The Secret to Low Carbon Buildings? WOOD
The following article appears in the Fall 2019 edition of Green & Healthy Maine HOMES Magazine.
Saco School Takes on Maine’s Most Ambitious Sustainable Building Project
By Lee Burnett
Maine’s most ambitious sustainable building project relies heavily on Maine’s most traditional building material.
The Ecology School’s new dorms and dining commons under construction in Saco will be the first in Maine to go beyond climate-harm reduction. The school is holding itself accountable not only for the carbon footprint of running the buildings, but also the carbon footprint of mining, manufacturing and transporting materials to the site. Wood is the go-to material.
“We just felt like we needed to raise the bar,” said Drew Dumsch, executive director of the school. “We knew there would be an extra cost, but we’re The Ecology School.”
A significant cost component of the $12.5 million project stems from adhering to the standards of the Living Building Challenge (LBC), the most robust building performance rating system. Fewer than two dozen buildings in the world have met the full requirements of the standard, which requires documenting the cumulative carbon footprint of sometimes many thousands of building components. The Ecology School must document “only 900” building components.
LBC prioritizes using natural materials from not-too-distant places. The Ecology School plans to use spruce framing lumber, northern white cedar siding, white oak flooring, tamarack decking and reclaimed-pallet wainscoting. The school also plans to use innovative wood products, such as wood-fiber insulation board, a desirable substitute for petroleum-based rigid foam insulation, and super-insulated wooden windows and doors.
“A lot of these materials are very traditional,” explained Chris Briley, whose firm, Briburn, is one of three architecture firms designing the project.
Until recently, the sustainable building movement has focused mainly on increasing the operating efficiency of buildings by reducing the energy consumed (and carbon emitted) in heating, cooling and lighting. Great strides have been made in design and technology in the last two decades. It is now practical to build a structure that is carbon neutral by employing super insulation, an airtight envelope, energy recovery ventilation, high-performance windows, managed solar gain and rooftop solar. The Passive House framework (also called Passivhaus from its origins in Germany) has become the gold standard in sustainable design.
But slashing energy use and carbon emissions is not enough to avoid contributing to climate disruption, according to the most complete analysis. Even before a building is occupied and any energy is used, the building has already contributed to climate change. This comes from the mining, harvesting, manufacturing and transportation of building products, which all have significant carbon footprints.
“You’ve already cooked the planet before you even start construction,” said Jesse Thompson, whose firm, Kaplan Thompson Architects, is also involved in design.
These pre-construction emissions, also known as embodied carbon, have usually been ignored in discussions about the construction industry’s contribution to climate disruption. But that is changing due to the narrowing window for making a difference. In order to meet the targets set forth by the Paris Climate Agreement signed in 2015, the building sector must be carbon-free by 2050.
The next 30 years is a very short time frame compared to the 80-100-year life span of a typical building and the time horizon for building energy analyses. In the long term, a building’s operational energy almost always eclipses its embodied energy. But during the first decades of a building’s life, a building’s embodied energy looms very large. “Emissions now hurt more than emissions later,” in the words of The New Carbon Architecture – Building to Cool the Climate, a 2017 book by Bruce King, which is popularizing the urgency of tackling embodied carbon.
Enter wood. While carbon is released in wood harvesting and transportation – such as diesel fumes from machines – these emissions can be quite modest compared to the offsetting absorption of atmospheric carbon by trees during their lifetime. By the genius of nature, the storage of carbon that begins in roots, branches and trunks continues in wood products such as furniture and buildings. In other words, wood used in construction runs the counter backwards in carbon calculations. “It turns out, you can store a whole whacka carbon in building materials,” said Chris Magwood, an Ontario sustainable building teacher and evangelizer.
Magwood, along with Jacob Racusin and Ace McCarleton of New Frameworks in Vermont, were the keynote speakers at the 2019 Northeast Sustainable Energy Association in Boston. They received a standing ovation for their talk, “Carbon Drawdown Now! Turning Buildings into Carbon Sinks,” which is posted on YouTube.
BEING THE FIRST PROJECT IN MAINE
The opportunity to design Maine’s first LBC project attracted strong interest from three Maine architectural firms with long track records in the sustainable building field: Kaplan Thompson Architects, Scott Simons Architects and Briburn. The three firms all acknowledged their trepidation in becoming the first to ascend the learning curve, but the boldness of the vision could not be resisted. “This turns on its head how we do things,” said Jesse Thompson. “It’s not just how we make things less bad, but how do we make things better.” Said Ryan Kantares of Scott Simons, “This is really aspirational.”
In a surprise move, the Ecology School declined to choose a single firm and asked them to work together, an unusual request that added complexity to an already complicated process.
“I suppose we could have said ‘No,’ but we were so excited about it that no one thought to say ‘No,’” said Kantares, who became the lead architect for Scott Simons.
Unlike other building rating systems, LBC affords little flexibility in documenting performance. Full certification requires meeting standards in seven performance areas, or “petals,” with a third-party audit conducted a year after completion. Some standards, such as for energy, are incremental advances to sustainable building practices. Other standards, such as for meeting all water and waste needs on site, are not that difficult in rural Maine.
The biggest challenge has been documenting the source and carbon footprint of all building materials right down to hidden materials such as gaskets, sealants, or the sheathing material on wiring. Sometimes that information is easily retrievable through Environmental Product Declarations, but sometimes it requires a two-hour phone call. The team hired Integrated Eco Strategy of North Adams, Mass. to assist. “People have no idea how many parts are in their building. We never knew, until this,” said Thompson. “Now we have the spreadsheets.” LBC bans use of certain materials altogether because of their carbon footprint or environmentally destructive manufacturing processes. This includes vinyl siding, expanded polystyrene, (rigid foam insulation panels), certain chromes in plumbing fixtures and polyvinyl chloride plumbing pipes. It’s not easy to find vinyl-free, higher voltage wiring. Compounding the complexity, LBC requires 20 percent of all building materials to be sourced within 300 miles (generally New England) and 50 percent from within 600 miles (includes some Mid-Atlantic states).
All that leg work is expensive. “It’s substantially more expensive than Passivhaus,” said architect Briley. He estimates it may be 50 to 75 percent more, although factoring out the cost attributed to LBC is very difficult because of many other cost drivers. “When a plumbing contractor learns he can’t use PVC, his price is going to jump. But it may also jump because the contractor is thinking, ‘There are other things that will catch me.’ Everyone is busy, costs are on the rise everywhere.”
Wood posed its own challenge because a separate forestry certification is required. Three quarters of the commercial forest acreage in Maine could meet generally understood sustainable forestry criteria: management by a licensed forester following sustainable forestry principles. A smaller percentage of woods – about half the commercial forestry acreage in Maine – are grown under one of three sustainable forestry certification programs. This is a formal process in which growing conditions are audited by a third party and the wood is tracked to market through a chain of custody process.