The Sustainability of Masonry in Construction TodayApril 13, 2016
Masonry is one of the oldest building materials used by man and has been around for thousands of years and is still the most widely used building material. The rich heritage of historic masonry buildings in Canada, Europe, Asia and other parts of the world bears testimony to the sustainability of masonry as a building material. This article looks at how a number of attributes of masonry contribute to sustainable design and construction. Some of these attributes are included in the LEED program; however, a number are not included in LEED. The table at the end of this article lists the attributes and the applicable credits.
Masonry units are durable and contribute to building assemblies that remain useful in the material cycle for long periods of time. The use of masonry units, if properly detailed, will minimize the risk and environmental costs of premature failure of building components. Most deterioration occurs to exterior wall components, therefore good building envelope design is essential. The Ontario Association of Architects (OAA) insurance plan only covers drained cladding systems or solid masonry or concrete systems that are moisture tolerant. Canada Standards Association (CSA) S478-95 (R2001) “Guidelines on Durability in Buildings” lists brick veneer with a design service life (DSL) of 50 years and concrete block firewalls with a DSL of 100 years. Masonry durability is recognized by OAA & CSA and should be part of building envelope design. Further, the Canadian version of LEED-NC gives a credit for durability.
Besides the durability of the materials used for construction, the actual assemblage of the wall system is fundamental in ensuring the durability of the building. An important aspect of the wall system is the presence of a drainage cavity or rainscreen wall system. The rainscreen wall system anticipates that water will get into the wall, either as permeating through the building materials, or by leakage through deficiencies in windows and other penetrations. The wall system is designed to direct this moisture back to the exterior. This drainage cavity is an important aspect of any wall system and is now a building code requirement for buildings in the high rainfall area (Moisture Index (MI) > 1).
One of the best reasons for using masonry is its durability and potential for reuse and salvage. Most masonry units can be reused when carefully dismantled. In fact, there is a significant market in Canada for reclaimed clay brick. However, the durability of the masonry units should be checked before reuse. Clay brick manufactured prior to 1950 was often fired in bee hive kilns. Brick on the outer edges of the stack were underfired and were lighter in colour (salmon). These bricks did not have the durability of facing brick and were used on the inner wythe of a multi-wythe brick wall. During demolition, it is important that these bricks are kept separate from the facing brick.
Another aspect to consider when using reclaimed clay brick is the absorption characteristics of the bedding face, which may have been compromised by cement filling the voids. This can affect the potential bond between the mortar and the masonry unit. The initial rate of absorption (IRA) should also be checked before reuse to ensure a proper bond.
Because of the durability of masonry and masonry structures, masonry buildings are often ideal candidates for building reuse. Masonry also compares favourably with Life Cycle Analysis (LCA) that includes materials, construction and energy consumption.
Masonry is also resistant to other forms of degradation such as fire, mould and termites.
Masonry is inherently fire resistant. Interior masonry fire partitions help stop the spread of fire. These aspects reduce the environmental impact of fires. Passive fire protection reduces the costs of buildings.
Masonry units are mould resistant and can be used in most environments where people work and live.
Structure / Finish Combination
Masonry can provide both the structure and the interior or exterior finish combination which reduce environmental and building costs. Both brick and block walls and columns have high structural load capacity. Most masonry structures are loaded to a fraction of their capacity. Furthermore, the face of masonry is visually attractive and does not need any coatings or finishes, whether installed in an exterior or interior application. LEED offers a credit where low VOC paints and sealers are used, but masonry does not need either, so VOCs are eliminated completely.
Masonry walls require very little maintenance, eliminating the need for regular upkeep and repairs and the associated cost and environmental impact.
The mass of brick, block, natural and manufactured stone can provide thermal storage (also known as thermal mass) that can moderate a building’s temperature. Masonry can store heat energy and slowly release it, keeping the building cooler during the day and warmer at night. Thermal mass is more effective when used on the interior of a building and insulated to the outside. This is ideal for cooler climates. By using masonry in this way, the heating and cooling needs of the building are reduced and less energy is wasted.
Construction Waste Management
Being modular in nature, and small in size, masonry products are less prone to waste. Designers can maintain the rigour of modular dimensions, reducing cutting of units on site. Concrete block is manufactured to a 200 mm height by 400 mm length modules (once the 10 mm mortar joint is added to the unit dimensions). Many clay bricks are manufactured to sizes to coincide with these measurements to facilitate coordinated modular construction. Sizes are listed in the table below:
|Units / block
|Metric Modular / Norman
|CSR / Engineer Norman
|Metric Closure / Jumbo
Masonry units are inert, so waste on a construction site can be crushed and used as landscaping.
Many concrete block manufacturers use flyash and slag as a portion of their cement in their products. These products reduce the quantity of cement and thus reduce CO2 emissions and increase the amount of recycled content. In addition, quantities of recycled aggregate can be used in some products.
For clay brick manufacturers, any waste unfired (green) brick is fed back into the raw material feed. At some plants, the fired brick (grog) is ground and is also used as raw material feed for brick making. If the grog is not used for raw material, it is ground up and sold as landscaping material, or used for repair of quarry roads. No material is wasted or sent to a landfill.
Local / Regional Materials
Because of the large number of manufacturers, most cities are within 800 km of a brick or block plant and these materials will help contribute towards the regional material credit.
The clay brick industry adheres to strict operating principles which ensure the choices of future generations are not compromised by activities of the current one. All clay brick quarries operate under License granted by the Ministry of Natural Resources (MNR), in accordance with the Aggregate Resources Act. The License requires an approved Site Plan that typically contains operational, water, progressive and final rehabilitation plans, which are prepared in consultation with interested parties including the MNR, Conservation Authorities and local levels of government. Additional targets including control of dust and effluent discharge are set by the Ministry of Environment (MOE). Once mining operations at a quarry are complete, the land is carefully and meticulously backfilled and returned to a state as close as possible to the original, to ensure the land continues to offer future generations equivalent potential for use and development.
Quarries do impact the environment to a certain extent, but it is limited to the area of the quarry and is very controlled. The benefits of the quarry are significant. For example, a 200 acre quarry will be able to provide sufficient brick to clad approximately 10000 houses (1.2 million square metre of wall area annually) or a total of around 500000 houses over the life of the quarry. By contrast, one would need approximately 12000 acres of farmland to produce enough straw bales to cover the same wall area.
The goal of the clay brick industry is to make clay mining operations environmentally neutral. In fact, from one perspective, the industry actually optimizes benefits from the land for current and future generations. If quarry land had actually been developed before the clay was mined, the mineral value of the land would be locked in and future generations would not have had the opportunity to access that clay. By extracting the clay, rehabilitating the land to pre-quarry use and then developing the land, the community has in fact achieved double the use of the valuable asset. Although the clay used to make brick is a very prevalent natural resource (existing resources will supply the needs of humans for thousands of years), brick manufacturers work diligently to ensure quarry sites are used responsibly and efficiently by developing them in a manner consistent with the criteria of the sustainability concept.
Reduced Environmental Impact to Manufacture
Another key criterion of sustainability is a reduction in the amount of energy required to produce building materials. Over the past 20 years, the clay brick industry has successfully committed to and accomplished a significant reduction in the energy needed to manufacture brick. In 2004, the energy required to manufacture one pound of material of clay brick is just over 50 per cent of what it was in 1981. Since 2004, there has been a further reduction in energy use of about 10 per cent due to improvements in the plants.
The dematerialization within the manufacturing process, also contributes to reducing energy consumption and the use of resources. In short, dematerialization translates into doing more with less. One of the goals of sustainability is to accomplish dematerialzation without compromising the quality or performance attributes of the product or project. The clay brick industry has achieved this in two ways:
- Over the last two decades, the thickness of the brick veneer has gone from four inches to three and a half inches to three inches, and still maintaining the same level of performance
- Investigating increasing the voids (cores) within the brick. Studies at the National Brick Research Centre (NBRC) at Clemson University, SC show that the Flexural bond strength, resistance to water penetration and compressive strength is not affected by increasing the voids up to 32 per cent
With the increased use of scrubbers on new and old clay brick plants, the clay brick industry has aggressively reduced environmental emission and effluent throughout all steps in the manufacturing process. Ten years ago, approximately 52 per cent of brick was manufactured from plants with scrubbers. Today that figure is 75 per cent and expected to grow.
Since clay occurs naturally, it is virtually inert and remains so when formed into brick. Consequently, clay brick is the only cladding material that emits no gases, needs no maintenance and is impervious to chemical leaching. Moreover, brick is naturally fireproof and requires no coatings or cleaning products which could potentially produce environmentally harmful off gassing, or toxic fumes when burning.
Case Study – Jeunes sans Frontieres Secondary School
The Jeunes sans Frontieres Secondary School in Brampton, Ontario, is the first LEED Silver certified school in Ontario. This building is a shining example of how masonry materials combine to create a design that is durable, uses regional material, is low maintenance, projects warmth and offers superior fire performance. The exterior of this particular school is 75 per cent masonry. The front is clad with Hanson Brick. The gym, classrooms and service rooms are constructed with concrete block. The school and the training centre are separated by a masonry firewall that provides the protection should a fire occur.
The development of this new French language secondary school provided an opportunity for the establishment of a campus-based landscape, one in which the active building systems are passively related to the site through a series of landscape features and treatments. A hierarchy of interface outdoor space acts as an extension of the interior building spaces and programs, where students come together as a community both socially and academically. The configuration of the building and landscape present a formal façade to the street and turns its back on the loading area of the adjacent industrial park. This provides an outdoor landscape oasis within the arms of the plan, protected from the disturbances of the adjacent traffic arterials. A teacher training centre for the CSDCSO is also attached to the school. The brick used on the school is Regency Red Matt from Hanson Brick.
The design of the school also included numerous sustainable initiatives, including a green roof and displacement ventilation. The school has achieved LEED Silver Certification.
The team on this project was:
Builder: Aquicon Construction
Masonry Contractor: Bernel Masonry
Project Manager: Peter Moffet of Robert Simmons architects inc.
The table below lists some of the attributes of masonry and credits they can achieve in the various rating systems.
|LEED – NC
|LEED for Homes
|NAHB – NGBS
|Protect open spaces
703 & 704
|Construction Waste Management
609 & 602
|Resource efficient materials
601 & 607
|Masonry fire place
Patrick Kelly is a LEED Accredited Professional and a Masonry Systems Manager for Hanson Brick.