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The floor component dilemma

Ventilated floor penetration components can be dangerous and do not seem to meet current regulations, however most twin wall flue manufacturers stipulate that they must be used when boxing in - which you have to in a bedroom or other storage space (unless you provide some other method of guarding the flue). For years flue manufacturers have been ignoring this problem (some do not even supply a non ventilated component) - we are very pleased that Selkirk UK have addressed the problem satisfactorily.

Selkirk STC twin wall flue was the first flue manufacturer to address the problem, although other manufacturers are now starting to follow which is to be applauded as safety will be improved..

Read about how Selkirk achieve this here.

So what's the problem with using ventilated floor penetration components and why do you have to use them anyway?

Boxing the flue in

When running twin wall flue in a storage space you must guard the flue - this is normally achieved by boxing in - read more in our building regulations section. A bedroom can be used as a storage space i.e. you or the next occupier can for example throw a shirt on the floor which could rest up against the flue pipe. Boxing in stops this sort of thing happening and is a good idea.
So a bedroom is a storage space and therefore twin wall flue has to be guarded/boxed in in a bedroom.

When boxing in twin wall flue, if you are using any twin wall flue other than Selkirk, then you need to use a ventilated floor component component to reduce the heat transfer to the air in the boxing. Every other type of flue fails testing when using a non-ventilated component (some manufacturers do not even make a non-ventilated component). Therefore the manufacturers installation requirements always specify using a ventilated component when boxing in. It is not permitted to not follow these requirements.

Ventilated twin wall flue floor components

Ventilated floor components reduce the heat transferral from the flue to the air in the boxing around the twin wall flue. Ventilated floor components were a necessary introduction to the UK when twin wall flue manufacturers started reducing the thickness of their insulation as well as shifting to safer insulation options from a health point of view. Some twin wall flue flue manufacturers now do not even supply non ventilated floor penetration components.

Twin wall flue ventilated floor components can be dangerous

They can allow the transmission of smoke into the room above. Even if the flue is boxed in in the room above the smoke can still get out to the room through the floor and/or gaps in the boxing in. This is potentially dangerous as the room above a stove is often a bedroom.

So to sum up:

  1. You have to box in (or guard) twin wall flue in in a bedroom (often the room above the room where the stove is installed).
  2. You have to use a ventilated floor penetration component for nearly every other type of twin wall flue available in the UK.
  3. Ventilated floor penetration components are potentially dangerous because of the transmission of smoke to the room above.

In addition the new Selkirk innovative ventilation technique allows recovery to the room of the heat given off by the twin wall flue - every little helps.

Selkirk STC twin wall flue being tested

The innovative ventilation technique that Selkirk UK came up with together with independent flue consultant Mike Loud was of course fullY tested to EN1856. This testing was carried out at the GASTEC laboratories at CRE - see the GASTEC website here).
Here you can see a Selkirk STC twin wall flue
system under test at the GASTEC CRE
laboratories to test the safety of the new
ventilation innovation when using the non
ventilated floor penetration component.
Selkirk twin wall flue under test at gastec cre uk
This is the view of the test system from the
1st floor. Heat sensors test the air temperature
in the boxing in and are placed throughout the
boxing in as well as under the firestop plate.
Selkirk twin wall flue under test at gastec cre uk

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