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Operations & Maintenance Design Intent

Last month I covered the importance of developing Design Intent Documents (DIDs) that reflect the integrated nature of today’s building systems. This month I’d like to take that concept another step further and recommend incorporating “maintainability” criteria into each DID.

One of the primary benefits of commissioning has always been preparing the owner’s operations and maintenance staff to continue operating the building at its “as commissioned” performance. With that in mind, I’d like to suggest that owners consider long term operations and maintenance issues when articulating the design intent for a new building or newly renovated building.

What does that mean? It means looking beyond the first tier of functional performance criteria (e.g., temperature, humidity, indoor air quality, noise, etc.) of the systems being commissioned to defining quantitative metrics regarding how maintainable all aspects of the building should be. In addition, let’s look at how maintenance practices may impact the ability of the systems to sustain their “as commissioned” performance criteria.

What are some metrics for “maintainability”? Labor hours per year is one that can be applied to just about anything: air conditioners, floors, lights, etc. Labor hours per runtime might be another for mechanical and electrical systems. The most common one that we’ve seen used is years of life expectancy, i.e., the number of years before the system/equipment will need replacement. I recommend including such metrics for systems in the DID to raise awareness and encourage the design team to look beyond standard performance criteria before making a system recommendation to the owner. It should help bring to the table the long term, life cycle impact of systems when making choices.

This approach will require an “integration” mindset, because maintaining one system may impact the ability of another system to achieve its DID performance. For example, if the cleaning solution required for a special floor material results in poor indoor air quality, then the facility will not be able to maintain its original design intent performance for air quality.

Similarly, carpet is easier to maintain (fewer labor hours per year) than hard floors that require waxing and buffing. Carpet also provides desired noise attenuation qualities to help achieve DID sound criteria, but care must be taken to select carpet that does not off-gas and negatively impact indoor air quality performance. Finally, carpet typically needs to be replaced more frequently than good quality hard floors. So, what is the right choice?

The choice is up to the owner, and each owner will have different priorities. The project team’s responsibility is to provide the owner with objective capability and maintainability performance metrics that the owner can use to make their unique decisions.

Another integrated system example has to do with vestibule entries. Mechanical engineers often consider vestibules a mandatory architectural feature in order to achieve the temperature, humidity, and/or pressurization requirements for a building. That may be true, but the maintenance staff also sees vestibules in terms of less cleaning. Less cleaning leads to fewer chemicals which could lead to improved indoor air quality and a more environmentally sustainable building.

In addition to being concerned about how often equipment/systems need to be maintained and/or replaced, the project team should be encouraged to consider the operational impact of the maintenance and/or replacement activities. The DID may specifically state that an air handling system be 100% redundant (fans, coils, electrical supply, etc.), but will it be possible to change out one of the coils or maintain one of the fans without shutting down the system? This requirement is best articulated in the DID in order to keep that requirement in the team’s minds throughout the entire project. It is likely to result in a more costly installation (additional space, dampers, valves, controls, etc.) and could easily be “value engineered” out if not included in the DID.

Finally, if the project team can help the owner quantify the life cycle cost reductions associated with planning for operability and maintainability, there may be a strong financial case to be made to the “people with the money” to shift some future operation and maintenance funds into the capital project. This should result in net present value savings for the owner and/or institution.


Engineered Systems, September, 2004

Rebecca Ellis, PE, LEED AP, CCP, CxA
Questions & Solutions Engineering
1079 Falls Curve
Chaska, MN  55318