Woodburner air supply?

[janedevon]

Hi  on our timberframe we have a small woodburner planned in the open plan lounge dining room the plan shows an air supply from an external wall to the stove this has to go through the srudy does this generally run under floor or can it be under the beams of celing, just trying to get the idea in my head of whats required prior to arranging floor finish.

 

[Jeremy Harris]

It needs to run under the floor and be sealed well to the external air inlet on the stove, to prevent cold air drafts coming in to the room through the vent.  Aim for as good a seal as you can possibly get, as these air vents are a significant cause of heat loss even when sealed well and are pretty horrific if not sealed properly.

The reason they always cause a big heat loss is because, when the weather's cool, but not cold enough to warrant lighting the stove, cold air flows through the vent and stove, turning it into a cooled box that draws heat out of the room.

Given the very high pollution levels from wood burning stoves (they are around 100 times worse than a good diesel car) have you thought of using an alternative?  They are a major cause of particulate emissions, in particular, and are well-proven to be pretty harmful to health, so much so that some places are now banning them outright.  I'll admit to being a bit biased, as I live in a valley which fills with toxic woodsmoke on calm winter nights, all from one selfish individual with a wood burning stove!

[Inchbyinch]

3 minutes ago, JSHarris said:

It needs to run under the floor and be sealed well to the external air inlet on the stove, to prevent cold air drafts coming in to the room through the vent.  Aim for as good a seal as you can possibly get, as these air vents are a significant cause of heat loss even when sealed well and are pretty horrific if not sealed properly.

The reason they always cause a big heat loss is because, when the weather's cool, but not cold enough to warrant lighting the stove, cold air flows through the vent and stove, turning it into a cooled box that draws heat out of the room.

Given the very high pollution levels from wood burning stoves (they are around 100 times worse than a good diesel car) have you thought of using an alternative?  They are a major cause of particulate emissions, in particular, and are well-proven to be pretty harmful to health, so much so that some places are now banning them outright.  I'll admit to being a bit biased, as I live in a valley which fills with toxic woodsmoke on calm winter nights, all from one selfish individual with a wood burning stove!

What alternatives did you have in mind? SWMBO is looking for a warm glow in the corner feel for our main room and id be interested in thinking about an alternative to a stove?

[janedevon]

Plus one for me thanks for the input tbh while i like a log burner, we currently have one and an open fire its probably not going to be needed in the new build and we may get away with an electric style fake fire especially judging on hearing people install them and then not use them.

but obviously its a decision to be made now before i flood the floor with concrete!!

[Jeremy Harris]

43 minutes ago, Inchbyinch said:

What alternatives did you have in mind? SWMBO is looking for a warm glow in the corner feel for our main room and id be interested in thinking about an alternative to a stove?

If you want real flames (the "caveman", or "cavewoman" thing ) but don't need the high heat output of even a small stove, then bioethanol stoves are worth a look.  They don't need a flue or ventilation, and so make the room they're in thermally more efficient even when they aren't in use, they have nice looking flames, but then burn without giving off masses of heat.  The only real downside is the cost of the fuel (which is pretty clean stuff - think vodka............).

A friend has what looks like a wood burning stove but it's really a dummy, one that has been converted so that it has an LCD screen behind the doors that plays video of a real fire.  My in laws had a very nice electric stove that looked very like a wood burner, so much so that people often asked how they were allowed to have it (they lived in a smokeless zone in the city).  Not the cheapest way of providing heat, but if you just want a focal point and don't use the heat much then they are worth looking at.

My personal favourite is the bioethanol stove, though, as they do have real flames and so can't ever really be called "fake".

[janedevon]

Does not putting the stove in alter any target values? If i dont put one in just wondering if i will regret it when i suggested it to the architect he just said its a nice thing to have in a new house. Im quite happy not to have a stove, excess cost and also messy just dont want to go,against any bregs. Also want to ensure new house is warm enough with out the stove!!!

[Jeremy Harris]

The wood burner should, if the regs were worded sensibly, be negative points, because of the high toxic emissions and the fact that they are far from CO₂ neutral in reality, but you're right, you will need to do a quick check of the DER and TER to ensure you're still OK (i.e. DER lower than TER).  This is a two minute check on SAP, just change the heat source and see what the DER does.  A bioethanol stove should score slightly better than a wood burner, I think (I don't have a copy of FSAP with me here to check right now).

I'm with you on the mess!  I fitted a wood stove to our second house when I was doing it up, around 25 years or so ago.  The amount of dust and debris from carrying wood through the house was a blasted nuisance, but it was an old stone cottage with no insulation and full of draughts, so we needed the heat and put up with the mess.  The next house we bought I made sure had central heating, with just a bottled gas coal-effect fire as a feature (which never really got used).  We've never had an open fire or stove in a house since, always because of the mess, but with the recent highlight on the adverse health affects from burning wood I've come around to the view that the things are really pretty harmful, as well as messy.

[Jeremy Harris]

I've just had a very brief look around, and it looks as if you'll get a slightly better DER with a bioethanol stove than a wood burner, as far as I can see.  The main reason is that a bioethanol stove is around 95% efficient, which is a heck of a lot better than a wood burner at around 60% or so on a good day.

I need to check with FSAP to be sure, but on the face of it you should get a slightly better rating overall with a bioethanol stove versus a wood burning stove, I think.

The look of the two is similar, but  with no flue or air feed needed at all for the bioethanol stove (and no mess or smell).  Cost may be an issue - the really nice bioethanol stoves aren't cheap, but against that you can offset the saving from not needing a flue or air vent.

[Rattyjohn]

Just been through the woodburner versus bioethanol issue with our build. Both Planning and Building Control almost insisted on a woodburner as a secondary form of heating, particularly during power cuts (which happen quite often up here). Neither of us particularly wanted one as we felt that in a well insulated, triple glazed house a woodburner would give out too much heat, plus there's the cost of the hearth, flue and fitting and also the faff and mess of cutting, seasoning and storing the logs. We didn't really want a hole through the wall for an air feed either. We therefore started looking at an easily controllable, clean burning bioethanol fire of about 3kW capacity as an alternative. Granted the cost of the fuel is a disadvantage but for the amount of use it would get there would be very significant cost savings over a woodburning stove.

After doing some research it transpires that the reason that woodburners have been specified up here for the last 10 years or so is that, if nothing is specified, the SAP calculations presumed that 10% of heating wiould be via electricity and, as this was always thought of as an environmentally damaging energy, the building failed. Now however, in Scotland at least, things have changed and the high proportion of wind and hydro generated energy is taken account of and the automatic 'fail' doesn't seem to happen now. The SAPS guy for our build said that as a bioethanol fire is classed as a biomass source then there shouldn't be a problem and it actually improves the SAPS calculations as a result of not now needing a flue or air feed. However, to satisfy both SAPS and Building Control the fire must be 'non-portable', ie fixed to a wall or floor.