Log Fires - the future?

[RaceDiagnostics]

That is about 700kg of dry wood.
This gives approx 3000kw/h of energy if dry. Not much different between any of the woods for the same weight - not volume of course.
At £240 = £0.08 per kw/h
At £160 = £0.05 per kw/h

Kerosene is about £0.05 per kw/h
Gas about £0.06p per kw/h

Electric - £0.24 per kw/h

So wood is still viable - much more so if it is free

The birch feels heavier than the larch so probably closer on cost per kWh/h

 

[JOEPRO]

Working out kw oil heating costs per unit in my house:
1l Kerosene = 10.35 kw of energy
Firebird condensing oil boiler @ 93% efficient
System losses allowance – 10%
= 8.59 kw per L
Cost per L inc Vat= 53.91pence
Actual KW unit cost on oil = 6.27p

You can go into system loses value based on house insulation etc but the above is a decent comparison between say Gas then and the efficiency of that specific boiler to see how it stacks up in real terms per kw of energy.

 

[addjunkie]

larch.......

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Those prices seem a decent enough if its kiln dried. Our supplier stacks ours for us to included in the price. Good job really as theMrs wont do it!

Working out kw oil heating costs per unit in my house:
1l Kerosene = 10.35 kw of energy
Firebird condensing oil boiler @ 93% efficient
System losses allowance – 10%
= 8.59 kw per L
Cost per L inc Vat= 53.91pence
Actual KW unit cost on oil = 6.27p

You can go into system loses value based on house insulation etc but the above is a decent comparison between say Gas then and the efficiency of that specific boiler to see how it stacks up in real terms per kw of energy.

Im inclined to agree at the current prices a decent oil system is as cheap as anything else. But regardless of how good your system and boiler are, or which heat source is used if your house isnt well insulated your paying to heat the fresh air in your garden, rather than heat staying in your house.

 

[Blobber]

Second log delivery of the season, the first delivery of 1.7m3 was of larch and has lasted 2 months and cost £160. This time I went with birch which was a lot more expensive at £240. Will be interesting to see how it differs, gut feel says I'll go back to larch.......

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The birch should be loads better burns hotter and longer I think, you can see it working already looks like sweat on Mrs Racediagnostics brow!

 

[gaz1]

That is about 700kg of dry wood.
This gives approx 3000kw/h of energy if dry. Not much different between any of the woods for the same weight - not volume of course.
At £240 = £0.08 per kw/h
At £160 = £0.05 per kw/h

Kerosene is about £0.05 per kw/h
Gas about £0.06p per kw/h

Electric - £0.24 per kw/h

So wood is still viable - much more so if it is free

youve forgotten your daily charge on the meter as that also needs adding

and theres cutting the wood up to smaller pieces

 

[JOEPRO]

What is also interesting is the true per kw cost of a coal multifuel stove is around 3x times that of oil heating:

Working out coal stove heating costs per unit in my house:
25kg Coal = 203.52kw of energy
Stanley Oisin Room heat only Stove @ 81.5% efficient
= 6.63 kw useful heat into room per kg coal
Cost per 25kg bag inc Vat= £10.50
Actual KW unit cost on coal = 15.79p

However, KW unit cost is really only one measure. Of course lighting a stove in one living room for a few hours each night is overall going to be much cheaper than running your oil boiler for a whole downstairs zone. (Since most houses are split by heating floor zone and not individual rooms)

There is guidance on the interwebs for specific species of timber calorific value too.

 

[winchman]

Just had a weekend away in a house with a log fire I was shocked at how much wood we used, glad it was included and not pay as you burn!

 

[Dilkris]

I think I can grasp the concept far better than many thanks
I run a large woodburner very hard. I have a modernish oil boiler and an oil fired aga. I also run electric heating and several Chinese diesel heaters along with a kerosene inverter heater so I have plenty of experience.

Well it would seem you most certainly have lots of experience in spending money..

 

[addjunkie]

Just had a weekend away in a house with a log fire I was shocked at how much wood we used, glad it was included and not pay as you burn!

Having holiday properties with log burners we find most only burn the basket of logs, as we charger for extras. Have also noticed if we set the fire ready to light, it gets lit regardless of temprature. If we just provide the materials they tend not to light them. There is very efficient underfloor heating too.

 

[Smallfry]

I don't agree with this airtightness thing. How can it possibly be healthy. Yes you can filter and dry the air, but what about oxygen ? Will still get condensation spores, bacteria etc.

Luckily we do not have to worry about efficiency, as we have a huge wood mountain, but of course there is a not insignificant cost and effort in collecting, moving, and cutting it all. We only really heat one room though and SWMBO sometimes cooks on the woodburner, which saves a bit on electricity. Also have an oil boiler to heat the DHW, but not filled the tank for about five years.

 

[Pigeon_Droppings2]

I don't agree with this airtightness thing

I assumed an air tight house was used alongside a whole of house heat exchanger?

The idea being that you swap the stale air for fresh air...and as you do it you scavenge the heat. This should be more efficient than venting rooms using cold air window vents.

I haven't got such a system...but I can see how it would be more efficient.

 

[Onoff]

Are airtight buildings good for people's health though I wonder?

You need to change the filter elements periodically in an MVHR system. Also clean the ducts every few years basically by pulling a "pig" through them.

The MVHR unit has a condensate drain.

The passiv haus build I went in had it and it was superb. Stale, moist, dusty, hot air out. Fresh, clean, cold air in. Circa 90% heat recovery as both streams pass through the heat exchanger.

I can imagine it'd be a problem if nextdoor has a bonfire next to your intake duct or if they're smoking strong weed!

 

[MattF]

Just had a weekend away in a house with a log fire I was shocked at how much wood we used, glad it was included and not pay as you burn!

It doesn't last long.

 

[Onoff]

You could always make your own:

 

[Erie Fred]

Outside wood stoves have become very popular around here.....

 

[Onoff]

We often take a couple of logs with us up the pub for the open fire.

 

[RaceDiagnostics]

We often take a couple of logs with us up the pub for the open fire.

I'll try that and swap for a pint.

 

[oldbikedavey]

In France , there is a system that uses a sheet metal flue that reaches up from the woodburning stove right up through to the roof exit.
There are then ductings that enable convection therefrom throughout the various floors of the building.
Highly effective , is that.
They do like as much efficiency as possible out there.
They'd skin a turd for a farthing, and three for a ha'penny....

 

[badabec]

Also clean the ducts every few years basically by pulling a "pig" through them.

Is that the same principle as dropping a live chicken down the chimney?

 

[gaz1]

What is also interesting is the true per kw cost of a coal multifuel stove is around 3x times that of oil heating:

Working out coal stove heating costs per unit in my house:
25kg Coal = 203.52kw of energy
Stanley Oisin Room heat only Stove @ 81.5% efficient
= 6.63 kw useful heat into room per kg coal
Cost per 25kg bag inc Vat= £10.50
Actual KW unit cost on coal = 15.79p

However, KW unit cost is really only one measure. Of course lighting a stove in one living room for a few hours each night is overall going to be much cheaper than running your oil boiler for a whole downstairs zone. (Since most houses are split by heating floor zone and not individual rooms)

There is guidance on the interwebs for specific species of timber calorific value too.

actually its not

having a back boiler on that stove is a much better option and would bring that value of efficientcy even higher than just a normal stove

with a normal stove you still loose alot of energy up the chimney that could be used elsewhere instead and just to be clear on high heat it is your looking at 1000f leaving your stove and going straight up the chimney

whilst a stove is better than a chimney fire with coal in the hearth