How many miles per gallon does your building do?

Author: 06/10/2014

One of the Foundation's Trustees, Liz Reason, looks at why the UK seems incapable of producing energy-efficient buildings, the need for a common language within the industry and the similarities between how much energy a building uses and how many miles per gallon a car achieves.

London is frequently in breach of international air quality standards set by the EU and the World Health Organisation and has some of the worst air pollution problems in Europe; some say that air pollution in the city sometimes exceeds that of even Beijing. At the current rate of improvement, non-compliance could continue until at least 2025.

The reasons for this are complex but analysis shows that, while the levels of some air pollutants have declined significantly in the UK over the past 20 years, the levels of nitrogen oxides (NOx) and particulate matter (PM) have remained stubbornly high in most urban areas. The London Air Quality Network, which is run out of King’s College, believes that diesel engines are "probably the root of the problem".

Climate change policies have led to a focus on carbon emissions. Diesel engines are more energy-efficient than petrol engines and therefore have lower CO2 emissions. The car tax regime has therefore been structured to provide incentives for cars with low CO2 emissions with the result that more cars are now sold with diesel engines than petrol. Efforts by the European Union to force manufacturers to produce cleaner diesel engines have met with limited success.  

In fact, the official published figures appear to show that new cars are getting much cleaner, but cars in use do not match those figures. Whilst engines are tuned and run to minimise pollution in lab tests, on the road, congestion and regular stopping and starting at junctions produces very different figures. Tests of the emissions of hundreds of cars in real traffic conditions have shown that the real world NOx can be three, four, or even five times the official values.  

What has all this got to do with the UK’s buildings?
There are many parallels. To highlight just three…

  1. Climate change policies have meant that since 2006, Building Regulations have been expressed in terms of carbon emissions targets. This has transferred itself to the higher profile policy objective of ‘zero carbon homes’. Purportedly this is still to be achieved by 2016, although the steps being taken to achieve it have been minimal in the last two years.

  2. The buildings equivalent of laboratory tests for cars is the methodologies used to model the level of carbon emissions that the building is designed to meet. These have demonstrated progressive improvements in emissions from both new and refurbished buildings.

  3. When buildings are tested for performance in use, it has been shown that the real world CO2 can be three, four, or even five times the official values.  

What are the implications of these three issues?

Carbon not energy
Unlike with cars, expressing Building Regulations targets in terms of kg CO2/m2.yr has had the effect of shifting the focus away from improvements in energy efficiency to one of substituting emissions from conventional energy use with energy from low and zero-carbon technologies. While this means that CO2 emissions might be reduced (if the kit has been correctly specified, designed, and installed and is operated properly), the capital cost of installing technologies is generally much higher than building a high-quality building fabric. And because it is often assumed that a low-carbon building must also be a low-energy building, building occupants can be surprised at the size of their energy bills.

Since 2010, the notion of a Fabric Energy Efficiency Standard (FEES) has been introduced to try and ensure that the basic building fabric is designed to meet a reasonable standard of energy efficiency – although it is not a very challenging target.

However, the recent report from the Zero Carbon Hub’s 'Closing the Gap' project[1] highlighted a series of fundamental problems with the house-building industry that underlines the need for a rapid and radical transformation of its knowledge and skills and their application in the real world. 

Design or regulatory compliance tool?
The National Calculation Methodologies used to estimate the intended energy and carbon performance of homes and non-domestic buildings – SAP and SBEM – are based on fundamentally sound energy models grounded in building physics. In the right hands, and with the appropriate level of granularity, energy and carbon design estimates based on detailed building designs should be accurate.

However, like the lab test versus actual performance for cars, the software has been used for regulatory compliance purposes rather than as a design tool. Most commonly, SAP is used by energy assessors to produce Energy Performance Certificates - often for the notoriously low figure of £50 – as part of a sale or Green Deal transaction. It is also used by sustainability consultants working with architects to establish whether building designs comply with the requirements of Building Regulations. This can mean that sustainability consultants propose design changes to ensure compliance – an exercise that is not properly integrated with the detailed design process required to deliver a given energy performance in reality.

The use of the tools for compliance purposes by what are essentially non-building energy experts also means that they make use of many simplifying assumptions. For example, the model will require a U (or heat loss) value for a whole window to be entered, when in fact, a window is made up of a number of different materials – the glazing, an inner frame and an outer frame, for example – each of which has a different U value. This can make a 20% difference in the amount of energy that will be lost through that building element.

Design versus actual
The real scandal is that few new homes are tested for compliance in the real world – and those that have been are found to be badly wanting. A ground-breaking study by Leeds Metropolitan University at a new development at Stamford Brook in Cheshire over the course of the first ten years of this century identified for the first time the myriad of problems besetting house-builders – and those purchasing new homes from them. Having demonstrated that the fabric of new buildings suffered from significantly higher heat loss than expected, the same team went on to test the fabric of sixteen new homes at various sites around the country, all built to 2006 Building Regulations.

The results have provided a graph that has become the classic evidence for those arguing the notion of the 'performance gap’. The existence of the gap is no longer disputed by those engaged at a national level, but the vast bulk of those working in the construction industry almost certainly remain oblivious to the concept and to the issues that create it. Testing of other homes, and non-domestic buildings, has uncovered a performance gap of four and five times – equivalent to the diesel engine example.

The need for a common language
The list of issues that need to be dealt with is so vast[2] that those trying to tackle it can sometimes feel overwhelmed – where do we start? But a consensus is developing around the need for us to have a common language to talk about energy and carbon performance in a meaningful way. And what better place to start than to learn from the language of car performance?

There are few car owners who cannot say approximately how many miles per gallon they get from their car. The equivalent for buildings is the number of kWh/m2.yr used by a building for space heating and for electricity – this is the language of Display Energy Certificates and the one that allows for comparison between buildings of similar type and occupation.

The need for a programme of energy literacy for the industry heads the recommendations from the Zero Carbon Hub. Energy literacy for architects is being promoted within the RIBA. And the National Energy Foundation, with its mission of improving the use of energy in buildings, has recently launched its programme of 10 Big Ideas projects, working together for an energy-literate UK.

And the book How Much Energy Does Your Building Use? published by Do Sustainability, in cooperation with the National Energy Foundation, sets out the scale of the challenge. Read it and ask what you can do to contribute to a more energy-literate industry.

[1] Design and As-Built Energy Performance – End of Term Report: Zero Carbon Hub. July 2014
[2] Closing the Gap Between Design and As-Built Energy Performance - Evidence Review Report: Zero Carbon Hub. March 2014