Woodburner...

[Billhook]

51 minutes ago, Canal Navvy said:

It would be fascinating to know how much lower the air pressure is in your house than atmospheric pressure outside 😉

Depends on my wife!

[Rob_the_Sparky]

I suspect you will find that an open fire will give more direct heat but less total energy so they might be nice to sit in front of but relatively ineffective at heating the room.  However, I'm more than happy with the radiated heat from a stove and would never go back to an open fire.  If a stove is over sized though you may have to run it cool to prevent it over heating the house.  In that case you will get relatively little direct (radiated) heat and just have a nice warm room.  Not sure there is a right sized stove but our stove is undersized so we run it more or less flat out all the time and rely on the central heating when it gets properly cold outside.

I'm sure though the right answer is not an open fire.

[openspaceman]

1 hour ago, Rob_the_Sparky said:

However, I'm more than happy with the radiated heat from a stove

I have been impressed at how much radiated heat I get through the glass of my stove, my previous Jotul had a solid iron door.

[peds]

We have an open fire to heat our old, poorly renovated, uninsulated cottage. I resent the speed at which it chews through firewood, and as soon as it's out, the room is cold again. We are renting, hopefully only here for another year or so whilst we build our house. I am weighing up the cost and hassle of converting the fireplace to a stove, which we'd bring with us to the new house anyway, compared to the time, energy, and timber it would take to chop 5 times as much firewood to keep the place from freezing.

 

Open fireplaces look great and are fun to play with, but they suck at heating anything further than a few metres away, and eat much more wood to do a bad job of it.

Edited December 13, 2021 by peds

[fcharlton]

Surprised that no one has mentioned the Tortoise firebox. It works by convection of air and is very efficient. However it is open at the front and there is the magic of seeing, hearing and smelling the wood burn which you dont get when the fire is sealed in a box with glass doors. Its like the difference between swimming in a river or the sea and swimming in an indoor swimming pool. Do some more research. There are efficient open fires.

 

 

[john87]

34 minutes ago, fcharlton said:

Surprised that no one has mentioned the Tortoise firebox. It works by convection of air and is very efficient. However it is open at the front and there is the magic of seeing, hearing and smelling the wood burn which you dont get when the fire is sealed in a box with glass doors. Its like the difference between swimming in a river or the sea and swimming in an indoor swimming pool. Do some more research. There are efficient open fires.

 

 

Just looked them up.. That might be just the thing to suit me!! They look like they would be easy to install in the space i have too [nearly 4 foot square but not very deep]

 

Thank you very much!!

 

john..

[Billhook]

I have been searching the web  for a study of the efficiency of open fireplaces compared to wood stoves and came up with this 2007 report.

https://core.ac.uk/download/pdf/61497708.pdf

 

To cut a (very) long story short they found that an open fire is half as efficient as a wood stove  30% as opposed to 65%

But the amount of variables in an open fire is huge.  Apart from the fireplace design and chimney design it makes a big difference if the chimney is on an outside wall, whether brick ,metal or lined or insulated flue and whether air is drawn in under doors and through inefficient windows.

I suggest that my Rumford would be far more efficient.  the proof is in the pudding.  I can put a handful of logs for overnight burn in both the Stratford and the Rumford and the embers will still be glowing eight hours later in both fires.

I will fix some chairs on the far wall opposite the Rumford and strap any disbelievers to the chairs until they beg for mercy!

8 minutes ago, fcharlton said:

Surprised that no one has mentioned the Tortoise firebox. It works by convection of air and is very efficient. However it is open at the front and there is the magic of seeing, hearing and smelling the wood burn which you dont get when the fire is sealed in a box with glass doors. Its like the difference between swimming in a river or the sea and swimming in an indoor swimming pool. Do some more research. There are efficient open fires.

 

 

Yes, I agree with you there are many different designs to assess., my neighbour has a Jetmaster and is very pleased with it but my Rumford is much better.

There is no way that you can put my Rumford in the same category as my parents old fireplace in the old house.

Open Fires | Mendip Fireplaces

MENDIPFIREPLACESBATH.CO.UK

---

Contemporary and traditional open fires shown with a selection of stone, timber and marble surrounds.

Going back to John who started this thread, I still suggest that he tries a Rumford in one of his fireplaces built to the correct specification.  I found the initial diagrams in a book called "Wood Heat" by John Vivian, you can find a copy on ebay for not a lot.  Vital  to have a large diameter air pipe taking air from outside to the fire to stop draughts.  Too small a pipe will cause the air to roar to feed the fire.

And yes John your metal will radiate more heat into the room.  I have put a smaller 2 foot square Rumford in the bedroom (24'x24') and put a heavy  cast iron plate at the rear which improves the radiated heat.  The Rumford in the living room (24'x18') is 3 foot square  

You will then be able to compare the two with more accuracy.

If it does not perform as I say then feel free to call me all the names you want on Arbtalk!

[john87]

4 minutes ago, Billhook said:

I have been searching the web  for a study of the efficiency of open fireplaces compared to wood stoves and came up with this 2007 report.

https://core.ac.uk/download/pdf/61497708.pdf

 

To cut a (very) long story short they found that an open fire is half as efficient as a wood stove  30% as opposed to 65%

But the amount of variables in an open fire is huge.  Apart from the fireplace design and chimney design it makes a big difference if the chimney is on an outside wall, whether brick ,metal or lined or insulated flue and whether air is drawn in under doors and through inefficient windows.

I suggest that my Rumford would be far more efficient.  the proof is in the pudding.  I can put a handful of logs for overnight burn in both the Stratford and the Rumford and the embers will still be glowing eight hours later in both fires.

I will fix some chairs on the far wall opposite the Rumford and strap any disbelievers to the chairs until they beg for mercy!

Yes, I agree with you there are many different designs to assess., my neighbour has a Jetmaster and is very pleased with it but my Rumford is much better.

There is no way that you can put my Rumford in the same category as my parents old fireplace in the old house.

Open Fires | Mendip Fireplaces

MENDIPFIREPLACESBATH.CO.UK

---

Contemporary and traditional open fires shown with a selection of stone, timber and marble surrounds.

Going back to John who started this thread, I still suggest that he tries a Rumford in one of his fireplaces built to the correct specification.  I found the initial diagrams in a book called "Wood Heat" by John Vivian, you can find a copy on ebay for not a lot.  Vital  to have a large diameter air pipe taking air from outside to the fire to stop draughts.  Too small a pipe will cause the air to roar to feed the fire.

And yes John your metal will radiate more heat into the room.  I have put a smaller 2 foot square Rumford in the bedroom (24'x24') and put a heavy  cast iron plate at the rear which improves the radiated heat.  The Rumford in the living room (24'x18') is 3 foot square  

You will then be able to compare the two with more accuracy.

If it does not perform as I say then feel free to call me all the names you want on Arbtalk!

I found a website of a firm that make the required bits and pieces, precast clay fittings for the flue adn things like that, but they are in the USA. How did you get the bits for yours or is it all homemade as it were?? [because they do appear the thing to have]

 

I will try to find one of them books now!!

 

john..

[Dan Maynard]

I'm fascinated by the Rumford fireplace, never heard of it before.

If you read the rest of the Wikipedia article though, he went on to invent a cast iron wood burner called the Rumford stove which was expensive but the efficiency gains made it economical in the long term.

So even Rumford gave up on the open fire.

[Billhook]

Big J  I am not arguing that the average open fire at 20-30% is in anyway near the highest 80% efficient stoves.

There are very different types of fireplace, just as there are very different types of wood stove.  I am not denying that the most modern and efficient wood stove with all the goodies will be the most efficient.  What I will argue is that a poorly designed wood stove fitted to a poorly designed flue will be probably outperformed by a properly built Rumford.

There are so many variables.

Variables in flue design, air control, insulation so a stove with poor features in these areas will soon be equivalent to a Rumford with good features.

 

A new very rich owner of a house nearby had some plumbing work done and the previous owner had installed a large wood stove.  This stove was built in Eastern Europe (badly) had double doors which did not seal. It looked good with polished brass handles.  Anyway the new owner asked the plumber if he wanted it, so he said yes please and took it home, but his wife said no, too big, too ugly so he gave it to me and we took it down to the log cabin.  It took three of us the lift it into position.  It never heated the cabin (25'x25') properly and took a large amount of wood to feed it.  No proper air control but I did fit an insulated flue above.  However this meant that you could put the back of your hand on the flue so none of that heat went into the room, it all went out of the chimney.

A year or two later some pleasant people came in the night in the middle of a blizzard, one climbed onto the roof and undid the lead flashing on the chimney, took the flue and the stove.  A kindly neighbour took pity and donated her heavy old stove with no glass and again double doors which wasnot much better than an open fire, but at least we could shut it up for safety in the wooden cabin.

So two examples of pathetic wood stoves and I can state that the Rumford is infinitely better than both.

 

There are other factors in the often quoted 20% versus 80% figures.  These always come from people trying to sell wood stoves

Going back to flue design and insulated flues, if the latter is fitted it surely means that a lot of heat is lost straight out of the chimney  In the case of my Rumford there is a clay flue surrounded by brickwork and any heat lost up the chimney goes into this heat sink and can be felt upstairs in the bedrooms.  This heat transfer does not seem to be taken into account during "scientific" stove tests.

This man has quite a good video on heat loss with a stove and his improvements

 

But heat efficiency aside, when people come into our living room for a Christmas drink and see the Rumford going, they are immediately drawn to it, conversation flows easily with the drinks and this does not happen with our wood burners in the same way.  They may comment on the Aduro and say how it looks good but there is something about an open flame.

Perhaps by opening the doors of the stove it would be similar but it is not the same.