Multifamily Case Study

Photo: Bill Horsman; courtesy of Bison Innovative Products

Project: 345 Harrison
Location: Boston
Architect: CBT Architects
Landscape Architect: Copley Wolff Design Group

The Project: The 345 Harrison apartments are located in Boston’s desirable South End neighborhood, which is home to vintage shops, jewelry stores, antique furniture markets, and hip urban eateries, all within walking distance of each other. As an upscale living option, and a way to differentiate the project from other apartment buildings in the area, the goal was to provide a variety of amenities for residents to enjoy.

The Design Solution: The apartment’s vast amenities include a rooftop dog park, pool, and lounge area with gas grills, comfortable, modern seating, and a 12-person firepit with glass details that express the building’s upscale vibe. These features all sit on a rooftop space made possible using wood tiles resting on adjustable pedestals. The specified system was selected based on its ability to provide modularity for different systems, such as 2-foot x 2-foot ipê wood tiles, traditional joist and plank decking, concrete pavers, and artificial turf. This installation exemplifies how a rooftop deck can incorporate a variety of surface materials. Clearly, it is important that all surface materials are properly supported to maintain a tight installation and limit the space between modules. The adjustable pedestals help to ensure that all surfaces are level with each other. When heavy-weight objects such as planters are installed, additional pedestals help to compensate for the extra load.

Versatile Redwood Decking

Outdoor decks and terraces of all types are popular on residences across the United States and Canada. For conventional, framed construction, there has been a surge of innovative decking products that are made from a combination of wood fiber and different types of plastic materials. These composite decking materials are sometimes selected and used based on an objective of finding a low-maintenance option that can blend with the residence and other deck components (e.g., railings, stairs, etc.). However, the plastic ingredients in these composite products raise questions about their structural performance (they are typically not as strong or rigid as solid wood) and their stability over time since they usually need plenty of room for expansion and contraction as their temperature changes. There is also the question of sustainability since the plastics are in fact petrochemicals that can contribute directly to negative environmental impacts.

This is a case where a traditional material is being looked at more closely as a preferred alternative compared to a newer, human-made one. That material is natural redwood decking, which is regarded as one of nature’s finest and strongest building materials. Structurally, redwood has a shear strength up to five times greater than plastic and composite decking. From a durability standpoint, redwood is known to be naturally resistant to decay and termites. This was first discovered in redwood forests in California, where fallen trees were found to have been laying on the ground for decades with no visible sign of any significant decay—very unlike other trees that can decay naturally quite quickly.

Regarding the appearance, many designers agree that no other decking material mimics the natural beauty and warmth found in real redwood deck boards and accessories. Its rich, warm color and grain pattern look great when installed and maintains its appeal even with age. Redwood can be left untreated due to its natural resistance properties and allowed to patinate over time, or it can be stained or finished to preserve a particular color and look. Either way, it is a lightweight wood that is easy to work with, which helps control overall construction costs.

Redwood decking naturally achieves a Class B flame spread. This means it is approved for use in California’s Wildland Urban Interface (WUI) fire-hazard severity zones without restriction. For situations where a higher degree of fire resistance is needed, it can be treated to achieve a Class A flame spread using proven and tested processes that are registered with building code authorities.

The design flexibility and performance characteristics of redwood decking mean it can be used in either renovation projects or new construction. Redwood decking also works well with innovative, newer deck components, such as glass panel railing systems or cable railings. The warmth of the wood complements a variety of the other materials, like glass and metal.

Photo courtesy of Humboldt Sawmill Company

Redwood has long been prized for its warm appearance on deck floors and ceilings, as well as its natural durability and longevity.

Sustainability and Redwood Decking

For a period of time in the 20^th century, there was a concern that different species of wood, including redwood, were being over harvested and their use was not sustainable. That concern has led to the creation of organizations like the FSC and others that have developed processes to ensure that wood as a natural resource is treated sustainably and responsibly. According to its website (www.fsc.org), “FSC is an international organization that provides a system for voluntary accreditation and independent third-party certification. This system allows certificate holders to market their products and services as the result of environmentally appropriate, socially beneficial, and economically viable forest management.” For architects and building owners, this means that products that meet the FSC criteria are certified as a sustainable product.

The FSC offers several different types of certifications for companies that grow, harvest, process, and deliver sustainably produced wood, including redwood. These certifications include:

• Forest Management Certification: It states, “FSC Forest Management Certification confirms that the forest is being managed in a way that preserves biological diversity and benefits the lives of local people and workers, while ensuring it sustains economic viability.” To receive FSC forest management certification, 10 principles must be adhered to by a forest operation. These principles include things like maintaining high conservation values, community relations, and workers’ rights. There are also requirements for monitoring the environmental and social impacts of the forest being managed. Each principle has criteria that are the practical means of determining whether the principles are being complied with. These principles and criteria are applicable worldwide and usable in all kinds of forest ecosystems and most cultural, political, and legal settings.
• Chain-of-Custody Certification: FSC Chain-of-Custody Certification is a standard used to verify that materials harvested from a certified forest have been identified and separated from noncertified and noncontrolled material. This is important because wood moves through a supply chain, from the forest to the market, and can change hands and ownership multiple times along the way. Having a process to differentiate FSC-certified material from noncertified material helps ensure that the products used on a construction project are in fact sustainable. Hence, the FSC allows organizations of all sizes and types to have the opportunity to qualify for Chain-of-Ccustody Certification, including single site, multi site, and groups of organizations.

The certification process is an important step in verifying that wood products used in construction are in fact sustainable. Therefore, any design professional or homeowner concerned about the environment or those with a preference for all-natural materials are well served by specifying FSC-certified redwood.

Photos courtesy of Humboldt Sawmill Company

Forest Stewardship Council (FSC) certification is one way to ensure that redwood products make their way from a sustainably managed forest all the way to a particular residential project (left). Environmental product declarations (EPDs) are used to communicate the life-cycle assessment (LCA) of different building products, including redwood.

Life-Cycle Assessment of Redwood Decking

The most accepted means of determining the overall sustainability of any building product is to conduct a life-cycle assessment (LCA) of the product. The Consortium for Research on Renewable Industrial Materials (CORRIM) in association with the California Redwood Association conducted a cradle-to-grave LCA on redwood decking in comparison to alternative decking products.

The LCA looks at the entire life of a building product, in this case redwood decking. It begins with the forest management (the “cradle”) and moves through the harvesting, transporting, and processing into decking products ready for delivery (the “gate”). It continues with transporting to wholesale/retail outlets, delivery to a job site, installation, service life (the “use phase”), and finally to removal and recycling and/or disposal (the “grave”). Each of these steps in the life cycle of the product is assessed in five common impact categories, which include 1) Global Warming Potential, 2) Ozone Depletion Potential, 3) Acidification Potential, 4) Smog Potential, and 5) Eutrophication Potential.

Environmental Product Declaration

The results of the LCA are best communicated in a standardized format known as an environmental product declaration (EPD). The use of EPDs in the construction industry has become recognized as a means of providing total environmental transparency in building products so that architects, owners, and others can compare different products and make the best decisions on which products to use. What is the environmental performance of redwood decking versus other non-wood alternatives? Based on findings in the LCA and associated EPD, it is generally much better.

In the redwood decking LCA and EPD, a significant environmental advantage is accounted for. Since redwood trees, like all other trees, consume carbon dioxide and emit oxygen, they naturally sequester carbon dioxide and thus remove it from the atmosphere. This directly helps to offset the global-warming issues caused by excess carbon dioxide emissions from other sources. As such, it is common to see wood products, including redwood, listed in an EPD with a negative number for global-warming potential. In fact, the amount of carbon stored in redwood decking is equivalent to about 10 times the total carbon dioxide emissions released during the manufacturing process.

Regarding the other impact categories, redwood performs favorably as well, particularly compared to other building products such as composite or petroleum-based plastic decking. Low carbon emissions during the manufacturing process and carbon storage during the service life of a redwood deck are both positive environmental attributes that should be considered when selecting a decking product.

A summary of the results as shown in the EPD for redwood are shown in the table below. This data can be compared to other such EPD tables for other decking products to determine comparative differences. Note that the unit of measurement is one square meter of redwood decking.

Jessica Hewitt is the Director of Marketing at the Humboldt Sawmill Company in Scotia, California. She has observed that “Segments of the population, often those that have attained higher education levels, prefer more sustainable materials.” As shown in the preceding paragraphs, redwood can help to meet this preference in beautiful, durable, and intelligent ways.

Source: Environmental Product Declaration for Redwood Decking prepared by UL Environment for the American Wood Council and the California Redwood Association