How much energy should your building use?

by Ben Gries, PE, LEED AP

How much energy should your building use? Is its usage comparable to similar buildings? How can you reduce it? These are relative questions and sometimes hard to quantify and assess, especially if you only own or occupy one building. However, the answers could identify potential savings for your business and reduce your building’s impact on the community and environment.

Recently, a client asked us to review energy bills for several buildings. A large corporate entity, they own similar buildings across multiple states. They recently opened a few buildings and were concerned about the utility bills. A couple of the buildings were operating at significantly higher costs than their other facilities – even ones nearby.

Different building types have different utility use characteristics. For example, hospitals tend to be heavy energy users with different profiles than schools or office buildings. Factors that play a role in energy use include:

  • age of the building
  • type of construction
  • building use
  • process loads and plug loads

An energy analysis can be a quick, general review of utility bills and a comparison to similar buildings. Or it can be an in-depth audit to identify potential improvements and energy conservation measures. The best place to start is with a general review of utility bills; if they are significantly higher than similar buildings there is greater potential for easy improvements.

One reason utility costs can be overlooked or ignored is the ownership/tenant arrangement. Typically building tenants pay utilities – either directly or pro-rated. This leaves little incentive for the landlord to monitor or improve the performance. It also limits the tenant’s ability to make improvements. Often, tenants are not allowed to make changes, and if they are allowed, their money will go to fund improvements in a building they don’t own.

Completing an energy analysis can provide valid information for negotiating lease terms with landlords to improve the operation and energy use of a tenant occupied building. It can also provide useful information to a landlord, because a high-performing building can be a valuable marketing tool and command higher rental rates.

In our client’s case, they build, own, and occupy their buildings. This puts them in a unique position to review the bills and facility usage to identify the problem. When they spotted the anomalies, they asked us to investigate. We have designed several of their facilities, and our designs were performing at lower utility costs than the facilities in question. The client provided utility bills for the offending buildings, bills for similar facilities in similar locations, and construction documents for the facilities in question. We analyzed the bills and construction documents, determined areas of concern and provided a summary review.

One facility was an easy fix. We found that the utility company was incorrectly billing for service. The utility bills showed a meter multiplier that was not realistic. This was identified by comparing the demand and energy measurements provided on the bills to the building design. The bills showed the facility was consuming more power than the design could have accommodated. After a few calls to the utility provider, they recognized the mistake and credited the client’s account.

The other facility showed 30%-40% more power use than comparable buildings. While reviewing the building design documents, utility bills, balance reports, commissioning reports and performance, we discovered that the building was unable to control building pressure, causing swings in building pressure from positive to negative. While working through a correction, severe leaks in the HVAC equipment were found. After correcting the equipment operation and sealing the access doors, utility costs decreased, but not to the levels of comparable facilities.

We took our analysis a step further and reviewed equipment sizing and system design. This showed space airflows that were in excess of the design in similar buildings. The additional airflow did not affect space temperature or occupant comfort, but did contribute to excessive energy use by the facility. To verify this assumption, we prepared energy models to see if actual performance matched predicted performance and if airflow changes would reduce energy use to levels found in comparable buildings. The modeling showed the excess airflow was a contributing factor to the increased energy use; the other factor was a lack of energy recovery on the exhaust for the facility. The modeled cost savings will pay for the system rebalance and engineering fees in less than two months – money well spent.

It is always a good idea to review expenses, because there may be easy corrections that save costs. Starting with a quick analysis of utility bills is the best way to determine the amount of energy wasted and if a full, detailed audit will be beneficial.