Twin Wall flue through the roof - Stainless Steel (1 or 2 story house)

This twin wall insulated flue system has been designed for a single or double storey straight flue, that runs through the inside of the house terminating through the roof.

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twin wall through the house

twin wall flue

1Diameter of flue liner:

WOODSTOVES & MULTIFUEL STOVES: The flue legally needs to be a minimum of 6" (150mm) in diameter if you are burning wood or coal. Unless when you install a DEFRA approved stove with a 5" flue outlet, in which case you can use a 5" liner (125mm).

What diameter of flue liner do you need?
125 150
The ideal flue size is typically determined by the exhaust outlet of the stove or appliance. It shouldn't to be smaller than the appliance exhaust hole.

The Building Regulations (Document J, page 30) require that the minimum flue size for stoves are as follows:
- Up to 20kW burning smokeless fuel - minimum 5" - 125mm diameter.
- Up to 30kW burning any fuel - minimum 6" - 150mm diameter.
So the regulations recommend a minimum flue size of 150mm for any stove (on which wood could be burnt) unless it is Defra Exempt.

OPEN FIRES including flame effect open gas fires:
Minimum 200mm diameter for fire openings up to 500mm x 500mm. Larger fires require a flue area equal to 14-16% of the total area of the fireplace opening. (Minimum flue diameter 180mm for gas effect fires).
2Choose the adapter between stove and twin wall flue

Many wood-burning stoves come with the choice of attaching the flue pipe to either a top or rear flue exit. All things being equal, it’s best for a flue pipe to go up in a straight line in order to achieve the best draw and most efficient burn from your woodburner. This is the set-up we will use here.

For the adaptor you have the following options:

- Single to twin wall adapter

To be pushed into the stove opening; sits inside the spigot of your stove and then connect to other twin wall flue pipe above.

- Single to twin wall adapter with a masking Flat masking shroud 500mm

Our flat masking shroud is designed to hide the adapter which is inserted into the spigot of your stove / appliance, where there is a step up in diameter. It is 500mm in length.

- Single to twin wall adapter - conical (for a better look)
This insulated twin wall conical adapter is used to connect the stove to the twin wall flue system; you can insert it into the stove's spigot being sure to cut the adapter down making it flush.With its tapered design it is more aesthetically pleasing than the standard adapter.

- Standard length (500 or 1000mm) with build-in adapter (for clean look)
A straight length with a built in adapter, designed to sit on top of the stove to give a clean look.

- Adjustable stove connector length (for clean look and easy maintenance)
A 500mm straight length with a built in adapter, designed to sit on top of the stove to give a clean look.

The adjustable stove connector length allows you to remove the stove for maintenance without the need to take down the whole system.

What kind of adapter between your stove and the twin wall flue?
Standard adapter (height 0mm) +£0.00 Standard adapter with masking shroud (height 0mm) +£0.00 Conical adapter (height 100mm) +£0.00 500mm length with build- in adapter (Starter Length) +£0.00 1000mm length with build- in adapter (Starter Length) +£0.00 Adjustable Stove Connector Length With Built In Adapter (Height 240 - 480mm) +£0.00 Increasing adapter 100mm (4") to 125mm (5") +£0.00 Increasing adapter 100mm (4") to 125mm (5") with masking shroud +£0.00 Increasing Adapter (5") to twin wall 6 - conical +£0.00 Increasing Adapter (5") to twin wall 6 with masking shroud - conical +£0.00
3Determine how many straight pipes need to be used

We need to calculate how many straight elements we need going upwards

Determine what the height (X) of the flue should be, from the adapter to the cowl

To determine the required height on the roof (G) see " Complete information" below.

You now can calculate how many mtrs of straight pipes are needed to get to the required height on the roof.

Total height of the flue = B+C+D+E+F+G
In case of a 1 storey house; D, E and/or F can be 0

Check: The total height from stove to end cap should be at least 3.5 meter (building regulation recommends 4.5meter)

You do not need to have the exact height, somewhat higher is also okay (and cheaper than taking an adjustable length)

You may have added some length into your shopping cart from a starter length or a adjustable connector length. You need to deduct that length of the total height you just calculated.

What height is needed from the straight elements?
Straight length: 2.38m +£0.00 Straight length: 2.88m +£0.00 Straight length: 3.34m +£0.00 Straight length: 3.84m +£0.00 Straight length: 4.30m +£0.00 Straight length: 4.80m +£0.00 Straight length: 5.26m +£0.00 Straight length: 5,76m +£0.00 Straight length: 6.22m +£0.00 Straight length: 6.72m +£0.00 Straight length: 7,68m +£0.00 Straight length: 8.64m +£0.00 Straight length: 9.60m +£0.00

Chimney Heights and Termination

A simple rules

Within 600mm from the ridge
The flue has to end minimum 600mm above the ridge.

More than 600mm from the ridge
The distance between the cowl of the flue and the adjacent roof/wall/structure should be higher than 2.3 mtr.

For the height on the roof this means:

Pitch of the roof Height on the roof.

25° 1070mm

30° 1330mm

35° 1610mm

40° 1930mm

45° 2300mm

50° 2740mm

All the rules

The minimum chimney height recommended for minimum performance of wood burning and multi fuel appliances is 4.5 m from the top of the appliance to the top of the chimney. In practice you 3.5m is often enough.

The distance between the cowl of the flue and the adjacent roof/wall/structure should be higher than 2.3 mtr.

Within 600mm from the ridge: Flue has to end minimum 600mm above the ridge.

The diagram below, taken from Document J (building regulations), shows the minimum flue discharge heights and positions for all wood burning and multi fuel applications.

In some cases, particularly when chimneys are towards the bottom of a sloping roof or at the eaves, it may be necessary to increase the chimney height above these minimum mandatory requirements. The reason for this is to clear pressure zones created by wind hitting the roof and nearby structures, like trees, which may interfere with the up draught required by the appliance or fire.

The maximum freestanding stack height above the roof for a traditional masonry chimney is 4.5 times the narrowest horizontal part of the chimney.
In the case of stainless steel system chimneys, the manufacturer’s installation instructions should be consulted; however in most cases it will be around 3 metres. This measurement is taken from the last point where the chimney stack passes the through or past the edge of the roof up to the chimney capping or termination. Tall chimneys may need bracing, always consult the manufacturer for advice.

For buildings with flammable roofs such as felted, thatched, or shingle roofs the flue or chimney the regulations are different. The flue or chimney must terminate at a minimum1800mm above the combustible surface.
4 How many floor support units do you need?

For a full explanation see "complete information" below

You can chose one of the following options:

Firestop plates
The passage through the floor can be done with 2 ventilated firestop
plates and one clamp (is one "firestop set")

Masking plate
This element makes for a more aesthetic finish of the ceiling entry.
It is placed under the firestop plates.



Ventilated firestop plate
A ventilated firestop plate can be used underneath the ceiling when the flue
enters into the loft.For aestetic reasons you may want to add a masking plate.

What floor support units do you need?
None (Flue goes straight up through the roof) +£0.00 One Firestop Support set with masking plate. +£0.00 Two Firestop Support sets with masking plate. +£0.00 One Firestop support set with masking plate (first ceiling), plus a ventilated firestop plate (to the loft) +£0.00

Firestop plates

The passage through the floor can be done with 2 ventilated firestop plates and one clamp (is one "firestop set")

Ventilated Fire Stop Plates must be secured into the ceiling or the floor whenever the system exits and/or enters a habited space. So if your attic is a habited space you will need 2x a firestop set plus a masking plate.

1.  Put a length through a pre-prepared wood box and slide down the firestop support plate and the support clamp.
The minimum distance between the insulated chimney's outer wall and the combustible materials is 60mm (G60).

2.  Scew the firestop support plate to the box and lay the support clamp on the support plate. Next, screw the support clamp directly to the jacket pipe of the length. Make sure the screws are short enough not to touch or puncture the core pipe.

Install the ventilated plate on the bottom. Additional masking plate can be mounted over the ventilated plate.

Masking plate

This element makes for a more aesthetic finish of the ceiling entry.

Ventilated firestop plate

A ventilated firestop plate can be used underneath the ceiling when the flue enters into the loft. For aestetic reasons you may want to add a masking plate.
5What kind of roof, and what is the pitch of the roof?

What kind of material material is covering the roof:

- Metal roof, non tiles roofs: we recommend an EPDM flashing

- Flatter tiles and slates: we advice a Aluminium - rubber flashing

- Normal house tiles: use a Lead based flashing - Determine the pitch of the roof (0° being a flat roof, 60° a sharp roof)

Automatically we ad a roof support and -when required- a storm collar.

What is the pitch of the roof and what flashing do you need?
Lead flashing Flat +£0.00 Lead flashing 5 - 20° +£0.00 Lead flashing 20 - 35° +£0.00 Lead flashing 35 - 50 +£0.00 Aluminium - rubber flashing (45° maximum) +£0.00 EPDM flashing (45° maximum) +£0.00
6Do you need a finishing plate?

A finishing plate can be used to cover the opening between the flue and the ceiling under the roof.

Do you need a finishing plate?
No finishing plate needed +£0.00 Finishing plate 0 - 30º 2 parts +£0.00 Finishing plate 30-45º 2 parts +£0.00 Finishing plate 45 - 60º 2 parts +£0.00
7What kind of Cap is required?

There are 3 type of rain caps to choose from:

Rain cap
Will keep vertical falliung rain out of the flue. In case of side winds, rain will enter the flue. In case of a flue outsie this is not a problem, as it can float out through the soot collector.

Rain cap with mesh
The mesh will keep birds from building a nest in your flue.

Weathering cap
Keeps rain out of the flue. Also blocks downwinds from entering your flue. Downwinds come from higher objects in the vicinity (up to 10mtr), and they will blow the smoke back into your house.

What kind of Cap is required?
Rain cap +£0.00 Rain cap with mesh +£0.00 Weathering cap +£0.00
8Do you need to support a free standing length of more than 1.5mtr

You need to support the flue over the roof if the free end becomes too long and requires additional support. We recommend to use a guy bracket and the telescopic support if the free end is more than 1,5m.

Every connection above the last support except for regular narrow locking band should be additionally secured with a wide locking band.

Do you need to support a free standing length of more than 1.5m
No support needed +£0.00 1.5 - 2m +£0.00 2 - 3m +£0.00

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