Dynamic Façades: Looking for smarter skins to improve efficiency and provide clean energy

by mdoyle | December 7, 2013 3:13 pm

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By Bob Marshall, P. Eng., BDS, LEED AP
As Canadian building code requirements become more stringent, and as the criteria for programs like the Leadership in Energy and Environmental Design (LEED) rating system become tougher, demand will increase for ‘smarter’ building skins—essentially, claddings with high thermal performance and the potential for energy production. World-class innovations from Europe, Australia, Asia, and the United States may strongly influence the dynamic façades that will change the landscape of Canada’s built environment. Designed to improve the energy efficiency performance of buildings, such assemblies are a new work item for International Organization for Standardization (ISO) Technical Committee (TC) 163/WG4, Thermal Performance and Energy Use in the Built Environment.¹[2]

At the group’s meetings in September, Canadian representatives—including this author—had the opportunity to share some of the preliminary findings from work on innovative hybrid curtain walls. The research was funded by the Industrial Research Assistance Program (IRAP). These high-efficiency systems include glazing that can generate electricity right from the façade. Based on the preliminary findings, game-changing innovations may make the ‘zero-energy’ building target for the 2030 Challenge quite achievable.²[3] In the near future, glass building skyscrapers could essentially provide a source of renewable energy for our communities. (Buildings offer high amounts of solar transmittance due to their large surface areas, but with current advanced glazing technologies, only about five per cent of the energy comes from the clean energy from the façade.)

[4]This author explored several innovative building projects at a German international exhibition, IBA Hamburg. In that city, the government showed leadership by relocating its new State Ministry for Urban Development and Environment headquarters from Hamburg’s downtown centre to Wilhelmsburg, rejuvenating a neighbourhood. The building itself (Figure 1) is also quite remarkable.

A performance of 70 kWh/m²/year of ‘primary energy’ was established at the concept stage. This metric includes source and distribution losses, rather than ‘delivered energy’ performance (at the building), which is mostly used in Canadian and U.S. buildings. (Essentially, ‘primary energy’ includes production energy and energy required to make up for the line losses, etc. If the building creates energy, it can be used in the building or fed into the grid, and will have much lower line losses.) A combination of passive and active measures are employed, including:

• increased insulation;
• appropriate glass areas of the façade (i.e. glass areas are approximately 40 per cent for optimal daylighting/energy efficiency);
• natural cross-ventilation via an open staircase atrium;
• geothermal energy; and
• ‘free’ cooling at night through an off-peak system that allows removed heat to be stored in geothermal loops.

Dynamic façades will allow architects and owners to continue to use glass to provide daylighting. With transparent, solar-power-producing glass and high-performance insulation technologies—such as vacuum-insulated panels (VIPs)—glass buildings can be significantly more energy-efficient.^3[5][6]

Before summarizing some of these innovations, it is important to emphasize ‘holistic thinking.’⁴[7] By integrating dynamic façades with other building systems, there is an opportunity to maximize performance benefits and realize cost savings. For example, a smarter skin can allow for a reduction in heating and cooling loads, leading to reduced initial capital costs, smaller mechanical units, and lower operating costs.

Smart solutions to meet code and LEED v4
It is smart to evaluate energy efficiency measures—including air leakage strategies and minimization of thermal bridges in window and wall assemblies—at the schematic and design stages. This is preferable to finding out after construction the building skin is not sufficiently airtight (potentially causing health problems), the windows need exterior shading, and the wall assemblies yield condensation leading to mould growth. Retrofitting additional heating/cooling equipment and remediating thermal anomalies in windows and walls is significantly more costly than appropriate construction and detailing.

Certain solutions should be identified at the new LEED v4-required⁵[8] prerequisite design review of the building enclosure (i.e. Energy & Atmosphere [EA] Prerequisite 1, Fundamental Commissioning and Verification)? It is important to remember any level of LEED certification is impossible without meeting all prerequisite requirements. Airtightness can be improved by specifying unitized curtain wall systems fabricated in controlled conditions and expected to meet higher energy performance standards. Unitized wall modules may be installed during inclement climate weather conditions common in many parts of Canada.

Window innovations include warm-edge (perimeter) spacers with slower heat transfer at the frames, and metal wall profiles with thermal breaks structurally integrated into the frame that improve U-values and reduce the risk of interior condensation. Solid wood buildings provide a natural thermal break and employ renewable raw materials. In Hamburg, there are many mid-rise solid-wood buildings, including Walderhaus Hotel (Figure 2), which was one of the destinations of this author during his dynamic façade excursions.

I[9]n Canada, code solutions should be suited to the specific building uses, with compliance particulars verified by a qualified building science professional. COMcheck is a free software from the U.S. Department of Energy (DOE); it can be used as it includes the Ontario Building Code’s (OBC’s) SB-10 requirements and an envelope compliance report. A compliance checklist is prepared for the OBC requirements, including insulation, fenestration/doors, and air leakage. (For other provinces, there are Model National Energy Code of Buildings [MNECB] and ASHRAE compliance checklists.)

LEED v4 will require more stringent energy efficiency performance than previous incarnations of the rating program. New York City already requires performance data to be published for large existing buildings, and it seems to be only a matter of time before other municipalities in Canada and the United States follow suit. Only by providing evidence of a building’s actual—and not projected—energy consumption can a project truly be considered ‘sustainable’ or ‘green.’ New York’s LEED Platinum-rated Bank of America Tower, which opened in 2010, was reported to use more than twice the energy per square foot as the 80-year-old Empire State Building.⁶[10]

The U.S. Green Building Council (USGBC) is learning from this experience by creating stronger integration between LEED credits and their performance outcomes. One of the most significant changes will be the result of the aforementioned building enclosure review prerequisite in LEED v4. The question is, who should conduct this review?

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For Canadian projects, it makes sense to have those qualified for LEED Canada’s Durable Building credit (originally, Materials & Resources [MR] Credit 8, but now Regional Priority [RP] 1) to complete this task. (These qualifications were established by a special Durable Building Task Force.) There are many similar building enclosure practices in North America that can be applied to all LEED buildings, so there are practical approaches to meet the LEED v4 prerequisite.

BECx and dynamic façades
Another significant LEED v4 change is the building envelope commissioning (BECx) option as part of EA Credit 1, Enhanced Commissioning, which is worth two points. BECx of the thermal envelope design details involves checking the compatibility of the numerous materials used in an assembly. Further, the built conditions of the envelope assemblies and interfaces are checked to verify they are properly constructed.

The interfaces between different façades, and between the façade and roof, are critically important for the building to be sufficiently airtight. Internal façade components need to be constructed to drain any moisture penetrating into the wall to the exterior, rather than causing damage and health issues for the occupants. The BECx process provides a greater likelihood the air barrier system is continuous, and moisture control measures are in place for better building performance.

Sustainable building should not stop at current codes or with LEED points and building certification. By setting energy performance targets, the creativity of the entire design/construction team can be unleashed.⁷[12] The proposed 2015 National Energy Code for Buildings (NECB) will be the first North American jurisdiction to require energy use intensities (EUIs). Therefore, it is smarter to identify higher energy efficiency measures that contribute to lower EUIs. At the same time, why not assess a zero-energy building target with use of renewable energy options? IBA Hamburg includes 60 projects to illustrate ways to make positive changes in the built environment in terms of energy-efficiency, social structures, and community planning.⁸[13] This article will now examine a few that could be considered for Canada.

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Bioreactor façades
Comprising 15 apartments, the five-storey residential BIQ building in Whilhelmsburg (Figure 3) is built to the Passive House standard.⁹[15] The building has southwest- and southeast-facing bioreactor façades. Two different types of algae (summer and winter grade) are cultivated for the generation of energy and to control the daylight and provide shading for the building. The algae in the glass bioreactor façades is constantly in motion and changing its colour.

The bioreactor’s façade is part of a holistic regenerative energy concept where the plate-shaped glass panels produce biomass and heat through photosynthesis and solar thermal energy. The heat is directly available to the house. The biomass is exploited in containers (Figure 4) to an offsite location and converted into biogas.¹⁰[16] Geothermal energy and a connection to Integrated Energy Network at Wilhelmsburg Central provide the balance of the heat supply during winter and serve as a long-term reservoir for the heat generated in summer.

[17]Textile membrane façade
A three-storey residential building in Wilhelmsburg comprises four family units built to the Passive House standard. A dynamic textile membrane façade (Figure 5) is not only a distinguishing feature, but also a smart curtain—it provides shading for the patios and includes flexible photovoltaic modules on the membrane strips. The strips rotate to optimize energy generation and daylighting.

From the first floor patios, all four units have a view of a canoe canal and the Island Park. The building consists of sustainable solid wood construction, including the walls and ceilings left as natural wood surfaces to achieve greater carbon dioxide (CO₂) reductions. High levels of insulation and airtightness are integrated into the building façades (Figure 6). Heat pumps provide the balance of the heating and cooling for the building.

Energy bunker
At IBA Hamburg and throughout Europe, social structure and community planning are also priority. An example is the restoration and reuse of the Energy Bunker in Wilhelmsburg. The sturdy and distinct air-raid bunker was built in 1943, sheltering up to 30,000 people during Allied bombing raids. Four years later, the building’s interior was destroyed by the British. The outer shell, with up to 3-m (9-ft) thick walls was all that remained undamaged for more than 60 years (Figure 7).

[18]It was once inconceivable a new use of this memorial would be found. However, the Energy Bunker has been covered with 400 solar thermal units on the roof and photovoltaic panels on the south elevation (Figure 8). In addition to the solar energy, energy derived from biogas, wood pellets, and waste heat enable production of approximately 22,500 MWh of heat and about 3000 MWh of electricity. This neighbourhood power station is an example of decentralised energy policy that creates local jobs and revenues.

Canada typically achieves enhanced energy-efficiency in public-private partnership (P3) projects and other landmarks when a specific energy performance target is set as part of the owner’s requirements. (It helps when the owner’s requirements are quantified in the specification in terms of eKWhr./m²/year, with the actual performance monitored. Some owner’s specifications have penalties and rewards if there is a significant difference. It is important to meet the target on a cost-optimized basis (i.e. lowest cost measures that provide the best energy savings); therefore, the contractor or cost estimator should be included for estimating real costs for different scenarios. This approach works, for example, on a P3 project where the energy target was 202 ekWh/m²/year (about 45 per cent below the proposed 2015 NECB EUI of 373 ekWh/m²/year). The winning approach was achieved with analysis and collaboration between the architect, engineers (i.e. structural, building envelope, mechanical, and energy), and contractor.

Solar power glazing façade
Advanced solar power glazing façades are another promising technology. (Though not showcased at IBA, they were presented at the ISO meetings.) There needs to be more work on these building-integrated photovoltaic (BIPV) systems, which employ nanotechnology as an integral part of the glass layers, while still offering transparent glazing. Pilot demonstrations in the Northern hemisphere are essential.¹¹[19]

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In the Southern hemisphere, however, the precedent has already been set. The new Government Communications and Information Systems Office in Pretoria, South Africa, is believed to be the first demonstration of advanced solar power glazing (Figure 9). Based on preliminary performance data, advanced solar power glazing could generate about 35 W/m² per façade (performance based on solar transmittance on each façade and obstructions). With other attributes that include more than 75 per cent transparency and more than 90 per cent of solar infrared blocked, the glazing also helps with daylighting while converting solar energy into a clean, renewable power source.

As the Greater Toronto Area (GTA) is the fastest growing high-rise capital of North America, testing and demonstration of this innovative technology here is a top priority on the list of many of those working in the dynamic façade field. Architects and building owners must assess the feasibility of integrating new innovative technologies into their projects. It is best to do this decision-making at the concept and pre-design stages. For the early adapters, possible government funding partners are available.

Conclusion
The importance of the thermal envelope and smarter skins for all buildings in North America is critically important. Based on current experience, it is expected prototype demonstrations will occur next year, with full-scale demonstrations soon following, depending on scale-up of production by a large glass supplier.

In the meantime, architects, engineers, and specifiers can prepare for this new energy future with a series of Ontario Association of Architects (OAA) workshops; an April class (Session IV) held in Toronto and Ottawa, is entitled “Skins: The Importance of The Thermal Envelope,” and will be presented by this author and other experts.¹²[21]

[22]Beyond ISO, other groups are currently engaging in testing and standards creation for dynamic façades. For example, it is important to have a standard measurement to define how to gauge electrical power for various PV modules. International Electrotechnical Commission (IEC) 60904-1, Photovoltaic Devices, is typically used—there are a few labs in Canada that are accredited for this method.

With code and LEED v4 compliances, Canadian design/construction professionals can help achieve smarter and more dynamic façades. As a result, the average energy performance of North American buildings (traditionally relatively poor) will significantly improve.

Of course, the information in this article does not only pertain to new builds. The many existing structures in Canada, where the façades are reaching the end of their useful service life, are another opportunity to integrate world-class innovation. The re-skinning of these projects will not only improve energy efficiency, but also yield potential for energy production.

Notes
¹ For more information, visit www.iso.org/iso/iso_technical_committee?commid=53476[23]. (back to top[24])
² Initiated by the Architecture 2030 group, the 2030 Challenge asks the global architecture and building community to ensure all new buildings meet a performance standard of 60 per cent below the regional (or country) average/median for that building type, and that an equal amount of existing building area be renovated annually to meet a fossil fuel, greenhouse gas (GHG)-emitting, energy consumption performance standard of 60 per cent of the regional (or country) average/median for that building type. It also requires the fossil fuel reduction standard for all new buildings and major renovations be increased to carbon-neutral by 2030. This may be accomplished by implementing sustainable design strategies, generating onsite renewable power, and purchasing (20% maximum) renewable energy. For more, visit architecture2030.org[25]. (back to top[26])
³ For more on VIPs, as researched by ISO/TC 163/SC 3/WG 10, visit www.iso.org/iso/home/standards_development/list_of_iso_technical_committees/iso_technical_committee.htm?commid=53530[27]. (back to top[28])
⁴ Further discussion on taking a gestalt approach can be found in this author’s article, “Time for Holistic Thinking: Integrated Building Energy Performance Solutions[29],” in the May 2010 issue of Construction Canada. (back to top[30])
⁵ While the new LEED v4 is for the U.S. Green Building Council (USGBC) program, its tenets will likely be adopted by CaGBC in a forthcoming LEED Canada rating system update. (back to top[31])
⁶ To read the New Republic article, “Bank of America’s Toxic Tower: New York’s ‘Greenest’ Skyscaper is Actually its Biggest Energy Hog,” by Sam Roudman, visit www.newrepublic.com/node/113942[32]. (back to top[33])
⁷ For more on this concept, see the December 2012 issue of Construction Canada for this author’s article, “The Need for Energy Performance Targets[34].” (back to top[35])
⁸ Visit www.iba-hamburg.de/en/iba-in-english.html[36]. (back to top[37])
⁹ To learn more about the Canadian Passive House Institute program, visit www.passivehouse.ca[38]. (back to top[39])
¹⁰ Biomass transported to make biogas is expensive and not very efficient (i.e. < five per cent). In Canada, some sewage treatment plants use the biomass in the plant to make biogas for running local generators. However, there is not yet a market to sell biomass on a grand scale. (back to top[40])
¹¹ Current cost/benefit analyses of BIPV dynamic façades, with feed-in tariff (FIT) incentives, are resulting in simple payback estimates of about seven to nine years. It is difficult to obtain real incremental cost estimates for the advanced solar power glazing versus traditional curtain walls, until specific project particulars and suppliers are identified. (back to top[41])
¹² Visit www.oaa.on.ca/professional%20resources/continuing%20education/undefined[42]. (back to top[43])

[44]Bob Marshall, P. Eng., BDS, LEED AP, is Canada’s appointed expert on the International Organization for Standardization (ISO)/TC 163-TC 205 WG4 on Energy Performance, and the voting member for TC 163/SC 2 on calculation methods, which includes dynamic façades. He has been appointed to the National Research Council’s (NRC’s) Task Group on Energy Use Intensity targets. Marshall founded Cedaridge Services, and is a senior building envelope engineer at Stephenson Engineering in Toronto. He can be reached at bmarshall@stephenson-eng.com[45].

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