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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.
Click on the product in the "your selections" box to get the details of the chosen product.Once you add this list to the shopping basket, you can make changes like adding or deleting products.
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:
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).
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 adapterTo 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.
You can chose one of the following options:
Firestop platesThe passage through the floor can be done with 2 ventilated firestopplates and one clamp (is one "firestop set")
Masking plateThis element makes for a more aesthetic finish of the ceiling entry.It is placed under the firestop plates.
Ventilated firestop plateA ventilated firestop plate can be used underneath the ceiling when the flueenters into the loft.For aestetic reasons you may want to add a masking plate.
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.
This element makes for a more aesthetic finish of the ceiling entry.
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.
Introduce an offset in your flue (see picture)
Determine how many mm the flue should move sidewards.To create the offset we can work with elbows of 15°, 30° or 45°. A lower angle is better for the draw.
Both elbows need to supported by a wall bracket. These brackets can be a roof support and/or a floor support.
Attention: You need to check if the required offset comes with an upward length that fits under your roof. If it does not; you need to find a solution, most likely go for a smaller offset...
We need to calculate how many straight elements we need going upwards; knowing that we already added some length to the flue through the adapter and the offset.
Step 1 : calculate how high the flue should be on the roof
To determine the required height on the roof (G) see " Complete information" below.
Step 2: Calculate the total height of the flue (stove to cowl)
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 4.5 meter).
You do not need to have the exact height, somewhat higher is also okay.
Step 3: Determine how much length is in your shopping cart already
In your cart is already:
- length from a starter length or adjustable connector (if you did chose one) - Question 2
- length from the offset - Question 4
Step 4: Calculate the length that has to come from the straight pipes
Total height of the flue - what is in your cart allready.
Note: a bit higher is okay, but do not take a lower height.
Within 600mm from the ridgeThe flue has to end minimum 600mm above the ridge.
More than 600mm from the ridgeThe 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:
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.
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, a trim ring and -when required- a storm collar.
A finishing plate can be used to cover the opening between the flue and the ceiling under the roof.
There are 3 type of rain caps to choose from:
Rain capWill 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 meshThe mesh will keep birds from building a nest in your flue.
Weathering capKeeps 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.
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.
Flue kits are based on general assumptions of the typical dimensions of houses and bungalows. You may need to add or take out certain items which can be done in the shopping cart. Other items can also be added to cart as necessary in the general Twin wall flue section. Flue-pipes.com does not take responsibility for the items installed in your flue system as this is merely a guide. Please check the twin wall flue pack is appropriate for your requirements. Refer to HETAS regulations, your installer and building regulations for further clarification.
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