[Note: this document contains notes on the first segment of the video of Chris Magwood's lecture. To watch the video, please click here.]
In his opening remarks, Chris Magwood describes himself as a “sustainable building omnivore” who built the 1st straw bale house in Ontario in 1997. He didn’t set out to be a builder, but he ended up working on lots of buildings over the years, finding out what works where, and when. He summarized his knowledge in his book, Making Better Buildings, where he ranked building materials against a list of criteria, including the energy embodied in the building materials.
The embodied energy statistics came from a free online database from a group at the University of Bath in England. The database included a number of natural building materials, including straw.
Magwood noticed that in addition to a column for each material on embodied energy, there was also a column for embodied carbon, the amount of carbon. He hadn’t heard of embodied carbon before, but thought that the number was “kind of interesting,” and decided to include the embodied carbon statistics in his research.
According to UN numbers, buildings are a big chunk of global carbon emissions. Between the embodied energy in the materials, and the emissions from operating, the building sector is responsible for almost 40% of global carbon emissions, with embodied carbon alone at 10-15%. =
Magwood designed a sample building and looked at the Embodied Energy and the Embodied Carbon in a 1000 sq. ft. house. Mineral wool insulation, for example, was responsible for a ton of carbon emissions.
Of all the materials he looked at, only cellulose insulation had a negative number, or negative emissions. Plant-based materials like cellulose involve the plant removing carbon from the atmosphere, and putting it into the plant’s body. So using cellulose as insulation in effect removed that carbon from the atmosphere, drawing down carbon and keeping it out of the atmosphere for the life of the building.
“Plants are the machines that do that work; we’re busy engineering machines to suck carbon out of the atmosphere and do something useful with it. We’re surrounded by carbon-capturing machines, really effective ones, they do it at a rate and a scale we can’t reproduce.”
Magwood was impressed by the numbers he was producing, but was concerned he didn’t understand what he was doing well enough, so he went back to school for a Master’s degree three years ago.
He continued to get what he calls “crazy answers…A single building could be responsible for adding hundreds of tons of carbon. But our buildings [using natural materials] were producing big negative numbers.”
He modeled two buildings, a 2000 sq. ft. bungalow, and a 10,000 sq. ft. 4-story apartment. He looked at 400 different building materials.
He found the data broke into four categories:
- Buildings that were very high in embodied carbon
- Buildings with materials in common use
- Buildings using the best materials you could buy at Home Depot
- Buildings using the best possible practices, similar to what he was doing in his own building practices.