important to work on reducing the amount of excess heat in buildings, we believe that the environmental and psychological benefits of natural light far outweigh the disadvantages of any additional solar heat gain. We do, however, work to control heat gain, and the negative effects of glare while maximizing the positive attributes of daylight.
Typically, an external solar shading device at a height of approximately nine feet creates a clerestory and shades the glass curtain wall below. At the same time, an internal light shelf aligned with the exterior solar shade reflects sunlight penetrating the clerestory off the concrete slab and deep into the building. The light shelf is coupled with a roller blind that lowers automatically [while the light shelf rotates upward] in response to solar intensity and potential glare. The blind never comes to the floor so some views are always maintained.
The additional ceiling height enables us to suspend indirect lighting fixtures fitted with T5 or T8 fluorescent lamps. The goal is to achieve even, ambient lighting. Experience has demonstrated that where there is too much variation the natural tendency is to enhance the dark spots by introducing more light. This of course uses more energy and costs more money.
We find that if we can achieve savings by designing for lower overall lighting levels, it is easier to convince clients to invest money in control systems that further improve energy efficiency. Maximizing indirect lighting also dramatically reduces glare which further increases human comfort.
In the previous generation of office buildings, there was a separation between the ceiling zone used for the distribution of services, and the occupied zones where these services were required. Though this was never an ideal situation, it remained workable for at least two decades. The modest amounts of cabling required could be run vertically through hollow cores built into partitions, columns and power poles, and horizontally through raceways and cable management systems built into furniture.
Again, as cabling requirements increased and the per person space allocations were reduced, a tipping point was reached. The capital cost of furniture began to increase as cable management became more complex, and the supposed flexibility of modular systems became more and more an illusion as the furniture was effectively hard wired.
Consequently, the cost of reconfiguring space — the so-called “churn” costs — which had been a minimal concern, began to increase dramatically, reaching $4 or more per square foot per year for the average large office user.
The access floor system, when combined with modular cable distribution and plug and play connections to flush in-floor boxes, has reduced churn costs for many of our clients to the cost of pizza for employees during reconfiguration.
Capital costs for installation have dropped considerably, and systems furniture costs have dropped by 20% to 25% now that cable management within the panel system is no longer required. Likewise partitions need far fewer vertical raceways or sockets.
This has opened the door to the economical use of movable walls and furniture-based systems rather than panel hung work surfaces and opportunities for further savings and choice in adjustable ergonomic furniture.
- GREEN BRANDING
Pretty much every major company in Canada realizes that to attract young and talented staff, they must be ‘future friendly’. Professing one’s ‘greenness’ on the company web site is one thing, but investing in a green building is quite another. By embracing LEED [or other certification system] for their building and/or interior, a company can point to an objective third-party assessment as proof of their commitment. Such buildings can become important emblems of a meaningful and sustainable change in corporate culture.
- COST SAVINGS
Using the various strategies described above, and working within budgets equal or very close to those used for standard commercial buildings, we have been able to deliver significant and immediately quantifiable cost savings due to:
• Lower energy consumption,
• Lower maintenance costs – simplified systems and equipment
• Real flexibility translating into lower churn costs, and
• Lower initial M&E, IT and furniture costs.
As these “additional rent” costs drop, the gross cost of occupancy drops and in a reasonable market this should translate into some increase in net rental rates, which in turn, should allow for more capital invested in better buildings and a higher rate of return for investors. Better buildings can further reduce energy costs and operating costs.
Attracting top lease rates and minimizing vacancies, while at the same time reducing base building operating costs, improves the pro-forma for building owners, while tenants benefit from lower gross costs of occupancy [fit out, reconfiguration and operating costs] as well as from the higher productivity and lower absenteeism anecdotally attributed to improved indoor environmental quality.
Some of our clients have begun the design process believing that a LEED Silver certification would be demonstration enough of their green credentials. However, in several cases, once the schematic design was completed, it became apparent that LEED Gold could be achieved at a very small cost premium — as little as $3/sq.ft.
This is because many of the credits achieved at the Silver level are based on solid strategic decision-making that with only minor modification or embellishment will attract additional credits. Once the principles are embraced and a certain momentum gained, the task of arguing for higher standards becomes a lot easier.
The Royal Bank and Telus towers are now acknowledged leaders in their respective fields as far as sustainability is concerned. Already some of their competitors have put out RFPs for new space of a comparable standard. With each such move, the bar is being raised and that ultimately will benefit us all.
Dermot Sweeny is a partner with Sweeny Sterling Finlayson & Co Architects Inc. in Toronto.
- RBC Centre |
- Design Architects Kohn Pedersen Fox Associates PC in collaboration with Sweeny Sterling Finlayson &Co Architects Inc.
- Architect of Record B+H Architects
- Photography Tom Arben, AKA communications Associates
- TELUS House at 25 York |
- Design Architects Sweeny Sterling Finlayson &Co Architects Inc., Adamson Associates Architects
- Production Architect Adamson Associates Architects
- Green Building Sciences Consultant Sweeny Sterling Finlayson &Co Architects Inc.
- Nocom Provided Digital Addressable Lighting Interface [DALI]
Print this article | Send by e-mail