woodburner / kitchen extractor question

[Marko]

We always put in vents for any fire/ log burner. Even more important in a new build as the whole building will need to be air tested for leaks.

 

If the building needs to be airtight, should the ducting not be direct to the fire?

[Marko]

Googled it. All makes sense now.

 

Room sealed stoves with external air supply

[neiln]

Hetas/building regs call for a vent to the room for all stoves over 5kw. some modern larger stoves have facility for the air inlet to be connected to the outside duct/vent but most just draw from the room. the regs call for the stove draw to be tested with all windows and doors to the room closed and any extractors running, and again with doors to other rooms with extractors open and those fans running (eg bathroom, or kitvhen if stove in lounge). not sure but i think the regs allow for a hot flue...i seem to recall something about heating the flue for a certain period with a blow torch before redoing the test.. if the test fails/smoke is drawn into the room, then more airbricks are needed.

 

i dont see what difference a carbon filter in the extractor makes....it'll reduce extraction rate slightly i suppose but its easily removed....you normally only bother with filters if a hob fan is merely recirculating.

[Mull]

Hetas/building regs call for a vent to the room for all stoves over 5kw. some modern larger stoves have facility for the air inlet to be connected to the outside duct/vent but most just draw from the room. the regs call for the stove draw to be tested with all windows and doors to the room closed and any extractors running, and again with doors to other rooms with extractors open and those fans running (eg bathroom, or kitvhen if stove in lounge). not sure but i think the regs allow for a hot flue...i seem to recall something about heating the flue for a certain period with a blow torch before redoing the test.. if the test fails/smoke is drawn into the room, then more airbricks are needed.

 

 

 

i dont see what difference a carbon filter in the extractor makes....it'll reduce extraction rate slightly i suppose but its easily removed....you normally only bother with filters if a hob fan is merely recirculating.

 

 

I was under the impression that carbon/charcoal filters were 'just' recirculating into the room, therefore not changing air pressure in room, in turn not affecting stove?

[neiln]

exactly.

 

Many hob fans/hoods can be set to extract, or recirc. I meant when on extract its normal to remove the filter as it is pointless and just gums up with fat.

 

Ahh... think i get it now... stove fitter wants the extractor removed. It can be replaced by a recircing hob fan. that's what he is insisting on. Sorry...I'm being slow tonight.

[Mull]

exactly.

 

Many hob fans/hoods can be set to extract, or recirc. I meant when on extract its normal to remove the filter as it is pointless and just gums up with fat.

 

Ahh... think i get it now... stove fitter wants the extractor removed. It can be replaced by a recircing hob fan. that's what he is insisting on. Sorry...I'm being slow tonight.

 

 

Ok, I didn't realise they could extract or recirc, but that makes sense👍, sort of! Bit of an eye opener for me this thread.

[Gbaz]

If the building needs to be airtight, should the ducting not be direct to the fire?

The vent doesn't need to be direct to the fire. Building regs on air tightness are a bit of a nonsense really. For regs it is necessary for all windows to be fitted with trickle vents and all bathrooms to have extractors. When the air test is done the vents/extractor grills are all shut or sealed with tape. What is the point of the building being air tight when all these leak points are normally open?!

[muttley9050]

The vent doesn't need to be direct to the fire. Building regs on air tightness are a bit of a nonsense really. For regs it is necessary for all windows to be fitted with trickle vents and all bathrooms to have extractors. When the air test is done the vents/extractor grills are all shut or sealed with tape. What is the point of the building being air tight when all these leak points are normally open?!

 

They don't air test all new builds only buildings that are supposed to be hermetically sealed under the passive house initiative. That is unless they started doing it in the last 3 years since I last built one.

Passive house building goes to a much greater extent to seal buildings than in standard building techniques. And in this method no trickle vents are required

Edited February 27, 2016 by muttley9050

[Gbaz]

We do one or two new builds a year. Every new build our company has been involved with has had to be air tested for the last few years. I can't remember when it started. Building control always want trickle vents. Regs change so often I'm not sure even building inspectors keep up with it.

[maria warwick]

If it is a stainless steel chimney on your extractor fan then there should be a plastic duct insert to deflect the flow of air through the side vents on the stainless steel chimney and hense back into the room. Then obviously use the re-circ filters.