Maximising energy efficiency improvements across a building stock portfolio

Author: 11/09/2013

Our Technical Director, Malcolm Hanna, discusses how and where to maximise energy efficiency improvements across a building stock portfolio - assessing where you are now, what the opportunities are, how big they might be and what to do next.

Energy used in non-domestic buildings accounts for 18% of total UK carbon emissions, but with a targeted focus on energy efficiency, many buildings could deliver significant savings in both carbon emissions and energy costs - often well in excess of 20%. Energy costs are predicted to increase significantly over the next decade so savings will become even more attractive. But, when your responsibilities extend to multiple buildings and the opportunities for energy efficiency improvements can be anything from light touch through to major retrofit, making savvy decisions on where and how to invest in energy efficiency improvements is a task in itself.

Where are you with maximising energy efficiency in your building stock portfolio now?

The first stage of a prioritised energy efficiency plan is to assemble key data and information about how the building stock is currently performing. This should comprise annual energy use and cost data for each building together with the treatable floor area (effectively the area you would consider to be inside the building). From this, you can calculate the annual energy use per square metre (kWh/m2/year). Armed with this information, and the building type (such as office, shop, depot, etc.), you can then compare performance of buildings across your own portfolio and against published UK benchmarks for different building types. You can use CIBSE TM46 or freely available on-line tools such as CarbonBuzz to do this. This initial review will give you your starting point and provide a good idea of how big the improvement opportunities could be. It will also help highlight good or poor performing buildings as a prelude to more detailed investigations. Creating a league table can help prioritise the buildings you might wish to focus on first – usually starting with the poorest performers. However, with a large building portfolio there is merit in selecting a representative sample of buildings across good, poor and typical performers, with different levels of intervention (and hence investment) in each category.

What are the opportunities for maximising energy efficiency in buildings and how big are they?

To identify and quantify specific improvement opportunities you will need to dig deeper into how and where energy is being used and also how much of the time certain energy uses are active. An energy appraisal, using for example CIBSE’s TM22 methodology, allows you to disaggregate energy uses within a building and thus quantify (and check) the main energy uses. You should also review the age, condition and performance of key elements such as building fabric, plant and equipment and controls as well as how energy is managed on site in relation to how the buildings are occupied and operated. The aim here is to compare what is found with good practice and to quantify the gap for each area and for each specific opportunity identified. You should be able to produce a list of quantified opportunities, based upon actual findings. Sometimes an external perspective and expertise can really help you to identify the wood amongst the trees.

Consider then the golden opportunities for action - which generally represent the best intervention points to improve building energy efficiency. These include: procurement decisions for energy-using plant, equipment and services; design and refurbishment; maintenance and training of staff and contractors. Responsibility for these areas often sits centrally within an organisation and decisions might be remote form site-specific knowledge. Absolutely DO NOT invest in new equipment or refit without considering the opportunities for improving energy efficiency and/or reducing energy demand – it will not be the ‘investment’ you thought it would be.

What should you do next about maximising energy efficiency in your buildings?

Having your list of quantified opportunities, the final stage is to produce a prioritised action plan – but there is no single solution to suit all circumstances. Organisations are likely to have different drivers including: reducing costs and improving business efficiency; meeting energy and carbon reduction targets in line with CSR aims; improving building comfort; improving property value and meeting legislative requirements. However, in most cases the main focus is on financial savings, cost to implement and a return on any investment. There are a number of tools which can be used to help prioritise actions including an ‘ease and effect matrix’. This involves plotting opportunities according to their relative ease or difficulty to implement against their relative size of effect or impact in terms of energy saving. More detailed approaches can include the use of Lifecycle Costing and Marginal Abatement Cost Curve techniques. Many organisations adopt a simpler approach which involves calculating and comparing the Return on Investment and any payback of different energy efficiency measures.

In general, the recommended approach is to focus first on the no and low capital cost opportunities, often with immediate or short paybacks of less than one or two years. These are generally operational in nature and might include changing control set points or the operating hours of key plant, to match building occupancy profiles and optimise performance. They can often be implemented quickly but might need communication, monitoring and training to ensure that they stick. These measures can help build momentum for your wider energy efficiency programme by demonstrating improvements early on and helping to engage interest. Not only do these interventions usually represent the best return on investment, they will also reduce the energy demand that will need to be considered when sizing energy supply equipment – hence reducing the investment needed for that too.

The next category of opportunities includes the low and medium cost measures, with paybacks typically between two and five years. These will often include the replacement or enhancement of controls or smaller elements of plant and equipment. The final category includes the medium to longer term opportunities with paybacks of over five years, including the replacement of larger plant or building fabric elements such as lighting systems, HVAC plant and additional building insulation.

And finally, if you have clear picture of current and projected energy improvements, you can rapidly assess the consequences of incentives offered through Government initiatives, supplier deals and the like, enabling you to retain control of your energy improvement journey whilst taking advantage of opportunities that really contribute.