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Buzzword alert: Embodied Energy / Carbon


Published by:

Landmarks Commission

How old buildings are helping Boston save the planet.

Climate change is forcing us to reexamine the way we do things. We now know that everything we do in our lives has a carbon footprint. This includes how we build, operate and remodel our buildings. One of the biggest contributors of  carbon in the atmosphere are our buildings. Both in building construction and the day to day activities such as heating and cooling. Today, cities like Boston are creating ambitious initiatives to make buildings more energy efficient. Efficient heaters, insulation, and renewable energy all help reduce the amount of pollution that buildings produce. These efforts are gaining popularity as they become more successful both in reducing energy needs and costs and reducing carbon. 

Policymakers, here in Boston and elsewhere, are now starting to look more closely at the carbon footprint of constructing and demolishing buildings. Buildings also represent  potential carbon storage; the actual building materials can store carbon within them. This is one reason why, for example,  wood composite frames are becoming more common.  With that in mind, buildings of yesterday that use quality, locally sourced, natural materials have long since eliminated their original carbon footprint to produce and distribute them.

If you take part in the trade of preservation construction or planning you’ve likely heard the phrase “embodied energy.” If you haven’t, here are some sources to get you up to speed;

The life cycle and embodied energy of a building

When we talk about lowering the emissions of a building we usually examine heating, cooling and weatherproofing. There is one other variable we should look at; built-in (embodied) carbon. Embodied carbon factors how and where the structure’s materials are sourced, shipped and installed. This concept also looks at how long materials will last before being replaced. Finally, once those materials are no longer needed, can they be up-cycled or recycled? For insight let's look at Boston's South End. Many of the row houses that make up this neighborhood are built using old growth wood. Old growth wood is more durable and resistant to rot than the wood you buy today. The granite and limestone used for the outside of these buildings were sourced from areas around Boston like Portland, CT, Rockport, MA and Quincy, MA. The bricks came from local brickyards. Locally sourced materials produce less pollution to ship and also keeps money in local economies while providing local jobs. Of course, with our growing population and the need for new buildings, it is not possible to source all our materials locally. What is possible is to preserve the materials and buildings we use now. Not only will this conserve our identity as a historic city, it will create thousands of tiny, livable “carbon storage” units. It is important to consider how long the materials used in buildings will last after installation. This will determine how much carbon is released into the atmosphere when producing these materials.

Old Windows, New View

Historic windows are often misunderstood. It is often cited that older windows increase heating and cooling bills, and are not as energy efficient as new, low-e or multi-paned windows. Let’s dive into this argument. As we mentioned before, historic builders worked with the materials around them. In New England, builders were fortunate enough to have access to millions of old growth trees, which are trees that are older than 100 years. Old window parts are made from the hard cores of old growth trees. Using this wood allows for builders to shape wood into thin but durable components. The end result is a window that can be easily repaired and designed to last for many lifetimes. This is why you see so many of these windows still in use today, even after 150 years of brutal Boston weather. The next time you take a walk down a historic street, take note of  the windows. Older windows often have slim, delicate dimensions with a slight wave to the glass. Old windows are often protected by storm windows which add additional protection during the harsh winter months.

Alternatively, new windows have a large carbon footprint from the beginning. It is estimated that a new window will take around 30 to 40 years of energy savings to become a carbon neutral asset. Unfortunately, most new windows have a useful life of around 25-30 years. Most of these windows don’t have the ability to repair non-functioning elements because they are mass-produced. Once these windows are replaced they end up in a landfill and virtually never break down.. This process grows the carbon footprint of the building year after year this cycle is repeated.

It’s often argued that historic windows are drafty and difficult to operate. This can often be resolved at low cost with modern weatherstripping, painting, storm windows, and proper maintenance. Some also argue that storm windows are unsightly. This may have been true in the past, but today’s modern storm windows are simple, lightweight and can be installed inside or outside of the window. The reality is that less than 10 percent of heat is lost through a home's windows. With a little maintenance your historic windows can be eco- friendly and last for decades. 

TIP: You can find local resources and window restoration specialists on the Windows Preservation Alliance website.

Old Building Deconstruction

While it is not ideal, sometimes there are no other alternatives to demolishing a building. When this is necessary, preserving the building materials that make up these buildings is critical. These materials can be assets for the property owners and cities looking to reduce their carbon footprint. Portland Oregon is leading the way in this practice. In 2016 Portland created a policy requiring all buildings built before 1940 to be disassembled by    a deconstruction specialist. After which, the parts are sorted and resold for future use. The result was less demolitions of Portland’s built heritage. There was also 70% less materials and debris ending up in landfills (5 million pounds a year). An unforeseen benefit? Job opportunities for construction trade workers to develop skills and build a career on. Old materials are not as plentiful as they were when historic cities such as Boston were first settled. This makes the materials that exist in our buildings today all the more valuable. By diverting materials from landfills we are not only reducing waste, we are storing carbon in buildings and preventing it from entering the atmosphere. In many ways we are already doing this. New England is world renowned for its antique shops and architectural salvage yards.

Boston’s Part

Our beautiful and historic city already has thousands of “livable carbon storage” buildings. According to Boston’s Climate Action Plan, half of the city’s (87,000) buildings were built before 1950. That’s a lot of carbon. However we all know that not every old building is worthy of saving. In those instances, we can make use of the existing materials that make up those buildings to support a carbon neutral future. At the same time we are maintaining our built heritage and maintaining Boston’s unique heritage that makes it so special to its visitors and residents alike. By combining preservation methods and material reuse, we can create a greener and more prosperous Boston of the future.