Sunday, August 25, 2013

Energy Efficiency - Why measuring ‘performance in use’ is the key to energy efficiency in buildings

Guest Article from Professor George Martin, Low Impact Building Centre, Coventry University

With approximately 80% of the properties that exist today still being in existence in 2050, the key issue for landlords in the run-up to the 2018 change is that they understand the scale, nature and cost of the various interventions that will be needed to update properties now

For the past 10 years or more I have been driven by the mantra - If you can’t measure it you can’t manage it. This applies to each and every key performance indicator linked to the built environment sector with energy arguably being the most important. It is for this reason that I consider it essential that the Government mandates the use of Display Energy Certificates (DECs) for all buildings as a vital first step to cutting carbon emissions.

The Display Energy Certificate (DEC) provides an up to date snapshot of how well a particular building is performing, based on actual energy consumption unlike its poor relation the Energy Performance Certificate (EPC) that only provides a theoretical rating based on assumed patterns of use and occupation and can be up to10 years old!  The DEC also reveals what the rating score was in previous years. Consequently it is possible to see at a glance the progress in making that building more energy efficient and less costly to run.  There is now considerable evidence (initially anecdotal, increasingly academic) that requiring energy usage to be professionally monitored and the results made visible, delivers enormous improvements in performance.

Landlords need to be aware that the Energy Act 2011 proposes to make it unlawful to lease residential or commercial buildings with an Energy Performance Certificate (EPC) rating of F or G from April 2018.  In addition, there is a requirement for all new build domestic to be 'zero carbon' from 2016 and for new build non-domestic to be ‘zero carbon’ from 2019.  However, the biggest challenge, especially for landlords, relates in particular to the UK's ageing property stock, not built for a world of high energy prices and carbon reduction targets, and lacking in investment in low carbon retrofit over time.

With approximately 80% of the properties that exist today still being in existence in 2050, the key issue for landlords in the run-up to the 2018 change is that they understand the scale, nature and cost of the various interventions that will be needed to update properties now. And that means learning in more detail about how properties actually perform in use.  A one-size-fits-all approach will not work and landlords will need to develop an evidence based approach, backed up with a robust whole life cost database for their properties.  Smart landlords will be using sensors to monitor energy use against temperature and other indicators such as relative humidity in order to identify more specific issues – so that they can identify whether the source of any inefficiencies is due to the building fabric, the equipment, the maintenance regime or indeed the behaviour of occupiers.

Property developers and landlords also need to ensure that their design, delivery and maintenance teams do not have a blinkered approach to energy efficiency and carbon reduction - as it is vitally important to ensure that the health of the fabric and the occupants are also considered. The existing stock of ‘leaky’ properties, whilst bad for energy efficiency, is good in terms of ventilation and here there is some distressing news from recent research that is showing that many - if not most - of the Mechanical Ventilation and Heat Recovery units installed in recent times are underperforming, which is seriously bad news for the occupants.

It is most certainly not right to assume that all 'modern' property will achieve a good performance in use just because it has a good EPC rating or indeed an ‘high’ BREEAM design rating.   Even the highest spec builds with energy efficiency in mind may not be performing as expected. The limited performance gap research available has demonstrated that design targets (and we must remember that EPC is a design tool) are missed by between 20% and an astronomical 500%. We must stop assuming that sustainability-minded design and construction methods are the whole story. Buildings need to be monitored and evaluated for performance once occupied.  Only then is it possible to gain a clear picture of the performance in use and capture the learning for future designs.

The property sector needs to move from making procurement decisions based on design tools (e.g. EPCs), capital cost and payback time to making primary decisions based on the performance in use (DECs)  and 'whole life costs', backed up by an assessment of the return on investment.  

In turn, as attitudes and understanding begins to evolve around performance  in use and whole life costs, the construction industry and here I include clients, designers and constructors, will become more focused on delivering buildings that perform sustainably i.e., environmentally, socially and economically.

Professor George Martin, Low Impact Building Centre, Coventry University

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  1. I think that DECs for domestic properties would be very misleading because there is no standard for heating a private house. The amount of energy used is dependent more on the number of occupants and their chosen comfort level or ability to pay for fuel than the design of the house.

    1. Ian

      My view is that something is better than nothing. Take cars for example, fuel consumption is published for Urban, Extra Urban and Combined. Could something similar not be developed for a domestic property?


  2. I can not see an environment where DECs for Housing would be introduced, not least because EPCs are as a result of European Law, but do you see an opportunity for making EPCs more fit for this purpose? Working with what we've got rather than going back to the drawing board? Hilary Grayson

  3. Probably a little simplistic but isn't the Occupancy Assessment as used in the Green Deal a step in this direction and one that has the benefit of not needing smart or sophisticated monitoring tools?