Woodburning stove recommendations please

fireman263

I am having a problem understanding all this science on woodburning stoves. These are not rocket science and were made well over a hundred years ago out of cast iron not steel. Chimneys were not lined. Chimneys were mainly brick. The main problems with these buildings were timber joist protruding into the brickwork of the chimney instead of being trimmed around them, thus sometimes causing loft fires. I would have thought that any modern house with a built in chimney was made to have a fire burning within. Condensation! Surely this will only affect metal or the newer modern building bricks but these would never be used in a modern chimney. Condensation would rise with the heat from the fire and once the temperature rises there would be no condensation,also brick holds heat for a long time. . I can see a liner usefull if a chimney is old and the lining material is breaking away but modern chimneys don't suffer this. There is a lot of hype since the old iron stoves are becoming popular with the rise of gas. Don't be taken in by people making a lot of money on selling products that you MAY not need.

Greenfires

It's a big subject - but the bare bones of it are:

There is massively reduced draught going up a chimney from a stove. Instead of room fulls of air charging up it every hour, the only draught up the chimney is what's passing through those little vents in the stove. That's why smoke from a stove chimney always looks lazy.

Most of the heat from the stove ends up in the room - not up the chimney - that's the whole idea of them. So there's less heat in the chimney, especially in the upper sections.

Many people think that wood should be dirt cheap "'cos it grows everywhere" So they scrat around for the cheapest they can find, which nine times out of ten is wet rubbish. This doesn't burn cleanly and puts a lot of smoke into the chimney. It also produces a fraction of the heat of the same amount of dry wood.

So - you've got smoke which is full of creosote and tar, a lazy draught, and a big cold masonry chimney. Most of the smoke will condense inside it and build up. Increased risk of a chimney fire, and not at all uncommon to get tarry stains on the chimney breast often upstairs. A fitter mate of mine recently took pictures of streams of tar running down an inside wall - an extreme case maybe - but it happens! Basically the tar in the chimney gradually eats its way right through the mortar until it makes an appearance in the house.

There is a lot of hype I'd agree - but on the other hand, the reason many installers will insist on a liner is that THEY are the ones who get it in the neck further down the line when a customer getting a job done on the cheap has problems - it's always the fault of the installer - and not the customer wanting to cut corners.

Unless a chimney is obviously leaking fumes, which isn't always that easy to find, then I'd always tell a customer they probably don't HAVE to have a liner. But for the reasons above, and also because stoves are generally much more responsive to the controls when they're on a liner, I'd almost always recommend one. They're also a whole lot easier and cleaner to sweep with a liner of course!

grahamc2003

Greenfires wrote: »

It's a big subject - but the bare bones of it are:

There is massively reduced draught going up a chimney from a stove. Instead of room fulls of air charging up it every hour, the only draught up the chimney is what's passing through those little vents in the stove. That's why smoke from a stove chimney always looks lazy.

Most of the heat from the stove ends up in the room - not up the chimney - that's the whole idea of them. So there's less heat in the chimney, especially in the upper sections.

Many people think that wood should be dirt cheap "'cos it grows everywhere" So they scrat around for the cheapest they can find, which nine times out of ten is wet rubbish. This doesn't burn cleanly and puts a lot of smoke into the chimney. It also produces a fraction of the heat of the same amount of dry wood.

So - you've got smoke which is full of creosote and tar, a lazy draught, and a big cold masonry chimney. Most of the smoke will condense inside it and build up. Increased risk of a chimney fire, and not at all uncommon to get tarry stains on the chimney breast often upstairs. A fitter mate of mine recently took pictures of streams of tar running down an inside wall - an extreme case maybe - but it happens! Basically the tar in the chimney gradually eats its way right through the mortar until it makes an appearance in the house.

There is a lot of hype I'd agree - but on the other hand, the reason many installers will insist on a liner is that THEY are the ones who get it in the neck further down the line when a customer getting a job done on the cheap has problems - it's always the fault of the installer - and not the customer wanting to cut corners.

Unless a chimney is obviously leaking fumes, which isn't always that easy to find, then I'd always tell a customer they probably don't HAVE to have a liner. But for the reasons above, and also because stoves are generally much more responsive to the controls when they're on a liner, I'd almost always recommend one. They're also a whole lot easier and cleaner to sweep with a liner of course!

Exhaust is 'lazy ' - should be if you are burning correctly. But some have the vents wide open all the time, in which case with a hot stove, the amount of air going up the chimney wil still be large (bot not as large as an open fire).

Most heat ends up in the room - depends on how the stove is operated. During overnight burning when the air is choked, about 95% of the heat goes up the chimney and not into the room. If the efficiency of a stove is quoted as 85%, then that means the maximum efficiency they've managed to get in whatever test they do with perfectly controlled (stoichiometirc) combustion is 85%. Depending on how well the stove is driven, the efficiency range in practice will be between 5% and 85%.

Wet wood - yeah, really counterproductive to try to burn. Although the same calorific value as dry wood, it produces less heat due to incomplete combustion, and much of the heat produced it is used to boil the water in the wood, leaving little to heat the stove.

Smoke full of creosote and tar - yeah, and soot. The point is that smoke is the result of incomplete combustion, and if you have complete combustion by operating the stove correctly, you don't get smoke and therefore don't get the gunk associated with it. You burn all the fuel by having the stove hot and the correct amount of air to completely burn all the fuel. Too little air (choking, as in overnight burning), and you'll get smoke, too much air and everything will be cooled down (the stove, the combustion chamber, the exhaust gasses and the chimney).

Liner - I had my chimney swept before I installed my stove, and the report said my 130 year old chimney was in good condition. The quote I got included a liner, and they said they never install without putting a liner in (which added over a grand to the cost). I installed without a liner and have had no problems at all in the 5 or 6 years since. (Also never had the chimney swept in that time, because I know I produce no smoke, not that I would advise others not to have a regular sweep). Liners have pros and cons, but installers naturally want to put them in, but in my case, I'd confidently say a liner wasn't necessary (or even advantageous overall).

A._Badger

The discussion about liners ebbs and flows and I must admit I can see both sides of it. As my chimney is over 450 years old (!) I bit the bullet and had a liner installed, but I really don't know whether I did the right thing - especially given the contradictory information about sulphur levels from burning smokeless fuel and their effect on stainless steel.

My suspicion is that nothing like enough scientific testing has been done on this subject and that much of the legend and lore of stoves and liners is based on theory, rather than empirical evidence.