Building Regulations Approved Document J, 2010 provides extensive guidance covering the installation and commissioning of a solid fuel appliance. We have included a link for your convenience http://www.planningportal.gov.uk/uploads/br/BR_PDF_ADJ_2010.pdf . The following sections provide information covering key installation considerations. Your Windsor and Eton Stoves surveyor / installer will provide the correct advice and agree a design specification to ensure great looks and a safe, efficcient installation.
Sizing Your Stove
The area of a room, and efficiency of insulation will dictate the optimum stove size.
Below is a simple calculation which will provide an estimated minimum heat output to meet your needs. (dimensions in metres).
((W x H x D) x factor) = min required gross heat output in kW @ 75% Gross Efficiency
Note: for modern well insulated houses*. These will only require a small amount of heat to maintain living temperatures. The guidance figures above will in most cases still suggest an output below that which can be offered from most nominal (average)stated outputs. Customers wishing to instal solid fuel appliances in these properties should be made aware that excessive heat is likely to be generated. An appliance for these circumstances should be very controllable or have good thermostatic control, such as a pellet stove.
The factor figure is dictated by the age of the property and therefore an assumed thermal efficiency and air permeability. This will provide guidance only. There are often many influencing factors which would only be highlighted during a site survey.
A stove requires air in order to burn safely and efficiently. In many cases additional room ventilation may be required. Ventilation requirements are directly related to the air permeability of a dwelling and not the age of a property, however as a rule of thumb for an appliance with no flue draft stabiliser then;
- For older dwellings air permeability is assumed to be high (>5.0m3/(h.m2)) then 550mm2 ventilation is required per Kw of stove output above the first 5Kw.
- For Modern well insulated dwellings air permeability is assumed to be low (<5.0m3/(h.m2)) inhibiting efficient combustion, therefore 550mm2 of ventilation is required for every Kw of stove output.
- See Building Regulations Document J, page 29, table 1.
Ventilation can be achieved either through addition of an external air vent or a direct air supply to the stove. A direct air supply ensures that the integrity of insulation can be maintained. Lack of adequate ventilation will inhibit efficient combustion and in many cases can be extremely dangerous.
In some cases draw can be to strong ( Draught exceeding 35 Pa) creating excessive heat and making control difficult. in this case a flue draught stabaliser will be required.
Distance to Combustibles
There are a number of considerations to take into account with distance to combustibles. These are outlined in two places;
1. Building Regulations Approved Document J, 2010
- Typically for a stove installed within a traditional hearth then at least 150mm to the sides and 225mm to the front for a closed appliance. Building Regulations Document J page 38, Diagram 26.
- For uninsulated flue pipe then the min distance to combustibles is 3 x the pipe diameter (450mm for a 6” flue pipe and 175mm for a 5” flue pipe) This can be reduced to 1.5 x the diameter through the introduction non-combustible shielding typically a steel plate and ceramic spacers used to create a 12mm air gap between the combustible surface and shield. Building Regulations Document J, page 33, diagram 19.
- For twinwall insulated flues then the typical distance to combustibles can be reduced to 50mm. Building Regulations Document J, page 25, diagram 13.
2. CE plate supplied with each stove. The CE Plate and specifications is unique to each model of stove.
IMPORTANT - For insurance purposes whichever shows the greater distance to combustibles will always take precedence.
Hearths are constructed of suitably robust materials and to appropriate dimensions such that in normal use they prevent combustion appliances setting fir to the building fabric. The Hearth consists of 2 parts;
1. Constructional Hearth often referred to as the Sub-hearth. Acting as a heat sink the constructional hearth is of solid non-combustible material such as brick or concrete and sits below the superimposed hearth (often referred to as the hearth) . The sub hearth is a building regs requirement. Minimum dimensions are as follows; Fireplace recess - Min depth 125mm, projection at least 500mm from the Jambs and 150mm across the Jambs. Free standing - Min depth 125mm, min dimensions 840mm x 840mm . Note: combustible material should not be placed beneath constructional hearths unless there is and air space of 50mm. When building up the sub hearth is it's important to consider overhang to the sides. The top hearth can only overhang the subhearth by a max of 25mm (prevents possible cantilever).
2. The Superimposed Hearth is of solid non-combustible material typically decorative such as slate, tile or stone. Minimum dimensions are as follows; Fireplace recess - 150mm from the stove sides and 225mm to the front of a closed appliance / 300mm to the front of an appliace that can be used with doors open. Free standing - 150mm to rear and sides and 225mm to the front of a closed appliance / 300mm to the front of an appliace that can be used with doors open.
See Building Regulations Document J, pages 37 to 39, diagrams 24 to 27.
For appliances that emitt 100 degrees or less to the hearth then a 12mm deep non-combustible hearth plate (typically glass) can be used.
Why Use a Flue Liner?
A correctly functioning flue is essential to ensure an efficient and safe appliance. The flue must release combustion gasses into the outside atmosphere at a steady controllable rate, this rate quantified under the term “Flue Draft”; too slow and combustion will be inefficient with low heat output and a fast tar build-up leading to danger of chimney fires; too fast and appliances will quickly overheat causing appliance and flue damage as well as danger of fire and possible chimney fires.
If your chimney is suitable then it is possible to install a stove using only a registry plate and cowl however we would never normally advise doing this. Windsor & Eton Srtoves always recommend lining whenever fitting a new stove. Why? A flue liner will ensure the following;
- A flue line ensures that deadly CO2 emissions can not leak through desiccated mortar, brickwork and plaster into your living space. Carbon Monoxide (CO) is an extremely poisonous gas that can be present in the fumes from the combustion of fuel's which aren’t burnt under the correct conditions
- A flue liner will restrict and contain the build-up of Tar. Chimney fires are often caused by the build up of Tar. Tar accumulates through inefficient burning and/or use of unseasoned fuels.
- A flue liner will contain and resist a chimney fire
- A correctly sized liner ensures even flue size and better draw. enabling clean, efficient burning and a lower operating cost. A good analogy is the below diagram where the balloons represent Flue sizes under the same level of heating. A narrow flue will enable gasses to rise more easily ensuring efficient combustion and a clean stove.
Our flue liners are all HETAS approved and satisfy Building Regulations. Our flue liners come with 10 year (316 Liner) and 25 year (904 Liner) manufacturers conditional warranty, HETAS approval and has been tested up to 1000 degrees centigrade.
Unlike 316 grade stainless steel chimney liner that is used in most domestic applications we can also supply 904 grade stainless steel chimney liner as Standard. This is normally used in situations where the liner will be subjected to very high temperatures. These liners should give a normal working life of 25 years or more when correctly installed, used and maintained. However these flexible liners whilst being easier to install and replace are non-permanent and prolonged periods of slow burning particularly using solid fuels, combined wit inadequate cleaning of the flue-ways can result in corrosion damage which reduces the expected life of a liner to less than 5 years. Our site survey engineer will recommend the correct flue type according to intended use.
Alternative Lining Systems.
A flue Liner may not be the correct solution for every situation. Windsor & Eton stoves offer a number of alternative solutions including;
- Factory made metal chimney
- Ridged stainless steel chimney relining systems
- Non-metallic prefabricated chimneys and chimney lining systems
Flue Technical Requirements
Flues work on that basis that heated air becomes lighter than the surrounding atmosphere and therefore rises as heavier air pushes the lighter gasses up the flue. There are a number of factors influencing the efficient working of a flue and appliance.
Flue Width. A correctly sized liner ensures even flue size and better draw. enabling clean, efficient burning and a lower operating cost. A good analogy is the below diagram where the balloons represent Flue sizes under the same level of heating. A narrow flue will enable gasses to rise more easily ensuring efficient combustion and a clean stove.
- For chimneys serving an open fireplace the liner should be either a minimum of 185mm x 185mm square or 200mm diameter.
- For non-DEFRA approved closed appliances up to 20kw (wood burning / multifuel stoves) minimum flue width is 150mm.
- For approved appliances then the flue width should be a minimum of 125mm so is generally sized in line with the stove spigot (Stove pipe connecting collar) with an exception of not less than 100mm for straight flues.
See Building Regulations Document J, page 30 , Table 2.
- Whilst there is no minimum legal limit to the overall flue height the minimum recommended flue height is 4.5 meters.
- There are a number of requirements governing flue outlet position this prevents fire (whatever the wind conditions) and also places the flue outlet in clear air.
- The affects of temperature, wind and surrounding trees and buildings can have an adverse effect upon an efficient flue / appliance, For these reasons every installation differs. Your surveyor / installer will provide the correct advice and design to mitigate most environmental factors.
See Building Regulations Document J, page 30 to 32, diagrams 17 to 18.
Maximum number of Bends. A flue needs to minimize resistance to the passage of gasses by minimizing the number of changes in direction, therefore;
- There should be no horizontal lengths except for connection to the appliance with rear outlets where the horizontal section must not exceed 150mm.
- Not more than 4 bends are permitted throught the length of the installation. (a 90 degree elbow or tee is treated as 2 x 45 degree bends).
See Building Regulations Document J, pages 26 to 27, diagram 15.
A Windsor & Eton Stoves Limited qualified installer will ensure that a flue functions within it's ideal parameters. This will ensure a safe and efficient installation.
Survey and Quotation
We will ensure that the proposed installation is safe, efficient and will provide many years of beauty, warmth and enjoyment. We pride ourselves on the accuracy and fairness of our no-obligation fixed price quotations. Call 0800 678 5041 now, to arrange one of our HETAS engineers to carry out a site visit.
Have you purchased a stove and need it fitting?
Do you need a flue liner installed?