Client Asking For An Outdoor Fire?

Rob Smith of Rivelin explains the pros and cons of the various fuel types.

Outdoor fires have been rising in popularity in the UK thanks to home-improvement shows on TV, but credit must also be given to our American cousins, for whom outdoor fires have been part of the culture for decades.

They are available  in various shapes and sizes and can vary in price from tens of pounds to  thousands of pounds.  Currently outdoor fires can be split into 3 categories based on the fuel they burn:

  • Solid fuel – generally Wood
  • Bioethanol –Liquid or gel
  • Gas -LPG or Natural gas

Solid Fuel Fires – Solid fuel fires are the most common and cheapest outdoor fire to get hold of. Any fire which runs on wood, charcoal, briquettes or biomass would be categorised as solid fuel. Solid fuel fires are incredibly flexible and a quick trip to any garden centre or search on the internet will reveal hundreds of options.

Most outdoor fire pits sold run on wood and  are simply dropped into place requiring  no installation expertise. Although  ease of  installation is an obvious benefit, this must be balanced  with the  smell and smoke  produced  by the  fire, the  inconvenience of  building the  fire and its maintenance once  lit. In addition, once you’ve  put out  the  fire and you retire,  there’s  the lingering smell of smoke on your clothes and  hair never  mind  the bed  clothes  in the  morning.   If cost is the deciding factor then a solid fuel fire has to be the  front runner.

Bioethanol Fires – These are  a more recent entrant to the outdoor fires market. Bioethanol is alcohol which has been produced using the by-products of sugar beet and other foods. The only by-products of the fire are water vapour and  carbon dioxide, making the fuel very  friendly  to the environment.

Unfortunately, most bioethanol fires are for decoration only with limited heat output of a few kw’s. With approx 6.7kw of energy per litre of bio-ethanol,  a fire manufacturers claimed  heat output and burn duration can be quickly verified. If a fire claims to have a 9kw output and a 2 litre tank,  then it will run for approx 1.5 hrs before it needs refilling. All bio-ethanol fires require around 0.5hr’s  or more to cool down before refilling. The advantages of bio-ethanol fires are that they are dropped into place often requiring no installation requirements and unlike wood fires they don’t smell. The disadvantages are limited heat output, they require  refilling often, and generally have a lack of control over the flame size  in addition to relatively high fuel costs.

Gas Fires – Outdoor gas fires can be fuelled  by LPG  or Natural gas. We are all familiar with LPG  from using a gas fired BBQ.   Which gas one selects, depends on the installation circumstances.

If a mobile unit is required, then LPG  is the most likely candidate. In this case,  the key question is where will the gas bottle be located. In the USA, gas bottles are often stored horizontally  inside the unit allowing units  below 50cm in height to be manufactured. Here in Europe we have to by law stand gas bottles vertically when the LPG is used as a gas and not as a liquid; as in the case of a forklift. The smaller the gas bottle,  the lower the recommended Kw off take before the valve can potentially freeze.  LPG has around 13.6kw of energy per kg so a 6kg bottle; which has a recommended off take of 10kw ; will last around 8hrs at 10kws.

One can quickly see that the inevitable conclusion is that here in Europe mobile units with gas bottles contained within  its structure, will have a limited heat output. To achieve  the typical 18kw (60,000btus) associated  with a gas fire pit which is to be used for heat, requires a larger gas bottle  of 19kg or greater. These stand around 800mm and cannot fit underneath a product so have to be located away from the gas  fire. Flexible rubber pipes can be used for short runs where is it visible  or permanent hard piping can be  installed beneath the  deck or patio  for a cleaner look. If a permanent installation is the preferred option then Natural Gas can also be considered.

LPG has more installation considerations than Natural Gas  because it is heavier than air, in addition  it is also generally more expensive p/kw than Natural Gas but cheaper than bio-ethanol. If you are considering a  gas fired unit , ensure that  it is  a CE approved unit. Most imported American units aren’t CE approved  and aren’t legal here in the UK.  Gas fires should be serviced annually so  make sure spare parts are easily available and ask about the build  quality.

The advantages of gas powered outdoor fires are that they can be  clean burning with no smell, instant heat with  no preparation,  no cleaning out,  completely controllable with manual or remote ignition,   heat outputs of 18kw and greater and can be instantly turned off. The disadvantages are that mobile units with contained gas bottles tend to have relatively low heat outputs and   higher Kw output units require a larger gas bottle which needs hiding or a commitment to a permanent gas pipe.  This commitment to a permanent installation obviously adds to the cost the job and should be considered before the patio is laid.

Outdoor fires are a great way to add drama to a garden and with something available for every budget,  there’s no excuse  to not include fire in your next project.

About Rivelin – Rivelin are based in Sheffield and design and build outdoor gas fire tables and fire bowls for architects, landscapers and garden designers. These fires have been installed in gardens and penthouses from Cornwall to John O Groat’s and have been exported throughout Europe and further afield.