Signs of building efficiency – HVAC Systems
By Stephen Gerhardt, LEED AP, Chief Engineer, Santa Clara Towers
The first and easiest indication of a building's efficiency is found through benchmarking. The best tool available is the EPA's Energy Star Portfolio Manager. For assistance with benchmarking a building on this tool look out for the upcoming Energy Star training session by the BOMA SV Energy and Sustainability Committee.
If your site is a commercial office space and your score is:
- Above 90: Congratulations! Your site is doing very well!
- Between 75 and 90: Even though you are doing well and do qualify for the Energy Star label the building has room for improvement.
- Between 40 and 75: The building has some definite room for improvement. The plus side to this is that there are probably some no or low cost measures that can be done for quick improvement.
What do I do if my building score is below 40? The good news here is that many issues should be easy to identify and again through low and no cost measures the utility expenses can probably be reduced significantly. Look for the following common energy wasting culprits:
- HVAC systems running nonstop or occupancy schedules are much longer than are needed
- Major ducting leaks
- Building lighting never turning off
Other indicators to look for:
Is the building running mechanical cooling in the winter? Most building AC systems are outfitted with some type of economizer system. That is a system that when it is cool enough outside pulls free cold air in from the outside instead of running compressors (mechanical cooling). If the controls for your economizer are not set properly you may be spending a lot more than you need to be.
Is the building running the heating system unnecessarily? Generally a heating system does not need to be running after the outside air temp (OSA) has risen past 65 degrees. A building running very efficiently will not use the heating system over 60 degree OSA.
Why not? When a building is at or above these temperatures human bodies and equipment (computers, printers, etc.) provide enough heat to maintain at least 72 degrees.
Oops! Turns out my heating system is running constantly, but we thought we needed it to because tenants are cold. What is causing this? Common problems that cause cold complaints on a warm day include:
- VAV boxes are putting out cooling when they shouldn't be due to a broken thermostat or VAV controls.
- VAV boxes are putting out heating and cooling at the same time.
- Poorly designed zone layout where two zones are fighting with each other, one in cooling mode the other in heating mode.
- Duct leaks are allowing cooling to drop down through open return registers.
Where do I start?
- Start with benchmarking on Energy Star! For assistance with benchmarking a building utilizing this tool look out for the upcoming Energy Star training session by the BOMA SV Energy and Sustainability Committee.
- Call your engineering team or building HVAC vendor. Have them assess the building operations and start
- Reach out to the local utility company. Many of these companies offer free services to identify areas your site can be improved as well as rebates on energy saving projects.
- Assign someone on your team to monitor hot and cold calls for patterns and potential problem areas. Start tack
ling those areas first.