21 May

When good buildings go bad…HVAC recommissioning

When good buildings go bad…HVAC recommissioning

Proptech. AI. IOT. Space as a service. Smart Buildings.

There’s increasing noise in the property industry about the importance of technology. You’re probably sick of the phrase ‘Data is the new oil’, especially if you’re tasked with trying to persuade a sceptical boss to invest in it.

Not surprisingly we have a lot of conversations about the ROI from environmental data, which can get complicated as there are many ways in which better insights into your environment create value. So we thought we might create a short series where we could share examples of what our customers are doing with this data and how they get ROI.

First up – how to reduce hvac energy waste

Fact: the energy consumption of commercial buildings tends to drift up over time. If you look at the lifecycle of a typical modern building over time the energy used to run this building will tend to trend upwards unless regular interventions – shown by the green line – are made to review and fix the problems that arise.

Why these occur is complex, but one of the most common and low cost causes is control drift, and that’s what we’re interested in. Studies in the US of over 600 commercial buildings show more than 50% have controls problems and that fixing these produces a simple payback within a year. These are very simple issues like scheduling, run time, set point adjustments, eliminating zone conflicts.

Further more, fixing them – recommissioning the building – is generally a very low cost win, requiring no new investment. So this looks like an attractive target for improving energy efficiency in any building, but to do this first you have to find the problems.

Causes of control drift

So it’s a common problem, it is low cost to fix – why don’t people pay more attention to it?

I think part of the problem is that, unlike lighting, HVAC control issues are invisible – the BMS is unlikely to flag it up as an alert, and identifying it requires expertise and time. If your buildings supports multiple schedules and set points – and we have come across academic set ups where there are hundreds of schedules for heating and cooling – then manual checking isn’t practical.

Furthermore many facilities managers are a bit sceptical of data reported from a BMS because they know sensors can drift without recalibration and they are often located away from the occupants. If managers don’t trust the data the BMS is producing, then they are less likely to invest the time in an audit.

The value of environmental data in these situations is that, unlike metering data, it is easy to locate exactly which part of the system is running out of control and implement the right adjustments.

The case for recommissioning

A quick back of the envelope highlights why this is worth doing – heating and cooling commercial space is typically 25 – 35% of the overall energy budget for a building. That means, at its simplest, that if the building systems are running for 10 hours where they could be running for 9, that extra hour is 2-3% of the energy budget for the whole building. Running at weekends is ruinous and not uncommon. In fact, based on experience, I’d go so far as to say if you have a building of more than 3 years old, its a stone cold certainty that parts of the HVAC will not be well matched to the operations in the building.

Fixing control drift – real world cases

Over the past two years we’ve seen so many examples of this, and not just in offices:

1) the 10 year old office building in a campus setting with conflicting HVAC zones and heating that was regularly 2 or 3 degrees above set point. Changes to reduce zone conflict and lower temperatures produced a 20% reduction on an annual 80k energy bill

2) a school with a large number of Victorian school houses and a wet radiator system that had extensive challenges with timing heating, incorrect sensor readings and furniture in front of radiators. Fixing these problems produced a 10% reduction in their gas consumption for these buildings.

3) an aircraft hangar with substantial overheating issues and heating systems running out of working hours. Purrmetrix data demonstrates that upgrading controls will create savings of over £100,000 across the whole estate.

Think you might have a silent controls problem? Get in touch  and let’s talk about how we can help.