# Does a staggered chimney cause problems?



## Corner (10 Sep 2009)

As part of our house design, our architect has produced a detail for a staggered chimney which shows it staggered through 45-degrees to ensure it rises in the corner of the bedroom on the first floor. I am concerned this will make the chimney less effective and restrict the "draw" of the chimney. Someone else has mentioned to me that it could lead to condensation problems within the chimney. The staggered part of the chimney in our sitting room will be 2.8m...basically it's staggered from the top of the fire place right up to the ceiling where it then rises vertically through the room above. Has anyone any advice or come across this issue before?


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## Peter C (11 Sep 2009)

Worth downloading Part J of the building regs, if the general design is within the regs I would not worry, there are thousands of chimneys with bends in them, it can improve the draught as a straight flue pulls the heat up the flue without restriction.


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## Corner (12 Sep 2009)

Peter C said:


> Worth downloading Part J of the building regs, if the general design is within the regs I would not worry, there are thousands of chimneys with bends in them, it can improve the draught as a straight flue pulls the heat up the flue without restriction.


 
Thanks Peter C, I checked up Part J of the building regs and it states that 

"Flues should be vertical wherever possible and where a bend is necessary, it should not make an angle of more than 37.5° with the vertical." This worries me as the design my architect has done is a 2.8m section of flue running at 45-degrees to the vertical. On the architectural detail, it it just looks suspect.


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## Peter C (14 Sep 2009)

We recently lined a chimney that had a similar bend running about 4 metres, the house was built circa 1930 with no known chimney problems, the reason we were lining it was to reduce the 9" diameter to 100mm to suit a new pellet stove. That said I would be inclined to bring the architects attention to part j.


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## onq (14 Sep 2009)

conormark said:


> Thanks Peter C, I checked up Part J of the building regs and it states that
> 
> "Flues should be vertical wherever possible and where a bend is necessary, it should not make an angle of more than 37.5° with the vertical." This worries me as the design my architect has done is a 2.8m section of flue running at 45-degrees to the vertical. On the architectural detail, it it just looks suspect.



Part J dates largely from the 1997 regulations, apart from some amendments.
Your archtiect should be aware of , and the flue should comply with, the Building Regulationss.

Many architects read Ivor H. Seeley in their formative years.
In the current edition section 5.1.2. Figure 5.1, Page 93 shows an elevations of the wall with the flue dotted in.
It cistes a 45-degree slopeas  being the minimum acceptable.
This is a "picture" and many architects assimilate information better graphically than via text.

However, when you look at P. 97, "Flue Installation", in the second paragraph of that section it states; -

_"Where bends are necessary, the angle of travel should be kept as steep as possible, preferably not less than 60_°_."_

My reading of this is "sixty degree from the horizontal" - that is thirty degrees from the vertical.

This accords with the 37.5° mentioned in the section you referred to above in Part J, on P.7;

_"2.5 Direction - Flues should be vertical
wherever possible and where a bend is necessary, it
should not make an angle of more than 37.5° with
the vertical. Horizontal flue runs should be avoided
except in the case of a back outlet appliance, when
the length of the horizontal section should not
exceed 150 mm."_

So gently berate him, but realise that the TGD are "guidance documents" and while they can give prima fascia compliance, they are not the only solutions.
Recommended minima of37.5° or 60°/30° may be desired, but that doesn't mean they are the only workable solution.

The real question for me is why you aren't simply; -

a) running it straight up abd using a built in wardrobe panel to hide it, or
b) projecting it to the outside of the wall and making an architectural feature out of the chimney.

For my money - well, its always _the clients_ money - there is nothing finer than a well-detailed chimney stack.
They are part of the language that defines a "house" separately from a modernist "box".
They are a vernacular feature of northern European architecture.

Still, you pays yer money and you makes yer choice.

FWIW

ONQ.


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## Corner (14 Sep 2009)

onq said:


> The real question for me is why you aren't simply; -
> 
> a) running it straight up abd using a built in wardrobe panel to hide it, or
> b) projecting it to the outside of the wall and making an architectural feature out of the chimney. quote]
> ...


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## onq (14 Sep 2009)

Well, not knowing what it looks like I'll just note this.
You mis-plan services and ducts, including flues. at your peril
They'll come back and bite you on the ass every time.

I'll also note something a wise architect once thought me.

_"Designing a building is a battle between:

a) what the client wants the building to be
b) what the architect wants the building to be and
c) what the building wants to become."_

To that I'll add what I have learnt, particularly with regard to private houses; -

1. Clients sometimes have unrealistic or contradictory ideas.
2. Architects' egos have an unerring ability to get in the way.
3. Buildings need to have their envelopes pushed - literally.

Judging from the problems you seem to be coming up against, you may have gone too detailed too soon.
Someone seems to have a particular view about fireplace positioning.

If might be very useful to look at other house plans that use the fireplace in a similar way to see how the upper floors have to work around it.
If you find a solution that seems to tick all the boxes, incorporate it into your design.
Don't think of this as plagiarism - its design research.



ONQ.


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## Corner (25 Sep 2009)

My chimney detail has now reverted to a 37.5-degree offset which complies with the regs. The length of the staggered section being so long is still a bit grey however some chimney people tell me there should not be a problem with this stagger even though the staggered part is now a 4-metre section (9-metre overall chimney length approx). Was considering the use of a chimney fan to assist wit the draw but was unsure if: 

(a) it would improve the chimney performance and therefore worthwhile
(b) i should opt for vertical or horizontal flow fan
(c) maintenance - it seems it needs to be cleaned once a year. My chimney is 2-metres high upon emerging from the roof. 
(d) is it recommended that the roof has lightning protection in some format as the electrical isolating switch will be mounted on the chimney controlled from within the house somewhere.

Would be grateful for any feedback!


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## DGOBS (26 Sep 2009)

Installation of a chimney fan is no substitute for poor design
and would not be advisable to overcome this issue. Design a flue that 
works


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## Peter C (26 Sep 2009)

Fully agree with DGOBS, fans should only be used as a last resort, they can be troublesome, assuming it is working fine what happens in the event of a power failure with the fire lighting ? Had a call recently where the stove was not working properly even with the fan on, the simple solution was to install a vent in the room, I doubt the fan was ever needed. The more air tight the houses become the more problems there will be with chimneys.


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## DGOBS (26 Sep 2009)

What is the point spending so much on air tightness testing only to fit an open flued appliance or chimney!

Do the building regs not require a minimum of 12000mmsq of ventilation in a room with a chimney?


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## Peter C (28 Sep 2009)

Fairly typical of a clash between the regs and what people want in their homes, I think it's half the chimney throat the minimum is 6500 mm2 permanent ventilation. There also appears to be issues arising from mechanical heat recovery systems and no permanent ventilation for combustion air.


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## DGOBS (28 Sep 2009)

But if you have mechanical heat recovery, then the pressure in the room would be negative and the flue/chimney wouldn't operate!
(wood need to be a room sealed stove)


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## Peter C (29 Sep 2009)

Yes, they are the issues I was referring to although there are more room sealed stoves coming available on the Irish market, people should pre plan the air ducts etc.


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## Corner (30 Sep 2009)

Thanks for all your comments! Have taken all your views on board. We have made numerous enquiries and the consensus appears to be that we will not encounter problems with the draw of the chimney. Unfortunately, there are constraints determining the "stagger" of the chimney. It was very useful to know that we need to install a vent in every room with a chimney.


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