by Catherine Haug, March 30, 2012
“The Greenest Building is Almost Always the One Already Built,” is the conclusion of Preservation Green Lab: a National Trust report, It offers statistical evidence that preserving or restoring existing buildings typically results in less negative climate impact than building a new green building.” Here are some highlights from that report (based on data from 4 US cities representing 4 different climate zones):
Report Highlights
- Annual US energy consumption: 98.003 quadrillion BTUs (how many zeros is that? 98,003,000,000,000,000)
- Potential annual cost savings by improving energy efficiency of US buildings by 10%: $20 billion ($20,000,000,000)
- Maximum energy savings through building reuse vs new construction: 46% (comparing buildings with the same energy performance level)
- Time for the average new, energy-efficient commercial office building to cancel out the negative climate change effects of its construction: 42 years
Clearly, we are missing the boat with all the new home and commercial construction in our valley. It’s time to rethink how we value existing structures, and the building design/construction techniques used in older structures.
Building Construction
Much of the materials used in building construction today are made, at least in part, from petroleum, which significantly raises the embodied-energy footprint of the structure. For example: glues in plywood, building-wrap and insulation materials, synthetic flooring, and so on.
How many years of improved heating/cooling efficiency will it take just to break-even with the negative impacts of petroleum and fossil-fuel-energy used to make the synthetic materials? The Preservation study (above) says 42 years for commercial construction! Yet we seldom take this into account. All we are interested in is saving energy expenditures going forward, without considering the energy expenditure required to create the materials. This type of thinking is not sustainable for the planet!
Sustainability considerations
So what would be more sustainable? Here are a few examples:
- Reuse existing structures, modifying them to fit our needs, using reused/repurposed materials as much as possible.
- Use older building techniques and natural materials when remodeling or building new (natural materials, like wood, have lower embodied-energy). However, if we continue with all the new construction but use all-natural materials, we will quickly use up all our natural material sources (like trees) – another reason to reuse what we have.
- Be smart in siting structures and landscaping to maximize shade in summer, light in winter. Include windbreaks if you live in a windy area.
See also my earlier post: Green Building, Recycling, & Housing.