Performing enhanced commissioning design review
Commissioning agents should inspect and test building systems early in the design process.
The activity known as building commissioning is usually associated with the inspection and testing of HVAC equipment near the end of the construction phase and has become a valued addition to the building owner’s repertoire to ensure that a project is delivered successfully. More often, the commissioning process is being started during the design stage when important concepts are being put down on paper and changes can be made economically.
The U.S. Green Building Council (USGBC) recognizes the benefit of early participation by the commissioning agent (CxA) and rewards this by providing a credit through its LEED rating system for what is termed “enhanced commissioning.” To become LEED certified, all projects must undergo fundamental commissioning, but a major differentiator between this prerequisite and enhanced commissioning is that the latter requires a design review by the independent third-party CxA. The review includes the owner’s project requirements (OPR), basis of design (BOD), and the design documents. The design review is to occur prior to the mid-construction document phase and is to focus on the following issues:
- Ensuring clarity, completeness, and adequacy of the OPR
- Verifying that all issues discussed in the OPR are addressed adequately in the BOD
- Reviewing design documents for achieving the OPR and BOD and coordination of commissioned systems.
The commissioning agent
In addition to possessing exceptional technical skills, a CxA needs above-average social skills. This person needs to add value to the project while working in a team environment that consists of engineers, architects, construction managers, contractors, suppliers, end users, and other owner representatives. The wrong chemistry can upset the delicate balance of egos, and the agent must work diligently to ensure that his deliverables and communications work to add stability to the project’s social dynamic. The agent can have an uphill battle in this regard as there are unenlightened design professionals out there that view the CxA as a “fly in the ointment.” However, like the physician, the CxA’s mantra should be “first, do no harm.”
How can a CxA do harm when reviewing documents? Are not all comments, if true, valid and worthy of being noted? First, it should be noted that there are many types of reviews that can be done, such as detailed checking, interdisciplinary coordination, value engineering, and constructability, to name a few. The review by the CxA is different than all of these in that the focus is on making sure the design will satisfy the owner’s requirements and also in that the completed systems can be adequately commissioned. The design firm will do its own checking of the documents at various stages and a sophisticated owner will have staff with the knowledge and ability to check design submissions.
My philosophy is to let these entities discover minor items such as spelling mistakes and ensure that they get corrected. It is also important to keep the comment list simple and short. For instance, if the north arrow is missing on a dozen sheets, this does not require 12 separate comments. As a member of the design community, I would not relish the thought of having to respond to thousands of comments. As an example, I was involved on a state university project that had top-notch national architectural and engineering firms designing a complex laboratory. The commissioning firm submitted nearly 600 comments on the construction documents, and I believe the university had a similar number. The engineering firm never responded to these comments and I do not blame it, as many were gratuitous. This does not add value to the project and only works to alienate the design firm from the CxA and the entire commissioning process. The design firm has a contract to provide a set of construction documents; this does not include responding to hundreds of inane comments that have no bearing on the outcome of the project.
Some might say that poorly crafted documents deserve a plethora of review comments. I would counter that a commissioning firm should not be required to review documents that are not yet complete and have obviously not gone through an in-house quality analysis/quality control (QA/QC) process. If this is encountered, the CxA should document why the deliverables are not ready for review and work out a solution with the client. I would also caution the CxA to avoid the use of “stilted” language in the review comments, which always tends to rub the recipient the wrong way and create bad feelings. Remember that the “audience” for the comments is the author of the design documents that are being reviewed. Formal, stiff language can come across as pompous and arrogant. The suggestion would be to avoid using big words when small ones would do.
So if spelling errors and missing north arrows are taboo, what should the CxA be looking for and commenting on when reviewing design documents? The commissioning effort revolves around the parts of a building that move and use energy, such as HVAC systems, lighting, and domestic water heating. Are these systems designed thoughtfully with proper service clearances and adequate valving for isolation to facilitate future maintenance procedures? Does the design reflect and capture the owner’s need for system redundancy and future expansion? Are specific environmental control needs addressed with appropriate systems and equipment? Are air systems set up with dampers on supply, return, and exhaust branches so that they can be balanced? Are there balance valves on each coil in large air handlers with multiple coils?
Big-picture items worthy of review include checking the capacity of central heating and chilled water plants early in the design and comparing them to rules of thumb. Request calculations from the engineer when system sizing appears to be suspect. Look for things that can cause problems during construction, such as pinch points where the structure may interfere with ductwork. Review floor-to-floor heights and focus on the structural drawings looking for deep beams. Take a pencil and draw quick sections of areas above ceilings that could be problematic, such as places where ductwork, cable tray, and beams converge. Also look where sanitary and storm piping are running as this work is rarely coordinated with ductwork; unless it is a simple building type, you can usually find some interferences. The use of BIM should make this less of an issue going forward. It should be remembered that this is a team effort and that the CxA can be an advocate for the MEP engineers by helping them make the case for getting more ceiling space, larger shafts, and bigger mechanical rooms.
When it comes to HVAC systems, some design engineers appreciate the importance of system diagrams, process and instrumentation diagrams, and sequences of operation and others do not. Some do a good job of putting these design elements together but for some reason have conceived very poor systems. One reason for the latter issue is that the drive for reduced energy consumption has forced the design community to abandon simple systems that have served us well for years, such as variable air volume distribution. Engineers are now faced with working with less familiar concepts, such as geothermal heat pumps, chilled beams, radiant heating and cooling, solar thermal, and heat recovery. Some engineers are having trouble piecing these together in a way that makes sense. When this is encountered, the CxA should convene a meeting to make sure the message is getting through and to get a design back on track.
Design review do’s and don’t’s
When reviewing documents as the CxA, do:
- Think of the big picture, using rules of thumb to see if items such as central plant equipment sizing is on target. If not, make a comment to see calculations.
- Keep functional testing and future operations and maintenance needs in mind – think “isolation valves.”
- Review floor-to-floor heights to make sure that building services will fit.
- Review service clearances for equipment.
- Review sequences of operation for completeness and correctness.
- Make sure the systems are appropriate and reflect the owner’s requirements for redundancy.
When reviewing documents as the CxA, don’t:
- Nitpick and generate a list of items such as spelling errors and missing north arrows.
- Review systems that may not be in the scope of work, such as telecommunications. Systems usually in the scope are ones that are major energy users or producers, such as HVAC, lighting controls, and renewable energy.
- Avoid stilted language that might give the air of superiority. Avoid using big words when small ones would do.
Owner’s project requirements
The owner’s project requirements (OPR) should contain the following information at a minimum:
- Owner and user requirements: Primary purpose, program, and use of the proposed project. Future expansion, flexibility, quality of materials, construction, and operational costs.
- Environmental and sustainability goals: LEED certification, Energy Star, etc.
- Energy-efficiency goals: Goals relative to ASHRAE Standard 90.1, orientation, façade, windows, roof, etc.
- Indoor environmental quality goals: For each area, describe intended use, occupancy schedules, environmental requirements (lighting levels, temperature, humidity, acoustics, air quality, ventilation), adjustability of system controls, and after-hours use.
- Equipment and systems expectations: Level of quality, reliability, type, automation, flexibility, and maintenance requirements for each system to be commissioned. Preferred manufacturers, efficiency targets, desired technologies.
- Building occupant and operations and maintenance personnel requirements: How and who will operate the facility? Desired level of training and orientation required for occupants to understand and use the building systems.
Basics of design
- Primary design assumptions: Space use, redundancy, diversity, climate design conditions, space zoning, occupancy, operations, space environmental requirements.
- Standards: Applicable codes, guidelines, regulations, and references that will be put into practice.
- Narrative descriptions: Performance criteria for HVAC, lighting, hot water, onsite power, and other systems to be commissioned.
Schultz is mechanical department head with URS Corp. and has more than 20 years of experience designing and commissioning mechanical systems for commercial and institutional facilities.