Recently I was asked to provide a key note address on Energy Performance Certificates (EPCs) and Display Energy Certificates (DECs), and a couple of issues were raised.
I'm afraid I caused some consternation with my views to encourage discussion.

First is that too many people compare EPCs and DECs, and that is like comparing apples and carrots, and I said that a DEC rating of E or F could be a more sustainable building option than a DEC rating of C or D.

The EPC is needed on construction, sale or rent/let of a property. It looks at the carbon emissions associated with the regulated energy demands covering fixed building services, i.e. heating, cooling, ventilation and lighting, whereas the DEC looks at the energy consumption carbon emissions of the whole building including catering, computing and all small power plug loads.

If you have an office building with more people than the standard EPC occupancy density, then you can expect the building to use more electrical energy and therefore have a higher operational carbon footprint.

This may give you a poor DEC rating, but minimises the need to build additional office space. Therefore is it better to have two DEC C-rated buildings with the same the floor area as the single DEC E-rated building, bearing in mind that all three buildings have an EPC rating of C?

To get better utilisation out of one building must be more sustainable than using two buildings.

We see many headlines berating buildings with DEC ratings that are F and G, but this is not always a sign that a building is not being controlled or run effectively. We must not expect buildings to have similar DEC and EPC ratings because we are looking at very different quantities and dealing with highly air conditioned buildings or buildings with commercial refrigeration loads are much harder to deal with than heated only buildings.

Let us work towards using buildings far more efficiently in terms of space use and hours of use while making sure we control our fixed building services in a low-energy, low-carbon manner.

Please do look at why a building may have a poor DEC and pay attention to the accompanying advisory report in particular.