Preservation: The Original Green
Photo from PreservationChicago.org
By Susan Turner
Philosophically, green design and preservation hold common values and goals. Both movements are comprised of stewards, protectors of environmental and cultural resources for future generations, and both strive to reduce energy consumption. Preservation is about more than keeping pretty marble foyers and handsome facades intact. It is about retaining a cultural resource that was inherently respectful of the environment, and was built to last hundreds of years. It’s about life cycle costing, and building for future generations.
It is better to preserve than to repair, better to repair than to restore, better to restore than to reconstruct. Adolphe-Napoleon Didron
This quote is equivalent to the green movement slogan “Reduce, Reuse, and Recycle” with respect to development. Preservation has been conserving embodied energy for centuries. There are so many benefits to preservation. It takes less energy to keep a building than to reproduce the square footage in a new building. A key finding of a www.emptyhouse.com study states: “Reusing an existing building has an initial savings of 35 tons of CO2 over new construction”. And that’s just for residential buildings. Preservation uses more labor and less material, creating jobs, while reducing demand for new construction materials. Retaining older buildings also slows the rate at which landfills fill up which, in turn, keeps millions of cubic yards of waste from flooding landfills. It is important to reduce construction and demolition waste (C & D waste), since it constitutes 30% of all landfills.
But, what about the energy consumption of older buildings? Typically, a building consumes 15% of its total lifetime energy consumption in the construction phase. Another 10% is consumed by major retrofits, such as upgrades, and remodeling. 75%, the vast majority, of a building’s energy is used to heat, cool, power and maintain the property.
Historic buildings (pre-1920) are traditionally some of the lowest consumers of energy, and perform as well as their new, efficient counterparts due to thoughtful design, dense urban fabric, orientation, mass masonry, operable windows, awnings, and sloped roofs over vented attics. They were also built to last, employing stone, brick, slate, plaster and heavy timber, all with the intention that the building would be durable and last for generations. When upgrades for reduced air infiltration or improved thermal performance are added, these buildings can perform as well as, or even better than, efficient new construction. LEED buildings, built since 2000, have only recently matched the energy consumption levels of historic buildings.
Keeping technology simple and controllable has energy benefits too. Traditionally, older buildings use three separate systems: heating (furnace/boiler), ventilating (operable windows), and air conditioning (drawing air from the basement), rather than clumping these functions together into a single HVAC system. A combined HVAC system takes outside air, chills it to 55°F, and then heats the air to maintain a consistent room temperature. This results in wasted energy, heating air that has been already cooled. Mechanical designers now trend towards using full fresh air and tempering it with local fan coils in each room. This helps to conserve energy and better meet the diverse needs of building occupants from room to room.
The bottom line is this: green building professionals can learn from historic building’s passive, low-tech systems. Knowledge of these historic buildings, combined with new technology, can inspire effective solutions for lowering a building’s carbon footprint.
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