[Greenbuilding] CF analysis of tearing down a house vs. renovation?

[Brad Guy]

There are alot of studies of this. However there are two other options not mentioned. One is retrofitting the existing home to be as energy efficient as it can be given whatever existing constraints, and on the demolition side, the deconstruction of the home to preserve and reuse as much of the materials as possible. These consider that the carbon footprint of the home is inclusive of both embodied and operating for some period of time post-demolition&construction/renovation. The standard is usually 60 years.

The deconstruction/new high-efficiency construction would have a much lower footprint and therefore shorter period of embodied energy payback for lack of a better term than the simple demolition/construction. The high-efficiency renovation typically shows a lower footprint in the beginning and reaches the point sooner than the new construction where the operational energy becomes higher on an annual basis.

One might ask if a complete deconstruction/reuse and rebuild, is a better or worse option than an energy-efficient retrofit in this day and age given all the increasing resources for these options.

No study is perfect unto itself as assumptions are made based on biases, so looking at more than one seems like a good idea. The Preservation Green Lab did a did a study called the "value of reuse", that is worthwhile and also Oregon DEP did an LCA study of residential construction in Oregon that is good as well.

It also seems that it is not exactly correct to compare the loss of older embodied energy in an existing home compared to new materials, as the technologies even 50 years ago were so much less efficient. One might assume some additional factor of carbon emission (from energy of production only) to an older equivalent material than whatever its production footprint is now reflected as a higher materials carbon footprint from the demolition of older structures.


 
Brad Guy, Assoc. AIA, LEED AP BD+C
Associate Director
Center for Building Stewardship
Assistant Professor
School of Architecture and Planning
The Catholic University of America
Washington, DC 20064
c. 814-571-8659
GUY at cua.edu


________________________________
 From: Matt Dirksen <dirksengreen at gmail.com>
To: Green Building <greenbuilding at lists.bioenergylists.org> 
Sent: Tuesday, July 23, 2013 8:29 AM
Subject: [Greenbuilding] CF analysis of tearing down a house vs. renovation?
 

I understand its "assumed" that tearing down an old house and building a new high efficient home is still going to have a higher CF than adding/renovation/energy retrofitting an existing home.

However, can anyone point me to any carbon footprint analysis of something like this? (And yes, I fully understand its  an apples to oranges comparison.)

Thanks much,

Matt


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