Decision making | Decision making criteria | Typical scenarios and outcomes | Post-construction issues | Highlights of interviews | Round table at SCE | Workshop at SCE
Highlights of interviews made with architects, engineers, and owner representatives
Interview with Maurya McClintock, Façade Engineer, Ove Arup & Partners, San Francisco, California, August 3, 2001.
Typical engineering firms involve mechanical, electrical, structural, and plumbing. There are special disciplines supported world-wide within Arup: civil, acoustics, façades, telecommunications, etc.
When is the engineer typically brought on to projects that involve complex façade systems?
Unfortunately, in comparison to both Europe and Austral-Asia, our experience has been that U.S. architects typically involve façade engineers much later in the design process - sometimes as late as 50% design development (DD) of the project. For advanced façade-building systems, a team effort between the architect and engineers is required to solve integrated design challenges, and to maximize these integrated performance benefits we have found that the team (everyone) must work together from project inception. In the case of a multi-headed client, where decision have to be made at multiple levels, it's even more important to get involved at this earlier stage.
Yes, the process of educating the client is typically longer for integrated projects, and an earlier involvement by more design team members implies a greater cost over time which is why we often see reluctance to involve the façade engineer until later (to reduce design costs). The price that is often paid is loss of potential interdependent performance and increased associated building performance cost.
To offset these higher design costs of longer design team involvement, we often get creative about appropriately limiting scope. We may propose to design/analyze façade performance impacts for the 1%- or 2%-design condition only rather than a full-blown investigation of the building's performance over a typical year. The level of analysis proposed is dictated by the client's desire and level of design team's need (depending on the complexity of the system) to understand the implications of the façade system design under typical operating conditions.
What does a high-performance facade mean to you?
Integrated design that looks at the façade as not merely the skin of the building but as a system that influences and is influenced by the local outdoor climate and the zone 15-20 ft inside the building. Integration and façade systems implies a design that balances numerous (and often conflicting) performance parameters.
It also implies a longer process and greater cost for engineering a system that considers cooling load, lighting and daylighting, comfort, operational, and aesthetic impacts. The client's mentality towards increased design time often drives the solution (we don't often get speculative developers as clients). Most of our current clients are 1-2% leading-edge clients. They demand specific not generic solutions, tailored buildings not a cookie-cutter design that's then transplanted to any place in the country without regard to local climate conditions. Having said that, with education over these last couple of years, we are starting to see a shift in what we call "the mainstream" client's attitude to high-performance, integrated design.
Why do you think there’s a trend now toward high-performance façade systems?
There's a number of new issues that are driving this trend. First, there is a perception that the occupant is driving the needs or program within the building and a desire of the building owner and client to competitively address those needs. In some cases, the needs can be equated to the desire for amenities (operable windows, motorized shading systems, etc.). In other cases, the needs can be equated with the desire for a more humane environment: access to fresh air, access to daylight, connection to outdoors, etc. Second, the ASHRAE 90.1-1999 and California Title-24 codes are stricter than before. To meet them and to achieve the aesthetic desired by some architects, such as an all-glass façade, one has to resort to more innovative and integrated façade system solutions. Third, there is a perception within the architectural and engineering design community that we should provide environmental stewardship for this world's future, a part of which is designing buildings which provide healthy environments while consuming less fossil fuels. The LEED benchmarking system for sustainable design is one way of tracking and quantifying the potential sustainable savings and is rapidly gaining recognition by the design community as a viable convincing mechanism. More clients are interested in obtaining a positive LEED rating. In some cases, cities or agencies are mandating minimum LEED ratings.
Are new technologies a requirement for high-performance façade systems?
Not necessarily. High-performance façade systems can be as simple as the application of natural (age old proven) processes in a simple (known) kit of parts that one assembles. (This was the technique we took with NBBJ on the design of the Seattle Justice Center façade. See the following NBBJ workshop talk.) However, there's no reason why new technologies can not be employed as viable parts of an appropriate design solution. However, at the moment many of these "new technologies" are expensive and one needs to rationalize the balance of costs with the architect and the owner. If, for example, the client wants a lot of clear glass and the orientation is southwest or west, the technological solution could be an operable internal blind (with local extract system) or an external motorized blind, or more advanced façades systems such as switchable glass or double-skin façade systems. The above is in order of increased performance but also increased first cost of the façade system. The client needs to be informed early on of these increased costs and tied to an understanding of resulting increased performance. The rough budget cost comparisons I typically work with during the early stages of design are: a "typical" curtain-wall is typically approximately $65-85/ft2 versus the cost of advanced façade systems can be upwards of $150-$250/ft2. There must be an education process that affords an early realization and full understanding of the implications, so that the client can make well-informed decisions to engage or walk away from proposed design solution.
What is the value of analysis?
The process of analysis results primarily in an educational process for the client. This process must show the interdependency between systems and provide protection from value engineering. It must also show the interdependency between cost and performance variables. It sets the ground rules, and this must be done early on.
Some decisions are based initially on rules-of-thumb and expert judgment that is then validated through engineering analysis. Our analysis typically includes a whole host of issues: daylighting/ lighting, energy performance, structural, waterproofing, acoustics, indoor air quality, thermal comfort, visual comfort, glare assessment; however, the specific concerns are dictated by the client. For some clients, glare and VDT computer use may be the key issue. The design team, together with the client, tailor the scope of analysis to the specific project and educational needs.
How do you convince clients to take an integrated approach?
Again, education - we try to educate the client so that they understand the balances provided by integrated design and life-cycle costing. However, the client must be willing to be educated.
In some cases, this takes the form of explaining building physics concepts such as control of solar loads and daylight and how that benefits operations and the occupant. On other occasions, we talk dollars. The dollars "argument" here in the U.S. is often critical.
The client must agree to justify increased façade system first cost over an agreed life-cycle of the building - accounting for other building systems, occupant impacts and operational + maintenance costs. This is often difficult in our U.S. "throw-away society" and we often make the comparison to European development attitudes as part of our "education process":
1. U.S. developers and clients often demand a payback on energy operation alone of less than 3-5 years. Compare this to EU buildings which are often justified over a 20-30 year payback, and paying anywhere from 3 to 6 times the energy prices of the U.S. We just can not make a convincing argument for such clients - their interest is not in the long-term performance of the building and its impact on occupants.
2. Another reason why we're seeing high-performance façades in Europe is because of their approach to the building's ability to meet the needs of the occupants:
- there are codes for access to daylight and fresh air in many EU countries,
- there is a different cultural mentality in the EU - occupants refuse to work in buildings that don't supply what they see as "requirements" of a healthy work environment - which then essentially drives the development and realty markets.
For these clients, the initial capital cost of $150-$250/face-ft2 of the façade can be more easily justified against the full operational cost/performance of the building.
We also try to discuss some of our past integrated building experience resulting in marginal increase in performance often obtained at no added cost. For example, for a 0-3% increase in capital costs, one can achieve 10-15% better performance (than stipulated by ASHRAE 90.1-1999.) For a 5-10% increase in capital costs, one can achieve 20-25% better performance.
How are advanced façade systems implemented in industry?
It is critical that the design team educate the contractors (and specialist sub-contractors) as well. The typical construction process often puts the burden (and risk) of engineering the façade on the vendor, particularly under design-build contracts which then carries a contingency cost. Some suggestions that have worked for us on past projects:
- One needs to involve the contractor and manufacturer early on, as part of the design team. For example, clients could pre-qualify the curtain-wall contractor and involve their expertise early on toward designing a least-cost solution that includes ease of construction, appropriateness and availability of existing components.
- One has to portray to the general contractor that the proposed façade system involves merely putting a kit of standard parts together in a slightly different way. Actuators, throttling flaps, power at the window wall may be perceived as unique, but such systems are used conventionally with mechanical systems and can be applied with the same labor in façade systems.
In addition, a number of European curtain-wall contractors provide generic solutions in the form of "standardized" advanced façade system units at a preliminary budget cost of around $120-$180/ft2 (with a few Canadian manufacturers following suit). However, a number of design teams have found that these same dollars can be applied to a project- and site-specific solution tailored to a specific architectural and engineering aesthetic for increased performance for the money invested.
Question/Information: eslee@lbl.gov