By Jim Stange

Across the globe, many businesses are working to ensure their operations are as sustainable as possible. Some are even working towards becoming completely zero waste. The Zero Waste International Alliance (ZWIA) defines this as “the conservation of all resources by means of responsible production, consumption, reuse, and recovery of products, packaging, and materials without burning and with no discharges to land, water, or air that threaten the environment or human health.”¹

This practice reduces a company’s contribution to the waste stream, lowers its negative environmental impacts, and strengthens its reputation. Such waste reduction strategies can also save the company money and even generate revenue if the waste is valuable to another industry. According to a study by MIT Sloan Management Review,² 90 per cent of today’s CEOs report sustainability is important to their company’s success.

In the building industry, sustainability has been a priority for some time. Determining a product’s sustainability includes considering its material makeup, manufacturing process, end-of-life care, and even its durability. With green building construction, sustainability equals durability. This is because, the longer a material lasts, the fewer new products will need to be produced.

When specifying exterior cladding or building envelope materials, building professionals have many options: wood, engineered cladding products, stucco, and brick and stone masonry, among others. A relatively newer product, wood-plastic composite (WPC) has been growing in popularity.

Sustainability of composite cladding

From its material makeup through the manufacturing process and performance/lifecycle, there are several factors that make composite cladding a highly sustainable option.

Material makeup

As manufacturers of WPCs continue to move closer toward zero waste, they have incrementally increased the amount of recycled material in their products—some are made with upwards of 94 per cent pre- and post-consumer recycled material—which prevents materials from being sent to waste streams and landfills, while preserving valuable natural resources. This makes WPC much more sustainable than many other building envelope materials.

Wood flour is recycled from sawdust, planer shavings, or other scrap material from window trim, door frames, lumber, or cabinet pieces that would otherwise be discarded. Through these recycling efforts, manufacturers of composite decking and cladding products can prevent more than one million trees from being cut down annually. This is equivalent to about 15,000 football fields of healthy forests preserved annually.³ Further, the manufacturing process of WPCs avoids using rainforest species, thus protecting endangered trees and reducing deforestation. Although WPCs can include any wood species, maple, pine, and oak are among the most frequently used. This selection not only leverages more abundant and sustainably sourced wood but also ensures the final products support environmental conservation efforts.

The plastic in composite cladding is derived from milk jugs, shampoo bottles, grocery bags, laundry detergent containers, and other recycled packaging material. The average family uses approximately 1,500 plastic bags each year, with each bag being used for an average of just 12 minutes.⁴ If not recycled, these plastic bags likely end up in landfills or the ocean, where they could remain for up to 1,000 years.⁵ That said, it is this same resistance to decomposing that helps make composite cladding last such a long time. As many as 2,000 plastic bags can be used in the manufacturing of a single WPC board, which means one manufacturer can recycle an average of 45 million kg
(100 million lbs) of plastic each year. That is the weight of approximately 227 Boeing 747s.⁶

Manufacturing process

Working toward zero waste, WPC manufacturers have, for some time now, been increasing efficiencies in the manufacturing process. These improvements are yet another reason WPC is highly sustainable.

Composite cladding manufacturers with dedicated recycling facilities can recycle both post-consumer and post-industrial polyethylene (PE)—the most common form of plastic waste. And thanks to automated material shredding and sorting, it is becoming faster and less expensive for manufacturers to incorporate recycled materials into building products.

Since it is important these plastics are not entering the waste stream, some manufacturers ensure 100 per cent of the material is reclaimed in the manufacturing process. When the PE arrives at a recycling facility, for example, it undergoes a battery of tests—including thermal, moisture, and infrared analysis—to confirm the molecular structure of the polymers and to provide insight into the history of the sample. Inspectors examine the individual physical properties of the samples, check for degradation, and determine whether any contaminants are present. If the samples meet strict quality requirements, they are staged in a warehouse for further inspection. If the samples fail, they are sent to alternate recycling operations with less stringent requirements.

While manufacturing composite cladding requires a constant source of water, some manufacturers use a closed-loop system to maintain sustainability. A closed-loop system uses a reservoir to store and recycle the same water every day, preventing billions of gallons of water—enough to fill 5,300 Olympic-size swimming pools—from ending up in the waste stream.³

Performance/lifecycle

Doubling the life of a building halves the environmental impacts of its construction, which is why the durability of a material along with its performance are crucial when considering its sustainability.

WPCs combine the best qualities of recycled wood—such as strength and low cost—with the long-lasting resilience of recycled plastic, which is less prone to water absorption and insect infestation. Blending these two materials together is the reason WPCs last so long, and why they are sustainable from start to finish.

Unlike solid wood, the durable composite core of WPC cladding ensures exceptional resistance to rotting, cracking, insects, and decay. A three-sided cap layer protects against fading and staining, which is common with solid wood cladding, and it has a finished surface on both the top and bottom to further prevent water absorption.

Composite cladding also never needs sanding, staining, painting, or sealing. There are environmental dangers associated with volatile organic compounds (VOCs) released from stain and paint. VOCs are the leading cause of ground-level air pollution and indoor air pollution, which can adversely impact the health of building occupants.⁷ When solid wood is stained or painted to maintain its durability, it will then need to be refinished with more stain or paint every couple of years, which creates a continual cycle of chemical emissions. The chemicals used in treated wood are generally not good for humans, either. Since composite cladding is highly durable and never needs to be stained or painted, it is free of these toxic chemicals and preservatives.

Further, when the WPC is finished being used as cladding, the material can be recycled into something new. Wood treated with chemicals, on the other hand, cannot be burned or recycled when its use as cladding is complete.

Performance of composite cladding

Compared with other building envelope materials, WPC stands apart as one of the most sustainable options available—both in terms of its superior durability and its environmentally friendly material makeup.

Wood Cladding

Appearance

Wood siding—including shiplap, tongue-and-groove, and board-and-batten—is prone to fading, chipping, and staining. It can also develop mould and mildew stains.

Installation

Wood siding requires multiple trades (carpenters, painters, etc.) to install and finish. The siding will need to be refinished (and sometimes repaired) every few years—which is a time-consuming process entailing scraping, sanding, pressure-washing, and re-staining or re-painting.

Durability

Wood splits, splinters, and is particularly affected by freeze-thaw cycles. Water absorption is dependent on the quality and age of the finish. If the siding is not maintained, the durability will be compromised.

Recycled content

Wood cladding contains no recycled content if purchased new. Some wood cladding is made from endangered hardwood species, which results in negative environmental repercussions.

Engineered cladding products
(e.g. fibre cement)

Appearance

While engineered cladding products may be embossed with a woodgrain pattern, they must be painted, which means there will be no multi-chromatic streaking that gives composite cladding the natural appearance of wood. Engineered cladding products are also prone to fading and cracking.

Installation

Since engineered cladding releases silica when cut, the Occupational Safety and Health Administration (OSHA) requires exposure controls and protective equipment for all installers. A specialized blade is also needed to reduce silica dust. The material can break under its own weight, so it requires careful handling to avoid product loss. Installation can vary based on climate and wind requirements, which makes scheduling more difficult.

Durability

Engineered cladding products tend to be brittle and can fracture if nailed close to the edge. The finish and face can spall (flake or break off) in cold environments. Like wood, the amount of water that engineered cladding absorbs depends on the quality and age of the finish, so it must be effectively maintained to prevent deterioration. Engineered cladding is highly susceptible to impact damage and freeze-thaw cycles.

Recycled content

Engineered cladding contains no recycled content.

Stucco

Appearance

Unlike plank cladding, stucco has a limited range of appearances, and there are limited trim options that work well with the material. Stucco is resistant to rot, mould, fire, and insects. Further, it is often used in drier climates since it is prone to moisture-related issues.

Installation

Stucco is very labour-intensive to install, requiring a two- to three-step application plus painting (dash, scratch, brown, and finish coats) by a concrete contractor. Since it is made of cement sand and water, stucco is heavy. All layers of stucco must be uniform to perform well. Additionally, stucco requires two layers of building paper or wrap plus lath reinforcing. Improper installation can result in extensive interior wall and structural damage.

Durability

Stucco is prone to cracking due to its brittle nature, particularly if the foundation of the building settles. Stucco is also porous and will absorb water more readily than other materials, which can cause it to develop dark spots or grow mould. The material is sometimes affected by freeze-thaw cycles.

Recycled content

Stucco typically does not contain recycled content, although some may use post-consumer recycled sand aggregate from crushed, screened waste concrete.

Brick and stone masonry

Appearance

Both brick and stone have a classic look often seen on more traditional homes. These materials have a wide range of esthetics beyond typical red brick and field stone. Brick is available in assorted colours and course patterns, and can be painted, while stone can be laid in a variety of patterns. Manufactured brick and stone veneers offer another option.

Installation

Brick and stone installations are quite labour intensive since the products are heavy. Exterior brick and stone require a wider foundation wall to support their own weight and accommodate the required
25-mm (1-in.) air space. They also require steel support lintels over windows, doors, and gable-ends, as well as brick ties, through-wall flashings, and weep holes for water drainage.

Durability

Brick is a durable product, but it absorbs water and can spall when exposed to excess moisture. Depending on the brick’s water absorption rate and saturated coefficient, it can be affected by freeze-thaw cycles. Brick is also subject to efflorescence, or crystalline deposits of water-soluble salt on the brick’s surface.

Recycled content

Some bricks may contain pre-consumer recycled materials, such as overburden from mining, washings from aggregate processing, grog, sawdust, and metallic oxides. This pre-consumer recycled content is typically low, around 15 per cent.

Composite cladding

Appearance

Composite cladding has an authentic wood grain and colour variation that gives it an appearance similar to solid wood—but without the fading, cracking, and decay that is typical of wood cladding.

Installation

Installation is safer and easier than most other cladding options. Composite cladding is available in longer board lengths than wood or fibre cement, which reduces splices and labour. Since the boards are pre-finished, they require no additional finishing steps or excessive ongoing maintenance, further reducing labour time and expense. Unlike fibre cement, no potentially harmful substances are released during cutting.

Durability

Composite cladding will not crack, splinter, peel, rot, decay, or suffer insect infestation, like wood. Composite cladding may absorb a negligible amount of water but is not affected by freeze-thaw cycles.

Recycled content

Composite cladding is made almost entirely of recycled content. It is manufactured without toxic chemicals and with zero wastewater. In addition, it can be recycled at the end of its life, unlike wood treated with chemicals, which cannot be burned or recycled at the end of its life.

Design benefits of composite cladding

Beyond its sustainability and performance attributes, composite cladding allows designers to provide the warm look of wood with a more durable material, while also staying on-trend with a mixture of exterior materials. While monolithic expanses of synthetic stucco (exterior insulation finishing systems [EIFS]), brick, wood, or fibre cement were once the norm, today’s buildings typically feature a combination of materials. Organic looking products with warm wood tones are now placed alongside poured-in-place concrete and glass or EIFS and stone. This approach is widely adopted in both single-family homes and commercial structures, offering a quick and straightforward method to achieve an esthetic nearly identical to that of newer buildings. It also introduces an element of warmth to the design.

WPCs can be used for many different components in the built environment, including decking, soffits, screen facades, rainscreen cladding, and even trim elements when cut to size. WPCs can also be manufactured in many different shapes, colours, and textures. Lengths and colours can be mixed and matched to create a unique, custom look, and boards can be installed vertically, horizontally, or diagonally. With these design options, architects can achieve a variety of styles, from subtle and rustic to bold and modern.

Inspired by nature

The embossing technology for WPCs has evolved to such an extent that the material now closely mimics the appearance of solid wood, making it almost indistinguishable. Further, colour options are abundant, not constrained by the regional availability of a particular wood species. Rich colour palettes and varied grain patterns are available in a range of browns and greys. Classic browns range from rich mid-tones to the deepest brown, with these colours adding depth and drama. The darker choices are especially well-suited to Craftsman-style or Mediterranean homes. Reddish browns are timeless and classic, yet still unique. The colours evoke the warm hues of cinnamon, the rich depth of rosewood, and the vibrant tones of western red cedar. Reddish tones provide warmth, energy, and a pop in the landscape. Blonde oak tones are trending in the industry and offer a subtle sandy hue for those drawn to the natural, Scandinavian-inspired look. Greys have undercurrents of blue or sandy beige, evoking thoughts of rocky shorelines and weathered wood. Grey cladding is the perfect choice for coastal homes but can add quiet sophistication to urban spaces as well.

When it comes to performance, ease of maintenance, and design capabilities, composite cladding outperforms many alternative cladding materials. It is durable and sustainable, and thanks to its nature-inspired embossing, it emulates natural wood better than alternative materials.

WPCs may well be the building material of the future, offering the ideal balance between sustainability and remarkable performance capabilities. If something is worth building, it is worth protecting.

Notes

¹ See the definition of zero waste: https://zwia.org/zero-waste-definition.

² Refer to the document by G. Unruh, D. Kiron, N. Kruschwitz, M. Reeves, H. Rubel, and A.M. zum Felde, “Investing For a Sustainable Future,” MIT Sloan Management Review.

³ For more information, visit https://balance.fiberondecking.com.

⁴ Also see National Geographic 2018: Fast facts
about plastic pollution, www.nationalgeographic.com/science/article/plastics-facts-infographics-ocean-pollution.

⁵ See “Degradation Rates of Plastics in the Environment,” by ACS Publications 2020, pages 3,495, 3,499–3,500, and 3,503: https://pubs.acs.org/doi/10.1021/acssuschemeng.9b06635.

⁶ Refer to the United States Environmental Protection Agency (EPA) 2022, Technical overview of volatile organic compounds, at www.epa.gov/indoor-air-quality-iaq/technical-overview-volatile-organic-compounds.

⁷ See “Fiberon Wildwood Composite Cladding,” pages 26–27, at fiberon.widen.net/s/npdt7xjgf6/lit_clad_brochure_wildwood-composite-cladding.