Log Burning Boilers or Wood Pellet Boilers?

If you are considering “biomass” as a heating system the most obvious choices are between log burning boilers and wood pellet boilers.

For some the clear advantages of log boilers are:

  1. Cost of installation
  2. Cost of fuel
  3. Sustainable use of wood

For others the clear advantages of pellets are:

  1. Automation of heating
  2. Higher efficiency
  3. Pellets are a waste product
  4. Space saving

Cost of Boiler

Log boilers such as the WBS active are MCS accredited and burn wood up to 90% efficiency. The boilers start at at a little over £1000 (20kW WBS) and this is a lot cheaper than the Pelleburn wood pellet boiler that starts at £3500.

Cost of Extra Water Heating

Wood pellet boilers modulate. This means that they can adjust to produce the  amount of hot water that you need to store for heating. Log boilers need to heat water when they are burning otherwise there is nowhere for the heat to go. This is often in the range of 30-50l per kW.

For instance a 20kW log boiler will need to heat 600-1000l of hot water.

You could choose an accumulation tank or a thermal store to do this.

An accumulation tank or “buffer store” can used to store the heat. They are well insulated and once heated can distribute the heat without the need for the boiler to be “on”. A 1000l buffer store is nearly 1 meter diameter by 2 meters tall. This does mean that you need to find space for this. The buffer store will be an extra £1000+ and there are extra plumbing costs in installation.

A thermal store can incorporate a hot water tank and heating hot water in one tank. A “tank in tank”. Assuming you need hot water for baths and showers, then you will need a hot water tank. Some houses already have these, some do not. Others are old and need replacing. A thermal store is a good solution if there is a need for a new hot water tank.

Wood pellet boilers do also benefit from the use of accumulation however they can burn efficiently for shorter periods of time and so need less water to heat. On smaller systems it is possible to work without one, however your boiler may need to come on more often. Using an accumulation tank may prolong the life of your parts.

In summary – log boilers need more accumulation than pellet boilers, and this will increase costs of installation. This will vary depending on the installation.

Space Needs

Wood pellet boilers that are completely automated generally infers a large pellet store that can be filled. This can take up a lot of space e.g. 10m3. This has to be dry and purpose built. Whilst there are pellet stores that can be outside for most homes the choice is between a top loading boiler (ie no storage) e.g. an MCZ Musa , an indoor pellet hopper e.g. Pelleburn or a purpose built hopper. This means that the storage needed varies in size depending on the location and budget. For those tight on space a 1.5m by 1m space is generally more than enough.

For logs the space is larger for the smallest boilers. The boiler is larger, needs more space for a larger flue, and accumulation tank. This is typically 2.5m2

Cost of Fuel

Often the most immediately available fuel is more expensive on the internet. Pellets do range in price, but are frequently £200 per tonne or 4.5p per kWh. (Oil prices were 65p per liter (6.5p per kwh in March and are currently 53p per liter, 5.3p per kWh)

Logs vary more in price and this also varies considerably regionally. For those with a ready supply there is the cost of cutting logs ie your time, or alternatively you can get fuel delivered often at £90-100 per tonne 

This makes the cost of logs about half the price of pellets.

Efficiency and Sustainability

A WBS log boiler can be 90% efficient and a pelleburn pellet boiler can be 94% efficient. Some of the efficiency difference can be put down to pellets being dryer and only pulp, ie no bark.

If your logs are from your immediate surroundings then there is no transport or significant processing costs. In addition some pellets have been artificially dried. Whilst not significant, pellets are transported and there is a manufacturing cost that involves drying wood pulp.

If your logs are the result of forestry or woodland management and the wood is offcuts ie cannot be used for other things, then it is sustainable. This is also true for pellets e.g. if as part of making paper there is sawdust and pulp left over then this waste product can make pellets.

There is a strong argument for logs in terms of sustainability and transport. Unfortunately this does not work for many people due to the availability of local woodland management for our homes and logs are not economic to transport.

Renewable Heat Incentive

Currently the non domestic Renewable Heat Incentive pays the same incentive for log boilers as pellet boilers.

A 30kW log boiler May get RHI payments of  30 (Size of boiler) X 8.3 (higher tariff) X 1314 hours = £3271 per annum.

For an installation of logs or pellets costing between £7-10,000 this would payback in under 3 years before you take into consideration the lower cost of fuel.

A Possible Compromise

If you are finding it difficult to decide whether you want logs or pellets. For many the logs do appeal but there is the extra work involved and will you be happy doing this?

The WBS range of log boilers all come ready to fit a pellet burner ie you can convert your boiler over at a later stage. The pp and pelle ranges of burner are easy to fit and with some minor adjustments to your settings you can be burning pellets.

For more information do get in touch with us using the form on the right hand side or by phoning 01225 580 401

Training and Development

In between our daily workloads we have been busy developing our know how.

On Friday 4 of us will be training with Solar Focus in Oxfordshire as part of our installer partner relationship.

Next week Mark will be training with EDS to develop his knowledge of solar thermal systems.

Early in Feb Adrian will be trained to install solar pv systems.

Last week I was in Bulgaria with Sunsystem for the second time, and this time being trained on their biomass products.

This has meant that Renewable Living will be developing what it does. We do work closely with Green Phoenix and will now be installing solar thermal and solar pv products for them in this area.

Ecobuild was booked a little while ago and we are helping Sunsystem develop the UK market for their appliances. Solar thermal, Solar PV, accumulator tanks, wood pellet boilers and wood boilers. There will be a separate website that showcases what products will be available in the UK. Again working with Green Phoenix (see new products on their site) to provide the expertise around solar, we are enjoying a very busy period at the moment.

Wood Pellet Boiler Installations – Some General Rules

As part of our service we assess requirements and properties to help you choose the right system or boiler for your heating and lifestyle choices. This post is all about Wood Pellet Boiler Installations.

For this we asked Tom Jacques, an architect and RIBA Client Adviser based in the South West for some comments.

Tom responded with 3 articles the third of which is below.

Part 3 General rules about wood pellet heating

Rule 1 – Most estimates on websites are unreliable

As the complexity of the system selected increases, the parts and the labour go up in price significantly. However the maintenance levels go down and the efficiency of the system goes up.

Expensive parts do include the pellet boiler which ranges in price from £3000 to £17,000 but also:

The flue – this can cost between £750 and £2000

Accumulation or climate control – between £850 and £2000

Pellet Store – You can use the integrated hopper that will last you a few days at peak load. Otherwise there are several options. A steel hopper may cost between £2000-£3000, as may a flexible liner in steel frame.

Pump sets and other plumbing equipment are also needed, especially if you have several heating circuits.

The labour charge varies from a few days to a couple of weeks depending on the design of the heating system proposed. This may be in the range of £1500 to £6000 with plumbing supplies (e.g. copper pipe) being extra.

Rule 2 – Everyone is an expert

We accept that the market is relatively new. Whilst most MCS accredited installers are very good and knowledgeable we have found that people’s knowledge varies. This includes consultants, other technologies, advice centres, builders, architects etc

If you have a budget and know what you want, do invite several companies to quote. Any risks that there may be can be identified and ironed out.

Rule 3 – Do the sums

We often suggest biomass as we think it has great potential as an alternative to oil and Lpg, particularly where heat loads are higher. Occasionally other solutions, including ground source heat pumps, air source heat pumps, solar thermal, and electrical generation and output devices may be preferable, or used in combination, and should also be considered.

All renewable technologies have the benefit of being able to have MCS accreditation. As such when your house is assessed, they should tell you how much heat you can get from their system, how much it will cost to install and run. It is then a fairly simple process of firstly doing the sums and then secondly having a feel about which technology you like best and works in your situation.

Key considerations for “doing the sums” are to:

  • Understand your own heating needs. What heat did you use last year? For instance if you used 2000 litres of oil you burnt about 20,000 kWhs of energy. At 60p a litre this is £1200. This costs 6p per kWh
  • Get a price for the equipment and installation along with the output or performance, probably in kWs.
  • Understand how the equipment works at its best and its worst so that you can get an idea of operating costs. ie. how many tonnes of pellets do I need to burn? Pellets often release 4800 kWhs per tonne. In the above example this would be approximately 4.2 Tonnes of pellets. This gives a fuel bill of about £800 and a saving of £400. This costs 4p per kWh

For Heat pumps understand the co-efficient of performance (COP). For instance a heat pump will perform differently based on:

The type e.g. Air Source heat pump or Ground source heat pump,

The job it is being asked to do e.g heating water to 60 degrees C

The temperature of the air or ground where the heat exchange is taking place, and maintaining optimum performance.

Each kWh of “free energy” needs electricity to power the heat pump. If the COP is 2:1 then you get 2 units of heat for 1 unit of electricity.

A recent study of heat pumps in 2010 – “Getting-warmer-a-field-trial-of-heat-pumps” by the Energy Savings Trust suggested that the COP or Coefficient of Performance for heat pumps varied between 1.2 and 3.6 with a mid range of 2.2 for ASHP and 2.3-2.5 for GSHP. If electricity is 15p a kWh (then you would be paying between 12.5p and 4.2p per kWh with the majority of outcomes being between 6 and 6.8p per kWh ie a total bill of about £1200. Clearly if you had a PV installation with spare capacity or a “special” rate then you can reduce this cost.

Similarly, if the electricity is obtained through the mains, system losses will be taken into account in any calculation of carbon consumption and overall efficiency.

With the Renewable Heat Incentive, the rates for non domestic RHI have been published and this gives you an idea of the possible rates for domestic RHI in the future. Biomass is 7.9p a kWh, Solar 8.5p, and GSHP 4.5p. For 20,000 kWh’s of heat biomass wood pellets would gain nearly £1600 per annum for 20 years.

Rule 4 – The price of fuel will go up in price

Unfortunately we are in a volatile period for prices. Electricity, gas and oil are likely to keep going up in price. No one really knows by how much. There is greater demand for a diminishing world supply, resulting in a shortfall in the amount of energy to go around. In general oil and gas go up in price when you need it most.

Wood pellets are being made all over the country and there are more pellet suppliers than there are electricity providers (or gas and oil producers). This means it is a more competitive market which is likely to remain price sensitive for some time to come. Clearly there is a potential limit for how many wood pellets can be produced. The main constraint is the supply of raw material either sawdust or recycled wood. Many providers have fixed their prices to give confidence in the industry and it is very unlikely that you will get a monopoly in the same way as other forms of fuel. Still, it is likely to make more sense to order when demand is lowest.

For a good idea of relatively up to date price comparisons do click here

Rule 5 – Simple is best

With all the above points there is a tendency to get confused or wedded to a particular solution which may prove inappropriate, or to get consumed by too much detail at an early stage. Do take advantage of your home as it is. If you are combining alterations with an extension, consider how best use can be made of each element, and what can be best located where. Do ensure that you minimise heat loss as this is usually the most cost effective intervention which can be made. For systems installed do consider carefully how you will use and maintain the buildings and systems installed, for example the trade off between filling a hopper once or twice a week against once or twice a year (and the increase in costs that will result). Do use existing chimneys where possible as this will decrease your costs.

If biomass forms part of your solution, some of the choices you will make will be substantial and make a difference to the costs and effectiveness of the system. Other choices will be a bit like choosing a car. Once you have narrowed down the options by essential criteria, the remaining options will largely do the same job, but preferences can lead to significant price differences even within a model.

Installation costs are normally quite similar between companies for the same job, (it is worth getting alternative quotations to verify this), but the more complex the system, the higher the installation costs.

Tom Jacques

Tom Jacques is an architect and RIBA Client Adviser based in the South West.

Alongside interpreting,defining and meeting clients spatial and aesthetic requirements, Tom prioritises environmental design alongside an understanding of building physics, the use of appropriate technology, and the performance of buildings and their systems in use.

He embraces different approaches in different circumstances, and works where possible with specialists in their fields. Many of his projects involve work with listed buildings and in sensitive settings, and where planning and listed buildings consent is required.

He is not a specialist in any particular product or technology, nor a building services engineer, but is able to offer advice and assistance on projects where required.

If you wish to contact Tom, please contact us and we will pass your comments on to him.

Wood Pellet Heating and The Home Owner

Part 2 – Assessing the issues to be considered by the home owner when choosing wood pellet heating

As part of our service we assess requirements and properties to help you choose the right system or boiler for your heating and lifestyle choices.

For this we asked Tom Jacques, an architect and RIBA Client Adviser based in the South West for some comments.

Tom responded with 3 articles the second of which is below.

1.Do you want your pellet boiler to be a feature or hidden away? Some boilers are designed to be part of the living space. Many of these are Italian. For instance MCZ use ceramic, marble and metallic styling to make their boilers attractive as well as a viewing plate on the flames. It may be more straightforward for these sorts of boiler to take advantage of available chimneys.

2.Do you want a large fuel store that will last at least a month and possibly 1 year? If so you may have to construct a separate fuel store. This will need more space and will increase your costs.

3.Do you want minimum maintenance? You can take advantage of features such as automatic cleaning of the grate and heat exchangers. This will increase costs and probably limit you to a choice of Austrian boilers such as Solarfocus.

4.Do you want Microgeneration Certification Scheme (MCS) accredited boilers and installers? The MCS scheme is about quality. Making sure that boilers are being made and installed properly. The scheme is government supported and gives access to government support.

5.Do you want access to grants or incentives? The government have introduced a Renewable Premium Payment scheme of £950 for biomass. The Renewable Heat Incentive or similar scheme is expected to be introduced for non domestic buildings in November/December 2011. The domestic RHI is expected to be late Summer/Autumn 2012. If you want to be informed about the scheme, use the contact form and receive updates.

6.Do boilers have different running costs? Each boiler has a different efficiency rating. For instance MCZ boilers are 90-93 percent efficient. Solarfocus boilers are up to 96.8 percent efficient. This is more efficient than a wood burner at between 75 and 85 percent efficient. A buffer or accumulator tank to iron out the peaks and troughs of heating and save fuel is often recommended, alternatively weather compensation may fulfil a similar function.

7.How do you choose wood pellets? Local supply should decrease costs of delivery. Do look at the latest lab reports that the pellet supplier has undertaken, alternatively they may have signed up to a quality assurance scheme operated by Hetas or Woodsure. Some pellets are made as a by product of waste and some from virgin wood. Pellets are much better quality than a few years ago. Your boiler may need to be cleaned by your installer, and in the worst cases it can stop working if pellets are of poor quality. Prices of pellets vary by size of load, distance of delivery, and method of delivery. This could be a lorry “blowing” pellets into a fuel store or a pallet of bags. Current prices are cheaper than oil by about 20p a litre and cheaper than gas by about 0.7p a kWh.

Tom Jacques

Tom Jacques is an architect and RIBA Client Adviser based in the South West.

Alongside interpreting,defining and meeting clients spatial and aesthetic requirements, Tom prioritises environmental design alongside an understanding of building physics, the use of appropriate technology, and the performance of buildings and their systems in use.

He embraces different approaches in different circumstances, and works where possible with specialists in their fields. Many of his projects involve work with listed buildings and in sensitive settings, and where planning and listed buildings consent is required.

He is not a specialist in any particular product or technology, nor a building services engineer, but is able to offer advice and assistance on projects where required.

If you wish to contact Tom, please contact us and we will pass your comments on to him.

Assessing a House for Wood Pellet Heating

Assessing a House for Wood Pellet Heating is a part of our service where we assess requirements, and properties, to help you choose the right system or boiler for your heating and lifestyle choices.

For this we asked Tom Jacques, an architect and RIBA Client Adviser based in the South West for some comments.

Tom responded with 3 articles the first of which is below.

Part 1   Assessing a House and its location for wood pellet heating

Many houses can benefit from wood pellet heating, but before you can install you do have to consider:

1.Is the house listed, in a conservation area, or smokeless zone? If so there are limitations placed on you. E.g.

  • You may have to consider Listed building Consent for flues or internal alterations
  • You may have to “hide” the flue, use an existing building for your fuel store or seek planning consent
  • There is a more limited list of boilers to choose from

2.Is there reasonable access for pellets to be delivered?

  • Some deliveries are “blown” through a tube to a maximum of 20m from the lorry.
  • Other deliveries are in 1 tonne bags which are moved by pellet truck.
  • Alternatively you can have 15kg bags (67 make up 1 tonne, and this is more expensive)

3.Has the house got a chimney which you think could be used?

  • It will have to be checked, and may need a flexible liner to make it safe.
  • If you have thatch you have to be more careful and you may have to check your plans with your insurance company and building control, but many situations can be dealt with.

4.If you are planning to use the chimney then the boiler should be located nearby, especially if your chimney is in a living area. This will affect which boiler you choose. For instance MCZ produce styled boilers for living areas.

5.If you have no appropriately located or serviceable chimney then you will need a new flue. There are building regulations concerning the construction of these. However as a rough guide you do need to disperse the smoke you produce, and this will need to be on your roof or to roof height. For this reason a back wall can be preferable.

6.Is there room for a fuel store? Fuel stores can be as large as 3 x 3m or smaller at 1.5 x 1.5m. Adjustable in height between 1.5 and 2.2m. They can feed a boiler using a screw feed if it is close, or by suction pump if it is up to 8 metres away.

7.How much heat do you need? You will need to have a survey to confirm your heat need, but you can approximate by calculating the volume of the house and if it is well insulated divide by 30. If it is not, divide by a lower number e.g. 25. A survey uses a version of SAP that looks at both the volume of the house and assesses the fabric of the building e.g. windows, insulation etc. This is then adjusted for temperature using “degree days”, a measure of climate in your area. Typically this between 10 and 20 kW for a 4 bedroom house depending on volume and construction. This then helps you choose the boiler that will do the best job for you.

8.The draw of air into a room with a boiler needs to be sufficient for the boiler to burn. Typically air bricks or vents are used to ensure that this is possible. For this reason “middle” rooms may be problematic as you have no direct access to the fresh air outside.

9.Biomass boilers are heavy, some are also quite large. All boiler manufacturers have specifications and show size and weight of their boilers. You will have to locate a boiler on a hearth. If there is not one it will need to be constructed. We also have to get the boiler into the room so doorways and access is important.

Tom Jacques

Tom Jacques is an architect and RIBA Client Adviser based in the South West.

Alongside interpreting,defining and meeting clients spatial and aesthetic requirements, Tom prioritises environmental design alongside an understanding of building physics, the use of appropriate technology, and the performance of buildings and their systems in use.

He embraces different approaches in different circumstances, and works where possible with specialists in their fields. Many of his projects involve work with listed buildings and in sensitive settings, and where planning and listed buildings consent is required.

He is not a specialist in any particular product or technology, nor a building services engineer, but is able to offer advice and assistance on projects where required.

If you wish to contact Tom, please contact us and we will pass your comments on to him.

Wood Pellets and Solar Thermal?

Do wood pellets and solar thermal work well together as a combination?

The simple answer is “yes” with the home owner taking advantage from both the sun and wood pellets or logs.

The disadvantages are that you have to pay for 2 pieces of heating equipment and for 2 installations. However there are plenty of bonuses.

1 The non domestic Renewable Heat Incentive

(for organisations and district heating)

The non domestic RHI will pay out 7.9p per kWh for small scale biomass and 8.5p per kWh for solar thermal.

The rates being slightly favourable for solar mean that each kW you heat using solar is more beneficial for your heating bills and your incentive tariff from hte government will be  a little higher.

2 The domestic Renewable Heat Incentive

Whilst tariffs are not yet decided it is expected to be similar in parity to the non domestic RHI.

3 During the summer

During the summer it is likely that solar can be the only form of heating/producer of hot water. This means no bills.

4 During the winter

During the winter solar takes the edge off your bills according to how sunny it is.

5 No struggling with heating

Solar can struggle to provide heating. Biomass wood pellets have few limitations in terms of “how much” heat you need.

Both solar and wood pellets provide cheaper fuel. The RHI does pay for the installations. With the non domestic RHI starting at the end of November applications can be made directly to Ofgem for these sorts of combinations.

How much is the non domestic RHI worth for wood pellets and solar?

@ 20,000 kWhs per year (small b&b and 15 kW boiler) – £32,000 over 20 years

@ 30,000 kWhs per year (small public house 23 kW boiler) – £48,000 over 20 years

@ 40,000 kWhs per year (Small office block 30 kW boiler) – £64,000 over 20 years

@ 50,000 kWhs per year (small hotel 38 kW boiler) – £80,000 over 20 years

@ 60,000 kWhs per year (3 homes in a district heating system 45 kW boiler) – £96,000 over 20 years

@ 80,000 kWhs per year (A museum) – £102,000 over 20 years

The RHI will pay for the equipment and installation. You also get the considerable benefit of “no more fossil fuel”.

Price watch on fossil fuels November 2011

Gas prices for Wiltshire are 8.850p for Tier 1 and 4.132p thereafter. This equates to about 4.7p per kWh for the average house.

Oil was 60p a litre or 6p per kWh

Both types are more expensive than Wood pellets at £190 per tonne or 4p per kWh.

Locally made solar panels

Green Phoenix make their own solar panels near Royal Wootton Bassett in Wiltshire. High quality and transparent pricing!

Do I need a hopper for a wood pellet boiler?

Wood pellet boilers use wood pellets for fuel. Wood pellets need 1.65 cubic metres storage per tonne and an average house will need between 4 and 6 tonnes of wood pellets in an average year for heating and hot water.

So the question is, Do I need a hopper for a wood pellet boiler?

The short answer is YES. Every pellet boiler needs a hopper, however many pellet boilers have an internal hopper that can be topped up by an external hopper of fuel store.

For organisations who want automated fuel delivery it is almost certain that you need an external fuel store or large hopper. For homes and smaller units the case is not quite so certain.

The financial case

Wood pellets can be purchased in 10/15 kg bags, 1 tonne bags, or you can blow in fuel into a fuel store.

Prices do vary, however at the time of writing bags can be purchased at £215 per tonne. From the same distributor a blown delivery is £195 per tonne. This £20 difference is reasonably typical.

Therefore for 4-6 tonnes a year you would be paying about £100 extra a year for your fuel unless you were able to get a bulk discount. Many delivery companies will give a discount, but normally when the delivery is more than 4-6 tonnes. e.g. every 10th tonne.

Hoppers and fuel stores do vary in price, however none are less (and certainly at the size needed to store several tonnes of wood pellets) than £1000. The payback on putting in a hopper or fuel store would be at least 10 years.

The convenience case

Wood pellets come in 10-15 kg bags. An internal hopper may be between 40 and 60 kg. During a cold spell this hopper may need refilling once every couple of days with 3 or 4 bags. During milder weather this is once a week.

If you go away pellet boilers do have a frost setting and the fuel can last for 2 weeks.

The convenience case for putting in a fuel store is not having to tip the bags into the hopper, and you would have the facility to go away for longer than 2 weeks during the winter without arranging for someone to go into your house.

Some houses do not have the room for a large pellet store, and many manage perfectly well without an external hopper. Clearly the size and insulation of a property are important. In our experience a large 4 bedroom, well insulated house manages perfectly well without an external fuel store.

A-Z of Wood Pellet Heating

There’s plenty to learn about wood pellet heating, and that’s why we’ve put together this A-Z of Wood Pellet Heating.

A – Automatic ignition

Most wood pellet boilers for domestic use have automatic ignition. This means that when heat is not needed the boiler can turn itself off. It can self ignite when there is a need for heat. These are service items and will wear out over time e.g. 3 years, and are easily replaced during a service visit.

Hoppers that do not have automatic ignition have a low burn or stoking mode where the embers of the pellets are kept alight. This does mean that extra fuel is used, but the benefits may be a cheaper boiler.

A – Ash, Ash chamber and maintenance

All wood pellet boilers produce ash. The smoke containing the ash goes from the pellet burning chamber or bowl through the heat exchangers before being removed through the flue.

With no automation the boiler owner is required to clean the burner bowl every 2-4 weeks and also clean the heat exchangers by rodding or a semi automatic rodding device. The flue also needs ash emptying on a monthly basis and sweeping annually.

Some boilers do contain automation that reduces the need for ash cleaning.

B – Biomass

Biomass is strictly the weight of living biological organisms within an ecosystem. It has been adopted as a collective name for fuel that has been grown e.g. wood, miscanthus, straw, pine nut kernels, palm oil.

For homes wanting the Renewable Heat Incentive biomass alternatives are wood gasification and wood pellet boilers. Larger systems (above 45 kW) that may include a wider variety of fuels will have to be approved by Ofgem.

B – Burn Chamber

A burn chamber is where the pellets are fed and burnt. Some burn chambers are round and some are open. Some are supported by automatic ignition and self cleaning.

C – Carbon Emissions

Carbon dioxide emissions are part of the cause of global warming. Space and water heating in homes makes up 70 percent of all emissions from the home in the UK.  If you are trying to reduce your carbon emissions this is the place to start. Either use less heat or use heat that has been produced from a low carbon source such as wood pellets!

D – Density of Wood Pellets

Wood pellets are very dense as they have been compressed. Compared to wood chip this means that you need less storage (perhaps 3 times) for wood pellets.

You know how many wood pellets you need to buy and what space you need to store. The transport cost is also lower.

D – Dusty wood pellets

Good wood pellets are not dusty. Buying your wood pellets from a trusted source that conforms to wood pellet quality schemes ensures (E.g. Hetas, or Woodsure) that you do not get the increased maintenance problems that may result.

E – Energy of wood pellets

Wood pellets produce about 4800 kW per tonne. If the average house needs 20,000 kWhs a year then 4-5 tonnes of wood pellets will be sufficient.

Heating oil generally delivers 10 kWhs per litre. The same house would need 2000 litres of heating oil.

F – Fuel supply

Wood pellets are an alternative to gas and oil as a fuel to heat a property. Currently wood pellets are cheaper to purchase than either gas or oil and come with the knowledge that there are lower carbon emissions that result.

The fuel is normally supplied in small bags (easy to carry e.g. 10kg or 15 kg), 1 tonne bags, or blown from a lorry into a large hopper or silo.

You can purchase wood pellets from a number of places. The best place to start is often the manufacturer where they will either organise themselves or have a directory of partners that they work through.

Your installer will have good experience of using wood pellets and they may also know how best to organise deliveries.

You can buy pellets at country stores in bags and this ensures that you would not run out.

F – Flue

All wood pellet boilers have a flue to take the gases of combustion out of the building.

Flues can be traditional chimneys from existing fireplaces. These suit attractive boilers such as MCZ or other similar Italian boilers. Your chimney should be checked for suitability with respect to the building regulations. This may mean that a liner has to be installed.

If you have not got an existing chimney or flue it is common to install twin wall flues that probably go on an outside wall and up to above the height of the eves. Internal flues can also be installed, but will need additional measures to ensure that they are not near to any combustible materials.

The flue needs to be sited so that it does not blow emissions through a neighbours window – and that it is sufficiently high to create enough draught to take the gases away from the boiler. A height of 4.5m is recommended as a minimum unless a suitable calculation can be provided.

G – Grants 

Wood pellets are a renewable and low carbon fuel. Increased adoption of them will help the UK to reduce its carbon emissions and reduce the UK’s impact on global warming.

The Renewable Heat Incentive is an incentive rather than a grant and is a payment based on heat need per annum rather than a grant to install. For further information please see our RHI page.

For domestic installations the government has introduce Renewable Premium Payments. This will be £950 for wood pellets and available for installations until March 31 2012.

H – Heat Exchange

When pellets burn they create heat. This is circulated within the boiler through tubes (which may be self cleaning) that in turn heat water that is circulating.

Heat exchange is used to provide heat to rooms through radiators or underfloor heating.

Heat exchange is used to make domestic hot water through passing the hot water from the boiler through a tube running through a hot water tank. This tube heats the water in the hot water tank.

H – Hetas

Hetas is the solid fuel body and an accredited assessor for MCS accreditation and competent installers.

“Competent” installers should have been through training to install and had an inspection of an installation.

Many installers will therefore refer to their Hetas training and accreditation in the form of a badge on their van or paperwork.

It should be noted that Hetas are not the only source of training and accreditation. There are a number of MCS accreditation bodies who each have their own competent person scheme. Details are currently emerging (October 2011) as to what these are.

If in doubt do ask your installer.

H – Hopper

A hopper is used to store wood pellets. This may be internally ie part of the boiler, or externally as a separate fuel store.

If you are tight for space then a boiler with an internal hopper may be for you. You would have to manually feed pellets into the hopper probably 2 or 3 times a week when it is really cold.

If you have lots of space you can have a large fuel store and benefit from bulk discounts and hand feeding your boiler. Your installation costs will be higher.

I – Ignition

A traditional biomass boilers might be a wood boiler with a back burner. This is lit with matches and either paper or similar fire starting catalyst.

Most multi-fuel and wood boilers also use this method.

Many wood pellet boilers have automatic ignition linked to a thermostat or boiler programme. This saves you time and inconvenience.

 J – Building Regulations Part J

Any installation of a wood pellet boiler must comply with Building Regulations Part J. As part of MCS accreditation installers can sign up to a competent persons scheme that means that they can sign off an installation. Equally Hetas courses for biomass can be used for a sign off without MCS accreditation – your installation will be perfectly valid with this, but you will not be eligible for the RHI (Renewable Heat Incentive).

If your installer cannot sign off your installation they can contact building regulations and pay a fee (perhaps £150) for an inspection and sign off.

Key issues raised by building regulations are:

The hearth – sufficient distance from the edge of the hearth to the boiler

The flue – size and siting

Ventilation of the room

Combustible materials and proximity to either the flue or the boiler

K – Kilowatts (kW) Kilowatt hours (kWh’s)

Kilowatts (kW) is a measurement of heat and is used to rate how much heat a boiler can produce. E.g. a 15 kW boiler. This is common to all boiler systems, although some of the old ones will be in BTU’s.

Each property needs an amount of heat during one year. An average insulated house may need 20,000 kilowatt hours from a wood pellet boiler.

Wood pellets provide about 4.8 kWs of heat from 1kg. The average house may therefore need just over 4 tonnes of wood pellets a year before you take into account the efficiency of the boiler.

L – Lambda Sensor

A Lambda sensor is an electronic device that measures oxygen. It is used within wood pellet boilers to adjust the air/fuel mixture to achieve the best burn possible.

M – Cubic Meters (m3)

Wood pellets need to be stored. By volume 1 tonne takes up 1.65 m3 of space. The average house that is well insulated may need between 4 and 5 tonnes of wood pellets in a year. You can therefore work out how large your storage space needs to be taking into consideration bulk discounts and available space.

N – NOx

NOx emissions are of concern because they are associated with the increased acidity of aerosol particles, cloud water and precipitation (acid rain), causing damage to aquatic and terrestrial ecosystems, as well as being responsible for the corrosion of building materials and affecting human health. NOx can act as a fertiliser in soils but, in excess quantities, leads to eutrophication (an overabundance in nutrients leading to oxygen depletion) in many environments. Furthermore, NOx emissions are of crucial importance in the formation of photochemical smog and oxidants, especially ozone (O3), in the lower atmosphere. (Coal online)

A DECC study found that NOx levels from UK produced wood pellets ranged from 0.13 kg per mWh and were similar to both oil and gas NOx emissions.

The advantage of wood pellets is that through their compression and clean burning there is a lower transport cost and this reduces NOx emissions.

O – Organic compounds

Wood pellets are made to European standards and there are wood pellet schemes in the UK.

Wood Pellets are made from non contaminated wood ie there are no coatings such as paint. This ensures that there are no emissions from halogenated organic compounds. Wood pellets are tested in a lab for emissions. If you are unsure do check the site of your supplier or ask them about emissions testing.

If you burn wood with coatings then you will be releasing harmful emissions into the environment.

P – Pelletising

Wood pellets are made from sawdust. This may be from the milling process in which case the sawdust will be “wet” and need drying. Dry sawdust can be sourced from mature non contaminated wood waste.

The sawdust is compressed mechanically through a metal ring dye that compresses the dust into the wood pellet and produces heat. This heat causes the wood to produce lignans which acts as a natural glue binding the sawdust together.

Wood pellets are most commonly made in 6mm width. This relates to the metal ring dye and not to the length of the pellets.

Q – Quality and Net Calorific Value (Q)

Wood pellet quality is often discussed in relation to the net calorific value (q). 4.6-4.8 kW per kg is often given as the range that you may find. Fuel suppliers do compete and try to offer fuel that is of a higher net calorific value (q) such as 4.8 kW. This does affect the cost of your fuel bill and it is sensible to calculate the cost of the fuel against its energy content in order to get the best value.

R – Renewable Energy Association

All MCS accredited suppliers of wood pellet boiler installations have to sign up to the REAL Assurance scheme  for customers. This provides the customer with confidence to purchase a micro renewable device such as a wood pellet boiler from a wood pellet installer.

S – Sustainable

Are wood pellets a sustainable fuel? Clearly if everyone in the UK wanted to use them all at once and at the moment, then no. However this is not the case. Wood pellets are made from wood waste that came from sustainably managed woodland or forest.

” FSC (Forest Stewardship Council) accreditation certifies that the biomass used in wood pellets (or for other uses) came from sustainably-managed forests. FSC is not the only such accreditation scheme in the global forestry market. PEFC(Programme for the Endorsement of Forest Certification schemes) is another. You will often see the phrase “FSC or equivalent” to denote wood pellets from sustainable sources.

Just as lack of quality accreditation does not mean that a product or service lacks quality, simply that its quality has not been verified independently, so lack of FSC or equivalent accreditation does not mean that a wood pellet is from unsustainable sources, just that the sustainability of its sources has not been verified indepedently. Many smaller producers will not be able to manage the cost and bureaucracy of accreditation of one sort or another. They may be using forestry and timber-mill by-products that are the most sustainable inputs to pellet production, as they would otherwise have been wasted, but be unable to provide traceability on these by-products to sustainably- or unsustainably-managed forests. In this context, that should not matter. You should not dismiss wood pellets that are not FSC or equivalent certified, but you may want to ask more questions about their provenance.” (Forever Fuels)

T – Thermostatically controlled heat

Wood pellets are an automated fuel. This means that fuel gets fed into the burn chamber as it is needed and tops up the heat in a property as needed.

Thermostats are placed in different rooms as per gas or oil heating to regulate the heat. Thermostatic valves are also put on radiators.

This means you can have different heating zones and heat different areas of the property to different temperatures easily.

If you wanted to choose wood gasification as an option the fuel cannot be fed automatically on a small scale. Therefore wood is burnt and heats up a lot of water. This is then released automatically on demand to the house.

U – Under floor heating

Wood pellets boilers produce hot water. Using switches you can divert the hot water to where it is needed on demand. Underfloor heating is on a different heating circuit to radiators (e.g. upstairs) and needs to be controlled separately.

Underfloor heating is very popular and it is as easy to use with wood pellet heating as with gas or oil.

V – Verses

In the days where it was only gas verses oil comparisons were quite easy to show.

Wood pellet comparisons (and indeed heat pumps, solar thermal etc) have broadened the choice of consumers and in doing so have made comparisons more complex.

Do you want a comparison based on environmental performance? Cost? Ease of use? Maintenance costs?

More difficult is trying to predict the future and future price rises and availability of all fuels.

There are no guarantees. Hopefully there is some information in this A-Z that helps give you confidence that wood pellets and wood pellet boilers can be an alternative. They can be cheaper to run and installed to a higher standard. The installation can be offset with the RHI (see above), and provide effective, automated, and no hassle, heating.

W – Wood

Wood is the only ingredient of wood pellets. Although any wood can be made into pellets it is normally the softwood that is used. This is partly as it is easier to pellet as it is softer, partly it is easier to grow, and often it grows more quickly.

Many people refer to wood as “biomass”. It is  a term that is not that helpful. Biomass is simply biological material from living or recently living organisms such as trees. Therefore when “biomass” is discussed on a large scale it could mean palm oil, pine nut kernels, straw, or anything that burns.

X – “X marks the spot”

When you want to install a wood pellet boiler it takes a little thought as there are a number of variables.

  1. Where can you put the flue?
  2. Where is there space for the boiler?
  3. Where do we want the boiler and which type do we want?
  4. Can I meet all building regulations part J?
  5. Am I in a conservation area (or area of outstanding natural beauty)?
  6. Do I have a listed building?
  7. Can I meet all regulations cost effectively?

If you are having difficulty with any of these issues do not hesitate to get in contact through the form to the right or on the contact page

Y – Yearly demand for wood pellets

Most people want to compare costs based on 1 year. Unfortunately we have had a few years of volatile temperatures.

In an average year with an average house you will need 20,500 kWh’s. Last year this would have been more as 2010/11 was one of the coldest winters on record. During this time you would have used oil, gas or wood pellets to keep you warm. No fuel is better or worse at doing the job.

With gas you do pay on demand. Therefore you do not pay the summer tariffs for the majority of your gas, but the tariff when it is coldest.

Oil can be ordered and depending on the size of your hopper you can try to get through the winter, but if you get cut short then there is a wait for delivery and the price will have risen considerably.

Wood pellets are like oil in that they have to be delivered. Fortunately that is where the comparison ends. Your storage is unrestricted if you have space enough. Either to store bags or a hopper. ie you can order enough for the winter and keep some in reserve.

Pellet suppliers are keen to look after their customers and keep their own costs down. Therefore it is not uncommon for them to ring you up if they are making deliveries in the area and “top up” your supplies.

Z – Zero Carbon Home

In order to combat global warming many governments have put in place schemes that mix taxes an incentives to help individuals and organisations to reduce their carbon.

In the UK there has been a debate about what constitutes a “zero carbon” home.

When you bury down into the figures, not just on  heating, but on construction and living (e.g. food, transport etc) it is very difficult to get within a reasonable distance of this figure not just on cost grounds, but being practical as well.

A good read is “one tonne life” a project about reducing carbon emissions down to one tonne from 7.5 tonnes.