That’s what it comes down to today doesn’t it? In this age of sustainable, environmentally smart, green consumerism we want buildings that are as green as we are. We want something that makes us feel like good stewards of the planet we have inherited from our fathers and will bequeath to our children.
That brings me to my third argument in the Proving Preservation series.
The greenest building is the one that is already built.
What Makes Old Buildings Green?
Without a doubt we can build structures today that are extraordinarily energy-efficient. There are even website dedicated to just that teaching like Green Building Advisor, Green Building Initiative, and almost every state has a green building coalition of some sort. Once built, these amazing building recycle water, have living green roofs that keep temps moderate indoors, are nearly net-zero (requiring no power from the electrical grid). We can build things today that require almost no carbon footprint to operate on an annual basis.
BUT…as efficient as these buildings are they still need raw materials (wood, metal, gypsum, paint, glass, plastics, etc.) in order to build them. And those raw materials need to be processed, shipped, packaged, delivered on site and assembled. That all requires a lot of resources and energy.
That is precisely why preserving and repurposing old buildings is a more sustainable option. Old buildings required the same huge list of resources and energy to assemble them 100 or 200 years ago, but the work has already been done. The materials are already in place. There are no more 2x4s to deliver or sheetrock to hang.
If you tear down that old factory to make way for a new super efficient office building, not only do you add hundreds of thousands of tons of debris to the landfill but you essentially throw away all that embodied energy.
What is Embodied Energy?
Old buildings are not just full of history and character. They are filled with the embodied energy from when they were constructed in the first place. What is embodied energy exactly?
Embodied energy is the total energy required for the extraction, processing, manufacture and delivery of building materials to the building site.
It requires energy to:
- Demolish the existing structure
- Haul away the waste from the original building
- Extract raw materials
- Manufacture construction-ready building materials
- Transport building materials to a construction site
- Assemble the physical structure
Facts & Numbers
According to a extensive study by the National Trust for Historic Preservation the following stats were found:
- An existing 50,000 square foot building, represents 80 million BTUs of embodied energy (the equivalent of 640,000 gallons of gasoline)
- Demolition of such a building would result in 4,000 tons of waste
- If only 40% of materials are retained, it would take 65 years for a new green, energy-efficient building to recover the embodied energy lost.
Many new buildings have a life cycle of far less than 65 years today. That doesn’t mean these new buildings aren’t green. It just means that demolishing a historic building to make way for a new energy-efficient building essentially eliminates any energy savings.
A study was done in Salt Lake City, UT regarding historic homes and their impact on the environment. The amount of raw materials that were used or disposed were calculated for the three scenarios below and the results were astounding.
- Rehabilitating a neglected single family home required 47.3 tons of materials
- Construction of new suburban housing required 182.4 tons of materials
- Demolition of existing historic home and infill of new “energy efficient” home required 351.8 tons of materials
That’s 7.5 times more raw materials and energy required to tear down and replace an old house with infill construction! There is nothing beneficial about tossing that much material into the landfill.
Donovan Rypkema is highly regarded as one of the finest minds in real estate and economic development, especially concerning historic preservation related matters. He has conducted hundreds of studied in 49 states and 30 countries on various topics related to the field. The Salt Lake City Study was completed by his firm with the following conclusions.
“The average historic house that was retained rather than razed reduced the impact on the landfill by 116.6 tons.”
That makes sense but what about the relative inefficiency of older buildings. Well, that’s something Mayor Bloomberg commissioned a study in New York City about. He wanted to make New York one of the greenest cities in the country and set about trying to find where the major energy use was occurring. What they found surprised them greatly.
It turns out that a multifamily structure built after 1980 uses 13% more energy per square foot than one built before 1920.
Building design, siting, passive heating and cooling devices like operable windows, better building materials, all these things played a part in making the historic building more energy-efficient than the newer buildings.
So, let’s stop regurgitating the same tired lies that new construction is better for our environment and communities. The truth is that restoring and reusing old buildings through adaptive reuse is by far the most energy efficient option for cities to grow. First restore and efficiently utilize our existing building stock. Then when we need more room build efficient, smartly designed new buildings. The is why an old building truly is a green building.