With at least 60% of existing commercial buildings likely to still be in use in 2050, retrofitting is crucial to meeting UK carbon targets. Paul Suff reports
According to the Intergovernmental Panel on Climate Change, retrofitting buildings has the largest potential of all measures to reduce greenhouse-gas (GHG) emissions by 2030.
In the UK, successful retrofitting of the built environment is key to meeting its target of reducing GHGs to 80% of 1990 levels by 2050. Emissions from buildings contributed 35% of the UK’s total in 2011, says the committee on climate change (CCC). Its latest progress report on meeting the UK’s carbon budgets reveals that 66% of emissions from buildings are from residential ones, while commercial and public sector emissions account for 25% and 9% respectively.
The UK tends to have a higher proportion of older buildings than many countries, with about half of existing commercial buildings predating the 1940s. Of the existing stock of non-domestic buildings, 60% will still be in use by 2050, and many are energy intensive. The Carbon Trust found in 2009 that the UK’s 1.8 million offices, shops, factories and hospitals use as much energy as Switzerland produces each year (330TWh).
Retrofitting such buildings so they are more energy efficient is therefore a priority in the transition to a low-carbon economy. Under the new Energy Efficiency Directive, member states will have to renovate public buildings and prepare road maps for the refurbishment of all buildings.
But the scale of the challenge in the UK is huge. The Energy Saving Trust reported last year that one building would have to be given a “green” makeover each minute from now until 2050 for the UK to meet its GHG emissions targets.
And, in addition to renovating buildings to consume less energy and help bring down emissions, many also need to be altered to cope with the impacts of climate change, including higher temperatures and greater risk of flooding. Any low-carbon refurbishment strategy delivered now needs to include sufficient flexibility to ensure immediate energy gains are not wiped out by the demands for future cooling as temperatures rise.
Opportunity knocks
Fortunately, given the poor energy performance of most buildings in the UK, the scope for energy savings is enormous. Data from energy performance certificates (EPCs) and display energy certificates (DECs) – first introduced under the original Energy Performance of Buildings Directive (2002/91/EC, and recast as 2010/31/EC) – show that, despite the introduction of the Carbon Reduction Commitment Energy Efficiency scheme, which aims to encourage the introduction of energy-efficiency measures, many non-residential buildings in the UK remain inefficient.
The CCC says that of the 336,630 EPCs issued by mid-June 2012, 18% recorded the lowest energy efficiency ratings, either an F or G, while just 8% achieved a rating of B or higher.
Similarly, of the more than 118,000 DECs issued to public buildings by the middle of the year, 12% were for the lowest, G, rating. By contrast, under one-quarter achieved a rating of C or higher, with just 748 buildings achieving an A rating.
The CCC notes that raising the rating of the 18% of buildings receiving an F or G EPC to at least an E could be achieved through the take-up of cost-effective measures such as installing better heating controls and energy-efficient boilers.
Likewise, the Carbon Trust says the non-domestic building sector can save at least £4 billion in energy costs by 2020 through low-cost measures, including lighting and heating controls, or better energy management and changing user behaviour. It also reported that the carbon footprint of offices can be reduced by 70–75% by 2050 at no net cost, using options that exist today.
Doug King, a consultant in sustainable buildings and visiting professor of building physics at the University of Bath, agrees. “You can make some very cheap interventions in how you run and use an existing building,” he says.
King believes that the energy performance of a building is influenced by many diverse factors, including its location, construction and use of information technology. “The form, frame, aesthetics and choice of materials will all influence the final energy performance of the building as much as the building services installations,” he says.
King advocates a retrofit hierarchy that starts with energy conservation, followed by recuperation (such as heat recovery), and finishing with generation (through renewable technologies).
He warns against bolting on “eco-bling”, such as photovoltaic panels, to energy-hungry buildings as there is little to be gained in terms of energy efficiency. Much more, however, can be achieved through simple, low-cost measures. “Good housekeeping, energy data and low-intervention controls can cut energy use by up to 40%,” claims King.
“After the ‘quick wins’ then you look at the insulation and more expensive measures. But dealing with the poor state of the fabric of many buildings must be a priority in refurbishment.”
Low-hanging fruit
The first step to conserving energy is to understand where it is used. “Install metering, including sub-metering, to identify where the energy is going. It’s often surprising how much is consumed when a building is empty,” King warns.
Reducing consumption by getting staff to turn off computers and other equipment when they leave the building can produce considerable savings. The US motor company Ford reported in 2010 that its roll-out of a PC power management system would save the company $1.2 million annually in energy costs and reduce its annual carbon footprint by an estimated 16,000 to 25,000 tonnes.
Simple retrofit measures, such as replacing 10- to 15-year-old, inefficient light systems with new T5 fluorescent tubes, for example, can pay back in two to three years at most.
Lancashire foundry business Lupton & Place recently reported that its electricity bill would fall by almost £8,000 a year as a result of installing energy-efficient lighting. It means that the payback time for the £20,000 project is just two and a half years.
Controlling heating, lighting and cooling also produces enormous savings. Commercial lighting, for example, consumes 42TWh of electricity in the UK each year, resulting in 22 million tonnes of carbon emissions, and installing lighting controls can reduce energy consumption by 30–40%.
The Carbon Trust estimates that, with heating accounting for more than 75% of a typical service-sector company’s energy bill, a 15% saving can be achieved by resetting timers and replacing old controls.
Installing variable speed drives on motors and pumps is another relatively cheap measure to consider. “Pumps are designed to deliver maximum flow during peak demand. But that only happens a few days a year, so they can run slower at other times,” explains King. “Variable speed drives have the potential to reduce energy consumption by up to 60%.”
DECC’s head office demonstrates what is possible through retrofitting. When the newly created energy and climate change department moved into 3 Whitehall Place in early 2009, the 1950s building, which had been refurbished in 2004–05, had a G DEC rating. This July, it received a C rating, even though it is now home to a larger workforce.
“The department has cut its HQ building’s energy consumption by 60% and slashed carbon emissions by half,” reported DECC minister Greg Barker.
Equipment changes recently made to the building include introducing more occupancy controls on lighting, installing intelligent load-optimisation control units on two gas-fired boilers and equipping fans with variable speed drives, which respond to demand rather than running at full speed all the time. DECC claims the measures have saved it around £156,000 in 2011/12 on energy bills.
“Many of the early changes we made in the building relate to more intelligent use of the building management system – to optimise the controls of our lighting, heating and cooling. These no- or low-cost measures have had – and will continue to have – a significant impact on our carbon emissions, with a short payback period,” reports DECC.
Similarly, the mayor of London’s Re:Fit initiative for public sector buildings focuses on energy conservation in retrofitting existing buildings.
Examples of conservation measures installed include variable speed pumps and fans, PC shutdown software, voltage optimisation, and lighting upgrades and controls. Transport for London, the London Metropolitan Police and the London Fire Brigade are among the organisations participating in the first phase of Re:Fit, which implemented energy saving measures in 42 buildings across the capital.
It’s in the fabric
More expensive retrofit solutions focus on keeping the energy inside the fabric of the building – its ceilings, doors, floors, walls and windows. Improving a building’s fabric involves taking measures to reduce the thermal exchanges to and from the environment, such as heat loss, from inside to outside, and heat gain, from outside to inside. Improving insulation and replacing old glazing systems, for example, can prevent heat loss or gain.
A poorly sealed building fabric – its airtightness – is a major source of energy loss. Basically, escaping warm air will be replaced by cold air, which will need heating, compromising the efficiency of the heating system and wasting energy.
Windows, for example, can be a major source of heat loss from both conduction and air leakage. Upgrading existing windows by replacing them with units that have a higher U value (thermal performance) will improve the energy performance of a building.
Complete replacement is often impossible, however, particularly if a building is listed. DECC encountered this problem at 3 Whitehall Place, as the windows are listed and could not be replaced with double-glazed units. Instead, the department opted for secondary glazing inside.
Improving the insulation of a building, by retrofitting outside, between or inside existing walls, floor and roof elements is the next stage in improving the energy performance of existing non-domestic buildings. A US study published last year found that insulation had the highest average year one savings, and at a cost per square metre that was significantly lower than that of HVAC (heating, ventilation and air conditioning) retrofits.
“Overall,” the researchers concluded, “insulation appears to be a profitable retrofit. While the total cost of insulation projects is much higher than the other types of retrofits, the savings in comparison are still remarkably high –enough that this type of retrofit would seem tempting.”
King warns, however, that improving the insulation and airtightness of existing buildings risks damaging internal air quality and heightening condensation problems. Colin Robertson, sustainability manager at building services company NG Bailey, acknowledges that this could pose a problem.
He explains that, although the firm improved the roof insulation of its head office, a grade II listed building (see below), it decided against other measures to improve the building’s thermal efficiency. “We had to consider what problems it would cause if we increased the insulation in a building that was designed for frequent air change,” says Robertson.
King says that any improvements in insulation therefore need also to protect against condensation and control ventilation through heat-recovery measures.
Nonetheless, retrofits that aim to enhance the insulation of a building may trigger wider beneficial changes. “Depending on the age of the building, efforts to reduce heat loss may involve recladding the façade. That provides an opportunity to increase the specification for insulation and glazing,” explains King.
Recladding may also make it possible to create a façade that maximises daylight while minimising solar heat gain. Heat gain can increase the demand for air cooling if not properly controlled. Windows are the main source of such gain. A relatively simple solution is the installation of solar film on the windows, which admits daylight and beneficial solar gains but reflects a lot of heat away, helping to reduce the need for air conditioning in summer.
However, the refurbishment of Elizabeth II Court, the head office of Hampshire County Council in Winchester – which included the façade being reclad in timber/aluminium composite cladding with brick on the outer façades to balance daylight, solar gain and airtightness – is an example of a more comprehensive solution.
When the 1960s office block was refurbished a natural ventilation system was also installed. Such systems lessen the need for mechanical air conditioning. The building now relies, in the main, on a natural wind-driven ventilation system, which incorporates ducts to draw air out and wind troughs at the top to create suction. At night during the summer the building is also ventilated using automated opening windows.
Overall, the retrofit, which was completed in 2009, has delivered a 70% reduction in energy use compared with the former building.
Overhauling HVAC systems is the most expensive type of retrofit to perform, but updating such systems can result in large energy savings.
Ideal world
A report last year from the Centre for Low-Carbon Futures, which examined the retrofit challenge facing the UK, concluded that the diversity of the country’s building stock in terms of age, use, materials, build type and quality, thermal mass, location, orientation and occupancy means that there is no “one size fits all” solution to effective retrofit. It also noted that retrofitting for energy performance is “always a balance between benefits and costs”.
Indeed, refurbishing existing buildings to a level of performance comparable with that of new low-carbon buildings might be prohibitively expensive. And, as only around one-third of the commercial property market is owner-occupied, tenants are unlikely to want to invest if landlords are unwilling to fund even low-cost measures when the benefits may be long term.
That is why the green deal scheme (see below) and the government’s plans to require all privately rented properties, including commercial buildings, to be brought up to a minimum energy efficiency standard – likely to be set at EPC rating E – by 2018 could hold the key to the wider adoption of low-carbon retrofit.
Empire state building
One of the world’s iconic buildings, the Empire State Building in New York, is undergoing a $20 million energy retrofit. When it is completed in 2013, the refurbishment will help reduce total annual energy use from the 443-metre-tall building by 38.4%, and cut energy bills by $4.4 million a year – meaning the investment will pay for itself in just three years. And, by 2025, it will have saved an estimated 105,000 tonnes of CO2.
“The success of the Empire State Building is not just millions in annual savings and short-term payback, but that any building owner can now follow this process and reduce its energy costs with advance knowledge about costs and economic return,” comments Anthony Malkin from the Empire State Building Company.
Each of the building’s 6,514 double-paned windows is being refurbished, reusing more than 96% of the existing window glass. The “new” windows, which include the installation of a heat-reflective film and an insulating mixture of gases, are up to four times more efficient at retaining heat and cooling. Beneath each window is a radiator. Each one will have an insulating barrier behind it that reflects 24% more heat back into the building. The radiators are connected to a digital control system to ensure energy consumption is minimal and controllable.
The Empire State Building was completed in 1931 and has four massive chiller units that cool the water providing the building’s air conditioning. Water is piped through the building to fan units, which force air past the chilled water to cool the building.
The retrofit involves installing variable speed drives to the fans and improved controls, resulting in a 5% reduction in overall energy consumption.
Air-handling units on each of the 102 floors cycle air in and out, cooling and ventilating the building. The introduction of variable air volume technology enables the output of the units to match the cooling and ventilating demands of different building spaces.
Every steam valve, pump, louvre, fan and other elements of the building’s HVAC system is linked to one of the world’s largest digitally controlled wireless networks, enabling 24/7 monitoring and control.
More than 20,000 people work in the Empire State Building in addition to the 3.5 million people who visit each year and tenants now have access to a web-based control system that enables them to monitor energy use. Also, every office suite larger than 232 square metres is individually metered, so tenants can manage their own consumption.
NG Bailey
Denton Hall in Yorkshire is the head office and training academy of building services company NG Bailey. The firm acquired the grade II listed building in 1979, and in 2006 it started work on improving its environmental performance.
“The first step was to understand fully how much electricity and heating oil the building was using,” says sustainability manager Colin Robertson. “Then we focused on the low-hanging fruit, such as the lighting and getting people to turn off computers.”
The company also installed wireless sensors and monitoring units to measure energy consumption, and an intranet-connected building management system (BMS) to control heating and lighting. The BMS is programmed in conjunction with the room-booking system, so rooms are only heated when they are (or will be) occupied, and a screen in the reception now displays real-time energy-performance information.
Lighting accounted for up to 60% of the electricity consumption at Denton. The hall has 17 chandeliers containing 344 light bulbs, for example, and NG Bailey had to work with specialist suppliers to replace these with energy-saving alternatives that also met the strict visual controls imposed on the listed building.
The next phase of the retrofit was the installation of 22 solar thermal panels to heat the water. Previously, heating oil accounted for more than 75% of the hall’s energy consumption. Siting the panels – on the ground at the front of the building – had to be carefully planned. The units are naturally camouflaged to comply with listed buildings regulations.
NG Bailey has also installed a biomass boiler at Denton Hall. It is fuelled by woodchips certified as sustainable by the Forest Stewardship Council, and provides heat and hot water.
The green deal
The government’s green deal scheme – which should see the first agreements signed in January 2013 – will enable consumers to install energy-efficiency improvements in their homes and businesses at no up-front cost. Instead, customers will pay back the cost of the improvements through resulting savings in their energy bills.
DECC believes non-domestic customers will be attracted not only by the prospect of not having to pay up-front for measures, but also by reduced fuel costs and the opportunity to demonstrate meeting the obligations of the Carbon Reduction Commitment Energy Efficiency scheme. The department says the green deal is likely to appeal to organisations that consume significant amounts of energy from air conditioning and computers, for example, rather than energy-intensive businesses.
The green deal process begins with an assessment. It will make recommendations for energy-efficiency improvements at a property and predict the likely energy savings were the improvements to be installed.
The assessment method for commercial buildings will build on the existing SBEM (simplified building energy model) methodology for producing energy performance certificates for non-dwellings; however, it will also allow the actual use of the building to be captured as part of the process, enabling the assessment to produce more accurate predictions of the likely energy savings.
DECC says that it expects green deals in the non-domestic sector to be shorter, to reflect payback in line with lease length. Under the plans, tenants will not be able to attach a green deal to a rental property without the consent of their landlord, while a the landlord will need to gain the consent of a sitting tenant in order to attach the green deal charge to their electricity bill.
Although there is theoretically no limit on the amount that can be borrowed to fund a green deal, any improvements must comply with the so-called “golden rule”, which states that the cost of the improvements must be paid for with the savings the improvements make. So, if the estimated annual saving is expected to be equal to or greater than the expected annual repayment costs, the deal will meet the golden rule and can go ahead.
