Moving in with energy efficiency

Buildings are responsible for almost 40% of the UK’s total emissions but in the new build sector, more stringent building regulations and environmental assessment ratings such as BREEAM are driving steady improvements.

The real challenge, however, lies in the existing building stock, where facilities managers are faced with a bewildering array of energy efficiency, low carbon and renewable energy technologies to reduce running costs and tackle emissions.

So where to begin? A natural starting point is an assessment of current energy use. Sub metering individual electricity circuits is an easy way to establish where consumption is highest and costing the most.

Heat metering is more complex and potentially disruptive, although meters which use ultrasonic flow sensors that clamp onto pipes are now widely available if expensive.

There’s often good potential for savings through three areas: energy efficiency investments, fabric improvement measures such as glazing and insulation, and the better use of heating and ventilation controls.

Examples of energy efficiency investments might include low energy lighting with presence detection, voltage optimisation which can be effective for some industrial loads, variable speed drives for industrial motors, more efficient appliances, and cloud computing to replace power-hungry in-house servers with an externally hosted service.

In some buildings tamper-proof thermostats can help to achieve better control of heating and ventilation. It’s not just building users who tamper with the settings either – maintenance engineers often override energy saving controls such as boiler weather compensation systems which, left unchecked, can result in hefty bills.

But there’s also good evidence that up to 10% of total energy consumption can be saved simply by behavioural change. Apart from the familiar “switch it off” campaigns, other savings can be made through less obvious behavioural changes. For example, not using air conditioning when the windows are open will result in significant electricity savings.

With budgets under pressure and capital especially tight, it pays to look at all these measures first for some relatively quick wins. Then it’s probably time to look more deeply into renewable energy and low carbon options for buildings.

Let’s think first about the available technologies for generating heat. Space heating loads can be met with heat pumps or biomass boilers, while buildings that use a lot of hot water are often well suited to solar thermal systems. All of these qualify for Renewable Heat Incentive payments which in many cases can make projects financially viable.

Heat pumps use electricity to pump heat from the outside environment to the inside of the building with a very high efficiency, normally using either the air or the ground as their source of heat. Designed and specified correctly, they can achieve significant savings and CO2 reductions over conventional fossil fuel heating systems.

Ground source heat pumps are even more popular with planning authorities because of their lack of visual impact. And as the grid becomes increasingly decarbonised through the generation of renewable energy, heat pumps that consume electricity to generate heat will become more prevalent.

Biomass boilers can also be used to heat buildings, normally in conjunction with gas boilers for back-up and to supply additional heat on the very coldest days. Biomass is classed as carbon neutral because the CO2 emitted during combustion is compensated for by the CO2 absorbed by the plants as they grow. The important thing is to establish a sustainable source of biomass fuel, whether it is wood chips, pellets or logs.

Recently constructed commercial buildings often have biomass boilers which were specified to achieve a particular BREEAM rating. Sadly, too many of these are not used because the fuel supply arrangements were overlooked and the building occupiers just use the gas back-up system instead.

Solar thermal technology has a bad name and a perception of high cost in some quarters – caused by the over-aggressive selling of grossly overpriced systems for domestic space heating in the 1990s and early 2000s.

But solar thermal can be another useful way of providing hot water with a relatively low installation cost and high efficiency – especially for industrial processes that consume large volumes. Since heat can’t be stored for long periods, correct sizing is the key.

Turning to technologies that generate renewable electricity, solar PV is suitable for many commercial and industrial buildings – and can often prove highly viable thanks to the feed-in tariff and plummeting capital costs. But planning issues, wind loading, shading and future maintenance requirements must all be taken into account before committing to a PV system.

Small scale wind turbines (up to 50kW) are worth considering on land adjacent to buildings, but are rarely suitable in a dense urban environment. This is simply because wind power works best when it’s strong and steady – not turbulent as it normally is in built-up areas.

Understanding the costs and benefits of alternative technologies – and choosing the most appropriate – is far from an easy task. Systems need not only be sized, specified and designed correctly, but also thoroughly commissioned with end-users fully trained and clear about how to get the best out of them.

Alex Savidis is a renewable energy specialist and associate director of Wardell Armstrong