Draft:Twin wall flues

Twin wall flues are a heating solution for a burner that lacks a brick chimney. The twin-wall flue system needs to ensure a safe outflow of smoke. They can be installed as the main out pipe and can go through standard walls and even through roofs and floors. A double-wall flue pipe is also suitable for wood, coal, oil, and gas burners.

Good twin wall flues can be used across many common appliances, wood, coal, gas, or oil. They should have at least 25 mm of insulation with the double wall flue pipe ensuring the passage of gases through the top of the chimney instead of releasing them into the vents whilst preventing condensation.

Twin wall flues need to be designed and installed carefully; the flue should be high enough to ensure sufficient draught to clear the products of combustion. The height necessary for this will depend upon the type of appliance, the height of the building, the pitch of the roof, and the number of offsets within the system. However, a minimum flue height of 4.5 metres should be achieved as recommended in the Building Regulations. Also, the flue should remain as straight as possible.

Where it is not possible to construct a vertical chimney, Building Regulations usually specify that no part of a chimney should form an angle greater than 45° from the vertical. There is an exception - it may be necessary to use a very short horizontal section (not exceeding 150 mm) of the flue to connect the chimney to a back outlet appliance. This can mean a 90° elbow is necessary.

Where the flue passes through a combustible floor or ceiling, an air gap clearance must be maintained, as per the manufacturer's installation instructions. In multi-fuel applications and where the flue gas temperature is greater than 250°C, the ventilated fire stops, and ventilated support components must be used at the bottom and top of the shaft.

For oil and gas applications where the flue gas temperature is below 250°C or where the chimney passes through a non-combustible floor, the standard fire stops, and support components can be used.

A study conducted by Europe's largest solid fuel firm, Homefire, shows that households that heat their homes with log burners are buying less fuel and attempt to make it stretch further.

Many European and UK homes use electricity or gas for their heating and other energy needs, but a large proportion rely on burning firewood or smokeless fuel. Smokeless fuel is a greener coal alternative. The substance looks like coal, but it is made of high-grade anthracite. That anthracite is ground up, mixed with organic material, and then pressed into lumps. The resulting smokeless fuel burns longer than wood and with less smoke than coal.

This is particularly the case with those with boat dwellers, poor insulation, rural homes, and off-grid homes. Many do this with log stoves or open fires, and less commonly with solid fuel powered boilers. Also, wood is a lot cheaper to burn than gas. Open fires are not often used as they are extremely inefficient (20% efficiency, while a woodstove has 70-80%).