Quality, Consequences and the Construction Industrial Complex (part 234).
Bravo to LEED certification for increasing awareness of Building Envelope Commissioning (BECx) and shame on LEED certification for letting it evolve into a meaningless paperwork exercise.
To get value from BECx you have to do it properly. To be clear BECx is not cheap, it involves physical attendance and testing. It is more than a nice haircut and ticking check lists.
Architects not building services engineers have the greatest influence on boiler and chiller sizing due to their decisions regarding building envelop. Building envelope decisions are driven by the 80 / 20 rule, meaning, 80% cost factor and 20% owners risk tolerances i.e.
- Owners risk comfort and level of experience
- Project size plus building envelope design and complexity
- Cost / benefit of BECx
The reality is that contractual latent defects clauses cover observable building envelope failures e.g. Nickel Sulphide glass failures. However, contractual latent defects clauses DO NOT cover building envelope performance failures.
BECx is the verification of building envelope design and installation via:
- Design reviews
- Factory and site inspections
- Physical on site verification testing
BECx has to be undertaken by specialists, with deep domain knowledge and experience.
Building envelope design, construction and commissioning is a “Game of Barriers” i.e.
- Liquid moisture
- Thermal (insulation, thermal bridging)
Air barrier is most important and unique because:
- Consists of multiple, tiny, invisible leakage points which can lead to large performance deficits
- Impacts through all six sides of building enclosure
Building Envelope commissioning includes:
- Façade cladding system
- Opaque wall area, insulation
- Roof system
- Horizontal waterproofing
- Measurement of air leakage rates
BECx is best suited to:
- IPD (Integrated Project Delivery)
- Design – Bid – Build
- Construction Management
BECx least suitable for:
- Contractor design & build.
- Fast track project schedules.
- Explicitly specify building envelope, pressurized escape staircases and air plenum air leakage rates.
- Issue a separate design / tender document titled “Façade & Air Plenum Performance Specification”.
- Explicitly specify BECx standards. Do not list all of them, just the ones that apply.
- Explicitly specify level and quantity of BECx factory acceptance testing plus field testing.
- Explicitly specify if a certified or independent third party BECx is required. BTW, this is always required!
If items 1 through 5 above are not done, the whole BECx exercise devolves into a meaningless paperwork exercise i.e. minimal added value.
BECx – Design Phase Tasks – (Quality Management Via Domain Expertise Input)
- Ensure OPR addresses building envelope performance, life expectancy & warranties
- BECx specification development plus review
- Envelope design and details review
- Design Phase BECx testing plan for inclusion in tender documents package
BECx – Construction Phase Tasks – (Quality Control Via Inspection)
- Ensure project schedule explicitly includes BECx tasks
- Factory acceptance testing (FAT)
- Submittal reviews for commissionability
- Periodic site installation inspections
BECx – Testing Phase Tasks – (Quality Control Via In-situ Performance Testing)
- Enclosure / whole building air leakage testing
- Barrier testing (water)
- Thermographic testing
- Final BECx report
So is BECx worth it? Hell yes, if you care about occupant comfort and long term energy costs.
Stay inside and be safe everyone.
BECx Resources & Information
Definitions from ATSM E2947
- BECx P – “Provider” = a duly authorized person or firm with domain expertise.
- BECx S – “Specialist” = a registered design professional who possesses the experience and technical skills needed to assess, critique, validate, verify and support the BECx team.
- BECx T – “Technologist” = Individuals or accredited testing agencies.
BECx Codes, Regulations, Guides & Standards
- Relevant and changing local Building Codes and Regulations
- NIBS Guideline 3-2012 Building Enclosure Commissioning Process.
- US Army Corp’s of Engineers Air Leakage Test Protocol for Measuring Air Leakage in Buildings.
- NEBB (2013) Procedural Standards for Building Enclosure Testing.
- BSRIA (BG 65/2016) Floor Plenum Airtightness.
- ATTMA Tech Std. L1 2010 – Measuring Air Permeability in the Envelopes of Dwellings.
- ATTMA Tech Std. L2 2010 – Measuring Air Permeability in the Envelopes (Non-Dwellings).
- ASTM E2947-16a Standard Guide for Building Enclosure Commissioning.
- ASTM E2813-18 Standard Practice for Building Enclosure Commissioning.
- ASTM E783 – 02(2018) Standard Test Method for Field Measurement of Air Leakage Through Installed Exterior Windows and Doors.
- ASTM E779 – 10(2018) Standard Test Method for Determining Air Leakage Rate by Fan Pressurization.
- ASTM D5957 – 98(2013) Standard Guide for Flood Testing Horizontal Waterproofing Installations.
- ASTM C1153 – 10(2015) Standard Guide for Location of Wet Insulation in Roofing Systems Using Infrared Imaging,
- ASTM E1213 – 14(2018) Practice for Minimum Resolvable Temperature Difference for Thermal Imaging Systems.
- ASTM C1060 – 11a(2015) Standard Practice for Thermographic Inspection of Insulation Installations in Envelope Cavities of Frame Buildings.
- ASTM E331 – 00(2016) Standard Test Method for Water Penetration of Exterior Windows, Skylights, Doors and Curtain Walls by Uniform Static Air Pressure Difference.
BECx Training & Certifications
- University of Wisconsin Professional Development Program
- ATTMA Training
- ASHRAE BECx Building Commissioning Professional
- NEBB BECx Certification
Edifice Complex Podcast
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