Saturday, February 12, 2011

Post # 26: Building Energy Use - A Major Sustainable Energy Challenge

We recently replaced thirteen windows in our thirty year old home with high-efficiency Energy Star-rated windows.  Wow - what a difference over those thirty-year-old wood-sashed windows!  We actually saw a non-trival drop in our residential heating bill the first month despite it being the coldest month of the year.  This inspired me to revisit the data on building energy uses in the U.S.

Building energy usage is the single largest consumer of primary energy in the U.S.  According to the DOE 2009 Buildings Energy Book (found at ), residential and commercial buildings are responsible for ~ 40% (100 quads) of total U.S. primary energy consumption.  (The Industrial and Transportation Sectors consumed ~ 32% and 28% respectively.)  The DOE data also break down the 2006 building energy usage data to reveal the specific sources of this energy usage:
  • 19.8% Space Heating
  • 17.7% Lighting
  • 12.7% Space Cooling
  • 9.6% Water Heating
  • 7.8% Electronics
  • 5.8% Refrigeration
These six uses account for just over 73% of the total energy consumed by our residential and commercial buildings.

These statistics prompted me to wonder how difficult it will be to significantly reduce total building energy consumption.

The most convenient opportunity to positively impact residential and commercial energy consumption is in the construction of new buildings.  A new build offers the opportunity to integrate modern energy-efficient technologies in a way that simply isn't possible with an existing building.  I found an enlightening presentation by S. Shyam Sunder of the National Institute of Standards and Technology entitled, "Building Energy Efficiency – Net-Zero Energy, High-Performance Green Buildings" ( ) that addresses this issue.  Sunder points out that the replacement rate of building stock in the U.S. is only ~1% per year, and that the majority of current building energy efficiency retrofits target only the 5% of our buildings (commercial and residential) that are categorized as "large" buildings.  With only a 1% replacement rate in buildings,  I have to conclude we simply cannot look to new buildings as the solution to our building energy consumption challenge.

By the way, I also ran across a dandy little residential buildings fact sheet from the University of Michigan's Center for Sustainable Systems ( ) that indicates the average residential area per person grew from 292 sq. ft. in 1950, to 850 sq. ft. in 2000 – almost a factor of three!  Wow... that's something to think about.

Anyway, where do these facts leave us?  The answer: WE NEED A BREAKTHROUGH IN AFFORDABLE,  RETRO-FITTABLE ENERGY CONSERVATION TECHNOLOGIES FOR EXISTING BUILDINGS.  Otherwise it will be almost impossible to dramatically impact the total building energy usage in the U.S. in the lifetime of anyone reading these words.

The bad news is (going back to the building energy usage splits cited above),  there's no one "silver bullet" that will accomplish a transformational reduction in building energy usage given the diversity of building energy loads.  The good news is that even small improvements are magnified by the "law of large numbers" – the fact we have so many buildings to which any given improvement can be applied.

So..., as I've said in the past, I believe the recipe for a sustainable energy future has four key ingredients:
  1. Energy Conservation - everywhere and in everything, but especially in buildings
  2. Nuclear Power for central station electricity generation - supplemented as we can with all other clean energy sources
  3. A Fortified Electric Grid
  4. Electric Vehicles (private and mass transit).

Go to run for now...


  1. Very interesting comments and i totally agree with you Sherrell. We are working with the commercial sector to showcase solutions to energy efficiency in existing buildings
    Well done and I hope you get some very interesting comments and support.

  2. Robert,

    Thanks for the comment. I was thinking... what we really need is a Manhattan Project to make our homes more energy efficient. That would be a high payback endeavor...