Wood Burner in Workshop

[BigClick]

Moving to a new home (bungalow) and I am looking to build a garden workshop.

Noticed that wood burning stoves are good because they don't cause condensation.

My question is how are people removing the exhaust gases and if a flue is used how do you get it through the roof and seal it?

[Radio Wrangler]

It rather depends on what sort of roof you have.

It may be better, from the viewpoint of leaks, to exit through a wall and leave the roof unperforated. But plenty of heat for the room/shed can come from the flue so you may not want to route it straight outside.

If your shed is draught-proof, make sure you have a carbon monoxide alarm.

David

[paulsherwin]

Pot bellied stoves were the standard method of heating outbuildings at one time. My granddad used to have one in his engraving workshop. You certainly need a flue, and that's where the water vapour goes. There are standard fittings to allow the flue to pass through the roof, or you may find it easier to have the flue exit through a wall with an external metal chimney. The chimney pipe does give out a lot of heat though, and it's a shame to waste it.

Remember that there's quite a bit of faffing about with a solid fuel stove - you have to fuel it, light it, wait for the room to warm up, and clean out the ashes. You will have plenty of wood ash for the garden though.

[Nickthedentist]

There have been a couple of serious fires around this bit of Oxford due to these recently. I believe storing of combustible stuff too close by was thought to be responsible. Worth bearing in mind in a potentially crowded workshop.

[chriswood1900]

Sealing a flue usually entails a purpose designed metal or heat ressisting flashing for the flue along with a collar to seal the flue to the flashing.
Something like http://www.stovesonline.co.uk/wood_b...-flashing.html
On the bright side you could use old worm-ridden radio cabinets as a source of fuel!
Chris

[evingar]

Originally Posted by Nickthedentist

There have been a couple of serious fires around this bit of Oxford due to these recently. I believe storing of combustible stuff too close by was thought to be responsible. Worth bearing in mind in a potentially crowded workshop.

This is a good point. Also bear in mind flammable "stuff" used in workshops that gives off vapours like Meths, IPA, thinners (etc).

As "romantic" as a stove sounds (think a frosty morning and jolly stove crackling away with the front door propped open and a pot of coffee heating on the top) I chose a radiator for the workshop I built a couple of years ago. It was, though built onto the outside wall of the house so the extension of the radiator system pipework was easy.

[dseymo1]

Fitting a stove is a 'controlled' activity under Building Regs (like so many things these days!), which more-or-less determines how you will be allowed to pass the flue through the roof or wall.
While I'm a great fan of my domestic stove, questions are being asked about particulate emissions in London, which might, of course, extend to other cities in future. Just something to bear in mind.

[Nickthedentist]

Originally Posted by evingar

As "romantic" as a stove sounds (think a frosty morning and jolly stove crackling away with the front door propped open and a pot of coffee heating on the top)...

https://www.google.co.uk/search?q=ox...LKyGgAaagbCYAg

[mark_in_manc]

I wouldn't leave mine running unattended for long! Drying out wood next to them works well (though it'll raise your humidity), but you need to ensure the pile can't collapse against the side of the stove. In my shed, the flue (old cast iron drainpipe) runs through a big hole in the plywood roof, and is flashed with alu sheet and lead. It works OK. One of my woodburners is a cut-up butane bottle. One needs to vent them well-and-truly (I blew mine on a small compressor - it smelt horrible) before applying a cutting disk. But yes - a CO alarm is a good idea - they're cheap enough.

[kellys_eye]

Might be worth reading the Building Regs (Part J) re woodstoves as there is a lot of good advice to be had therein albeit such in a workshop doesn't really fall into the classification we are talking something with many potential risks if installed wrongly.

[paulsherwin]

A carbon monoxide detector is certainly a good idea where anything is being burnt indoors.

[ms660]

Originally Posted by BigClick

Moving to a new home (bungalow) and I am looking to build a garden workshop.

Noticed that wood burning stoves are good because they dont cause condensation.

My question is how are people removing the exhaust gases and if a flu is used how do you get it through the roof and seal it?

For what it's worth in your situation you should use an insulated flue system, full stop.

The flue must be cleaned at regular intervals.

Only burn "dry" timber, for logs always be cautious if buying "seasoned logs"

Fresh felled timber that's then ringed and split and stacked to dry for a year can dry out sufficiently but quite often it doesn't.

Different folks will tell you different tales but believe me when I say that the logs need to be below 22% moisture content otherwise trouble looms, best outside drying here where I live is about 19%, I'm lucky as I have a supply of standing dead trees that have been standing for years which didn't quite make it to the canopy...in effect as dry as they're going to get down here.

So, proper insulated flue system, with a rain hat/cowl and a roofing/flashing system to match the roof type and profile.

If you happen to DIY then follow the regs for combustible material distances from the stove/flue and the size/projection of any hearth and the size of a permanent air vent etc etc. For safety treat the woodburner system in your shed as though it were in the house.

Exposed uninsulated section of flue to steal some heat....be careful if you do, you can do that and fire your new installation up and wonder what all the safety advice fuss was all about....different story if months of tar ignite and your exposed pipe starts to glow red...Clean flue...always. From memory there's a max length for uninsulated flue.

Logs to burn....dry Beech is always my favourite if it comes along, beats Ash any day for me. Most of my logs are Sitka Spruce though, burns very well, with very very little residue left in the fire bed. I've quite a large stove (18KW, 9 to the room, 9 to the water) but to start the fire it's a fire lighter six dry Spruce kindling sticks, some small quartered logs and that's it, guaranteed burn....Dry logs, always the golden rule for fuel...Don't forget.

Good luck.

Lawrence.

[emeritus]

I would think that a significant reason for "not causing condensation" is that a solid fuel stove will force several changes of air per hour, and so will positively extract the non-negligible amount of water vapour that is produced by simply breathing. Simply heating air in a sealed room e.g. with an electric fire, does not remove water vapour, less humid air from outside must be drawn in to dilute/replace the damp air, otherwise you will get condensation when everything cools down.

[kellys_eye]

Has anyone done a cost-benefit analysis for using a wood stove?

Purchase, installation, running etc.... can add up considerably and equate to many, many hours of use from a standard electric heater.

For the most part I think people run these at a loss (compared to electric heating) and only those that have access to a ready supply of wood (we live in a forest and our annual heating bill is £50 - no, that's not a typo!) will make them work in a true financial sense.

[Nymrod121]

kellys_eye wrote: "Has anyone done a cost-benefit analysis for using a wood stove?
Purchase, installation, running etc.... can add up considerably and equate to many, many hours of use from a standard electric heater."

Yes, indeed I have and in my case (10' x 6' well-insulated shed), it doesn't make financial sense. Once my workshop's completed, I will be using an 800 watt mains convector heater (~£22-25) in conjunction with a small dehumidifier unit (~£35-45); the heater will be fed via a thermostatically-controlled relay as trace-heating and the dehumidifier will run 00:30 - 07:30 (winter-time) on Economy 7. I'll choose to by-pass the relay when warmth is needed in a hurry - and I won't become too concerned about moisture build-up due to breathing as the d/h will take care of it overnight.

(Hope we get mhennessy's input on this subject, for reasons which will become apparent in any post he might make, I'm sure)

I'm happy that the principle works in that our UK-built caravan (stored at the side of our house) has just such an arrangement to keep the damp levels down.

[ grabs coat / exits smartly, to avoid temptation of embarking on OT rant about UK caravan industry, damp issues and 'transient warranty' ]

Best wishes
Guy

[emeritus]

Before we had access to a free supply of hard wood from a local place where they were just burning old fallen trees on bonfires, I found that non-returnable pallets were a good source of free wood. A local shop was happy for me to take them away as it saved them the cost of paying for their disposal. Likewise, builders are often happy to let you take old wood (and sometimes surplus new wood from bales that is not worth their while taking away with them) from skips: the more you take, the fewer skips (at £250/time) they have to pay for. I don't have a stove in my shed ( heated in winter by a thermostatic electric radiator with the thermostat set to "1" and left on 24/7), but we do have an open fire in the living room.

[Peter.N.]

If you have your own wood supply then the heating will be virtually free but if you have to buy it using anthracite will probably be more cost effective.

For many years I used 28" caravan as a workshop which had a multi fuel stove and it worked very well and didn't cost to much, kept it very dry as well.

We have a multifuel stove indoors which provides most of the heat for the living area which is quite large and in the very cold weather we use about two 25kg bags of small anthracite nuts a week at a cost of about £20. In the spring and autumn we use wood as we have a fairly plentiful supply from fallen trees - largely depends on how much I manage to get cut up!

I replaced the caravan with a sectional concrete building which I thoroughly insulated with 2" polystyrene on the walls and under the floor, I used to heat that with a 1kw storage heater and that was quite adequate except in the very coldest of weather then I use a convector heater as well.

Peter

[Nymrod121]

I was looking only last week at the possibility of using a storage heater but the cost (even of the smaller ones, second-hand on auction sites) put me off. Perhaps summer will be a better time to look!

Guy

[ms660]

Pallets or builders throw outs, nails/metal fixings in firewood can sometimes play havoc with grate riddling systems not to mention whatever you're sawing it up with, if you happen to be using a chainsaw and it happens to hit metal the chain will need a proper going over, and unless you like lots of accurate filing an accurate re-grind will usually be needed to remove any damage to the cutting edges and to get back to the chromium and get the cutting edges back to full sharpness.

Lawrence.

[Boater Sam]

The heat going up the flue is not all waste, its vital for products of combustion removal.
In a timber building floor and hearth and wall adjacent to burner and flue require careful heat & fireproofing.
Flue has to be as long as the minimum length the makers decree and shorter than the maximum. Proper twin wall flue is now essential, old cast iron pipe is banned by regs. Twin wall makes roof flashings easier too.
Any flue bends add to the effective flue length, as a rule 90 degree bends are a no-no.
As a guide, my well insulated 50ft steel boat Squirrel stove runs hot water and radiators, in winter it consumes at least 100kg of mixed smokeless eggs and anthracite a month to keep us toasty, @ £36, burning wood it would be twice as much fuel. That burner is 5kw/hr output into water when stoked up and about 4kw off the flue and cast iron stove.
Beware of burning old construction timber, besides the nails it will have lead paints.