Frequently Asked Questions

Why should I buy from Stova?

Our experience and commitment to quality control. It’s that simple. In just the past four years (from 2005), we’ve offered over 2,500 clients services that ranged from stove repairs to full design and installation projects.

Do I need a chimney liner if I am using an existing chimney?

An existing chimney may have only its masonry duct forming the flue way, which is completely unsuitable for a stove for several reasons. The masonry will be capable of absorbing moisture from the atmosphere which, unless the stove was used continuously, would never dry out. This moisture would absorb so much heat from the flue gasses that they would begin to condense which would deposit even more moisture into the masonry. The walls of such a flue represent such a huge, unnecessary, surface that even if the masonry was dry the heat losses would cool any flue gasses to an unacceptable temperature. The walls would have a large surface area even if they were smooth but with the deterioration of the mortar that would have occurred the total surface area will have increased with voids, cracks and loose or missing masonry. The poor standard of wall surface will cause turbulence to the flow of gasses further slowing and allowing more heat to be extracted. 

Fitting an acid resistant stainless steel liner to the chimney is a simple solution to the problems of thermal and friction losses in the flue. Although almost all drawings of flues illustrate a straight vertical path from the appliance to the terminal, this has more to do with the illustrator's idleness than reality because many chimneys follow a torturous route of bends and twists to align the flues from several rooms to an orderly group of terminals at the top of a single chimney structure. For flues such as these a flexible stainless steel liner designed specifically for wood and coal burning appliances can be fitted, this not only gives a smoother wall but also radiuses the typical abrupt changes in direction that are so often found. For additional insulation vermiculite or similar insulating materials can be poured between the liner and the chimney duct.

What should I get: a fireplace insert or a stove?

This depends on a number of variables and aesthetic considerations. How big is the space you want heated, for instance? Which will match your interior décor? Have a chat with our friendly and knowledgeable Stova staff.

About stoves and insert:

A wood stove is the most popular, flexible and economical wood heating option and is defined as space heater, designed to heat directly to the room.

A stove can be located almost anywhere there is enough space and where its flue can be properly routed.

Wood burning stoves are generally used as  a secondary heat source, but in open plan areas can heat a large proportion of a property. By choosing the right type you can, in conjunction with existing fossil fuel central heating, reduce co2 by heating the areas you spend most your time in.

Not all types of stoves perform the same way. For example, some stoves are designed for continuous operation and will burn hour after hour, and offer over-night capability. Other designs have great features such as fast heat up and an attractive flame and are ideal for quick room comfort. Heat storage stoves collect a proportion of the heat produced and release it slowly over several hours. Insert stoves are another option and often chosen where space is limited. Within the Stova range whatever type of wood burning system, style or functionality a perfect solution can be found.

When choosing a stove it is important you consider how the stove will operate and fit in within your life style. Stoves operate in three distinctive different ways.

Intermittent operation -  A Stove which is designed for short quick heating often used for evening and short period operation.

 Heat storage - A stove constructed often using stone or ceramic exterior or internal stone mass to collect heat quickly from intermittent operation and then release the stored energy slowly over a period of time.

Continuous operation is an advanced designed appliance with very accurate combustion air control over the fires activity. This control allows for long periods of operation without user input such as overnight burning.

Pellet stoves offer similar aesthetics to a wood burning stove without the complication of logs

It all starts with lighting the fire. You only need to push a button or set the desired ignition time for when you want heat. The onboard controller then automatically controls the burning operation. Wood pellets require far less manual handling than logs.

The pellet fuel is more energy dense than logs and the hopper of the stove can hold sufficient pellets for several days burning, depending on the model. Pellet stoves are easier to regulate than log burning stoves, and can be left to burn all day with minimal attendance.

A pellet stove consists of a hopper to store the pellets and screw feed mechanism to transfer the pellets into the combustion chamber where they burn under controlled conditions. The heat output is controlled by regulating the flow of pellets into the combustion chamber by choosing a preset heat output (30 – 100%) or by a room thermostat. Because of the highly efficient combustion the ash pan may only need to be emptied infrequently.

Pellet stoves can offer the same level of control as oil and gas appliances, making them an attractive choice for many. Use the simple controls on the stove itself or have a remote pellet control system with external room thermostat and time clock or telephone control from outside the house using a mobile phone. Decide the heat output required from 30 – 100% of capacity. Chose the start and stop times to suit your way of life.

Why might I choose an enclosed fire appliance like a stove?

First of all, there is no smoky smell. More importantly, it’s generally more efficient as less heat is lost, while wood consumption, soot and ash are kept to a minimum. In the long run, this translates into a substantial financial saving.

Are fireplaces and stoves environmentally friendly?

Absolutely. First of all, wood is a renewable resource. Firewood comes primarily from domestic forests and does not need to be treated or processed the way oil and gas do. More importantly, wood is carbon neutral: burning wood releases the same amount of carbon dioxide that it extracted from the atmosphere during its lifetime.

Am I allowed to burn wood in my neighbourhood?

Again, check with our Stova staff. Many of our enclosed fire appliances are DEFRA approved, which means they can burn wood even in smoke controlled areas such as London and Birmingham.

What kind of wood can I burn?  A guide to choosing and drying logs

Wood was the traditional fuel in Britain until the industrial revolution. It has been replaced by coal, oil and gas over the last two hundred years. Our increasing awareness of the environmental damage caused by our use of fossil fuels has led to growing interest in using wood as a sustainable, renewable, low carbon alternative. Wood is a major source of renewable heat energy and, burned efficiently, it produces virtually no smoke. As trees grow they absorb carbon dioxide (CO2), incorporating the carbon into new growth and returning oxygen to the atmosphere. When the wood is burned this carbon is oxidised and released as CO2. As a result, using wood from sustainably managed trees reduces net CO2 production (small amounts are released by the activities of processing and transportation) compared to using fossil fuels. This means that heating using wood can significantly reduce our reliance on fossil fuels while also reducing our CO2 emissions.

The woodland area in Britain is limited, but with effective management, there is more than enough timber to meet foreseeable demand for many years. Managing woodland improves biodiversity and increasing the proportion of managed woodland supports jobs in the forestry industry. Replacing imported fossil fuels for locally produces wood fuel improves fuel security and encourages local community.

 Choosing logs

When choosing wood for burning there are two significant factors which have an effect on the net calorific value (CV) or the amount of available heat per unit (volume) of fuel:

1. Moisture content

2. Wood density

 1. Moisture content

The moisture content of wood has by far the greatest effect on net CV. Any water in the timber has to evaporate away before the wood will burn, and this will reduce the net energy released as useful heat (as opposed to steam up the chimney). If you can get them to light at all, logs that aren’t dry will result in a fire that smoulders and creates lots of tars and smoke. These tars can be corrosive, potentially damaging the lining of the flue and increasing the danger of a chimney fire. Wet logs will tend to blacken glass in stoves even if the stove is designed to keep the glass clean. Well seasoned logs can have approximately twice the CV of green logs.

You should always take care to burn only dried (seasoned) wood, either by buying it dry, or by buying green logs and drying them yourself. Radial cracks and bark that comes off easily suggest well-seasoned wood.

The moisture content of a piece of wood is a measure of the relative weight of water and weight of solid wood. This can be expressed as either ‘dry basis’ or ‘wet basis’, most fuel suppliers use a wet basis measurement (weight of water divided by weight of wet log).

 The effect of drying on Calorific Value

Graph

This graph shows how significant moisture content is in determining the CV of wood. A fresh green log of about average moisture content has only around half the energy content of an equivalent, well seasoned log. While the type of tree the log comes from can have some impact on the calorific value, it is usually extremely small. Most of the variation in calorific value between species is due to natural differences between moisture content in fresh cut logs (e.g. Ash has a particularly low moisture content when green).

2. Wood density

When buying logs, it is common for the seller to let you know whether they are from hardwood or softwood tree species (or mixed). The general difference is that hardwoods (deciduous, broadleaved tree species) tend to be denser than softwoods (evergreen, coniferous species). This means that a tonne of hardwood logs will occupy a smaller space than a tonne of softwood logs. Denser wood tends to burn for a longer period of time meaning fewer ‘top ups’ are required to keep a log stove burning for a given length of time. If you buy wood by volume you will receive more kilowatt hours (kWh) of heat from a cubic metre (m3) of hardwood than softwood (at the same moisture content).

 How to dry your own logs

Green logs are considerably cheaper to buy than seasoned logs, but will be heavier and will require space to stack and dry before use.

Timing of felling is important as standing timber will be driest in winter. Many stove manufacturers often specify 20% moisture content or less, and this is likely to take two summers or more to be achieved by air drying.

Drying timber should be stacked by bearers (off the ground) in a sunny, windy location, ideally under some form of waterproof cover with open sides. Ideally the prevailing wind should blow through the stack. If possible, cross cut logs should be split to less than 10cm diameter. This allows moisture to move from the centre of the log to the surface more easily.

To achieve low moisture content for burning, bringing cut, split logs indoors for a few days or more before use will help.

 

Using logs efficiently

Open fires

An open fire is the traditional way to burn logs and can be attractive and cosy. It is however, a very inefficient method of heating as the uncontrolled air flow takes the hot as air from the fire up the chimney, and draws warm air in from the rest of the house as well. This is replaced with cold, outdoor air drawn in to the house through drafts and vents. Often an open fire will run at very low efficiencies (≈25%) resulting in large amounts of smoke and ash for very little useful heat output. It is also worth remembering that when an open fire is not in use then the chimney can allow large amounts of cold air into the room (products are available to close off a chimney when not in use). So an open fire may well be increasing other heating costs. Open fires need a solid base to retain an ash bed in the smallest practical fire base. A coal grate is not suitable for wood, the best solution to this is to cover it with a metal base plate. All open fires need a fine mesh spark guard.

Efficient stoves

Traditional log stoves provide radiant heat to a single room. They offer an attractive, renewable, low carbon heat source that can be relatively cheap to buy and to run. They achieve significantly higher efficiencies than open fires (≈70%), and this results in a lower fuel requirement (and fewer trips to remove ash). Choose the smallest fire box you can for your heat requirement (the installer should be able to help you with this), with controlled hot secondary air, and ash retained in the base of the fire. Operating a stove with doors open considerably reduces efficiency. An insulated chimney is essential. Whenever water vapour is in the chimney, the temperature at its outlet must be above 100° C to avoid water condensing. Visible smoke emission from the chimney is a sign of inefficient combustion. Log stoves are also available with a back boiler to provide hot water, but this usually reduces the efficiency.

 Operation

After adding fuel, set to fast burn ensuring all of the gases are fully burnt. Only set to slow burn when all the wood has been reduced to charcoal and ash. Newly added wood set to burn slowly will create smoke and tarry deposits in the chimney. Stoves should not be banked up with logs overnight. A bright fire which has turned wood into charcoal should be left with the day’s ash, secondary air and no primary air. Users of older stoves are advised to consult their stove centre about current recommendations on how to achieve the best results.

Contamination

You should not burn anything that has been contaminated or treated with paint, varnish or other coatings and preservatives. Contamination can affect the amount of tar and deposits building up in your chimney, and release noxious chemicals into the smoke. Contaminated wood often leaves melted debris in the ash, and can have serious health implications when burnt. In particular, old CCA treated (tantalised) wood contains arsenic and should never be used as fuel.