Consulting Engineers Explain the Difference Between Commissioning and Energy Audits

Michael Tobias
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    Commissioning and energy audits are often confused - both services involve a building inspection by consulting engineers, but their goals are different. Commissioning and energy audits should not be viewed as competing options, but rather as complementary services. Getting both simultaneously is a smart approach, since consultants can gather all the relevant data in a single building inspection.

    In simple terms, the difference between commissioning and energy audits can be explained as follows:

    • The goal of commissioning is to keep all building systems operating as specified in design documents and technical specifications.
    • The goal of energy audits is to identify viable measures that improve the energy performance of a buildings, reducing the consumption of fuel and electricity.

    In New York City, commissioning and energy audits are mandatory at 10-year intervals for all buildings covered by Local Law 87 of 2009. This law is part of the Greener, Greater Buildings Plan, which aims to achieve a citywide improvement in energy efficiency, while cutting down greenhouse gas emissions.

    Boost building performance with commissioning and energy audits.

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    Building Commissioning

    When a construction project is completed, the commissioning process ensures that all building systems operate as specified in the project documentation. Commissioning is also carried out after major renovations, where building systems undergo significant modifications.

    Commissioning a project only once after construction is not enough; when a building starts operating, the performance of its key systems tends to decline over time. There are many possible causes, and the following are some examples:

    • Mechanical components are worn down with use, which has a detrimental effect on performance. In the case of rotating equipment, components may start suffering from unbalance and misalignment, causing vibration and noise.
    • The configuration of controls and sensors may be modified accidentally during maintenance activities, affecting the performance of building systems.
    • Quick fixes and undocumented chances to building systems may cause operating conditions different from those specified in project documents.

    The term retro-commissioning is used when a building has never been commissioned before, or not in a long time. On the other hand, the term recommissioning is used when a building is commissioned at regular  intervals. However, both concepts refer to commissioning for existing buildings.

    Commissioning can be considered an attractive investment, since it provides a building performance boost at a relatively low cost. A typical commissioning process only involves skilled labor from technicians and engineers, along with minor reparations and part replacements. There are no major capital expenditures involved in commissioning, and the payback period can be less than one year.

    A detailed inspection of HVAC installations is very important during the commissioning process: HVAC systems account for the largest share of energy consumption in residential and commercial buildings, and they have many interacting components that can suffer a loss of performance over time. In addition, malfunctioning HVAC systems have poor control over temperature and humidity, which is detrimental for occupant health and comfort.

    Energy Audits

    An energy audit seeks to reduce the energy consumption of a building without compromising performance. It involves a building inspection just like commissioning, but the purpose is to identify upgrades that improve energy performance, exceeding the operating conditions specified in design documents.

    Some of the most commonly proposed energy efficiency measures are LED lighting retrofits, HVAC replacements, variable speed drives for pumps and motors, automatic controls and building envelope upgrades.

    The two main energy inputs used by buildings are fossil fuels and electricity. Fossil fuels are normally used for space heating, domestic hot water and backup generators, while most other building systems operate with electricity.

    • Heating systems typically run with natural gas, but some buildings using other fuels such as heating oil or propane.
    • On the other hand, backup generators normally use diesel.

    Electricity is not commonly used for heating applications, since the operating cost becomes very high. However, modern heat pumps offer a high efficiency, and can match the heating cost of gas while using only electricity.

    There is a wide variety of energy efficiency measures that can be deployed in buildings, and the best options change depending on building conditions - measures that are very effective in one property may only yield small savings in another, and this is why energy audits are important.

    Energy audits can also include a feasibility study for renewable power:

    • Solar photovoltaic systems are cost-effective for most properties, as long as they have a suitable area that is not covered by shadows.
    • Wind turbines are more demanding in terms of site conditions. However, they are viable for some properties.
    • For buildings with access to large amounts of organic material, biomass power can also be an attractive option.


    Building commissioning has the purpose of keeping optimal operating conditions according to design documents, while energy audits aim to improve building performance. Many consulting engineers are qualified to offer both services, which saves times because you only need to get one building inspection.

    Commissioning and energy audits are both recommended are regular intervals, since they reduce the operating cost of your building. The commissioning process can also reveal building systems malfunctions when they are still small, allowing corrective measures before they cause a major equipment failure.


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    Tags : building performance commissioning energy audit

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