We have our embodied energy model down pat. But when we're looking at teardowns, that's only half the equation. The ACHP report also provides a concept model for demolition energy, or "the amount of energy needed to raze, load, and haul away construction materials."*
The concept model provides a second table for demolition energy. The math is simple. Demolition Energy = Gross s.f. multiplied by the demolition energy of materials per s.f. of construction for buildings of similar size and construction type in table 2.
TABLE 2 Demolition Energy of Construction Materials for Existing Buildings
Small Building Size (5000-15000 s.f.)
Light (e.g. wood frame)............3100 BTU/s.f.
Medium (e.g. steel frame)..........9300
Heavy (e.g. masonry, concrete)...15,500
Medium Building Size (50,000-150,000 s.f.)
Light (e.g. wood frame)............2400 BTU/s.f.
Medium (e.g. steel frame)..........7200
Heavy (e.g. masonry, concrete)...12,000
Large Building Size (500,000-1,500,000 s.f.)
Light (e.g. wood frame)............2100 BTU/s.f.
Medium (e.g. steel frame)..........3600
Heavy (e.g. masonry, concrete)...10,500
Now, many (most) homes don't even register on the "small" scale above. But seeing as how demo energy decreases as a building size increases, we think we're being conservative by using numbers meant for 5000-15,000 s.f. buildings to calculate the demo energy of an typical single family home. In other words, the actual energy expended is probably higher.
So, back to our "model" home: 3000 s.f. frame house X 3100 BTU = 9,300,000 BTU. If the same home was made of brick, we're looking at 46,500,000 BTU. Add that to the existing embodied energy, and you're on your way to making a solid case for preserving homes from an energy conservation perspective.
* You are a NTHP Forum member, right? You should be. The journal is great and members can pick up the ACHP report on embodied energy in the pdf file cabinet. Go now!