How is the tried and tested gas-fired boiler faring against the green wave of renewables? Andrew Brister says don’t write off this humble servant just yet.
Biomass, Heat Pumps, solar thermal, CHP...the market for traditional boilers is certainly under attack. The Government has put carrots in place, such as the Renewable Heat Incentive, that are changing the status quo, with most of the major boiler manufacturers expanding their product portfolios to include renewable energy technologies.

It would be premature to write off the humble gas-fired traditional boiler, however. Industry commentators argue that commercial boilers still have a key role to play in cutting carbon emissions. 'While renewables and microgeneration technologies will take an increasingly large share of the market in the coming years, boilers will still be relied on to provide the lion's share of commercial heating,' says Dave Lacey, commercial director (UK & Ireland) at Vaillant. 'This will be particularly apparent in areas where the market is strong, such as in schools and retail properties.'

It's worth remembering also that the drive to reduce carbon emissions is not just about new building stock and many refurbishments may not lend themselves to installation of renewable heating. 'We need to make good old buildings, not just build new,' says Mark Northcott, managing director at Remeha Commercial. 'There's no denying that renewable technologies are great headline hitters. Yet, while the Government encourages take-up of this emerging sector for new build projects, the Building Research Establishment reports that 60 per cent of the buildings that will be standing in 2050 are already built and 40 per cent predate 1985 (the year that Building Regulations concerning fuel and power were first introduced under Part L).

'So if the UK is to come anywhere near meeting the Government's target of reducing greenhouse gas emissions by 34 per cent by 2020 and 80 per cent by 2050, it is vital that we look at simple energy efficiency improvements to our existing building services.'

Many in the heating industry believe that the integration of traditional and renewables technology will be paramount. 'There are situations when the most energy-efficient solution may be to combine biomass and conventional boilers to give the highest overall efficiency, in relation to the way the building is used and the demands it makes on its heating systems,' says Adrian Walker, managing director at Hoval. 'An obvious example would be where the biomass boiler meets a constant load and is then 'topped up' by a condensing boiler as and when required.

Effective integration and control

'In many projects, such solutions may also be combined with heat pumps and/or solar thermal systems, so effective integration and control of heat sources becomes paramount in delivering optimum efficiency for the end client,' he continues. 'Therefore, specifiers and installers need to understand which heating technologies will work well together in a controllable fashion, in the context of the project, and ensure they have access to the specialist expertise that is needed to ensure the best performance.'

Mark Northcott agrees, arguing that the new low carbon technology is very dependent on existing technology. 'We anticipate a 50/50 split, not putting the entire load onto the biomass, heat pumps or solar but using the gas boiler as a back-up.'

Others would say a 50/50 split is a conservative estimate: 'For forward-thinking installers with a long term eye on business expansion, commercial boilers, whilst still a reliable source of heating, may soon have their market share overtaken by renewables,' comments Mike Southall, director of business development for Buderus. 'As fuel costs continue to increase and a greater awareness of environmental issues now resounding at board level, there is every possibility that the drive to sustainability will continue to grow apace. It would be safe to say that whilst boilers may be a reliable asset in the short term, the industry's future lies with renewables,' he argues.

When you are using a conventional gas-fired boiler, an effective controls strategy can dramatically improve performance. 'Manufacturers have been working hard to ensure that their boilers are as efficient as possible, not only to assist specifiers in meeting the requirements of Part L2 of the Building Regulations but to also help reduce the impact of the Government's CRC Energy Efficiency Scheme, which can be a real burden for commercial and public sector organisations,' says Alister Maclachlan, product director at Vokèra.

'Many commercial boiler manufacturers have realised the importance of advanced controls, which improve efficiencies by making heating systems more responsive to the end user's needs,' says Maclachlan. Weather compensation technology, for example, has now become a standard feature in many commercial boilers. With these controls the boiler responds to external factors and temperatures, providing an accurate measure of how warm the internal environment needs to be.'

Get controls strategy spot on

Dave Lacey of Vaillant also stresses this point: 'It is imperative that we continue to make our commercial boilers as efficient as possible and, when they are working in tandem with renewables, to get the configuration and controls strategy spot on. Condensing boilers will only achieve their maximum efficiency in situ if the flow and return temperatures are closely controlled. This is why weather compensation control is being included in more of today's designs, in order to keep systems in condensing mode for longer without compromising on comfort.'

Paul Hardy, managing director of Baxi's Commercial Division, believes a major change in the way the supply chain is structured is urgently required if the industry is to be able to deliver the massive programme of heating retrofits envisaged. 'Our current supply chain remains rooted in the Victorian era when it was first established,' he says. 'So much has changed in the decades since, in terms of technology and building design, but the method for delivering projects remains stubbornly hierarchical and linear. To meet 21st century sustainable standards we need a new fit-for-purpose supply chain that is inclusive and team-based.'

Hardy calls for greater involvement of manufacturers in the design and integration of carbon-reducing technologies to create a more sustainable built environment. 'Much of today's specialist knowledge now resides with manufacturers and the Government's new construction strategy places a real responsibility on all members of the supply chain to unlock that expertise,' he says.

'The big challenge facing us is refurbishment, which also requires the industry to adopt new approaches. We have to refurbish at least 60 per cent of our entire building stock over the next 40 years - nothing on the same scale has been attempted since the Second World War,' adds Hardy. 'To deliver such a massive programme, we need everyone working hand-in-hand and we cannot afford to be delayed by the old inefficiencies and legal disputes created by out-dated ways of working.'

Most h&v contractors will say amen to that.

Tackling boiler dry cycling

As heating systems become more efficient and the building fabric is improved to minimise heat loss, base heat loads are reduced and the boilers may be required to fire less frequently. 'This can have the effect of increasing boiler dry cycling or short cycling- resulting in unnecessary energy consumption and carbon emissions,' says Tony Willis, technical sales director at Sabien Technology.

All boilers can suffer from standing heat losses ie, the boiler cools down below the current set point of the boiler's internal thermostat / load control. When this happens, the boiler may fire simply to recover the temperature of the wasted heat - even though this energy is not being used to meet the current demand for heat from the building. And the majority of building management systems (BMS) are not typically configured to prevent boiler dry cycling by individual boiler because they may measure blended temperatures across all boilers.

'In our experience, the energy wastage caused by boiler dry cycling ranges from 10 to 25 per cent, depending on individual site conditions and loads,' says Willis. 'Any control of boiler dry cycling must be established without lowering or changing set-point temperatures, as this will compromise comfort or conflict with existing controls,' he continues. 'Early attempts to tackle boiler dry cycling did not address these criteria but the newly-developed adaptive software in our M2G units do. This is because they constantly monitor the boiler's thermal response to changing loads in real time, calculating the temperature decay over time and determining when the boiler should fire and when firing should be inhibited.'

Crucially, the boiler set point has to be reached before these calculations can be made, so this technology cannot and will not change the set point. This ensures that it works in harmony with the BMS and other existing controls, such as weather compensation, rather than causing conflicts.