Internal flue pipework route? Exposed or buried?

[ashthekid]

Hi,

 

I’m not sure if there is an obvious answer to this question but I attach a CGI showing the layout of our kitchen/living area where we are planning on having a wood burning inset corner fireplace(to the right) where the flue cannot go straight up out of the roof so the plan is to either have the flue run along side the internal vaulted ceilings and then out the top on the opposite sloped roof side.
Is there a regulation limit to the length of flue internally? Can it have bends? And finally could this flue be buried between the rafters/insulation board? There is 100mm gap between rafters and then another layer of 100mm insulation of top of the rafters so plenty of room but I’m not sure of regulation it safety. I’ve outlined the potential route in black if it’s exposed. It would be approx 3m.

[Temp]

I think they recommend bends are limited to 45/135 degrees so the flow is always within 45 degrees of vertical.  

 

1 hour ago, ashthekid said:

There is 100mm gap between rafters and then another layer of 100mm insulation of top of the rafters so plenty of room

 

That's not a lot of room. Most hot flue pipes are 150mm diameter and combustible materials need to be three diameters away...

 

Diagrams here are from Approved Doc J..

 

https://www.stovefitterswarehouse.co.uk/pages/rules-for-wood-burning-stoves#:~:text=The key rule for all,from combustibles in any direction.

 

Quote

Any combustible material must be three times “X” away from the flue pipe where X = the diameter of the flue pipe. This means that your 5″ flue pipe should be 15″ away from combustibles and your 6″ flue pipe should be 18″ away from combustibles in any direction.

 

 

 

 

So some sort of twin wall insulated flue will have to be used. Others are more familiar with the rules for those. @pocster perhaps.

Edited August 5, 2021 by Temp

[ashthekid]

Assuming an insulated flue pipe can be used I could still maybe conceal that flue pipework in between the rafters as long as it’s boxed in with an air gap inside the box?

 

I attach what I think may or may not be relevant:

 

[crispy_wafer]

I dont have a lot to add, other than twinwall flue allows you to router a lot closer to combustable materials, this usually means an extra couple of inches on the O/D though - which could be worth bearing in mind if there are obstacles en-route.

There are some rules regarding number of bends too. 

Give consideration to sweeping too.