Water penetration and condensation can cripple a building. With 85% of U.S. construction-rated claims tied to uncontrolled rainwater penetration, it’s a common issue — especially when design and construction timelines are stretched to meet demand.

Data centers may be at the highest risk. Not only due to their quick turnover schedules, but because the smallest water penetration in a critical location can lead to equipment downtime with an average cost close to $9K per minute.1 

What can be done to help create a quality data center when various trades, time, and climate are influencing overall quality?

Enter building envelope commissioning (BECx). A low-cost additional service when compared to the cost of a down facility.

BECx is a head-to-toe third-party review of a building’s envelope during all phases of a project from design through occupancy. The goal of this review is to identify areas of concern for air/water leaks, sequencing, constructability, and more before they become costly issues to resolve post-construction. BECx also serves as an opportunity to educate facilities staff on how to maintain a building to meet its intended lifespan.

Projects that adopt BECx have the potential to achieve two valuable LEED® points under Enhanced Commissioning Option 2: Envelope Commissioning. To achieve this credit, there are no required envelope tests; rather, the client is to engage with an experienced BECx authority (BECxA) to help determine what envelope tests make sense based on the data center’s complexity, budget, and goals. To date, LEED has been the primary driver for a recent increase in BECx at data centers.


Getting BECX right – the process

It’s recommended that a BECxA is contracted by mid-design (50% design development) to deliver the greatest ROI. This follows the 1-10-100 rule,2  where issues are less costly to resolve during the design stage versus during or after construction. The following steps summarize ESD’s recommended BECx process which follows LEED v4’s requirements and referenced standards: NIBS Guideline 3-2012 and ASHRAE Guideline 0-2005.


Step 1: Hire an experienced and accredited third-party BECxA with the following credentials:

  • Has previous project experience on at least two similar projects

Holds one or more of the following accreditations:

  • Professional architecture licensure (AIA, NCARB, RA)
  • Building envelope accreditation (BECxP, CxA+BE, RRC, NEEB Certified, RBEC)

Spray hoseFIGURE 1. Spray hose test at roof to wall intersection. Simulated wind driven rain to test for water penetration.


Step 2: Conduct envelope design review

The BECxA is to review the envelope drawings at least twice — once at 50% design development followed by a second review (back-check) by 50% construction documents to ensure the comments were reviewed/addressed by the architect to meet the LEED v4 requirements. More design reviews are recommended if a project’s design is complicated (e.g., multiple materials, complex shape). In addition to the BECxA providing envelope reviews, the roofing consultant will review the roofing drawings to ensure the design of the roof assembly isn’t affecting the roofing warranty.

The main benefit of the design review is that potential issues are addressed and corrected (e.g., air/water penetration, redundancy, sequencing, constructability), keeping the project on track and within budget. Additionally, the design review highlights areas to test during construction or at a mock-up to test pre-construction. These areas of concern are commonly at material interfaces (e.g., metal panel wall to window) and intersections (wall to roof).

The design review mentioned above would satisfy the LEED Fundamental Commissioning prerequisite, and design review requirements for projects in California subject to Title-24 2016 to achieve the two LEED points under Enhanced Commissioning: Option 2 Envelope Commissioning, the following steps are the major scope items.

Step 3: Envelope testing during construction

As noted in Step 2, the design review highlights areas of concern to test during construction identified by the BECxA. Other sources that can help determine which envelope tests to perform can be found in: NIBS Guideline 3 Annex U.3, the material manufacturer’s specifications and in the owner’s project requirements (OPR). Both the manufacturer specs and the OPR are helpful sources since they tie back to known issues. For example, where a manufacturer’s louver connects to the metal panel wall or failure at a previous project noted in the OPR.

Once the BECxA and team determines which envelope tests to perform, the BECxA will place these tests into the construction schedule to make sure they are performed at the right time. The roofing consultant is to do the same.

The installing contractors traditionally perform the tests and rent/purchase the testing equipment while the BECxA creates the test checklist and sequence, witnesses the test, and documents any issues in the issues log. This is similar to traditional MEP commissioning.

What if there’s a failure? Because there are typically many miles of hand-laid bricks and/or sealant at the building’s exterior, installed by multiple trades simultaneously, failures are common. BECx should not be viewed as a test/fail process. It’s still possible to earn the two LEED points in the event of an envelope failure. Curative action is required to resolve the issue captured in the issues log.

Step 4: Report it

The BECxA will create the BECx report, including the testing reports from the installing contractors (reports to follow AAMA requirements) as well as the current issues log. If the project is pursuing LEED Enhanced Commissioning: Option 2 Envelope Commissioning, the project team will need to upload the required LEED documentation.

Sealant adhesionFIGURE 1. Sealant adhesion test at wall penetration. Ensured that sealant was properly installed to mitigate water and air penetration issues.


Step 5: Facilities and maintenance training

This step is the most overlooked by owners/operators but arguably just as valuable as the others. Maintenance personnel training helps preserve the integrity of the envelope long after the BECx testing concludes. Traditionally, per Division 01 specifications, training falls under the contractor’s jurisdiction. However, there’s an added value to include additional training by the BECxA.

BECxA training could include reviewing the manufacturer’s operations and maintenance documents with the facilities and maintenance staff so they understand how often to maintain each envelope system (e.g., sealant, garage doors) for continued performance, maintenance, and cleaning. If the wrong soap or water pressure is used to clean the building, for example, it could lead to deterioration and a potential risk for water penetration.

There’s no one-size-fits-all approach when it comes to training, and each envelope will have different product maintenance to cover. Generally, training need not be more than an hour, and can be conducted remotely.

Missing sealant at louver jambFIGURE 3. Missing sealant at louver jamb (electrical closet immediately below potentially receiving water).




Maintaining data center envelope integrity

BECx acts as an added layer of quality control for the team as deadlines and budget are also driving factors. BECx is both essential to assessing and testing the envelope, but also to resolving any issues and challenges to help ensure that water penetration is mitigated for these critical projects.


Cited works

1 Eaton, https://switchon.eaton.com/plug/blackout-tracker

2 https://blog.masterdata.co.za/2017/06/20/the-1-10-100-rule/



  • Reduces water penetration issues that can damage critical equipment

  • The envelope design review acts as a second pair of eyes for the owner on the quality of the drawings, especially for international projects that may have less stringent building codes for safety and performance.

  • Helps detect envelope air leaks (drafts), water penetration (damaged critical equipment, mold), and missing thermal insulation (cold spots) during design and construction to minimize added cost to resolve during occupancy

  • Aids in the creation of a high-quality envelope during fast design and construction timelines

  • Ensures that envelope maintenance training is provided to the O & M staff to help prolong the life of the building

  • Helps resolve issues during warranty periods to reduce out-of-pocket costs



  • Follow ASHRAE Guideline 0 and NIBS Guideline 3

  • Approach BECx as a team. There is no one-size-fits-all, and with everyone’s heads together a higher level of quality can be realized. The BECxA shouldn’t be the only one providing suggestions to make a quality building since the entire team has experience.

  • Thoroughly communicate with the team the areas of concern and figure out who the installing contractor is for the critical piece (e.g., sealant, flashing).

  • Ensure that the test checklist is all encompassing and includes required equipment and site access (e.g., plenty of water pressure from the water source, testing schedule is not in conflict with concrete pour occurring at grade).



  • Size: 375,000 sq. ft., eight data halls, one administrative office
  • LEED Pursuit: LEED v4 BD+C Gold

Reducing potential water penetration issues was a chief goal for this data center, as was acquiring LEED Gold. The data center was already utilizing ESD for MCF Cx, but to hit their LEED v4 Gold target and address their water penetration concerns, they contracted ESD to perform Enhanced Commissioning: Option 2 Envelope Commission-ing for two LEED points. ESD:

  • Reviewed the envelope drawings, specifications, and submittals to highlight areas of concern for water penetration
  • Created a list of recommended envelope tests and brought forth those already included in the architectural specs to ensure they were included in the construction schedule.

ESD worked with the architect to pinpoint the envelope sampling locations. Tests witnessed by ESD as the BECxA included:

  • AAMA 501.2 (spray hose test) on the curtain wall, insulated metal panel wall, mechanical louvers, doors, and expansion joints
  • Method A, ASTM C1521 (sealant adhesion test) at critical penetra-tions and joints

ESD also performed thermal imaging during each field visit to sup-plement the tests above and the roofing consultant’s observations.

Ultimately, issues were highlighted and tracked from design through construction and closure. ESD also provided training to O&M staff on how to properly maintain the envelope over time to reduce the potential for new areas of water penetration during oc-cupancy. At the end of construction, ESD submitted the required LEED documentation.

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