All posts by Elaina Adams

Better Late Than Never: Retrofitting sound-masking to improve acoustics

Photos © Zahid Ghafoor. Photos courtesy K.R. Moeller Associates Ltd.
Photos © Zahid Ghafoor. Photos courtesy K.R. Moeller Associates Ltd.

By Niklas Moeller, MBA
It is an all-too-common scenario—a company moves its employees into a highly anticipated new facility only to be met with complaints regarding speech privacy and noise levels. Perhaps the building’s acoustic performance was not adequately planned before construction, or consequences of various interior decisions were not understood. Regardless, the poor results are undeniable and, unfortunately, familiar.
In the last decade, sustainable, flexible, and collaborative design trends have systematically eliminated many methods of controlling acoustics. The percentage of open-plan space has grown and so have occupant densities. At the same time, partitions have lowered or disappeared altogether, and the use of absorptive finishes has diminished, allowing noises to travel further and last longer.

Closed rooms are increasingly built using:

  • glass walls;
  • walls stopping at the suspended ceiling;
  • demountable partitions; and
  • sliding doors.

While these choices may have some esthetic appeal and help meet particular objectives or short-term budget goals, they have also diminished the acoustic performance of many workplaces by reducing room-to-room isolation.
The work environment sets the stage for employee performance and plays a role in absenteeism and retention rates. Therefore, investing in solutions for this type of ‘facility malfunction’ is easily justified.

According to the 1998–2008 BOSTI Associates study, “Disproving Widespread Myths About Workplace Design,” employees typically account for about 82 per cent of a company’s primary costs, over the 10-year period of the study. This amounts to more than a building, its operations and technology combined; employees are an organization’s biggest expense, and also its greatest asset. Effective acoustics are essential to providing speech privacy and freedom from distracting noises, as well as enabling employees to work normally without disrupting others.

AcousticsAcoustics_mobile

To create this type of environment, acoustic professionals apply techniques to absorb, block, and cover noise (i.e. the ABC rule) (For more, see the article, “The Green Soundscape” by Niklas Moeller, in the July 2010 issue of Construction Canada). Each of these strategies contributes differently to overall acoustic performance. Consequently, when problems in an existing facility are encountered, the source is usually in the omission of one of the methods mentioned, or imbalanced application within the space.

In the last decade, many methods of controlling acoustics have been systematically eliminated. The percentage of open-plan spaces has increased, partitions have lowered or disappeared, absorptive finishes have been replaced by hard surfaces, and floor plates have narrowed. Photo © iStockphoto/Goran Bogicevic
In the last decade, many methods of controlling acoustics have been systematically eliminated. The percentage of open-plan spaces has increased, partitions have lowered or disappeared, absorptive finishes have been replaced by hard surfaces, and floor plates have narrowed.
Photo © iStockphoto/Goran Bogicevic

At this point, the organization must determine:

  • which acoustical treatments are capable of addressing the issues;
  • budget available for solutions; and
  • degree of operational disruption the workplace can weather during their implementation.

The answers to these questions largely determine the course of action. It often comes down to which treatment offers the greatest opportunity for improvement, with minimal upheaval.

The missing element
Due to advances in construction materials and mechanical systems, modern facilities are often missing an appropriate ambient (or background) sound level, which would serve to cover conversations and noise. Today, ambient levels are typically in the mid-30 to low-40 decibel range. Levels are even lower in buildings using alternative ‘green’ HVAC systems and facilities with underfloor air distribution (UFAD) systems because they lack the traditional noise created by forced air ventilation. This ‘pin-drop’ environment allows noise and conversation to be easily heard, even from a great distance. Further, the background sound present does not exhibit the correct mix of frequencies needed for speech privacy, noise control, and comfort.

The lack of adequate background sound can be addressed using a sound-masking system. This technology consists of a series of loudspeakers installed in a grid-like pattern in the ceiling, as well as a method of controlling zoning and output. The loudspeakers distribute a comfortable, engineered sound, maintaining the facility’s ambient level at an appropriate and consistent volume. Though the sound is similar to softly blowing air, it is specifically designed to mask speech frequencies. It also covers up unwanted noises or reduces impact on occupants by decreasing the magnitude of change between baseline and peak volumes in the space.

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Advancing bridge performance with UHPC

MTO---HODDER-4
Photos courtesy MTO

By Raymond Krisciunas, P.Eng., Peter J. Seibert, M.Sc., MBA, P.Eng., and Philip D. Murray, M.Eng., P.Eng.
Over the past several years, ultra-high-performance concrete (UHPC) field-cast joint connections have become a common bridge solution in Ontario and gained acceptance in various states, such as New York, Iowa, Montana, and Oregon. However, the Ministry of Transportation Ontario (MTO) recently enabled this material to be used in new ways, relying on its combination of superior properties—including improved strength, durability, and bond development—to overcome significant bridge design obstacles. (For past Construction Canada articles on UHPC, see “Whitemans Creek Bridge” by Vic H. Perry, Wade F. Young, and Brent I. Archibald (July 2012), “An Ultra-high-performance Upgrade” by Gaston Doiron and Kelly A. Henry (December 2011), “Precast Solution for Performance Cladding: Ultra-high-performance Concrete for B.C. Building” by Don Zakariasen and Peter Seibert [September 2010], and “Restoring the Rialto: Specialized Precast Cladding Revitalizes an Old Hotel,” by Perry and Lisa M. Birnie [Sept. 2009]. Visit www.constructioncanada.net and select “Archives.”)

Currently, MTO is embarking on an aggressive four-laning project in Northwestern Ontario that involves construction of about 30 km (19 mi) of highway and up to 30 structures in an area with extremely rugged terrain, ranging from deep swamps to massive rock cuts.

As part of this project, a new ‘parclo’ (partial cloverleaf) interchange was required at the intersection of Highway 11/17 and Hodder Avenue in Thunder Bay. The structure, founded on a combination of hard till and bedrock, spans over a total of six lanes. (The authors would like to thank the Hodder Avenue Underpass project team, which includes the Ministry of Transportation Ontario and Hatch Mott MacDonald, for their collaborative partnership throughout the design and construction of this project).

The need for a striking design
Since the interchange is the first structure drivers encounter when approaching the city of Thunder Bay, it was desirable to elevate the appearance from the somewhat utilitarian style frequently encountered in urban highway settings to a clean, slender, and open design. Given the location and exposure, it was also desirable to use precast elements throughout. Consequently, a two-span concrete box girder configuration was the most practical and cost-effective solution—however, these structures are typically rather bland and can appear bulky.

To counter this challenge, a design concept was developed whereby the pier cap beam could be incorporated into the superstructure, appearing to be integral with the box girders while providing a frame that seems to go directly into the superstructure. This appearance is achievable with the use of conventional post-tensioned cast-in-place superstructures, but extremely difficult to achieve using pre-fabricated elements.

FIgure 1
The Hodder Avenue Underpass, a partial cloverleaf interchange that is located in Thunder Bay, Ont., was the site of a new bridge project relying on ultra-high-performance concrete (UHPC) and traditional precast.

Other challenges included a relatively shallow superstructure in which to incorporate the main pier cap/cross beam and analytical complexity of two-way behaviour by virtue of the continuous box girders intersecting the transverse cross beam. In the final configuration, the pier cap/cross beam had to become integral with the box girders in the longitudinal direction and provide a continuous span between the piers and cantilever over the ends (Figure 1).

The initial design, using 60-MPa (8700-psi) concrete, necessitated no fewer than four pier columns to support the superstructure. Visualizations using this configuration demonstrated the structure still appeared bulky because the superstructure and pier cap depths could not be increased without dramatically affecting the rest of the bridge. An alternative was required.

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Specifying overhead and coiling doors

Photos courtesy Northwest Door
Photos courtesy Northwest Door

By Richard Sivertsen, CTR
Sectional overhead door systems (sometimes referred to as ‘panel doors’), as well as coiling (i.e. ‘rolling’) and high-speed door systems can be found on most commercial, industrial, and institutional buildings. Material options for these doors vary so much one regularly sees different thicknesses with steel, and aluminum in four finishes (i.e. mill, clear, coloured-anodized, and powder-coated). High-speed doors will be either fabric or rubber.

For single-purpose structures, at least one of these door systems can be found in:

  • condominium and office towers;
  • industrial plants;
  • automotive buildings;
  • multi-tenant warehouses;
  • aircraft hangars;
  • mine truck shops or processing plants;
  • police and fire stations;
  • schools;
  • recreation facilities;
  • manufacturing plants;
  • waste recycling facilities; and
  • fabric, wood, steel, and concrete structures.

However, within the overhead and coiling door industry, there is still confusion about how best to specify these assemblies. When a subcontractor bidder views the project bid documentation, he or she is relying on all the data being in agreement. However, discrepancies are not uncommon between the specifications and drawings.

This clear anodized door system is used where maximum clear view is required. The glazing should always be tempered glass, and is used mostly in the automotive industry and restaurants.
This clear anodized door system is used where maximum clear view is required. The glazing should always be tempered glass, and is used mostly in the automotive industry and restaurants.

Sometimes on a tender open to the public, there is no manufacturer or model specified (i.e. no basis of design [BOD]); rather, technical and performance qualities are taken from several particular proprietery products. Worse, the descriptions from numerous manufacturers’ models are often mixed together. Some bidders view this as a future opportunity for change orders. Those subcontractor bidders confident in a successful future change order will confidently submit an undervalued (i.e. low) bid. Low bidders get awarded the most contractors. Therefore, nonsensical specifications foreshadow change orders.

The specifications attempt to describe the owner’s needs (e.g. full vertical lift), but the drawings may indicate this cannot be achieved due to limited head room. Another problem can occur when the technical requirements in the specifications may not agree with the BOD product specified. The specifier should know the difference between full vertical-lift, high-lift, standard-lift, and low-lift overhead doors. When specifying a particular manufacturer with alternative names, he or she should know the various manufacturers’ products all have different limitations and know what they are. Bearing all this in mind, some design professionals may wonder how a single manufacturer’s product can be the basis of design.

There are groups of specification writers that run independent businesses; they work well with many architectural firms on contract, and have a lot of knowledge to offer. Some architectural/engineering (A/E) firms have internal specifiers for their projects using both online and hard-copy printed literature to choose products, as well as discussions with manufacturers’ representatives. Communication between specifiers, architects, and draftspersons could be the cause of nonsense bid documents.

Some of the difficulty is also found in the industry’s terminology:

  1. Is it a sectional, overhead (is this also called a vertical lift door?), coiling, or rolling door? It is best to discuss this with a hardware consultant when identifying the style of door system required.
  2. Can a door be called a shutter? This is normally based on door size.
  3. What is the difference when it comes to fire-rated doors or shutters? Shutters are normally mounted against a window or on a countertop.
  4. When it comes to motors and their controls (which are many), does one call for a wall-mounted drawbar operator, a ceiling-mounted drawbar, or a jack shaft? Most of the time, this depends on the style of the door’s lift.
  5. Should push-button controls be mounted locally or remotely? (If the latter, how far away from the door?) Which section is the conduit part of? The answers to these questions are normally governed by the client’s needs and should be discussed with a hardware consultant as controls have limitations of use. The conduit is usually provided by the electrical trades to the motor, and from the motor to the local controls by the installing company. There should always be a discussion concerning long-distance wiring and conduit.

Clarification needed
A general R-value requirement is often mentioned in the specification of a sectional or a coiling door system—sometimes R-16, R-12, or R-6 is called out. However, there is still some confusion as to what this means to the overall door assembly, and whether these are estimated door insulation values or individual section or slat variables. Since these individual R-values can be achieved through various door thicknesses, there may be questions over whether polystyrene or polyurethane is the acceptable product to use and what their limitations and R-values are. Is one really looking for a defined R-value or for a fully weather-sealed option? When designing for a fully glazed overhead door, is there any point in making the glazing double-glass?

When calling for different types of sectional door hardware, it is difficult to know whether a 50-mm (2-in.) or 75-mm (3-in.) track is required. Is it to be angle-mounted track or not? What is the difference? The draftsperson should know each has a side-room requirement and they are different when it comes to the needed head room. When designing the wall structure around the opening, these details need to be understood, otherwise there will be a conflict between the drawings and the specifications. Does one specify the same kind of tracking system for a sectional door as one would for a coiling door? Is 75-mm track relevant to coiling door systems?

Concerning the door schedule, on numerous occasions it appears fire shutters are not listed, missing from the window schedule, or shown only on the floor plan. A door subcontractor bidder doing his or her ‘take-offs’ may not see it among all the other notations on the drawings. (Submitting a bid with a missed door will perhaps guarantee the award.)

Alum-Parking-Gate
This specialized gate has safety-backing at various points to prevent vandalism to either the photocell controls or the drop-down arm of the motor at the head. It is used in parking garages. The electronic controls always need to be discussed with the gate manufacturer to ensure operational efficiency.
Photos © Richard Sivertsen

Applications come into play as well. These include the answers to questions such as:

  • Will the specification be written with a view to include the stresses on the door system as far as its use is required?
  • Does the door operate 10, 50, or 100 times a day?
  • Doors run in cycles (i.e. up and down once is one cycle), but how can one specify the cycles of the spring?
  • What bearing will these cycles play on the type of hardware to be used on the door system, the number of spring cycles or the motor requirements, or even the type of door system to be specified?
  • What safety mechanisms are to be called for?
  • What are the limitations of torsion springs, and are they to be galvanized or oil-tempered?
  • Is there a problem when specifying a motorized door with slide-bolt locking mechanisms without calling for an electrical interlock?
  • Does a door require a slide lock/interlock if there is a ‘brake’ on
    the motor?

This author frequently sees this last omission; it is a costly option. The door’s size and weight has a bearing on whether one needs a slide-bolt lock together with a motor. How is this so? What kind of controls are needed, and who provides the conduit?

There are many components coming into play when specifying a product in the overhead/coiling door industry, with myriad manufacturers hoping to get a tight specification written to exclude as much competition as possible. At the same time, door installation firms are either bidding as per the specifications (sometimes as per the plans and specifications if they are not in conflict) or applying for an ‘alternate,’ ‘equal,’ or ‘substitute’ without really knowing the difference between the three. When a rolling steel door is at its limit, would a rubber assembly be more suitable?

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Higher-performing Balconies: Integrating manufactured structural thermal breaks

All images courtesy Schöck Canada
All images courtesy Schöck Canada

By Dieter Hardock, Dipl.-Ing., and Dave André, P.Eng., LEED GA
In Canada, it is widely stated buildings account for approximately 35 per cent of the total primary energy use, and roughly 30 per cent of the country’s total greenhouse gas (GHG) emissions. In the continuous quest to achieve better building energy performance, the  design/construction community must develop and use innovative tactics to minimize operational energy use.

One significant aspect of energy loss involves conductive heat transfer through the building envelope, meaning the heat flow through solid elements due to temperature differences between interior space and exterior space. Common strategies to minimize this process by increasing the envelope’s overall R-value include:

  • specifying high-performance glazing, such as improved double and triple-glazing with higher performance framing systems to reduce U-values;
  • improving the façade insulation with increased R-values by using better and thicker insulation; and
  • reducing the window-to-wall ratio (WWR), as windows are usually the thermally weakest areas of the wall.

These assemblies are largely responsible for the overall thermal performance of an exterior wall. Traditionally, not a lot of attention has been paid to the various thermal bridges that are integral to these larger envelopes because they were thought to represent a relatively small percentage of the overall energy loss.

As an example, one can consider the exposed concrete slab edges of a typical 1970s, lightly insulated, high-rise apartment building. The heat loss at the slab edge would be a relatively small percentage of the whole building’s losses. As the thermal performance of overall wall systems is improved, however, the heat loss through thermal bridges becomes a much greater percentage of total building energy loss, and thus more important to consider and control.

The thermographs pictured here and on page 32 show that if thermal bridges at balconies are not taken care of, the balconies act as ‘cooling fins,’ conducting the heat off the building and cooling the adjacent rooms.
The thermographs pictured here and on page 32 show that if thermal bridges at balconies are not taken care of, the balconies act as ‘cooling fins,’ conducting the heat off the building and cooling the adjacent rooms.

Although there are manufactured structural thermal breaks available for numerous connections, this article focuses on concrete balconies. Balconies remain a popular design feature for residential construction in Canada. Often formed by extending the concrete structural slab through the building envelope, these penetrations can represent a significant energy loss that can result in reduced thermal comfort and possible condensation.

Recent three-dimensional heat transfer analysis—published in American Society of Heating, Refrigerating, and Air-conditioning Engineers (ASHRAE) 1365-RP, Thermal Performance of Building Envelope Details for Mid- and High-rise Buildings—indicates there can be as much as five times the amount of heat loss through an exposed concrete slab compared to an insulated one. The result is an increasing demand for, and interest in, thermal bridging solutions that will reduce these effects.

The popularity of off-the-shelf manufactured structural thermal breaks has steadily increased in Europe, thanks to this type of product’s performance, as well as the material and system testing being completed by those manufacturers. Now considered standard building practice across the Atlantic, these products have recently come to the Canadian market.

Thermal bridging
Thermal bridges are localized assemblies that penetrate insulated portions of the building envelope with thermally conductive materials. The associated heat loss results in a reduction of the indoor surface temperatures, which may create conditions for condensation and mould growth.

Generally speaking, there are many different structural elements that penetrate the building envelope and may form thermal bridges, such as balconies, canopies, slab edges, parapets, or corbels. These are common architectural features or essential structural elements in residential buildings as well as in hotels, schools, museums, or gyms.

In the case of uninsulated balcony slab connections, the interaction of the physical geometry of the balcony slab, the ‘cooling fin’ effect (i.e. increasing the exterior surface area leads to increased heat flow), and the material properties (i.e. the reinforced slab’s thermal conductivity) can result in significant heat loss.

Uninsulated balcony connections can be critical thermal bridges in a building envelope. Buildings relying on them have significant incentives for adoption of structural thermal break technology to improve thermal comfort, energy efficiency, and possibly indoor air quality (IAQ), by reducing mould growth potential.

Conductive heat escapes from concrete balconies when the design does not take special measures to curtail this loss.
Conductive heat escapes from concrete balconies when the design does not take special measures to curtail this loss.

Thermal break performance
Structural thermal breaks reduce heat flow between the inside to the outside, while also conserving structural integrity. With uninsulated balconies, for example, the reinforced concrete at the connection is replaced with an insulating material while continuous reinforcement bars are used to transfer moment and shear loads.

In some instances, these bars may be replaced by stainless steel where they penetrate the insulating material as this metal is much less thermally conductive than conventional reinforcing steel. The use of stainless steel not only reduces thermal conductivity, but also ensures longevity through its inherent corrosion resistance. Other materials are also used in some proprietary systems with the aim of lowering thermal conductivity,  such as including concrete modules to transfer compression loads.

The combination of all these aspects means structural thermal breaks can average an equivalent thermal conductivity as low as 0.2 Watts per metre Kelvin (W/m·K), instead of typical values of 2.3 W/m·K for reinforced concrete at an untreated balcony connection. This reduces the thermal conductivity at the connection by up to 90 per cent, which significantly reduces the heat flow and also substantially improves the indoor surface temperature in the living area.

Typically, a range of structural thermal breaks are available from manufacturers, depending on the load requirements and deflection criteria. This selection allows for customizable solutions between structural and thermal performance to be found.

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Design on track

All images courtesy Dorma Americas
All images courtesy Dorma Americas

By Jim Beaulieu
Increasing applications for interior manual and automated sliding doors that traditionally would be swing doors are being specified and installed. On the other side of the Atlantic, sliding doors have always been popular for interior and exterior installations, but even in Europe there have been recent substantial increases both in sheer numbers and in the scope of use for such doors. That trend is quickly catching on here as the North American taste for more creative and personal designs align with European flair.

In residential applications, European designers commonly feature sliding interior doors in such locations as bedroom and bath entries. In the Canadian commercial sphere, however, the use of sliding doors appears to be growing—they are being specified in office row arrangements, where individual enclosed offices are arrayed side-by-side facing the communicating hallway to maximize space utilization. In Japan, where available space has been at a premium deep into the nation’s history, the sliding door remains a predominant selection for the widest possible range of uses.

In part, the specification and installation of sliding doors is accounted for by familiar advantages of space conservation and esthetic appeal. Nevertheless, there is reason to suppose recent popularity growth worldwide also reflects solid improvements in door and hardware technology. Such developments have made doors of this kind—both manual and automatic—more useful and versatile than ever in many applications.

Interior automated sliding doors have advanced dramatically in the last few years. Now, rather than clunky, oversized belt-driven versions of the recent past, there are practical and robust solutions for exterior high-traffic applications. Technologies, such as linear magnetic-driven panels that literally float on magnets like a monorail train, provide a sleek minimized profile and are extraordinarily quiet.

All automated sliding doors work under the same principles—some form of actuator triggers the door panel to open or close. This could be a motion sensor that automatically causes the door panel to open as soon as movement is monitored in the sensor range or a simple push-button. At its basics, this is just an on/off switch, but, budget-willing, there are numerous additional features for security, safety, fire alarm, and privacy purposes. A matter of switches communicating to the system what function it should perform, such add-ons have become very cost-competitive, with software advances creating many new features at lower prices.

Sliding doors can help eliminate the feeling of being enclosed in a box. Minimizing materials and maximizing space are accomplished by concealing sliding panel hardware in overhead tracks that remove passage and view obstructions.
Sliding doors can help eliminate the feeling of being enclosed in a box. Minimizing materials and maximizing space are accomplished by concealing sliding panel hardware in overhead tracks that remove passage and view obstructions.

Constraints on specifying sliding doors
Minor constraints have historically been involved in using sliding doors for certain applications. Many such issues have fallen away as the quality and technology of sliders continued to improve. In terms of esthetics versus privacy, ‘bulking up’ the door panel or trim to maximize privacy may lessen the desired affect intended for the application using a sleek sliding panel.

In the past, there have been sound transfer issues with sliding doors as compared to equivalent hinged models. In these cases, choice of materials for sliding panels and the surrounding opening become key considerations for the end user, and can often minimize or eliminate any problems.

Hinged doors may perform better than sliders at limiting the heat transfer from one space to another. In interior applications, this is often a minor issue. The temperature differential between rooms is normally less than between building interiors and exteriors. As such, heat transfer may be of minimal concern.

In most cases, interior sliding systems (whether manual or automatic) are unsuitable for fire separations due to their limitations as a smoke/fire barrier. Further, they typically do not swing out, impeding quick exit in an emergency situation such as a panicked crowd. The heavy-duty automated operators common to the front of a retail store offer these features, but this article is directed towards smaller sliding systems more suitable to a residential or light commercial application.

Some sliding door designs can be easier to compromise than hinged models. As is true with HVAC concerns, this is commonly less significant in all-interior installations. For most buildings, the most critical security requirements are at the perimeter.

While sliding doors have traditionally cost more at installation than their hinged counterparts, this is rapidly changing as many new designs are smaller and lighter, requiring less reinforcement and fewer fasteners. Some installations that required two people can easily be managed by one and in less time. (This is strictly concerning interior low-traffic applications and is in no terms is referring to a commercial heavy-duty application.)

The old adage still holds true that in most cases you get what you pay for. This means while prices may be falling, there is still a cost level for quality whether it is in the material or the labour going into installing it. This will also affect the longevity and maintenance aspect of the sliding door. Sliding doors generally require more adjusting than swing doors, but from a maintenance and longevity view, the lifespan should be similar if handled properly and adjusted on a regular basis if something should change in performance.

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Québec hockey arena scores with heat recovery system

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The new ice rink facility was equipped with suspended textile air dispersion ductwork, which provides comfortable temperatures for skaters and spectators. Photo courtesy Enerconcept Technologies

The Pat Burns Arena in Stanstead, Qué., used HVAC air distribution and heat recovery systems in its design for significant energy savings and a more comfortable environment for skaters and spectators.

The $9-million, 4459-m2 (48,000-sf) facility was commissioned by the municipal government and designed and updated from the original Stanstead College Arena constructed more than 50 years ago. The original facility relied on cold weather to freeze the ice, until being equipped with a more conventional refrigeration system in the 1960s. However, these systems became old-fashioned and updated installations were required to improve ventilation, indoor air comfort for skaters and spectators, and temperature control.

The new structure was built on the Stanstead College campus and replaced the former arena. It now includes:
• regulation-size 61 x 26-m (200 x 85-ft) ice rink;
• spectator seating for more than 500 and standing-room capacity;
• mezzanine restaurant;
• locker rooms;
• offices;
• physical therapy rooms;
• gym facility; and
• multi-function rooms.

Contributing to the indoor air comfort inside the arena is the suspended textile air dispersion ductwork, separating the spectators from the ice. The 51 m (167 ft) of non-porous textile duct evenly disperses air without drafting from one end of the arena to the other. An in-duct cylindrical tensioning system was also installed to keep the textile ducts extended and more esthetically pleasing. The systems keep the facility at a relative humidity (RH) of 40 per cent and a set temperature of 14 C (58 F).

Conventionally used metal ducts require more maintenance than the textile ducts used at the Pat Burns Arena. For example, textiles will not require replacement costs if hit with a hockey puck and dented, like a metal one would. Also, they can be commercially laundered to rid contaminants and maintain a high standard of indoor air quality (IAQ) rather than needing anti-corrosive coatings that may negatively affect the IAQ. The fabric duct system also cuts down on energy costs by allowing more even air dispersion throughout the entire facility, from the skating rinks to the change rooms.

The new refrigeration system is also able to save on energy costs for the facility by using heat recovery to supply the duct. Additionally, a cooling coil in the arena’s air handler eliminates any fogging by dehumidifying the air within the building. This keeps the skating surface at optimal conditions. For high RH instances, there is also a backup dehumidifier.

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An introduction to gypsum shaftwall systems

All images courtesy CertainTeed Gypsum
All images courtesy CertainTeed Gypsum

By Pamela M. Shinkoda, P.Eng., CSC
Shaftwall systems are a crucial component in the design and construction of commercial buildings, serving a variety of important functions for the structure. They house elevators and stairwells, as well as HVAC, telecom, and electrical equipment. However, their most important function is to provide an extra layer of fire resistance between two adjacent areas of a building—such as an elevator shaft and hallways—to help protect building occupants during a fire scenario.

With these factors taken into consideration, it is important for architects to understand the components of gypsum shaftwall systems and where and how they are typically used. This article reviews some of the basics of shaft design that are independent of materials and illustrates some of the fundamental features of shaftwall design by comparing the traditional masonry shaftwall with its more contemporary gypsum counterpart.

Design essentials
A shaft is any enclosed space that extends vertically through one or more floors of a building, connecting successive floors and/or the roof. A shaft may consist of:

  • the opening in which elevator cars travel;
  • exit stairways;
  • vertical HVAC chases;
  • telecom and electrical chases;
  • laundry chutes; and
  • dumbwaiters.

There are two standard approaches to the design of shaftwall systems that influence the material type used to build the shaft wall—masonry and gypsum.

Masonry
In more traditional shaftwall designs, architects create a structure that encloses the shaft before construction of the building that surrounds it. This approach typically uses concrete masonry units (CMUs) or poured concrete.

Since the basic task of the masonry shaftwall is to support itself and provide fire ratings, it needs to be structurally sound and fire-resistant. Its dense mass provides good sound attenuation, keeping noise from the stairwell or elevator confined to the shaft. However, due to their dense mass, masonry shaftwalls require engineering attention to create the footing needed for support.

Additionally, because these shaftwalls are usually erected before the rest of the building, they need their own slot in the construction schedule. Though they rate high on the performance end, masonry systems are also difficult to co-ordinate and install, making them a more time-consuming, expensive part of the project.

Gypsum
Another option involves creating the shaftwall from floor to floor once the building structure has been constructed, precluding the need for a standalone system. About 40 years ago, gypsum board was engineered as a 25-mm (1-in.) shaftwall material that helped make this design approach more popular. Gypsum systems must be constructed of noncombustible components best-suited for the building type being constructed.

Gypsum shaftwall systems offer a more balanced mix of performance and installation benefits. Their components are lightweight compared to masonry, allowing more design possibilities and simplifying the installation—a two-hour fire-resistance-rated gypsum shaftwall system weighs only 44 kg/m2 (9 lb/sf) and is only 95 mm (3.75 in.) thick. In contrast, masonry walls for two-hour fire-resistance are typically 200 mm (8 in.) and weigh between 146 and 439 kg/m2 (30 to 90 psf). Therefore, gypsum wallboard can be installed more quickly and more economically than masonry. Gypsum is naturally fire-resistant as, chemically speaking, it contains water—the material can be written as CaSO4 2H20. (The water is gradually released as vapour during a fire, providing protection until it is all consumed.) The shaftwall systems include acoustic insulation and sealants
to minimize sound transmission from the shaft.

One-hour rating, shaftwall finished on one side.
One-hour rating, shaftwall finished on one side.

Basic anatomy of a gypsum shaftwall
A gypsum shaftwall system consists of:

  • 25-mm (1-in.) gypsum shaftliner panels;
  • Types X or C gypsum board;
  • studs; and
  • J-tracks.

Gypsum shaftliner panels are 25 mm thick, 609 mm (24 in.) wide, and come in lengths of 2.4 to 3.7 m (8 to 12 ft). They are available in three facing options:

  • moisture-resistant paper-faced;
  • treated mould/moisture-resistant paper-faced; and
  • glass mat-faced.

Paper-faced gypsum shaftliners meet ASTM C1396, Standard Specification for Gypsum Board, while glass-mat gypsum shaftliners meet ASTM C1658, Standard Specification for Glass Mat Gypsum Panels. The latter are moisture/mould-resistant and can be exposed to normal weather during construction.

Two-hour rating, shaftwall finished on one side.
Two-hour rating, shaftwall finished on one side.

Types X (fire-resistant) and C (improved Type X) gypsum board are installed in one or more layers on the corridor side of the shaftwall system. The number of layers typically equals the hourly fire resistance rating of the shaftwall system. Each board meets requirements for ASTM C1396. In addition to fire resistance, abuse-resistant Type X gypsum boards provide resistance to impact and surface abrasions.

Manufacturers of steel framing produce three different profiles of shaftwall studs:

  • C-H;
  • C-T; and
  • I.

The studs are installed 609 mm (24 in.) on centre (oc) to match the width of the shaftliner panels. Common gauges for metal studs are 0.454 and 0.835 mm (i.e. 25 and 20 gauge), and common depths are 64, 102, and 152 mm (2.5, 4, and 6 in.).

J-tracks provide a way of anchoring the shaftwall to the existing structure. A J-track is used at the terminal ends, top, and bottom of shaftwall assemblies and is anchored to the concrete slab, existing walls, or structural steel framing. J-tracks have three depths—64, 102, or 152 mm—as chosen to match the depth of the stud. The thickness of the J-track is also chosen to match the gauge of the stud.

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EIFS and thermal bridging

Eifs&Thermal-figureA study by Pennsylvania Housing Research Center (PHRC) showed significant reductions in centre-of-cavity R-value for steel-framed wall assemblies, reducing it by as much as 56 per cent when a framing factor (i.e. thermal bridging) was taken into account to measure R-value. (See Robert Bombino and Eric Burnett’s Design Issues with Steel-stud-framed Wall Systems [PHRC Research Report Series 58, May 1999]). The only practical way to negate the effects of thermal bridging caused by steel studs is to place insulation outboard the studs—something that can be accomplished with exterior insulation and finish systems (EIFS).

For example, an R-11 (1.94 k•m2/W) batt-insulated steel frame wall assembly is effectively R-6.6 (1.16 k•m2/W) (Ravg), a 45 percent reduction in the centre-of-cavity R-value (Rcc) which results in only a 55 per cent thermal efficiency (Ravg/Rcc). Yet, when the same assembly has the batt insulation removed and R-10 (1.76 k•m2/W) exterior insulation added (slightly more than 64 mm [2.5 in.] of expanded polystyrene [EPS] insulation), the effective R-value is almost equivalent to the centre-of-cavity R-value of the batt-insulated assembly, and the thermal efficiency is 99 per cent. When batt insulation and exterior insulation are combined, the effective R-value of 17.8 (3.13 k•m2/W) and thermal efficiency of 81 per cent are significant performance improvements to the assembly with only batt insulation. The improvement in effective R-value performance through the use of exterior insulation is clearly demonstrated in the graph on the right.

For more on EIFS and sustainable design, click here.

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The nuts and anchor rods of lighting poles

Photo © Dreamstime/Rubens Alarcon
Photo © Dreamstime/Rubens Alarcon

By Bill Yao, P.Eng.
It is common to see lighting poles in shopping mall parking lots, walkways, roadsides, and residential areas. Generally, they are galvanized or painted steel tubing, with the bottom end welded to a steel base plate that has holes matching the pattern of anchor bolts embedded in a concrete footing. The lighting pole is then secured atop the footing with anchor bolts and nuts.

There are two kinds of concrete footings for base-mounted lighting poles: one where the top is raised slightly above the grade (Figure 1), and another where the footing is raised 600 to 1000 mm (24 to 39 in.) above grade (Figure 2) . Lighting poles mounted to raised-concrete footings are often found in parking lots because they are strong enough to withstand possible
vehicle collisions.

A lighting pole structure can be separated into the following three components:
• cantilever column above the ground;
• concrete footing buried underground; and
• connection between the lighting pole and the concrete footing—typically a set of anchor bolts and nuts.

Lighting poles should be planned to support single or multiple lighting luminaires, and be able to withstand environmental loads, like ice and wind forces. The isolated concrete footing should be proportioned to resist factored loads and induce reactions in the ground. The footing can crack if inadequate reinforcing bars are used; an undersized footing could result in the pole tilting or leaning.

The design and capability of a lighting pole and its footing to withstand wind or ice loads is beyond the scope of this article. Instead, this author will focus on how to improve the concrete footing’s durability, and protect the anchor bolts to provide relatively maintenance-free service life.

Concrete durability
Durability of concrete is determined by its ability to resist weathering action, chemical attack, abrasion, or any other deterioration process. Concrete can protect embedded steel from corrosion through its highly alkaline nature. However, the presence of chloride ions in de-icing salts can destroy or penetrate the concrete’s film. Once the chloride corrosion threshold is reached, an electric cell is formed along the steel or between bars and the electrochemical process of corrosion begins.

Figure-1ab
The concrete footing’s top is raised slightly above the grade.

Several deterioration modes are defined in sources such as the Cement Association of Canada’s (CAC’s) Concrete Design Handbook which includes the Canadian Standards Association (CSA) A23.3–04, Design of Concrete Structures, and the Precast/Prestressed Concrete Institute (PCI) Design Handbook. Examples include:

  •  freezing and thawing;
  • alkali-aggregate reaction (AAR) which occurs in concrete between highly alkaline cement paste and non-crystalline silicon dioxide and is found in many common aggregates;
  • chemical attack;
  • corrosion of embedded metals; and
  • abrasion.

These modes are also explained in American Concrete Institute’s (ACI’s) Building Code Requirements for Structural Concrete (ACI 318-05) and Commentary (ACI 318R-05).

Most lighting poles and concrete footings are close to roadways, sidewalks, or within parking lots and are exposed to de-icing chemicals in winter months. The designer, contractor, and owner should recognize the harmful effects of freeze-thaw in a wet environment, chemical attack, and corrosion of embedded metals.

Figure-2ab
In this example, the concrete footing is raised 600 to 1000 mm (24 to 39 in.) above grade.

Low water-cement ratio
Water-cement (w/c) ratio plays an important role for concrete durability. Generally, the lower the w/c ratio, the better the material performs. Water-reducing admixtures (WRAs) should be used during concrete mixing to improve durability. Concrete with a low w/c ratio (0.4 or lower) is more durable than concrete with a high water-cement ratio (0.5 or higher).

Air-entrained admixtures
The most potentially destructive weathering factor is freezing and thawing while concrete is wet, particularly in the presence of de-icing chemicals. Deterioration is caused by the freezing of water and subsequent expansion in the paste and aggregate particles.

With the addition of an air-entrainment admixture, concrete is highly resistant to freezing and thawing. During freezing, the water displaced by ice formation in the paste is accommodated so it is not disruptive; the microscopic air bubbles in the paste provide chambers for water to enter and relieve the hydraulic pressure generated. Concrete with an air-entrained content of five to eight per cent and a low w/c ratio should withstand a great number of freeze and thaw cycles without distress.

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EIFS and sustainable design

Photo courtesy Pillar Construction
Photo courtesy Pillar Construction

By Dale D. Kerr, M.Eng., P.Eng., BSSO, and Tom Remmele, CSI
Exterior insulation and finish systems (EIFS) can economically provide energy efficiency and reduced carbon dioxide (CO2) emission levels. (An earlier version of this article appeared in the August 2007 issue of The Construction Specifier, the official publication of the Construction Specifications Institute [CSI]). However, without durability as the cornerstone of sustainable design, most other ‘green’ attributes of products or systems are lost. Fortunately, with proper installation and integration, these cladding assemblies also offer long-term performance and durability.

From an architectural perspective, EIFS offer the ability to replicate almost any architectural style or finish material, coming in myriad shapes, colours, and textures. Low in cost and lightweight, they can be installed over existing buildings—this reskinning allows design/construction teams to reuse the original shell instead of demolition and introduction to the waste stream.

Further, a building’s overall energy performance and interior environment can be greatly improved by placing the insulation on the outside of the building. This strategy minimizes thermal bridging and helps keep the structural members at a consistent temperature, improving their expected longevity.

Due to concerns with earlier iterations of exterior insulation and finish systems (EIFS), using mockups to ensure proper drainage and drying is critical. Images courtesy STO Corp.
Due to concerns with earlier iterations of exterior insulation and finish systems (EIFS), using mockups to ensure proper drainage and drying is critical.
Images courtesy STO Corp.

By keeping the temperature of structural members constant, they are less susceptible to the movement and stress caused by temperature swings that could lead to cracking in concrete, masonry, and stucco walls. (In turn, this cracking could lead to water penetration and degradation, such as spalls or corrosion.)

Additionally, with sufficient insulation outboard of the structure, a dewpoint is eliminated and the potential for condensation from vapour diffusion is minimized. Mould, corrosion of metal fasteners and framing members, and deterioration of batt insulation and its R-value are a few of the potential effects of condensation that can be avoided.

Traditional, or ‘face-sealed,’ EIFS assemblies have typically consisted of five components:

  • insulation board;
  • adhesive and/or mechanical fastener to attach the insulation board to a substrate;
  • reinforcing mesh for impact resistance;
  • base coat to embed the reinforcing mesh and provide weather resistance; and
  • decorative and protective finish coat.

While traditional or face-sealed EIFS were associated with some water intrusion issues in the residential industry, it is important to note the materials themselves were not the root cause. As buildings were made tighter and more energy-efficient, they became somewhat less forgiving of poor workmanship and water damage became more frequent.

Windows (and their installation) have also been a source of leakage into walls. This, combined with poor construction practices and tighter building envelopes, can affect durability, regardless of the cladding—brick, stone, EIFS, concrete, wood, or vinyl siding.

New generation of EIFS
In response to these water intrusion issues, building wraps or asphalt-impregnated sheathing paper and felts were installed behind EIFS to provide moisture protection to the wall structure. These wraps are relied on for providing water resistance, but they are often punctured and/or have the potential for tearing and mislapping during installation. As they are not fully adhered, they are also susceptible to billowing under wind load, which affects the wall’s pressure equalization performance.

Further, where sheathing paper, felt, or building wraps are used, mechanical attachment of the EIFS becomes necessary, as the specialized adhesives do not stick to sheet goods. Mechanical fasteners create thermal bridges, rendering EIFS less thermally effective. (The fasteners can cause ‘ghosting’ through the finished wall surface.)

Some of the newer EIFS products incorporate a fluid-applied waterproofing membrane along with an air barrier directly applied to the sheathing behind the wallcovering.
Some of the newer EIFS products incorporate a fluid-applied waterproofing membrane along with an air barrier directly applied to the sheathing behind the wallcovering.

Newer EIFS products can overcome the limitations of traditional moisture protection and mechanical fasteners. These materials incorporate a fluid-applied waterproofing membrane and air barrier directly applied to the sheathing behind the EIFS wall covering (Figure 1). Rather than simply a cladding, these systems can be considered a complete exterior wall assembly, providing multiple building envelope functions.

Weather barrier
Most exterior wall problems are caused by water, primarily rain. When water gets into the wall system and wets the assembly’s materials, it can accelerate deterioration of those materials and create conditions conducive to mould growth, compromising indoor air quality (IAQ).

When the wall is designed to prohibit rainwater penetration, durability is drastically improved. In an EIFS wall, the lamina (i.e. base coat, mesh, and finish coat) acts as the initial defense against rain. Any joints in the exterior wall system, such as those between dissimilar materials, must be designed to resist rain penetration. Joints and flashing should be designed and constructed to slope toward the outside of the wall to prevent gravity flow of water inwards. Where appropriate, two-stage joints, drip edges, and capillary breaks should be incorporated to avoid inward water movement.

Water-resistive barrier
Incorporating a secondary means of controlling rainwater penetration—a water-resistive barrier (WRB)—can be beneficial in both preventing damage during construction, and keeping the building interior dry even before the lamina cladding is installed. In other words, this improves the wall’s long-term durability.

In the case of some newer EIFS styles, fluid-applied waterproofing applied to the substrate serves as the WRB; its purpose is to stop water getting past the lamina and insulation.

Newer proprietary EIFS products also provide an air cavity behind the insulation. Depending on the manufacturer, this may involve use of slots cut into the insulation and/or vertical ribbons of adhesive. Regardless, such air cavities provide a drainage space—should water get through the outer EIFS surface at a crack, it flows downward via gravity. Flashings installed strategically at floor lines and at the wall’s base direct the water back outside the wall where it cannot damage internal components.

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