For some people there is only one metric that matters when thinking about energy in their buildings – the bill. And the only outcome that is interesting is driving it down.

We’ve all lived with people like this. Sometimes we have argued with them over the setting for the thermostat. Or even found ourselves sitting in the dark as a light automatically switches off.

These incidents make an important point about energy efficiency: one that we know intuitively. A simple focus on the input (the energy bill) can lead to poor decisions on how a building is used. At its most extreme it can undermine the purpose of a building – to shelter its occupants and foster productivity – completely.

A more fruitful way to think about building energy efficiency is to understand what outputs we want from a building for the energy we put in. Although this is harder to do, it results in buildings that are both truly efficient and more productive for those working in them.

So if building energy efficiency means using less energy to provide the same service, how can we measure this? And what can it tell us?

Measuring true efficiency

To benchmark true efficiency you need to find metrics that can be used across a wide range of very different buildings. So it is standard in energy efficiency to talk about energy consumption per floor area and energy consumption becomes KWh/m2.

This helps with comparisons between buildings but tells you very little about why some use more energy than others – are their lights on for longer? Do they need more heating energy because they are draughty? Measuring outputs not only gives a more accurate picture of energy efficiency but it can also help identify where waste happens.

Where energy is used

Energy in buildings is turned into a lot of outputs and a complete accounting of these is impractical. How can you compare output used to charge a phone against the load required to boil a kettle?

However, the majority of energy used in commercial and domestic buildings goes on two significant and measurable outputs – keeping comfortable air quality (temperature, humidity and ventilation) and keeping the lights on. These two end uses will typically account for nearly 70% of the energy footprint in offices and homes, so if they can measured and compared, a much clearer idea of the relative energy efficiency can be produced than relying on bills alone.

In practise, this can be turned into a measurement of Kwh/m2 of usable space, where ‘usable space’ is space that meets requirements for air quality and lighting.

How Purrmetrix can help

This philosophy is already reflected in processes such as PAS2035 and post occupancy evaluations, where monitoring and verification are used to confirm that energy efficient buildings are delivering the outputs they are meant to.

For property professionals who are delivering such evaluations, our mission is to make it easy to collect the data you need on building performance and turn it into useful information.

With sensors for temperature, humidity, lighting and CO2 and a sophisticated analysis platform the data can be turned into simple metrics of building output, so you can explore how investments in energy are paying off.

Accurate and detailed data on building performance lets you go beyond benchmarking and identify opportunities for reducing energy through optimising building controls and improving building fabric.

And measuring performance before and after improvements provides evidence on what works – and what doesn’t.

Get in touch if you would like a peek at what can be done with environmental data.