Is gas still the best choice for home heating?

Blazing summer might not seem the best time to consider space heating, but for selfbuilders warmer weather can make a considered view a lot easier than when wintry beasts from the east are raging outside.

Britons, after all, have become chillier mortals over the past couple of generations. In the 1970s the average expectation of internal comfort was a balmy 12°C. Today, it’s 17°C, with main living areas at around 21°C.

But that’s come at a price. Space heating uses up to 60 per cent of our average domestic energy usage, while hot water takes up another 18 per cent. At the time of writing British Gas, EDF and E.On have just raised their prices by averages of 1.4 to five per cent and it won’t be a surprise if the rest of the ‘big six’ energy suppliers follow suit.

The better news is that bills would be even higher if the past half century hadn’t seen the introduction of a range of energy efficiency measures, largely dictated by the Building Regulations. They include double glazing, much increased home insulation and high-performance central heating boilers, though it’s the latter, arguably, which has benefitted from the most development.

Seventy per cent of British homes are now heated by gas – a choice initially prompted by the 1956 Clean Air Act which banned the smog-producing coal that had previously kept most home fires burning.

The discovery of cheap North Sea natural gas in the mid-1960s only added to its appeal, and made it the obvious fuel of choice for domestic central heating when it took off in the 1970s.

Boilers then were relatively straightforward in design. Gas entered at the bottom, was atomised into fine droplets and ignited by electrodes, achieving temperatures of between 250°C and 350°C. The burning gas rose through a heat exchanger made of cast iron or steel, heating water-filled pipes as it went, and exited via the flue close to the combustion temperature.

The design was simple, reliable and easy to install. But it wasted a lot of energy to the open air.

So-called ‘energy-efficient’ or ‘condensing’ boilers tackled this problem from the 1980s onwards. These extract more energy by using either larger or secondary heat exchangers.

The exhaust fumes pass over pipework containing cooler water returning from the central heating system. This causes steam in the burning gas to condense out, releasing latent heat which raises the temperature of the water before it reaches the main heat exchanger. As a result less energy is needed to heat the water fully.

Condensing boilers can now achieve efficiencies of up to 92 per cent, 20 to 30 per cent higher than conventional boilers. But it took a change in the Building Regulations in 2005 requiring all new installations to be condensing boilers to give them market dominance.

Unpopular

It wasn’t a universally popular decision. At the time condensing boilers were considerably dearer than the conventional variety and, due to their complexity, generally less reliable or durable. It also wasn’t widely known that the condensing mode only operated when the temperature of the water returning to the boiler was at around 55 °C.

In fact return flow temperatures in most homes are closer to 70°C. The cooler returns are only regularly achieved with low-temperature underfloor heating or systems using deliberately oversized radiators. The boiler was still more efficient than its predecessors, but not dramatically so.

Today reliability has improved and prices, in relative terms, are lower. Durability, however, is less certain. But improvements have come in other ways, mainly through external controls.

Many of these are neatly summarised in new regulations, known as Boiler Plus, introduced in England this April.

“Gas could be the most sensible long-term choice for your future home.”

Newly installed gas boilers must now be fitted with an independent time control, a room thermostat and thermostatic control valves (TRVs) on radiators – features most of us would regard as standard. However, combination boilers – the UK’s most popular – must also have at least one of the following:

• weather compensation via an external sensor which varies the boiler’s output as conditions change;

• load compensation, which does the same internally;

• a smart thermostat, which automatically learns your heating habits and optimises your system; and

• flue gas heat recovery (FGHR).

Doesn’t a condensing boiler have the latter anyway? Yes, it does but FGHR devices, which sit on top of the existing flue, claim to extract another seven per cent of efficiency. Their high cost, however, only makes them economic for upgrading existing conventional boilers.

Super-efficient or not, gas boilers are still cheaper to buy and run than those using oil, LPG or sustainable alternatives such as biomass or ground and air source heat pumps. But as natural gas prices continue to rise how long can that last? Is gas still the best choice for a ‘forever’ home?

Sustainable power sources produce ‘free’ electricity from wind and sunlight, but unpredictably. Until battery power can store it cheaply and easily, it can’t undercut gas.

There is, however, an alternative, as a recent study carried out in Leeds by Northern Gas Networks established. And that’s to use hydrogen which is abundant, clean, more powerful than petrol and produces no harmful emissions.

The H21 Leeds City Gate project found that the existing natural gas infrastructure could easily be adapted to distribute hydrogen throughout the city, and local production could be economically viable.

To use hydrogen, boilers and cookers would also have to be adapted, but these appliances underwent similar changes, very successfully, in the 1960s when natural gas replaced coal gas.

In an uncertain world gas could be the most sensible long-term choice for your future home.

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