Burning softwood or hardwood does it matter?

[ericmark]

I was told in Winter when very cold burn hard wood and when not so cold burn softwood however when I look on the Forrestry Commission website I note there is very little in the heat outputs of soft and hard woods when measured by the kWh/tonne or GJ/tonne (divide or times by 360 to change between the two).

However when we fill a stove we fill a set volume not a set weight so with the old idea of banking down stoves and burning 24/7 then clearly soft and hard woods would make a difference.

However because of particular emissions stoves need to be run hot and excess stored in a heat store Megaflow, Gledhill and Willis for example and then called upon when the stove is not lit so no longer should we run stoves 24/7 at least not if we are trying to be eco-friendly.

Some stoves are very good at controlling the flue temperature where others are not so I would consider much will depend on the make and type of stove but where the flue becomes hotter with hard wood than it is with soft wood then it would seem more heat is leaving the house up the flue so hard woods may in fact not be as good as soft woods assuming bought by weight and it would be silly to buy by volume.

However the guy who asked me to look into wood burner efficiency only has very old wood burners so there is no way for me to test a modern eco-friendly system to show if using hard or soft wood matters.

I am sure there must be people with these modern systems which will comply with HETAS (Heating Equipment Testing and Approval Scheme) and DEFRA (Department for Environment, Food & Rural Affairs) rules plus all the Part L, J etc building regulations who can report what in real life does using hard or soft woods mean when using a wood stove. Theory is great but what about in the real world?

Clearly at £11,000 to fit a system ( Which guide) without knowing what to really expect is not something I would want to do and the guy already has the woodland and he is not allowed to change type of tree grown as it is a SSSI site.

Any input would be appreciated.

Eric

 

[chapeau]

Some stoves are very good at controlling the flue temperature where others are not so I would consider much will depend on the make and type of stove but where the flue becomes hotter with hard wood than it is with soft wood then it would seem more heat is leaving the house up the flue so hard woods may in fact not be as good as soft woods assuming bought by weight and it would be silly to buy by volume.

The efficiency of combustion is dependant on temperature - higher the temperature, the more efficient the burn.
If you buy your wood by weight you are open to being charged for excess water.
Softwoods not only burn at a lower temperature, they muck up your flue faster than hardwood.
Well seasoned hard woods are by far the best fuel supply. Well seasoned firewood is hard to find though.

 

[ericmark]

The efficiency of combustion is dependant on temperature - higher the temperature, the more efficient the burn.

That does seem to be what many sites say at least over 600 deg C to burn off particular emissions but unless you can remove some of that heat before it goes outside then although an efficient burn the energy is still wasted. Although there are some really good water cooled systems where over 90% of the energy is used these are not the normal type of wood burner found in most homes. I have looked at the instructions for cheaper types and I just can't see how anyone not brought up with wood stoves would every work out how to run in an efficient manor?

If you buy your wood by weight you are open to being charged for excess water.

I see your point but it would seem there is a legal requirement for approved fuel merchants to declare the moisture content so this should only be the case with illegal sales. I will admit I was rather surprised at number of regulations and I do wonder how many do break the law?

Softwoods not only burn at a lower temperature, they muck up your flue faster than hardwood.

It would seem from what I read this depends on the design of the stove. And this is the real problem of all the people with wood burners I know only one has a quality stove and he was saying how he can burn near anything. It has all the automated draft and damper controls to extract the maximum and store until required in a water store. I look at how much wood he uses and there is a marked difference to how much others use but since he also has solar panels.

Well seasoned hard woods are by far the best fuel supply. Well seasoned firewood is hard to find though.

That does seem to be the case.

 

[Burnerman]

Dry hardwoods (less than 20% moisture) give you the most heat, in a nutshell - and oak and beech are the most popular.
Ash can be burnt almost straight from the tree because the moisture content is low anyway.
Fast growing softwoods like spruce burn fairly quickly if the logs are small, but smoulder a bit if the logs are large.
Its a reasonable idea to get a moisture tester from Toolstation, and a flue pipe temperature thermometer from Stovax or similar......anything to prevent resins forming in the flue.
John

 

[ericmark]

I have been testing moisture but I have long been saying the flue temperature was the key but until you named them I had not found a device which could easy be installed.

I was using a thermocouple and a hand held meter but no idea as to temperature I should be looking at until your post.