Feb 16, 2018
Recent trends in biophilic architecture stress the importance of bringing the natural world into your home. That does not mean that you don't need to protect your home from the exterior elements. While large windows and interior plants can offer a natural feel to any home, those same homes need to be protected from elements like rain, wind, moisture, and outside temperatures.
Exterior cladding, commonly referred to as siding in the United States, functions as the protective "skin" of a house. Protecting the interior and structural parts of the home from different outside elements. Often, the exterior cladding will be made up of several layers, including a wall's outer surface, a plastic wrap to keep out moisture, insulation, and vapor barriers, among others. Plastic siding and brick are two of the most commonly used exterior cladding materials. Modern-day construction materials offer several different exterior cladding options.
Below, we will look at the pros, cons, and prices of different exterior cladding options, emphasizing the embodied energy for each type of material. We calculate the embodied energy for each material through the process energy requirement (PER), which is the amount of energy directly utilized in the material's manufacturing. This is measured in megajoules per kilogram (MJ/kg).
Bricks are one of the most commonly used materials for exterior cladding. Besides being beautiful, this material is easy to find, and source and most contractors have experience building with brick and mortar.
On the plus side, brick and mortar cladding is sourced from natural materials, namely, clay soil that has been burned in kilns to form bricks. Fricks don't need any exterior painting, and they can last for a lifetime. Bricks offer a thermal mass that can be used to capture heat for passive solar homes. The space between the wall sheathing and the exterior brick cladding also provides added insulation to the house.
Many innovative companies are now producing bricks from recycled materials such as fly ash, a byproduct of coal power plants. A recent World Bank study found that these bricks can vastly reduce carbon emissions associated with the building industry.
The main environmental drawback to brick cladding is the enormous energetic cost needed to make the bricks. Since bricks are burned in kilns, vast amounts of energy are used to make bricks. The mortar used to bind the bricks contains cement, and the carbon footprint of the cement industry accounts for 5% of global carbon dioxide emissions.
The PER embodied energy of clay bricks is 2.5 MJ/kg, while the cement used in the mortar has a PER embodied energy level of 5.6 MJ/kg.
On average, the cost of brick ranges from $1 to $3.50 per brick. You'll require approximately four bricks to make up one square foot, resulting in a material cost per square foot of $4.00 to $14.00. Additional material costs include house wrap ($0.50 to $1.00 per square foot), mortar ($0.45 to $0.50 per square foot), and masonry shims, which can be purchased at varying quantities and price.
Vinyl siding is the most commonly used exterior cladding on new homes, with over 27% of households built since 2015 utilizing this siding alternative. Vinyl is a type of plastic siding made of polyvinyl chloride (PVC). It often mimics the look of wood grain, providing a similar look to painted clapboard or shingle siding. It's available in various shapes and sizes and is popular due to its affordability, durability, and relatively low maintenance requirements.
On the upside, vinyl siding has an extremely long lifespan, routinely lasting for over 50 years with little maintenance required. Vinyl is one of the least expensive exterior cladding options. If you opt for insulated vinyl siding, you can boost the R-value of your home's overall insulation capacity. Vinyl siding reportedly consumes less than half the energy and fuel to manufacture than brick siding.
The most obvious negative aspect of vinyl siding is that it is sourced from a non-renewable resource. Polyvinyl chloride (PVC), which makes up vinyl siding, is a known human carcinogen. It can cause serious health problems to people who are exposed to the dioxins during the manufacture and if the PVC material catches fire in the future.
The reports on the embodied energy of the PVC used in vinyl siding are varied. One report claims that the embodied energy of PVC is 80 MJ/kg. Another report claims that it takes a whopping 93,000 megajoules of embodied energy to clad a house in vinyl siding over its estimated 50-year lifespan.
Vinyl siding is one of the lowest-cost siding options from a material and installation perspective. For strictly material, vinyl siding costs $0.85 to $2.50 per square foot. Due to its low material cost, it's a fairly popular option in North America. Most siding professionals offer installation costs more economical than many alternatives.
Wood is an exceptionally versatile building product. Exterior siding options are abundantly available locally and include board & batten, shiplap, bevel, shake, shingle, clapboard tongue & groove, to name a few. Wood siding is also available in types and species, from reclaimed wood (many various species) to cedar, pine, redwood, Douglas Fir, and many varieties in between.
The main benefit of wood exterior siding is that it is sourced from a renewable resource. When the wood siding is FSC certified, the homeowner can rest assured that the lumber was sourced from sustainably managed forests.
There are several ways to further “green” exterior wood siding options. Charred wood siding is a traditional Japanese technique wherein wood is slightly burned and cured with natural oils. Besides offering a beautiful finish, this technique also protects the wood from weather and bugs without any chemical preservatives or pesticides. High-temperature thermal modification is another method for adding durability and weather resistance without chemicals. This type of wood lasts a long time and is resistant to moisture, insects, and mold, and can be applied to almost any wood species. You can also create decorative exterior wood siding from reclaimed boards, such as those from barns. Reclaimed wood can give your home a rugged, traditional look while upcycling wood that would otherwise have been lost.
Wood that isn't FSC certified may be sourced from unsustainably managed forests, mainly illegally logged tropical hardwood forests worldwide. Most wood products need to be protected with varnish and other products to withstand the elements and deter bugs such as termites. These products can be made from dangerous chemicals that release harmful VOCs. Consider a non-toxic wood siding option like charred wood or thermally modified wood.
The PER embodied energy of wood is one of the lowest of all building materials. Air-dried sawn hardwood has an embodied energy rating of only 0.5 MJ/kg. If you can source your lumber locally, the embodied energy will decrease as the energy used to transport your lumber will be minimal.
Wood siding costs range between $1.00 and $5.00 per square foot, on average. Installation costs vary between cities and regions but usually average $2.00 to $5.00 per square foot. The material cost is impacted by the type of wood used and the style of siding. Cedar, Pine, Redwood, Cypress, Douglas Fir, Hardwood, Accoya are common types of wood siding available. Most local wood siding manufacturers or suppliers provide board & batten, lap, log, shake, shingle, tongue & groove. Each type offers a unique look and associated cost.
Composite siding is a low-maintenance exterior cladding product often made from sawdust, scrap wood, and other products. Binders are often low in VOCs, and there is minimal production waste. Composite siding is made to mimic the aesthetics of real wood. It is usually less vulnerable to water, debris, and the elements. It's important to note that a few additional products are part of the composite family, including PVC Composite and Fiber Cement, which we cover below.
Composite siding is long-lasting, lightweight, low maintenance, and cost-effective. Unlike some alternative cladding products, composite is resistant to moisture, insects, and fire. It also does not expand or contract. While earlier versions of composite siding experienced moisture-related failures, a substantial amount of R&D has increased durability and longevity. For skeptics, since real-world research is still new and relatively limited, most manufacturers offer warranties that exceed most alternatives.
Composite siding is still new to the market. There is little information on return on investment over the product's lifetime, and warranties do vary. Materials and manufacturing processes can dictate if the product is reusable or recyclable at the end of its useful life. It's essential to ask the manufacturer about the manufacturing process and whether it can be recycled or reused at the end of its lifespan. While these are a form of recycled building products, they could have high formaldehyde levels or other glue materials that off-gas dangerous VOCs. Manufacturers can answer questions relating to their sourcing and manufacturing process to address any environmental concerns you may have. It's not uncommon to find environmentally conscious manufacturers whose products are recognized by green building bodies such as LEED - keep an eye out for them!
The embodied energy of composite cladding products varies greatly. Common considerations are how and where the raw materials were sourced, and the paint's embodied energy, and the overall manufacturing process, which can differ by product type and manufacturer. You should consult the manufacturer for specific embodied energy metrics.
The cost of composite siding varies based on location, availability, and the style you choose. Composite is available in a wide range of choices such as dutch lap, beaded, vertical, log, shingles, clapboard, or board & batten, to name a few. Expect to pay $2.00 to $10.00 per square foot for materials. Dependent on climate, composite siding should be pressure washed every 1 to 3 years and repainted every 10 to 12 years. Keep an eye out for composite manufacturers whose products don't require repainting and offer longer-term shade-resistant warranties.
Stone siding is pieces of quarried stone used as an exterior finish of a house. Stone is a natural material, easy to maintain, and lasts longer than many other siding types. While stone veneer is usually less expensive, natural stone will last roughly twice as long. The most common stone types used for home exteriors are flint, limestone, travertine, granite, Quartzite marble, and sandstone.
Real stone siding is naturally produced and extremely durable when exposed to the elements. Stone gives a home an authentic appearance, does not fade, and, under proper care, lasts for decades. It is also resistant to fire, insects, and mold, and it can be recycled at the end of its useful life. The energy required to quarry and process stone is significant but less than cement or steel production.
Real stone siding is much more expensive than alternative types of siding. The mining process negatively impacts the environment and requires burning fossil fuels. The embodied energy of real stone related to shipping is relatively high due to the stone's weight. Stone siding should be installed by a professional mason who can be costly. It can be challenging to repair if damaged and, if installed incorrectly, can crack, allowing moisture buildup and the potential for mold.
The embodied energy of stone depends on its sourcing. Locally sourced stone siding can have an embodied energy of 0.79 MJ/kg, while imported stone has an embodied energy of 6.8 MJ/kg.
Stone siding ranges between $10 and $14 per square foot, on average. The price is directly tied to the type of stone you choose and its local availability. You can expect to pay $20 to $40 per square foot of stone, including the stone and Installation. While it is an expensive siding option, it does boast an excellent R-Value, lasts much longer than alternatives, and increases your home's resilience.
Polyvinyl chloride (PVC) composite cladding is a plastic exterior siding used to simulate dutch lap, beaded, vertical, log, shingles, clapboard, or board & batten and closely resembles the shape and cut of real wood.
PVC composite exterior cladding lasts a minimum of 30 years and maintenance-free. While vinyl siding is made of PVC, composite siding is typically 500% thicker than vinyl commonly found on homes today. Thanks to the increased thickness, PVC composite siding offers additional R-value and noise reduction compared to traditional vinyl siding. Most PVC composite siding is made with recycled materials and recycled at the end of its useful life.
PVC Composite exterior cladding is still new to the market. While testing proves to be fairly positive, some may find the lack of long-term real-world validation concerning. Manufacturers have spent a significant amount of money on R&D and often stand by their products by offering more extended warranty periods when compared to traditional siding options.
The embodied energy of PVC is 77.2 Energy MJ/kg, 2.41 Carbon kg CO2/kg. According to the U.S. Life Cycle Inventory Database, recycled PVC has an embodied energy and carbon footprint that is up to 97% and 95% less, respectively. The use of recycled material does not impact the quality of the durability of the product.
PVC siding costs $6.50 to $10.50 per square foot, with an average cost of $8.50. PVC composite siding should be pressure washed every 1 to 3 years. As with other composite siding products, fading can occur over time, and you will likely have to repaint the siding every 10 to 15 years. Look for manufacturers that offer non-fading with their warranty and that don't require repainting.
Fiber cement siding can be made to look like wood sidings such as board and batten, clapboard, and shingles. Fiber cement siding is made by mixing cement, sand, and fiber. Fiber cement siding is often referred to as "Hardie board" or "Hardiplank," named after the most notable fiber cement siding manufacturer James Hardie.
Fiber cement siding is designed to be waterproof and hold up against salt air, heavy winds, rain, hail, rot, insects, vermin, and, unlike other siding products, is not flammable. Many manufacturers offer warranties up to 50 years, and it's often assumed that the life span of fiber cement is even longer. The appearance of fiber cement siding is remarkably realistic as it can be made to look like real wood, brick, or stone. If you select a solid color, you can easily paint fiber cement to get that perfect look. Fiber cement siding is often considered environmentally neutral, meaning it does not release toxins when broken down.
Though fiber cement siding is environmentally neutral, it is not recyclable. Fiber cement siding requires little maintenance, but you will need to wash the siding every two years and paint every 10 to 15 years. The exact maintenance schedule will depend on the local climate and conditions. The installation cost of fiber cement siding is often 2 to 3 times more than vinyl; however, the siding lasts significantly longer.
The embodied energy of fiber cement siding is roughly 70,000 megajoules. As a comparison, vinyl siding has an embodied energy of approximately 90,000 megajoules. Wood siding, such as cedar, is much lower, with an embodied energy of 28,000 megajoules.
Fiber cement siding material costs range from $2.00 to $8.00 per square foot. Depending on your climate, fiber cement siding should be pressure washed every 2 to 3 years and repainted every 10 to 15 years.
Metal cladding is a type of exterior siding that is both durable and low maintenance. Common metal siding types include galvanized steel, aluminum, zinc, and copper. Similar to composite, metal cladding is available in a variety of different architectural styles and finishes.
The main benefits of this exterior cladding option are the low maintenance and longevity associated with metal siding. Once installed, the metal cladding will last for decades. It is not damaged by rain or snow and does not provide a medium for mold or fungal growth, both of which can cause health problems to home occupants. Metal siding is essentially insect-proof, meaning that you will not have to spend money spraying your siding, as with wood, to keep the insects away. Metal siding is fireproof and will help protect your home in the unlikely event of a fire.
Metal siding requires mining, which is not always environmentally friendly. However, metal is a recyclable material, and several companies are now offering recycled steel roofing and siding panels. Metal cladding can also dent easily. While steel is generally more resistant than aluminum siding, it is more expensive, and heavy hail can cause dents that could be expensive to replace.
Aluminum's embodied energy is at 170.0 mJ/kg, while Galvanized Steel is 38.0 mJ/kg. Zinc has the lowest embodied energy among non-ferrous metals. It has one-fourth the embodied energy of aluminum due to easier extraction and less heat required during production. Copper's sitting between aluminum and steel at 100.0 PER embodied energy MJ/kg.
Metal siding material costs can range between $2.20 to $9.00 per square foot. Material costs can be impacted by the type of metal, style, finishing, and whether it is insulated or not. Aluminum siding is the most common and least costly type of metal siding, followed by steel.
Stucco is a cement plaster typically made with Portland cement, sand, and water. Traditionally it was made with lime, sand, and water. Sometimes fibers or horsehair are also used. Acrylic stucco, also referred to as synthetic stucco, is sometimes used to provide a crack-resistant finish over cement plasters. It can be directly applied to masonry or concrete walls and wood-framed walls over metal lath. Stucco can be colored by adding pigments to the mixture.
Stucco is an energy-efficient siding material. It works as an excellent insulator to help maintain warm or cool temperatures inside your home. Its tight sealing properties help to reduce sound, and it also acts as a fire retardant. Stucco is a durable material, it's resistant to mold, mildew, and rot, and it requires little maintenance throughout its long life expectancy.
Stucco has a high cost of installation since it requires multiple layers. While it may be water-resistant, it is not suitable for wet climates or areas with heavy rains. Stucco can be repainted; however, existing stucco requires sandblasting to allow the new paint to bond to the surface.
The embodied energy of every square meter of stucco is approximately 8 megajoules.
Stucco mix is sold in bags. Each bag costs $6.00 to $9.00 and covers approximately 25 feet at a 3/8" thickness. Multiple coats may be required. Finish coat stucco costs $17.00 to $23.00 and covers 70 square feet. The coverage does vary by manufacturer and should be notated on the bag or in the application instructions.
Tobias runs an agroecology farm and a natural building collective in the mountains of El Salvador. He specializes in earthen construction methods and uses permaculture design methods to integrate structures into the sustainability of the landscape.