Which building systems provide the biggest potential for "green" cost savings? Lets assume we are looking at a twenty year old commercial office building configured for multi tenant occupancy. Just wondering if anyone mught be able to ballpark some numbers on what kinds of savings may be attainable when doing some refurbishment to 20 year old systems.

Thanks

Greeniac 102

Typically most buildings can expect savings between 20% to often over 50% reductions of the total energy usage, and if engineered correctly should be achieved under a two year payback.

People often assume that the age of the building is always related to energy efficiency. Actually the age often has very little to do with the building be energy efficient or not. The first step is to benchmark the energy consumption of the buiding.

First take the last years monthly kilowatt hours and add them up and divide that yearly number by the conditioned square feet. That will provide you with a kilowatt hours per square feet value. Lets assume the building is on the West Coast and is a typical office building. The building should only consume 12-16 kilowatt hours per square feet per year.

It is common for most buildings regardless of age to be operating at levels much higher that range. If a building is operating at a higher rate the next step is to look at performing an energy audit.

Energy Audits should be performed by a professional engineer and a team of skilled technicians to thoroughly examine all of the building systems to identify the where all of the energy savings are located. That audit should provide a list of all of the energy savinngs with turnkey fixed cost proposals not estimates.

I've read that the largest energy-consuming property of a home is usually insulation. It makes sense since air conditioning and heating are the two things that always run up your energy bill. And fixing old insulation might be less expensive than purchasing new appliances, which are another big energy waster.

Age actually has no relavance as to the amount of energy waste. Most people assume that an old building is naturally more inefficient when in many cases they can actually be more efficient than a new building if optimized correctly. The reason is most older buildings were built with more generous sized systems and when you optimize a more generous system many cases things lke air or water restictions are less and if engineered properly they can actually consume less than a brand new building.

I would say that at least 75% to 90% of all commercial buildings are inefficient. Their energy waste is anywhere from 20% to sometimes over 50% and the typical savings that I achieve in commercial buildings is usually 30% to 40% reductions in the buildings total energy spend per year. This can be done cost effectively usually under a two year payback guaranteed.

In commercial buildings the building envelope is usually not a cost effective energy reduction measure compared to other options such as optimizing the HVAC systems. I do not mean replacing equipment but rather re-engineering them to work more efficiently. Insulation is ideal before it is built and higher levels are well worth it but after it is built is often is not a short payback.