Do your own energy audit: calculate the annual changes in utility bills for major projects for the building envelope.

Energy Auditor 2.0 has a long history, starting with a mathematical system developed by the U.S. Department of Energy (DOE) during the oil embargo of the 1970s.  There was an urgent need in America to reduce energy consumption in buildings, and so the government developed a series of nomographs (fancy graphs with several inputs and one output) to help engineers calculate the annual energy use in buildings and to evaluate the energy savings from major changes to the building envelope and the engineered systems.

We’re once again amidst another energy crisis, demanding swift and urgent measures to reduce energy consumption on a global scale.  Buildings consume almost 80% of all electricity used in the U.S. and almost half of all total energy use.  Worldwide, energy used in buildings represents 20% of total energy consumption.

I downloaded the original DOE energy-conservation design documents from the National Technical Reports Library.  There are two volumes, Guidelines for Saving Energy in Existing Buildings (1) the Building Owners and Operators Manual ECM 1 and (2) the Engineers, Owners, and Architects Manual ECM 2 Volume 1 is a general introduction to saving energy in large buildings.  Volume 2 shows detailed energy-saving calculations using many nomographs.  These two books still have the clearest, most concise, most accurate presentation of energy conservation projects that you will find anywhere.  (Since the two volumes were created by the federal government, they can be distributed for free with no copyright issues.)

Nomograph Math

These nomographs were the industry-standard way to calculate the savings from energy conservation projects from the date they were published in 1975 until well into the new millennium.  Thirty years!  Only with the advent of very fast computers that could crunch gigantic computer programs (current DOE 2 versions are 127 megabytes in size), did the nomograph method go out of favor.

In the late 90’s I was a consulting engineer with a firm that had a contract with the Texas LoanSTAR program, a program funded by oil-overcharge funds to pay for energy conservation projects in state and local government buildings throughout Texas.  My employers in Austin, O’Connell, Robertson, and Associates (ORA), won a state contract to do energy audits of a dozen small hospitals in central Texas as part of the Small Hospital Energy Management Program.  I helped to collect data on several hospitals, to be used in energy conservation analyses.  We were using the standard calculation method: the DOE nomographs.

NOTE: Small, rural hospitals are again in dire straits.  They’re closing at a record pace!  We saved a dozen small hospitals from closure back then by drastically lowering their utility bills – we can do the same now!

I came up with the idea of converting the nomographs into mathematical equations, to then be built into an Excel spreadsheet to automate the calculations.  I presented the methods I developed at a national engineering conference a year later.  ORA later asked me to build a commercial software program using dBase to do annual energy audits, using the equations I developed.  I did so (Energy Auditor 1.0), but I left the firm and started grad school before they got to marketing the program.

A few years later, when I was in graduate school at the University of Texas, studying for a Ph.D. in orbital and celestial mechanics (mathematical physics), I refined the Energy Audit equations and suggested to my Ph.D. advisor that the method be used to design structures on Mars.  There are only a couple of weather inputs, for Langleys (annual solar insolation), and annual Heating/Cooling Degree Days, which can be easily modified to suit the weather environment of the Red Planet (or the moon).

Back Down to Earth

I recently wrote up my new algorithms in a formal paper, DOE 2 in a Spreadsheet, and submitted it to several journals for publication.  They rejected the thesis outright:  too primitive for modern methods, they said.  Granted, the modern monster programs give more accurate results, but at what cost?  It’s reasonable for a licensed Professional Engineer to spend 3-6 weeks inputting all the minutia of data on a large building into one of those monster programs, to do a comprehensive engineering analysis.  Spending $100,000 for the engineering analysis for $10 million projects is justifiable.  But paying a licensed expert $8,000 to input the data on a small building where the energy conservation projects proposed might only cost $50,000? I dare say that’s a waste of good money.

My Energy Auditor 2.0 spreadsheet (free download) lets a builder, contractor, or savvy homeowner input all the data in only a few hours.  It gives results that were good enough for 30 years for even large buildings; and in the late ’90s for small hospitals – the most complex of all buildings.  Just because mega-monster programs requiring a master’s degree and a professional license to understand are available doesn’t mean a small spreadsheet like Energy Auditor 2.0 doesn’t have its place.

Why spend $8,000 for the full-blown, infinitesimally accurate analysis by an expert when you can get almost as good a result for free, and spend that $8,000 on actual projects?  As far as that goes, the weather is so variable – getting more variable year by year, thanks to the extremes of global warming – why use the 30-year average of weather data if those figures will be moot in just a few years?  Engineering is a practical science – if the weather varies by two significant digits year to year, it’s irrational to do the calculations to ten significant digits – and a waste of good money.  (Not to mention the 15% “safety factor” engineers always use on calculations like this.)

Energy Auditor 2.0 is applicable in a limited range of projects – modifications to the building envelope and to the efficiency of the HVAC system.  I dare say, it gives valuable and actionable results within the scope of its calculations.  I provide it here for free as an “educational tool,” with the proviso that it can be used by a knowledgeable contractor, designer, architect, or engineer for actual projects – but only after a rigorous evaluation of its merits.  You have all the documentation to authenticate the results:  the original DOE nomographs, the actual equations converting the nomograph into mathematical equations, and a spreadsheet to test the results.

Energy Auditor 2.0 download

Energy Auditor Case Studies (examples)

Finally, you’ll find many additional nomographs in the DOE volumes that can be made into mathematical equations using the methods delineated in my conference paper.  Also, Energy Auditor 2.0 has only a few rows and columns, but you can add many more to your own spreadsheet to do calculations on a building of any size or complexity.  The weather inputs can also be customized to your location, even adjusted to the microclimate of a specific location (shading, inner-city temperature anomalies, etc…).

It would be wonderful to take this kernel of an idea and for others to make many elaborations available in the public domain so people everywhere can save lots of energy!

Expert Access

If you want to customize the spreadsheet to your particular situation, here’s the password to unlock each page: