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Thermal Breaks Cut Balcony Heat Loss

<![CDATA[A rendering of Oceana PARC and its two buildings highlights balconies, parapets, and shading eyebrows. ]]>

The PARC Retirement Living’s Oceana facility design insulates parapets and balconies with 2,000+ structural thermal break.

A rendering of Oceana PARC and its two buildings highlights balconies, parapets, and shading eyebrows.

On the Johnston Road Corridor in the city of White Rock (Metro Vancouver area), PARC Retirement Living, Vancouver, British Columbia, is implementing innovative building-envelope technology and sustainable design throughout its Oceana PARC residence. PARC director of construction Bob Fritz stated, “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 and lower heating and cooling bills.”

As with two of PARC Retirement Livings’s other Vancouver-area retirement residences, Cedar Springs PARC and Westerleigh PARC, Oceana PARC’s energy-saving measures include a planted roof with drought-tolerant vegetation and a robust building envelope of 6-in., semi-rigid stone-wool insulation on the exterior and 3.5-in. fiberglass batt insulation inside the walls. The building envelope also incorporates 5,970 linear ft. of Isokorb structural thermal breaks that significantly reduce energy loss at the balconies.

Additional energy-saving measures at Oceana PARC include heat-recovery ventilators, rooftop high-efficiency boilers feeding hot-water-storage tanks, a hot-water recirculation system, exclusive use of LED lighting, and concrete parapets insulated from the heated building interior by structural thermal breaks.

This view of the building’s south face shows the significant amount of balcony footage involved in the design. Thermal breaks will keep the living spaces to which they’re attached more comfortable for occupants.

Stopping heat loss

Thermal bridges occur where balconies, parapets, canopies, rooftop equipment, and other structural elements penetrate the building envelope. Like heat-sink fins, these penetrations draw heat from interior concrete and structural steel through the insulated envelope, dissipating it to the exterior. In addition to increasing energy use, carbon emissions, and costs, thermal bridges chill the interior side of structural penetrations. This creates an environment for condensation and mold growth, and results in uncomfortably cold floors adjacent to balconies—an issue of particular significance for retirement residences.

Of Oceana PARC’s 199 residential living units, 181 include balconies, which are insulated using Isokorb 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 the PARC team mitigated by installing Isokorb Type CPA structural thermal breaks engineered for concrete parapet-to-roof-slab connections.

Supplied by Schöck North America, Princeton, NJ, and Ottawa, Ontario, the structural thermal-break modules comprise a longitudinal block of foam insulation traversed by rebar that is cast into the slab on one side and the balcony or parapet on the other, providing load-bearing support equivalent to that of monolithic extensions of floor and roof slabs. The rebar crossing the foam insulation is made of stainless steel for corrosion resistance.

Schöck finds that its concrete-to-concrete structural thermal breaks reduce heat energy loss at envelope penetrations by as much as 90% and as much as 14% for the overall building, depending on the number of balconies, length of balconies/parapets, and other variables.

“On the Cedar Springs and Westerleigh retirement residences, we installed Isokorb thermal breaks in the slabs at the balconies and eyebrows,” said Fritz. “In those buildings we didn’t have conditions where we had upstand parapets. While working on the Oceana PARC design, Schöck told us about a new thermal break product that specifically deals with thermal bridging at parapet upstands. And we have quite a lot of parapets on this project. So, we incorporated those thermal breaks as well.”

Two buildings comprise the Oceana PARC complex—a 23-story tower main building and a two-story auxiliary building. Containing 199 residential units, the tower building provides approximately 202,800 sq. ft. of gross floor area. The two-story auxiliary building adds another 8,600 sq. ft. of gross floor area, and connects to the main building by an enclosed bridge. Also included is a two-level underground parking garage totaling 68,500 sq. ft.

Parapets occur at the perimeters of levels two and three in the auxiliary building and at the roof level of the main tower for a combined 1,100 linear ft., so thermal bridging needed to be avoided.

Isokorb Type CPA thermal breaks for parapets await poured concrete after being installed at the vertical wooden parapet forms and tied into the rooftop horizontal rebar.

Parapets cut costs, carbon emissions

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, particularly where railings, covers, or fasteners pierce the insulation, requiring repair and maintenance.

Parapets wrapped with insulation barriers remain part of the heated-building mass. Parapets insulated and supported by structural thermal breaks sit outside of the heated-building envelope above the roof slab, allowing the building to efficiently retain heat energy while supporting loads equivalent to monolithic parapet structures.

The Isokorb Type CPA module is a longitudinal assembly fabricated to the same width as the parapet. Graphite-enhanced expanded polystyrene insulation is placed between stainless-steel reinforcing bars, creating a structural insulated module capable of transferring the loads from the parapet to the concrete roof slab that supports it, while minimizing thermal conductivity between the two concrete masses. U-shaped stainless-steel rebar, projecting from the underside of the module, is cast into the roof-floor slab. Vertically oriented stainless rebar, projecting from the topside of the module, is cast into the parapet, transferring moment and shear forces from the parapet to the concrete-slab structure.

After the slab is cast, insulated infill units are placed between the CPA modules to complete the continuous thermal break along the length of the parapet upstand wall.

PARC’s White Rock project team also installed 1,820 Schöck concrete-to-concrete thermal breaks for the balconies in 181 residential units.

Insulating with structural thermal breaks is also said to simplify the formwork process, reducing construction cost by as much as 10%, compared with wrapping the parapet with insulation, and allows the internal surface of the parapet to be finished for terrace applications.

“This was a new product for us and for Ventana Construction, Burnaby, British Columbia, which installed them,” added Fritz. “It’s been a bit of a learning curve to make sure that we get the installation right. To help, Schöck has been doing a formal inspection before we pour concrete.”

Oceana PARC will serve as a cornerstone for development in White Rock’s rezoned urban town center. According to Fritz, “A number of other properties are in for development permits, but we’re the first in construction.”

PARC Retirement Living is the first developer/owner of senior residences in the Vancouver area to use structural thermal breaks for balcony and parapet applications. Fritz explained, “We’re always looking to improve on the comfort, efficiency, and sustainability of our facilities. So, White Rock was the perfect setting for us to work with Schöck on incorporating the thermal breaks for parapets. If you’re going to be an owner/developer and your facility has parapets, this thermal break has significant benefit for you.”

Schock North America

PARC Retirement Living

Ventana Construction

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