A glossary of
Closure plate: See ‘Register plate’.
Combustible materials: Anything that will burn should not be close to a stove, and different stoves and flues will have different specified distances to combustibles, which must be observed for an installation to conform to Building Regulations. Culprits are not just the obvious, such as wood, thatch, plastic and wallpaper, but also plasterboard, wiring in the wall, or even paints containing organic materials or plastics.
Convection stove: A traditional stove radiates heat from its entire metal surface. A convection stove is typically designed to temper this radiant heat at the back and sides of the stove and to convect the heat instead. Some purpose-built convection stoves have an inner convection chamber housed in a separate casing. Air is heated in the gap between, which then convects from vents at the top, or front of, the stove. Others simply have convection panels added to pre-existing models, to achieve a similar effect. Convection stoves can usually back up much closer to combustible wall materials like wood or plasterboard, although care must always be taken to select suitable flue materials with similar insulating qualities.
Cowl: A chimney terminal. These take many different shapes and forms, depending on the function it is to perform. Generally, we use a simple covered cowl (to keep out rain) with a mesh guard to keep out birds. This has the merit of simplicity and also of being easy to clean from the inside with standard sweep’s brushes. When circumstances dictate, we will use anti-downdraught cowls (which squat on the chimney pot like massive fungi) or rotating Aspiromatic cowls.
Cravat: An adjustable collar to seal the gap where a rigid flue pipe penetrates a register plate.
Flexible liner: Stoves should have an integrated flue system to evacuate flue gases as effectively as possible with the minimum of condensation and temperature loss, which should also be easily swept. Where there is an existing brick chimney, the best solution is to line it with a flexible stainless steel liner. Class 1 flexible liners for solid fuel use are not the same as liners for use with gas appliances. There are two grades of solid-fuel liners, suitable for use with either just wood or for wood and smokeless fuels.
Free standing stove: An imprecise term, sometimes used to refer to any stove other than an inset stove (i.e. a stove with legs, which can ‘stand’), and sometimes to any stove which is installed independent of an existing fireplace or chimney (i.e. usually with a modular twinwall flue system). Within this context, the term is sometimes used to refer only to purpose-built convection stoves, which are specifically designed for this kind of free-standing application, although conventional stoves (designed to go into a masonry-clad fireplace) can be and often are installed in a free-standing capacity. Confused? Context usually clarifies!
Hearth: A non-combustible surface on which a stove stands and which extends in front of a stove or fire, usually constructed of stone, tiles or brick. Slate and granite are traditional hearth materials which are particularly suitable with a wood burning stove. Different rules governing precise dimensions pertain to different kinds of installation, but the principle is the protection of the floor from burning debris and the prevention of heat transfer to combustible materials underneath.
Inspection length: A section of flue pipe with a door to allow the insertion of flue brushes and rods for sweeping of the flue. These are essential flue components for stoves that cannot be ‘swept through’ and for flue systems that make use of numerous bends, where the ability to inspect the flue at multiple points is essential.
Inset stove: A stove designed to recess into an opening and usually with a frame to fit flush to the wall. Although some models with dramatically wide or tall windows require an opening in the wall to be formed to particular dimensions, many inset stoves, especially from British manufacturers, are designed specifically to fit a traditional British fireplace with minimal modification, which can save on installation costs.
Leca: Lightweight expanded clay aggregate. This is the insulating material which is used, when possible, to fill the chimney void around a chimney liner. Liners fitted to inset stoves are not usually insulated.
Register plate: Usually constructed of vermiculite board (but sometimes pre-cast concrete or steel plate), this is a horizontal plate at the top of a fireplace recess, which has the dual purpose of closing off the fireplace from the chimney (thus keeping the heat in the room) and retaining any insulating materials in the chimney void.
Single wall: Rigid stainless steel flue pipe. Single- (as opposed to twin-) wall, this is uninsulated fluepipe, to be used over short distances and never in proximity to combustible materials.
Telescopic length: A section of rigid flue pipe of adjustable length. Where space permits, a telescopic length is often used below a register plate to facilitate the future removal of a stove, otherwise you may have to cut through and replace the fluepipe if the stove ever needs to be detached.
Twin wall: Confusingly, this term is frequently used interchangeably (even by the British Flue & Chimney Manufacturers Association) to describe both insulated modular flue systems and double-skinned flexible flue liner.
At the wood Burning Centre, we use the term ‘Twin wall’ to describe the former: a rigid stainless steel chimney system consisting of modular lengths with an inner skin surrounded by an inch or more of insulating material which is in turn sheathed by a second skin of stainless steel. These lengths can be assembled to create a complete functional chimney for a wood burning stove.
We refer to the latter simply as flexible flue liner. This is a flexible tube which is cut to the requisite length and introduced into an existing brick or masonry chimney to provide an integrated consistent-diameter flue between the appliance and rooftop terminal. In this case, ‘twinwall’ refers to the two thin skins of steel used in the manufacture of the liner: a smoother skin on the inside, a flexible, corrugated skin on the outside. These two skins also differentiate solid fuel liners from thinner gas liners.