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IST Or No IST, That Is The Question!

IST or no IST, that is the question!

Quality, Consequences and the Construction Industrial Complex (part 183).

Why is building integrated systems testing (IST) not explicitly specified in specifications?

Owners assume their building systems have been tested as an integrated whole i.e all systems cause & effects, including their software and hardware interfaces work as designed. This assumption is false, it is an outcome of the silo approach to building design, construction and commissioning.

In my experience, there is no industry agreement on what IST has to be done as a minimum or as good practice. As IST is a multi-discipline activity, I guess people find it difficult to assign responsibility across the silos. Let me clear this up right now. 

  • Who is responsible for this failure to specify IST and assign responsibility? MEP design engineers!
  • Who is the logical entity to undertake IST? MEP commissioning engineers!

What exactly is IST? 

In a global industry of competing standards and cultures, IST has several different names:

  • IST – Integrated Systems Testing
  • GIT – Global Integration Testing
  • SIT – Systems Interface Testing
  • IT – Interface Testing (CIBSE Commissioning Code M)
  • FPT – Functional Performance Testing (Systems)

Shout out to the Brit’s. At least they reference interface and performance testing in CIBSE Commissioning Code M. 

A generic definition for IST I like is: 

“Verification of functional performance and interconnectivity of all MEP systems within the whole building context.”  IST begins with the end in mind, is an event involving the whole project team and is outcome based.

Key tools for IST are:

1. Cause & Effects Matrix; “A diagram in matrix form where “causes’ are listed in the left section while “effects” are listed in the top section. The marked intersection between both means that they are related as cause & effect and are marked with an “X” to denote equipment and system interconnectivity.”

2. A senior commissioning professional, a systems thinker who actually knows what they are doing from an engineering and leadership perspective. Harder to find than you may think. 

What constitutes IST good practice? IMHO, there is a hierarchy based on building type and use:

  • Minimum – Life Safety systems
  • Recommended – Life Safety + Mission Critical systems 
  • What owners believe they are getting and have paid for – Whole Building Testing

IST Hierarchy

IST Hierarchy by System

IST Hierarchy by System PDF

I have never seen an IST test pass on the first run. In my experience there is some fix required and several iterations of testing before all systems are working as specified. From a life safety perspective IST matters. 

Unless IST is explicitly specified and a single entity tasked with doing it, it will not get done. Developers/owners need to insist on it and engineers need to specify it. 

Twitter: @BLDWhisperer

Related posts & links:

#40 – GIT – The must do test that delivers working buildings ( )

Edifice Complex Podcast


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