Woodburner good, chimney height bad, what to do?

[88v8]

Chimney height....

Never had a woodburner, but having gone through our first winter with ye olde Yeoman Devon ( primary air only, and makes the cottage prodigiously dusty - here it is )

we are definitely hooked, and thoughts of oil heating have been abandoned.
In our other living room there is an inglenook with open fire & canopy, which already has a good register plate, and the fire opening is large enough for another woodburner. A Clearview Solution 400 would be the right size for the room, although with the large pane of glass it looks a little modern.

But.... to comply with the HETAS regs, the flue outlet has to be 6ft above the ridge. My ladder is in store, and peering from the ground I can see that probably we have no more than 5ft of freeboard above the thatch. The stack is stone, moulded, disproportionately posh for the cottage, and with an octagonal stone pot. I had thought to put the flue cowl on top of the pot, mounting it on a brass plate folded over to grip the top moulding of the pot.

The height.... the stack cannot be raised without destroying its history, and I am very disinclined to change the pot for a taller one, even supposing that it were permitted. This cannot be an unusual problem, although an installer I consulted was not forthcoming as to solutions.

What options are there? Do I add a narrowboat-style metal chimney & coolie-cap cowl to the pot?
http://www.limekilnchandlers.co.uk/index.php?act=viewProd&productId=470
or... might it be that the CO could 'persuade' Building Control to give a derogation? This would be the best option.

The existing Yeoman, there for 20+ years, exits quite happily through a chimney which I guess has less than 4ft of freeboard.

Any thoughts would be appreciated.

Ivor

 

[Penners]

My first thought is... how certain are you that the flue discharge height is truly only 5ft, and not the required 6ft?

I reckon it's very difficult to estimate the height of a chimney stack, looking up from ground level. The foreshortening effect can often make it look a fair bit shorter than it actually is.

Before you start spending money on an alternative arrangement, I'd recommend getting that ladder out of store, shinning up and having a proper measure.

 

[Flyfisher]

Firstly, I agree with Penners about the measurements. It's surprising how large chimneys can look when standing right beside them.

But mainly, I would definitely contact the CO and ask their advice. I tend to agree that this must be a common issue as wood burners become increasingly popular.

However, my main concern would be the insurance position and I'm not at all sure how an insurance company would deal with a non-HEATAS installation should the worst happen. Seems like a three-way discussion is going to be required.

 

[CliffordPope]

Measure the height by counting the number of chimney sweeping rods it takes before the brush pokes out at the top.

 

[garnett]

Hi

If you have a non HETAS installed burner in a thatch building you have a serious issue. Most insurers that cover thatch now have a get out clause because that fires are up 4 x since 2000 due to woodburners with single skin liners. It must be a double insulated liner for thatch.

Take a look at the master thatchers web site as they have researched this well.

Garnett

 

[garnett]

Further to my last, do you really need to raise the height of your chimney or has it been overthatched so many times that you have traveled up the chimney?

It is not oncommon for there to be 10-12 ft of thatch working its way up the chimney which again contributes to the fire problem because the stack is extreamly well insulated in this zone.

Garnett

 

[Penners]

It must be a double insulated liner for thatch.

To my simplistic mind, that sounds odd. The flue of a woodburner is lined to ensure that the hot gases don't cool on the way up, such that they condense. So it seems to me that there's more chance of glowing sparks spewing out of the top of the chimney with an insulated liner than with an uninsulated one.

Or have I misunderstood?

 

[AMc]

I thought spark arresters were fitted to the top of the flue to discourage sparks, I vaguely remember this from my parents' installation.

I thought the problem is that the fires can begin as a result of the flue bringing the thatch to the point of smouldering deep within the covering - where the thatch is insulated by the thatch above it trapping the heat and letting it reach the ignition point. I thought sparks were less likely to cause problems but should clearly be avoided!

Some helpful hints from an insurer
http://mymutual.nfumutual.co.uk/articles/thatch/thatch-fire-safety.htm

A caution.
I don't know how it started but I cycled past this place yesterday which is very similar to my parents' thatched house near by.
My heart goes out to the owners it must be absolutely devastating as the house appears to be completely gutted.
http://www.edp24.co.uk/news/firefighters_from_across_norfolk_battled_blofield_thatched_roof_fire_1_1342961

 

[garnett]

Hi

The spark and firework issue has long been blamed for thatch fires, but the vast increase in the last ten years has been researched by the master thatchers and has been discounted. It is really difficult to set fire to somthing below a heat source because heat rises and it is easy to put out because you can pour water on it.

The fire cause is often in the most insulated area, the thatched zone of the chimney. It happens when a tiny bit of the unlined flu touches the brick or stone and causes a super hotspot in excess of 1000 degrees which slowly ignites the core thatch. The first thing you know about it is when the fire has worked its way right along the super dry core thatch to the other end of the building and it then gets air several hours later and away it goes in minutes. Down here in Devon the fire service see this and start salvaging the possessions because there is no way to put this type of fire out. You can’t get water to it. That is the difference between a spark fire and a flu fire.

Devon & Somerset Fire Service in conjunction with the Devon Conservation Officers' Group now have all thatched buildings recorded now. Devon has a 6th of the thatch in the UK so it is a huge issue for us. They have a new foam injection system that uses long lances to try and inject a fire break into the roof. These units are strategically located in the county and rely on people having heat detectors in the roof space.

It would be really useful if PPUK could do a proper story on this. I have a DVD of the Master Thatcher’s joint conference with the Devon & Somerset Fire Service that I could loan if that helped?

Thanks

Garnett