Making the Case for Re-Commissioning

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Re-commissioning an existing building can take place for several reasons. Here, the CSA explains why building owners and managers might consider a re-commissioning project.

Firstly, the building may not have been commissioned properly in the first place. This may have been because there were cost or time constraints and a building user desperate to occupy the building. If their previous accommodation had reached the end of the line, or they were expanding and just had to have the space, there might have been some shortcuts. It doesn’t really matter what the reason was, it seemed the right thing to do at the time. Having got past the short term need to utilise the space, the realisation has now dawned that things are not quite right.

Secondly, many buildings are multi-tenanted (or have a single tenant whose business is undergoing continual development). This ongoing ‘churn’ of the building’s occupants can result in a few areas in the building being subject to change and being put to a different use to that in the original plan. This can go so far as heat loads changing or floor plans being altered, e.g. less partitions, more partitions.

Another reason, especially if the building has been in use for some time, is that there may have been a plant failure. Whereas the solution a few years ago would have been a simple like-for-like replacement, the pace of change in MEP plant (and especially control of that plant) requires that the solution to the problem must also include an evaluation of potential changes / upgrades.


So, there are many reasons why buildings may not be operating as effectively as they could be. This can manifest itself in excessive energy consumption (and thus costs). Another symptom can be poor space conditions and thus less than optimum output from the occupants. Either situation is likely to result in an unhappy building user.

In fact, really smart building managers can realise that, even if none of the above circumstances are applicable, a regular comparison of current performance figures against the original values can identify issues before they become real problems and allow solutions to be implemented without delay so as to maintain the building’s performance. In that situation, it need not be a full recheck of the building. A sample of some major systems might be sufficient, especially if different systems were sampled every year, building up a picture across three or four years.

But, if there is a real problem, what should the building’s facility management team be looking for? Firstly, the energy use should be compared to that predicted in the BREEAM Guide prepared when the building was constructed. Although they may not be exactly in tune, the relationship should be broadly the same, e.g. if actual use was 2 or 3% more than predicted to start with, but has suddenly become 15% more, you can be pretty sure that there is an underlying cause that can be addressed. Secondly look for changes to conditions. The BMS is a good start point for this. Trend logs can often be used to compare space conditions and / or plant performance over time.

Sick building syndrome

Another check is for occupant complaints about their environment. There has been much conjecture about the effect of ‘Sick Building Syndrome’ over the years. What is true is that, if staff feel that building conditions are not as good as they could be, efficiency is adversely affected. Once a building gets a reputation for poor conditions, it can be extremely difficult to change people’s opinions.

So, what can be done?

The obvious first step is to engage a professional commissioning company. Not only will they have the necessary skills and instrumentation to carry out investigations, but they will almost certainly have carried out similar exercises previously.

Secondly, review the evidence. What are the symptoms? What do they indicate as the potential cause of the problem? Can changes to the building be the cause of the problem? If so, is there a history of what, how and when the changes occurred, or does there need to be a survey?

The third step is to find out what the systems are currently doing. What are the air system and water system flow and pressures? How do they compare with the originally commissioned figures? Is there an obvious discrepancy or just several minor variations?

Once the true state of the building is known, the information needs to be looked at by an MEP designer, especially if the building has changed over time. This should result in either confirmation that the original flowrates are valid (and need to be re-established and re-certified) or that things have changed, and the systems need adjustment to suit the new reality.

Whichever course of action is required, it is again underlined that it is a professional commissioning company that will be best placed to do the work.

Of course, there will be practical difficulties in working through all the above steps, not the least of which is that the building is occupied. Much of the work may therefore need to be carried out at night or at weekends. It might also be necessary to have several interim stages in order to maintain reasonable conditions throughout the process.

Obviously, we at the CSA recommend that facilities management teams ensure that it is one of our member companies that is engaged to re-optimise the building. Not only will they use trained and experienced engineers, but they will have the technical expertise of the CSA behind them if they need help in solving any problems.

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