In recent years, multiple factors have converged to create increasing demand for green and sustainable buildings. Stricter building codes, along with LEED and other building performance systems, have boosted the call for more extensive engineering in wall systems.
Manufacturers have responded with a flurry of new products that combine distinct elements such as masonry systems and structural framing. Structural masonry and esthetic masonry have also been blended in some systems. These advances in wall systems have resulted in buildings with improved energy efficiency, structural integrity, and cost effectiveness, while also maintaining the desired appearance.
The systems approach supports the adoption of LEED, Green Star, BREEAM, and other building performance rating systems, enabling architects and specifiers to identify green building products that are backed by a reputable manufacturer, and that help projects stay on spec and budget.
Contractors and masons can more easily specify materials that save installation time, minimise callbacks, and meet some green objectives. Systems also support the needs of developers and building owners, who value LEED certification as a competitive advantage. Building owners and developers also strive to decrease expenses and increase property revenues by using durable, high-quality, and user-friendly materials.
Rating system details vary, but generally they evaluate and award points based on water efficiency, indoor air quality, materials and resources, energy use, building site, and location and transportation. These factors support green building, but true sustainable design is another step down the path. Sustainable buildings meet today’s needs without compromising the ability of future generations to meet their needs. It’s a more holistic approach that must also include evaluation of social and economic impacts of the project.
Life cycle assessments (LCA) are useful for this, and employ a “cradle-to-grave” approach to evaluating the environmental impacts of materials and projects. The cradle-to-grave approach typically will consider everything from material acquisition to manufacturing practices through projected maintenance through expected life span of the structure. The life cycle assessment can be used to develop an environmental product declaration (EPD), which is a report about products and materials.
An EPD should include information about:
- energy use and efficiency
- emissions to air, water, and soil
- waste generation
- content of materials and amount of chemicals.
LCAs and EPDs aid builders and developers in specifying materials and products that are more sustainable. Elements to consider include:
- efficient use of raw materials, minimising waste
- bio-based, renewable, and recycled materials
- locally and regionally produced materials
- durable and reusable materials
- avoiding construction site waste.
In response to market demand and the use of LCAs and EPDs, manufacturers have developed an array of more sustainable products. Dry-cast concrete, for example, can be moulded into thin or full veneers with greater strength than traditional veneers. Dry-cast concrete offers a choice of finishes, such as natural stone and mechanical finishes, and these are less vulnerable to fading, moisture, and freeze/thaw cycles. Their integrated color eliminates the need for specially moulded corners, and minimises the effects of chipping. Dry-cast products are made with a low-moisture mixture that includes fine aggregates, Portland cement, admixture, and colourant that is densely compacted into moulds, then cured with high humidity.
Dry-cast veneers can be used in hybrid wall systems with wood studs to create structures that offer the look of solid masonry and stone at a lower cost. This approach is frequently used in shopping centres, multi-family projects, and low-rise structures.
A project in Milwaukee, Wisconsin called Avenir made use of the hybrid approach to create a mixed-use development of retail and housing in an historic neighbourhood.
According to Scott Drees, director of construction for Wangard Partners, the project needed to blend in with the existing structures, but natural stone was cost prohibitive. Using a hybrid wall system allowed for the look of natural stone with improved thermal performance and acceptable cost.
Developers constructed the wall system with masonry stone, brick, expanded polystyrene insulation panels, special anchors, and a high-performance proprietary mortar. The system adhered to demanding energy codes while offering a continuous thermal barrier and excellent water management.
In addition to advanced materials and products, sustainable buildings require specific approaches to design details. The building envelope must be tight and make proper use of both insulation and thermal mass, which is most effective when placed on the inside of the building envelope. Masonry products provide thermal mass, which absorbs and releases heat to smooth out temperature variations. That may also enable a reduction in the size and cost of heating and cooling equipment. Energy analysis programs can demonstrate the value of thermal mass as they analyse building performance over time.
Sustainability factors can also be addressed at other areas of the site. Permeable pavers, for example, are useful for minimising stormwater runoff and reducing the heat-island effect often noticed in cities. By allowing stormwater to percolate into the site, the need for retention can be lessened, which can also increase the buildable area of a site. In addition, concrete pavers are available in multiple colors that meet solar reflectance specifications and minimise temperature gains, especially when combined with increased site vegetation.