You may have heard the buzz about the Timber Towers: one architectural firm's proposal for an interesting alternative to the usual steel structures that we see along the Philly skyline. The firm, Hickok Cole, proposed a timber structure at site of the rumored third Comcast Tower for the Skyhive Skyscraper Challenge: of course we had to get an interview with a few of the team members-Anthony Maiolatesi, Sean McTaggart, and Rosa Zlotkovsky- for more information about the company and their proposed design.
- How did you become interested and involved in this project and in this line of work?
We’ve seen hypothetical mass timber projects on design blogs for years, but one event that really kicked things into gear was “Timber City”, an exhibit at the National Building Museum in DC last year. Inspired by what we saw and read about, a small team in our office then partnered with DPR (contractor) and Arup (engineer) to develop a cost & design comparison between mass timber, steel, and concrete structure. Our nation’s capital has a 130’ height limit, and most work downtown is concrete structure. Philly is the closest market that could support a true “skyscraper” and has no such height limit, so we saw that as a logical next step to push the envelope of what is possible with the material of wood. The vehicle for this exploration was “Timber Towers”, our submission for the Skyhive Skyscraper Challenge, which challenged participants to re-think construction materials and technologies in the near future.
- How has the response been from people working in and living in these buildings in Tokyo, Minneapolis & Newark?
Readers should note that the Tokyo skyscraper is still at least a decade from being built, and is currently just a schematic design. There are similar hypothetical projects in London, Chicago, and NYC. The 8-story T3 office building in Minneapolis is complete, and the developer Hines is currently constructing another one in Atlanta. Michael Green Architects (recently acquired by Katerra) is also in the early phases of 10-story timber office building in Newark. When it comes to the human experience of living and working in these buildings, the term we often hear is biophilia, the idea that humans inherently prefer over synthetic materials. While there is a short-term cost premium, mass timber office buildings have happier employees, demonstrated by fewer sick days and increased productivity. Furthermore, the property managers, in turn, are also seeing rent premiums of up to $8 per square foot.
- Is there a climate or area of the world that these structures are better equipped to be built?
Wood structures are much lighter than steel or concrete, and as a result their foundations can be up to 30% smaller. Mass timber is especially great for areas in which excavation is either difficult or prohibitively expensive. They are also better at handling lateral loads, such as wind or earthquakes. Therefore, in areas prone to inclement weather and/or seismic activity, turning to mass timber makes sense. The US military has also shown interest in mass timber construction for lodging accommodations, not only because of its accelerated construction schedule capabilities, but also for how well it performs in blast testing.
- It's mentioned that the 2nd Comcast Center could have been built faster & for less of an expense if wood would have been the main material in construction, how was this calculated and how would it change the structure as we see it today?
That's true, and we settled on a 60-story Timber Towers design to serve as a direct comparison with the existing steel Comcast towers that are each roughly the same height. Generally speaking, mass timber projects can be built 20% faster, and with a much smaller construction crew. A skyscraper construction schedule is approximately 3 years, and so theoretically we could shave 6 months off that, allowing an earlier return on investment. Steel and concrete pricing is typically 50 /50 materials & labor, but mass timber is something like 80/20, and so union-heavy cities like Philadelphia can really see some serious cost savings. Which isn't to say that this is a “work-around”...T3 in Minneapolis was built using union labor. Off-site, prefabricated construction is a much safer working environment, and its efficiency results in fewer on-site truck deliveries, less noise, and ultimately a building that can be assembled using a power drill.
- Is there a limit to the height to which you can build using lumber as opposed to steel/concrete?
"Mass timber" is not to be confused with "stick-built" or "light-frame" construction that is common for single-family houses. It is an engineered, solid-wood system that technically falls under Type IV construction, or "Heavy Timber." The current height limit for this category is 85 feet, if you build a concrete podium with mass timber above, which likely allows for 5 or 6 stories. The 2021 International Building Code will soon allow for 18 stories, having looked to Brock Commons, an 18-story mass timber student dormitory in British Columbia, as the gold standard. As far as the physical limitations of mass timber construction, our design for the Skyhive Skyscraper Challenge showcased a range of building heights, demonstrating what our partners at Arup considered the realistic limits of a purely wood building. The 30-story residential tower consists of regularly spaced CLT shear walls, utilizing the redundancy of residential modules, which are typically narrower. The 45 and 60-story office towers are a hybrid structure, combining mass timber (CLT slabs, columns and cross-bracing) with a steel core and steel connections.
- Where are materials sourced for these buildings - are the local to where they are being constructed?
I think most people assume that wood buildings are a West Coast obsession, considering the plethora of forests in the Pacific Northwest. However, more mass timber projects have actually been built east of the Mississippi River, and the vast majority of privately owned forests - as opposed to state or federal lands - are on the east coast. At this moment, however, Canada is one of the biggest providers of construction lumber, as is Austria and Germany. Transport by shipping container is cheap, but loading these panels onto trucks tends to get expensive, and so it helps that Philadelphia is a major port city. We’re all somewhat uncertain as to what the long-term effects of this administration’s steel and aluminum tariffs will be, but that is definitely something to keep in mind as well.
- How does the interior feel differ in a wood skyscraper, do you have images of any current buildings?
Architect Michael Green refers to wood as "nature's fingerprints", and consequently, people have an affinity towards nature – this is the foundation of biophilic design. In a mass timber skyscraper, occupants will be much more connected with natural elements through sight, touch, and even smell, and these connections can have a profoundly positive impact on their overall “wellness.” By comparison, concrete office buildings typically feel cold and sterile, lacking the warmth and tactile properties of wood. CLT floor slabs usually still have a finish floor material, but the undersides are often left exposed, and these wood ceilings, beams, and columns truly create a beautiful work and living environment.
- Is there any update to the shortlist for the Skyhive Skyscraper Challenge?
That’s a wrap for the competition, and we were proud to receive honorable mention. Building from this momentum, we really want to establish Hickok Cole as a regional leader in mass timber design & construction. We recognize that the time has come for architects to find ways to reduce our carbon footprint, minimize waste, and truly re-think the construction process. It might be another generation before a project like Timber Towers can be built, so right now we need to educate clients, GCs, and the general public about the benefits of mass timber as an alternative to steel and concrete. Talking to industry experts, attending seminars, and meeting with code officials is crucial, and this sharing of research and knowledge helps facilitate a collective understanding of mass timber’s potential.
- What has been the biggest struggle or misconception when presenting this idea to metro area officials?
The two most popular questions I get involve 1.) fire safety and 2.) sustainability. First, some variation of "Won't this burn down? Is this really safe?" David Barber of Arup is likely the foremost expert on the topic, and he explained that mass timber quickly forms a protective char layer in the event of a fire, and actually holds up longer than unprotected steel in some fire tests. The beauty of mass timber is that it can serve as a finish material and also provides the required fire rating. The second question is "Why are we cutting more trees down?" In North America, growth exceeds harvest by 40%. Some countries do struggle with deforestation, but the main culprit is typically agriculture and mining, not the logging industry. Wood is the only truly renewable material on earth, and can remove carbon from the atmosphere. On the other hand, steel and concrete are finite resources, and the extraction of these is not only inefficient but incredibly harmful to our environment. While it may initially appear to be a absurd proposal, building tall with wood is an effective way of tackling climate change on a large scale.
As you can see, Hickok Cole has some fascinating ideas that will surely be game changers for the future of the construction industry.