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A building renovation is a major expense, but it also provides an excellent chance to improve performance. Energy efficiency measures can be added to the project, achieving a permanent reduction of electricity and gas bills. Water conservation and onsite renewable energy systems are also viable measures that reduce operating costs.


Energy efficiency measures are especially useful in places with expensive electricity, such as the San Francisco Bay Area and Northeast. A retrofit project that saves 25,000 kilowatt-hours each year represents $2,500 in a building that is charged 10 cents/kWh. However, the savings are increased to $5,000 for a building owner paying 20 cents/kWh. When many energy efficiency measures are deployed in a large building, thousands of dollars can be saved each month.

Which Are the Best Energy Saving Measures for Buildings?

Air conditioning and space heating are the two highest energy expenses in most residential and commercial buildings. The largest of the two changes depending on the local climate, but together they represent over 50% of energy use in many buildings. For this reason, upgrades that improve heating and cooling efficiency tend to achieve the highest savings.


There are three main strategies to reduce HVAC costs in buildings, and they apply for both residential and commercial properties:



  • Improving the thermal envelope of the building. This can be accomplished by increasing insulation and sealing air leaks. Double-pane or triple-pane windows with low-emissivity coating are also helpful.
  • Upgrading the mechanical equipment. Modern air conditioners and space heaters can achieve the same effect as older units of the same capacity, with a much lower energy consumption.
  • Controlling thermostat settings. A common habit that wastes plenty of energy is setting the thermostat at the lowest value during summer and the highest value during winter. Plenty of energy can be saved with more modest temperature settings, without sacrificing comfort.



A building will achieve its optimal heating and cooling efficiency when the three recommendations are followed. For example, a building can have the most efficient HVAC systems in the market, combined with automatic controls. However, if the building envelope is poorly insulated and full of air leaks, plenty of energy will be wasted.


Space heating and air conditioning systems are characterized by the variety of options available. HVAC engineers can specify the equipment and system configuration that achieves the best performance, considering the needs of each building.


Lighting fixtures and water heaters also consume plenty of energy, although they have a smaller footprint than space heating and cooling equipment.


  • Lighting systems tend to consume more energy in commercial buildings, and the common areas of multifamily buildings.
  • Water heating costs tend to be higher in homes and individual dwelling units.
  • Some commercial buildings also use plenty of hot water; two examples are restaurants and laundries.


LED lamps are the most efficient lighting option that is commercially available, especially when combined with automatic controls. In hot water systems, the lowest cost is normally achieved by heat pumps or tankless gas heaters.

How Buildings Can Reduce their Water Consumption

The US Environmental Protection Agency created the WaterSense program for plumbing fixtures. It covers many types of fixtures, including showerheads, toilets and faucets.


  • Plumbing fixtures are tested extensively by independent laboratories, and only those that reduce water usage by at least 20% get the WaterSense label.
  • Significant savings are possible when upgrading old and leaky plumbing fixtures. In these cases, WaterSense fixtures can achieve savings that are much higher than 20%


Water conservation also contributes to energy efficiency, since it reduces the workload on pumping systems and water heaters. The pumping savings are significant in tall buildings, and  hot water savings are higher in places with cold weather. Buildings can further reduce their water consumption from the utility service with rainwater harvesting. The collected water can be used for functions like irrigation and flushing.

Adding Renewable Energy Generation to a Building

A renewable energy system does not reduce the consumption of a building. However, electricity bills are reduced because the power meter registers a smaller net consumption. Onsite renewable energy also reduces the environmental footprint of a building, since many power companies are still strongly dependant on fossil fuels.


Solar power is a common option for buildings, since all it requires is a roof area that is not covered by shadows or equipment. Depending on local conditions, a wind turbine or biomass generator may also be viable options. Having one large turbine is more cost-effective than having multiple small ones, since the wind is steadier high above the ground. Biomass can be effective for companies that have access to large amounts of organic waste.


The combination of energy efficiency, water conservation and renewable energy can greatly reduce the operating cost of a building. There is also a significant environmental benefit. Considering that buildings account for around 40% of energy consumption and emissions, these types of upgrades have promising applications.


Michael Tobias, PE, LEED AP, CEM. 


He is a graduate of Georgia Tech class of 2004, with a Bachelors of Mechanical Engineering with honors. His innovative approach to MEP engineering comes from graduating GE’s Engineering Leadership Program, where he designed wind turbines and biofuel power plant engines. Michael’s passion within design is energy efficiency and green technology. His focus is on integrating MEP/FP engineering design with architecture to create as seamless a system as possible. He is an advocate for green design and technologies, and has designed to both Passive House and Net 0 energy standards. He has spoken numerous times at the AIA, been featured in Georgia Tech’s Alumni magazine, and is an engineering expert on Discovery Channel’s show “Impossible Engineering”. 
