Fact Sheet»

Description

Exterior cladding systems, such as brick and wood siding, have both an aesthetic and a functional role in residential construction. Aesthetically, what is on the exterior of the house creates the first and often lasting impression of the home. Functionally, the cladding material protects the house's structure from the elements, mainly rain and wind driven moisture. Cladding should be selected based on cost, aesthetics, durability, maintenance requirements, and environmental impact. While no siding option is completely maintenance free, there are options that require a low level of maintenance. The following analysis examines the relative economic, energy, and environmental impacts of the following eight types of siding: stucco, brick, wood, fiber-cement, aluminum, vinyl, hardboard, and wood-resin/plastic composite.

Recommendations

The appearance of a traditional home can be achieved with fiber cement siding, which balances first cost, durability, and environmental impact and is recommended as a lap siding. Stucco should be considered as an alternative for residences that require extremely low maintenance alternatives and have an anticipated life span of 50 years or more.

General Guidelines for selecting a cladding system:

• Choose a system that will be serviceable at least through the end of the first mortgage term, usually 30 years.
• Compare life-cycle costs for siding, including first cost, maintenance costs, and replacement costs to determine best selection.
• Use products that come from sustainable sources or those made with recycled or waste material to reduce overall environmental impacts.
• Use products that are recyclable.

Cladding Alternatives

Criteria Summaries

Cost: Vinyl siding is widely used today because it has the lowest first cost, low maintenance, and is relatively durable. Fiber-cement board is gaining popularity due to its relatively inexpensive cost and anticipated longevity. First cost for fiber-cement siding is $0.44 per square foot more than vinyl. Wood siding is more than twice the cost of vinyl and 40% more expensive than fiber-cement. As with many building materials, those with highest first costs, brick, stucco, and wood, have the greatest durability.

IAQ: Sidings and other cladding systems are exterior products, and, therefore, do not have a substantial impact on indoor air quality.

Expected Product Life: Cementitious materials such as stucco and brick are the most durable and have the longest expected serviceable life. Properly maintained they can last 100 years or more. Fiber-cement, wood, and aluminum siding have a 50 year life expectancy, but life expectancy for wood is contingent on painting. Vinyl has a 25 year expected life, however, it may be replaced earlier because it tends to look less presentable over time due to fading and cannot be painted. Fiber-cement board has twice the life span of vinyl. Taking this into consideration, its lifetime cost is actually less than vinyl. Likewise, stucco has double the first cost of vinyl, but lasts at least twice as long and therefore is less expensive over the lifetime of the house. Wood composite products have the shortest useful life span - around 10 to 30 years. As the house's first line of defense against moisture intrusion, correct installation and maintenance of the cladding system, regardless of type, is critical to the continued function and durability of the exterior wall system. This includes proper flashing and detailing of openings and continued maintenance such as painting and tuck pointing.

Life Cycle Thinking:

• Energy consumption (non-renewable, fossil fuel energy): Wood siding alternatives, such as cedar shakes, bevel or lap siding, have the lowest primary energy use and total embodied energy and, if sustainably harvested, the lowest overall environmental impact. However, they do require the most maintenance over time in order to maintain their integrity as a rainscreen and prevent mildew and rot. Brick leads the group in highest total embodied energy, followed by steel and aluminum. Hardboard and composite products, because they use waste or low-quality materials, which would otherwise end up in landfills, reduce energy used to extract, harvest and process virgin materials. However, the manufacturing processes for these products are highly energy-intensive.
• Pollutants generated in production: Brick, steel or aluminum, and fiber-cement siding have the highest water and air pollution indices (in that order), caused during extraction and manufacture. Steel has the highest negative impact on water use, from extraction through the full manufacturing cycle. Vinyl siding sits right in the middle of the products in its impacts through pollution. It has the potential to leach pollutants, including dioxins and pthalates, into the air and water after installation and is considered a substantial risk for pollutant generation (dioxins) during a fire. Wood siding, if it comes from non-sustainably managed forests, creates water and air pollution through erosion, sedimentation, and poor harvesting practices.
• Potential for off-gassing in the building: Because these are exterior products, their effects on the indoor environment are minimal.
• Durability of the product: Fiber-cement sidings, with warranties of upwards of 50 years and a painting maintenance cycle of from 5-7 years, are the most durable selection. Sealant joints and joint detailing are an important component of the overall durability of fiber-cement products and installations. Steel or aluminum sidings, with polyester coatings, have a long life cycle if properly maintained. Vinyl sidings, although durable, may discolor and will lose plasticizers over time, fading and becoming brittle. However, they require little in the way of maintenance over time. Wood siding and shakes require more maintenance to preserve their characteristics and ensure a full life cycle, but with proper painting and repairs can last for decades. Hardboards and composites, similar to wood, require more maintenance, painting and sealing seams, to ensure their full life cycle performance. Composites, with their blend of resins, are more durable and stand up better to moisture than hardboards. Brick and stucco systems are very durable, wear well over time, but do require maintenance on joints where water infiltration may occur. Maintaining sealants, flashings and weeps within the systems is essential to full life cycle performance. Brick and stucco (true plaster systems, not EIFS (Exterior Insulation and Finish Systems) have aesthetic appeal and lend a feeling of permanence and quality to residential construction.
• Potential for future recycling: Steel and aluminum are highly recyclable, and are currently being made from high recycled content material, thereby reducing their initially high embodied energy debt. Fiber-cement siding can be reground and used, in some cases, as fill, but there is currently no program for incorporating recycled materials back into production. Stucco is not recyclable, although the metal lath in the system is. Brick can be salvaged (cleaned and reused) or ground up for landscape uses or fill. Wood is biodegradable, but stains and paints can affect its reuse and limit its use as mulch or landscape amendment. Vinyl can be recycled, depending on the quality of the PVC; however there are no programs currently in operation to return the material and it is generally landfilled when removed.

Practice: All of the siding selections examined here are common and use standard installation methods, although fiber cement siding installation may require some additional training for cutting the material and proper sealing of joints.

Environmental Context

Sidings provide aesthetic and protective components to residential construction. Many of the more sustainable alternatives use fiber-cement, recycled metal and plastic materials as panels or planks. Some alternative wood siding products use wood fibers and other by-products from waste, recycled and managed sources, which are manufactured into various types of sheathing or finish siding. Wood and plastic composite materials may off-gas Volatile Organic Compounds (VOCs), such as formaldehyde, from the binding agents used. Engineered wood products are more resource efficient and durable than solid wood. Metal and fiber-cement sidings, which use recycled content, reduce the environmental impacts associated with extraction and processing of virgin materials. Stucco and brick systems have the greatest negative impacts due to high embodied energy and the overall use of non-renewable resources.

The following chart, based on Life Cycle Assessment data from the ATHENA Sustainable Materials Evaluation Tool, provides a basic snapshot of the environmental impacts associated with the base materials in major siding selections:

Sustainability of Building Materials

Citation
The Athena Sustainable Materials Incentive