Woodburner questions

[mh12]

Dear All

Thinking of having woodburners installed in 2 ground floor rooms of semi detached property. The rooms in question have gas fires fitted and functional chimneys.

However both chimney breast show evidence of either water ingress from open top chimney pots or from salts causing condensation in the chimney breast

Gas fires have not been used in the property for about 4 years.

Questions (and apologies if they are naive):

1) Will the introduction of heat into the chimney stack and breast with woodburner use aggravate the salts and cause spreading of damp on chimney breast?

Chimney pots are squared types and will have cowls fitted to limit water ingress

2) If you have had a woodburner installed have you been, overall, pleased with heat output and do you feel the installation was worth it?

3) Probably a daft question but will the wood burner just keep the immediate room warm or has it the potential to warm the upper floors 1 and a stretch 2 warm as well provided the door to the room with woodburner is kept open?

thank you

 

[a twig]

1) More likely to dry it out - get the installer to skip the vermiculite backfill around the flue if you are worried about water ingress, as that water will turn the vermiculite into mush. It’s what we did and installer was very happy to not have to carry all those 25kg bags up a ladder to pour down the chimney.

2) Absolutely - even the small morsoe burner we have in this place will get a 25 metre squared room up to 23’C if I drive it enthusiastically enough.

3) It depends on how you big you size the burner and the airflows and layout in your house but diminishing returns and all that - probably best to think of it as a potential positive side effect rather than something to aim for.

 

[jamest]

Definitely second twig's last two points - we have a 5kW rated burner in a 87 cubic metre room and it will heat it nicely if driven. If your burner is rated higher than 5kW, then regulations demand that you have sufficient air flow from outside and your installer could insist on installing a vent of some kind in your wall (which I definitely did not want). It doesn't noticeably heat the rooms above, probably because there is too much insulation between the floors, but once it's gotten going it will heat the room next to it (if the connecting door is left open). I did the heat loss calculations and the two rooms lose about 3 kW, so I guess it's not surprising.

 

[Kearn]

The stacks will require a stainless liner with a burner, which minimises heat through insulation, but certainly the bricks getting warmer will only help.

Salts will be drawn out as the bricks dry, but should be more into the internal chimney. That’s a good thing all round. Heat won’t ‘spread damp’.

There’s no need for anything else in the chimney, such as insulation, counter intuitive really.

Woodburner prices fluctuate, summer is a great time to shop. And shop around.

Stay under 5kW, otherwise you technically need an external vent for airflow. The rating is also often the minimum output, even if not, 5 is more than enough!

Get a decent, British brand, as with most things, you get what you pay for - quality, output, performance and maintenance. I’m getting Clearview and Stovax, Charnwood also good.

In terms of the heat spreading/rising, that’s going to be limited by your insulation etc. but some heat will move around the house, but that’s a bonus only as some supplementary heat.
It’s a style thing too, but size it to the opening, within reason so it looks proportional. Some have full swing doors, single or double, so you can have a sort of open fire too, but that’s for the sound and smell, performance is better if closed.
Mine will be shallow, and wider, as both openings are huge, but I don’t want to go over 5kW.

Both downstairs rooms that will have burners, I have slightly undercooked my rad heating output with the intention that when it’s cold enough, the fires will supplement output to balance out. There’s only so much output feasible from UFH!

 

[Flyfisher]

Just be sure to factor in the cost of firewood from whatever sources you may have, because it's not particularly cheap to buy. We have three multi-fuel stoves (Stovax fwiw) and they are wonderful things, but we also have a free source of firewood (well 'free' after a lot of chainsawing, splitting and seasoning for a year or two).

 

[paulc]

I installed a multifuel stove a few years back. Rated at 7kW, so needed an air vent, for which I used a Rytons AC3LP. Took a little bit of persuasion to get the HETAS installer to accept that it was suitable. Once I showed him the numbers, he finally accepted it.
The uninsulated liner runs up through the chimney breast in an upstairs bedroom, and having the stove running for a few hours, the bedroom benefits from the heat being stored in the brickwork. As for the chimney breast in the lounge, that acts as a huge thermal battery, and the room is often nice and toasty in the morning even after the fire has gone out.
In the last year or two, I've found that cheap/free logs to be in short supply - Way too many people chasing after a limited resource. For winter 2006/7, I've stocked up on wood pellets and ecologs. Already used a few, and when mixed with regular logs, the pellets & ecologs burn for quite a long time.

On reflection, I should have fitted a 5kW stove, as 7kW is just too much. The lounge door stays open, and the heat helps to warm the rest of the house. Not really a surprise, as the gas boiler will run at 5-6kW to do the same job (at tick over, even 3.2kW is enough to maintain temperature). But I chose the stove for appearance (and price) over power output. Even so, I wouldn't be without the stove. Side note: The average house only needs 6-8kW to heat the whole place and maybe 3-5kW to maintain the temperature.

One final note - I find my stove runs best with the door closed at all times. Sometimes you get wood that likes to spit hot embers out, and the closed door will contain the sparks.

 

[Alex_]

2) If you have had a woodburner installed have you been, overall, pleased with heat output and do you feel the installation was worth it?

3) Probably a daft question but will the wood burner just keep the immediate room warm or has it the potential to warm the upper floors 1 and a stretch 2 warm as well provided the door to the room with woodburner is kept open?

We have two downstairs we use for heating - only electric ufh for heat otherwise- both rated at 5kw, but one is square the other is rectangular, and the rectangular one puts out a lot more heat so take the kw ratings with the nudge and the wink intended. The heat spreads and they easily keep the rooms they are in at 20C+ and the adjacent and above rooms get a decent amount of heat too if you're burning all day, as we tend to do working from home. As mentioned above, heating the brickwork in the surround and chimneys really helps as well, there's a lot of energy you're storing in there for slow release overnight.

Wood isn't cheap unless you can source your own though - current prices for seasoned hardwood around here are about £140-160m3. We used 5m3 overwinter.

 

[paulc]

Wood isn't cheap unless you can source your own though - current prices for seasoned hardwood around here are about £140-160m3. We used 5m3 overwinter.

That 1m³ is usually for a loose load. Once stacked, the actual quantity can be rather disappointing. If you are lucky, for every cubic metre of loose, you might get a half cubic metre when stacked neatly.

 

[Zebra]

It might or might not heat the upstairs. My small living room with a big wood burner also contains an open staircase directly to the bedroom but the heat doesn't go up there because there's nowhere for the cold air to come back down again, so no circulating current.

 

[skierhughes]

Just to add our experience to the others.
We have two wood burners.
One also has a back boiler connected to a 1000l store and 200l DHW tank. This is 43kW and has an outside air source. It heats all the radiators, 28, and will do a great job of keeping it all warm whatever the temperature.
The small one is a 5kW in my wife's office, we also bother work from home, so we heat the house all day everyday. I haven't worked on my office yet, but when I do, a wood burner will also go in there, so I can either wear less clothes or not freeze to death. When we work we use the small fire to heat the room and let the dogs and cats freeze!!
The house is large, our internal doors stay open all the time.
The heat does move around the house, but it does not heat the other rooms particularly.
We only have floorboards as our ceilings, so we do get heat movement from below to above, so the lounge will also heat two bedrooms.
The Aga in the kitchen heats our bedroom
We use about 16m cubed of stacked wood in a cold winter just for the big burner and about 2 for my wife's office.
We also have Heat Genius wifi valves on each radiator so we can heat all of the rooms as we wish to what temp we wish, we have a few rooms that are not used on a regular basis.

 

[Lacan07]

Dear All

Thinking of having woodburners installed in 2 ground floor rooms of semi detached property. The rooms in question have gas fires fitted and functional chimneys.

However both chimney breast show evidence of either water ingress from open top chimney pots or from salts causing condensation in the chimney breast

Gas fires have not been used in the property for about 4 years.

Questions (and apologies if they are naive):

1) Will the introduction of heat into the chimney stack and breast with woodburner use aggravate the salts and cause spreading of damp on chimney breast?

Chimney pots are squared types and will have cowls fitted to limit water ingress

2) If you have had a woodburner installed have you been, overall, pleased with heat output and do you feel the installation was worth it?

3) Probably a daft question but will the wood burner just keep the immediate room warm or has it the potential to warm the upper floors 1 and a stretch 2 warm as well provided the door to the room with woodburner is kept open?

thank you

You generally want the unit to stand slightly out of the recess with the use of an 2 elbows, otherwise a lot of wasted heat goes into the back wall.

 

[skierhughes]

otherwise a lot of wasted heat goes into the back wall.

Our chimneys are nearly all back to back, out of 10 only 2 are on an outside wall., but that is a useful point for any that are.