Role of structural thermal breaks in senior housing projects

by arslan_ahmed | February 1, 2024 3:37 pm

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By Tracy Dacko

Today’s new senior residences appeal to a growing customer base by offering the comfort previously associated with high-end apartments and condominium living.

Skylights, green roofs, balconies, courtyards, nature walks, theatres, fountains, and other amenities abound. However, less obvious but critical to the comfort and health of seniors are warm interior floors adjacent to exterior walls and doors, and mould-free air recirculating within the sealed building envelope—improvements which were made possible by insulating concrete and steel structures that penetrate the building envelope.

Correcting an old problem caused a new one

While architects employ a myriad of techniques to incrementally reduce heat from escaping through walls and ceilings, heat energy often finds an easy escape route through thermal bridges. A thermal bridge is created when highly conductive components, such as the concrete slab of a balcony or the steel beam that supports an entranceway canopy, penetrate the insulated building envelope.

When winter temperatures chill the outside air, the obvious outcomes are high heating costs and cold interior floors, but building owners now face an even larger problem: condensation and mould caused by the higher interior humidity of today’s well-sealed buildings.

Prior to air-tight building envelopes, air leakage caused interior humidity levels to equalize with exterior humidity levels of approximately 25 per cent during cold winter months, which is too low for cold interior structures to reach dew point or form condensation.

With interior humidity levels now ranging from 40 to 50 per cent, the interior side of chilled penetrations can reach dew point, form condensation, and support mould growth on adjacent interior surfaces and in stagnant cavities. Mould can become airborne years before it becomes visible on interior walls and ceilings, exposing building owners to significant liability and remediation costs.

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Insulating against energy waste, chilled floors, mould growth, and additional costs

Balconies, slab edges, eyebrows, canopies, parapets, rooftop equipment, connections, and other structural penetrations can be insulated by installing structural thermal breaks at the building envelope.

Thermal breaks reduce heat loss at the penetrations by up to 90 per cent, often allowing a corresponding reduction in HVAC mechanical system size/capacity, capital cost, and operational cost. Since penetrations remain too warm to reach dew point, form condensation, or support mould growth, the building owner also avoids related liability and remediation costs.

Structural thermal breaks raise the temperature of interior floors adjacent to penetrations by up to 34 F (19 C), allowing senior occupants to enjoy greater comfort and usable space. The elimination of thermal bridging is increasingly required in building codes and certifications. Vancouver’s code calls for eliminating all thermal bridging in the building envelope. Passive House buildings aim to minimize minimal thermal bridging and provide continuous insulation (ci) throughout the building envelope to reduce heating/cooling demand and improve comfort.

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The importance of structural thermal breaks

Pacific Arbour Retirement Communities (PARC), which operates several senior residences in British Columbia, has incorporated structural thermal breaks in five buildings to avoid thermal bridging at balconies, rooftop connections, and canopies, which also contributes to the requirements for achieving LEED gold certification.

Constructing senior residences for sustainability, PARC targeted 25 per cent in energy savings at its Cedar Springs location through design elements such as an insulated exterior wall system, shade-producing eyebrows, triple-glazed windows, and structural thermal breaks.

“If we design something that’s efficient from a utilities-usage standpoint, that’s always helpful to us from an investment perspective,” says PARC vice-president of development and construction, Russell Hobbs. “Long-term efficiencies are a big consideration for us.”

Using structural thermal breaks to reduce heat loss contributed to the building’s overall efficiency, creating more comfortable and consistent interior floor temperatures while using a smaller, less expensive heating system.

Going green adds to occupant comfort

Located in one of West Vancouver, B.C.’s most exclusive communities, PARC’s Westerleigh Retirement Residence is a seven-storey facility that incorporates a green roof with drought-tolerant vegetation, reduced use of potable water, and innovative heat recovery strategies which helped it to achieve LEED gold certification.

The 13,020 m² (140,000 sf) facility contains 129 rental suites, more than 100 of which have access to balconies that wrap around the south and west sides of all seven floors.

“The continuous 1.8-m (6-ft)-deep balconies wrap around the bottom four floors of the building and then step back on floors five through seven, which are smaller,” explains project architect Shane Friars, principal at BFA Studio Architects. “In addition to providing amenity space, they shade the south and west sides of the building.”

As with Cedar Springs, to prevent the balconies from conducting heat from interior floor slabs into the exterior environment, structural thermal breaks were installed at the point of penetration through the building envelope.

“Without them, there would be quite a lot of exposed slab and thermal bridging,” says Friars. “Tenant comfort is compromised when uninsulated balconies chill interior floor slabs—an issue of particular significance in residences for seniors.”

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Sustainable, urban design

Another PARC facility, the Oceana, is located in metro Vancouver, B.C. As with other PARC properties, Oceana’s energy-saving measures include a green roof with drought-tolerant vegetation, and a robust building envelope of 152.4 mm (6 in.), semi-rigid stone wool insulation on the exterior, and 88.9 mm (3.5 in.) fibreglass batt insulation inside of the wall.

Other energy-saving measures include heat recovery ventilators, rooftop high-efficiency boilers feeding hot water storage tanks, a hot water recirculation system, and exclusive use of LED lighting.

Out of Oceana PARC’s 199 residential living units, 181 include balconies, which are insulated using structural thermal breaks in the same manner as the Cedar Springs PARC and Westerleigh PARC balconies. However, Oceana PARC presented additional thermal bridging concerns at its parapets, which was mitigated by installing structural thermal breaks engineered for concrete parapet-to-roof-slab connections.

The conventional method to reduce heat loss through parapets is to wrap them with an insulation barrier. However, wrappings are prone to damage and water penetration over time, particularly where railings, covers, or fasteners pierce the insulation, requiring repair and maintenance.

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In addition, parapets wrapped with insulation barriers remain part of the heated building mass, whereas parapets insulated and supported by structural thermal breaks sit outside of the heated building envelope above roof slab, retaining heat energy more efficiently.

“We’re an owner/operator, so energy efficiency is very important to us, not only for our residents’ comfort, but also because of lower operating costs, lower heating and cooling bills,” says PARC director of construction Bob Fritz.

Building to Passive House standards

Another owner-occupied senior residence, built by the Hellenic American Neighborhood Action Committee (HANAC) in Queens, New York, is the first affordable senior housing development in the U.S. to meet the Passive House Institute design standards for energy efficiency and ecological footprint reduction.

HANAC met the standard by building its senior residence with passive solar design, high-impact under-slab insulation, triple-glazed windows, balanced ventilation, efficient heating and cooling systems, a thermally-broken rainscreen system, energy recovery ventilation systems, and a continuous super-insulated building envelope.

To preserve the integrity of the envelope, HANAC installed structural thermal breaks where steel elements penetrate the insulated envelope to support rooftop ventilation equipment and two steel canopies.

“We’ve done LEED projects for years, but Passive House is a much more specific and robust system,” says Jack Esterson, design partner with project architect, Think! Architecture and Design. “Passive House certification makes perfect sense as HANAC holds onto and operates its buildings for a long time and wants to keep energy and maintenance costs low. Being able to save between 60 to 80 per cent on your energy bills is a real benefit.”

The Passive House standard looks to maximize occupant comfort, which is important as seniors are more sensitive to temperature,” adds Esterson.

Designer Brian Dobrolsky explains, “This is a concrete, cast-in-place building. For the two 2.8 x 3 m (8 x 10 ft) canopies, we have steel that is anchor-bolted back to the beam. One canopy shields the entrance of the early childhood education facility, and one shields the residential portion. Inside the canopies is steel tubing. So, for these connections, we needed to add structural thermal breaks at those points.”

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“We also have structural thermal breaks at the steel dunnage on the roof at the feet where the two large energy recovery ventilation units sit. The units are a requirement for Passive House projects.”

“Every multifamily building has a lot of equipment on the roof and typically at least one canopy extending from other floors. These are structural elements that must connect to the building. Except for structural thermal breaks, the only other way to connect them is with continuous steel beams, which are very thermally conductive,” says Gahl Spanier, a Passive House consultant with the Association for Energy Affordability (AEA). “Without the structural thermal breaks, thermal bridges would impact the thermal performance of the building and might cause moisture accumulation and other problems. Passive House has no tolerance for that, and therefore in the places where we have thermal bridging, we have to use structural thermal breaks.”

Emphasizing thermal comfort

The Valley Stream Retirement Residence in Ottawa, Ont. is a 10,172 m² (109,500 sf) privately-owned and operated facility designed by S. J. Lawrence Architects, housing 193 units, a movie theatre, billiards room, gym, and social areas for residents on manicured grounds.

The building entrance canopy, which creates a portico for automobiles, is structurally supported on one side by the main building. With a structural steel frame and two hollow steel section beams connecting directly to the building’s concrete slab, the canopy is a potential thermal bridge, which could cause significant energy and heat loss as well as dampness and mould growth.

To insure a high-integrity building envelope, the design team installed steel-to-steel structural thermal break modules. This thermally efficient load-bearing connection eliminated the thermal bridging problem.

Construction technology offers sustainable solutions for livable spaces

Using innovative design and the latest construction technology, including structural thermal breaks, owners/operators can construct buildings that are attractive, sustainable, comfortable for occupants, and economically viable over the life of the building, enhancing return on investment (ROI) by avoiding near-term energy loss and long-term remediation.

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Tracy Dacko has more than 20 years in strategic marketing management, including eight in the building products industry. She is a member of Passive House Canada, Reinforcing Steel Institute of Canada (RSIC), l’Institut d’Acier d’Armature du Québec (IAAQ), and the Architectural Institute of British Columbia (AIBC). She also served on the Board of Trustees for PeopleCare Center for Human Services, and has authored numerous articles and published works.

Source URL: https://www.constructioncanada.net/role-of-structural-thermal-breaks-in-senior-housing-projects/

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