saveasteading

Interesting, and currently counter-intuitive...but I am here to learn. I can't see how 2m of exposed flue before it is insulated for the rest of the journey can not provide spare heat...otherwise it is flying wasted to the sky. The early stage fire chucks flame and smoke up the chimney which would be wasted but heats the flue then room. The later stage fire sits and glows very happily, and a lot of the heat inevitably goes up and away. Best capture some. As long as there is enough heat and gas flowing up (to waste) the fire will burn well. Now for the real-time example: I am looking at ours now. Started with tree prunings from last year, an hour ago, and about to put the first proper log on. The flue is 1.5m long exposed before it is insulated (rockwool in plasterboard) and then goes into a chimney (stuffed with rockwool) The heat coming off the flue feels like 2kW to me (and I did remember to mask off the heat rising from the stove). The enclosed length of flue does not feel warm at all, which is just as well as it goes through a wardrobe. The room temperature has risen from 17 to 21 in an hour.

I hoped you might know.

We have had this discussion before. I think the conclusion was that a metallic foil face onto an air gap is good, but not as good as the figures allowed in the calculations. ie in time the foil is not so shiny (even in the dark) and the effect reduces towards that to any other surface. So to some extent you can use it to tick the box on the U value calculation and improve the rating considerably, and get some real benefit, but the reality will be slightly ;less. Therefore probably the pir performs a lot better than the air gap. BUT that service void is very practical. It allows the services to pass unseen, but also means that sockets etc that are under 30mm will not break the VCL. Conclusion: we will go for the shiny membrane because we might as well and it takes up no thickness, and the void will help in the reduction of accidental draughts that the electrician /plumber might not be interested in.

And if you are happy then I am happy that you are happy. Re the efficiencies, yes we know the difference between lab test and real life, in many fields. I would intuitively say that our burner is probably 70% at best and 60% when not working efficiently, including the many kW noticeably coming from the metal flue. And before this fire we used 4kW of electric heat, nearly 24/7 and it took days instead of hours to find the 5C rise we were looking for. Does anyone know if it is working well when all a mass of orange glow, and no smoke to be seen?

I think our room of that size (with very poor insulation and a lot of cold thermal mass, heats by 4C in an hour, at full blast with dry oak. That would be 5 big logs of 1kg each? After that the fire is turned down to minimum air or it gets too hot, and it is a log per hour.

A modern burner is declared at about 80-85% efficient. Then if you keep a large area of a metal flue exposed in the room, there is a lot of heat from that. Presumably in real life it is less than that. Meanwhile, "more than 60% of energy used for electricity generation is lost". ie 40% efficiency from carbon fuel to kW output at end-user.

I think there are some very all-encompassing exclusions and get-outs in the sign-off. It covers what the BCO has seen (which is snapshots) and does not include all the work or all the quality. The checking Engineer does not know all the context either. For example if a concrete footing was laid on ice and on a frosty day, the BCO would not know if it was understrength. If some reinforcement was missing? If some of the timbers were ungraded instead of C24? And so on. Not only accidental or through ignorance but, from tales I have heard from BCO, of deliberate deception. If the BCO was a Clerk of Works then we would all have to allow for the costs and delays for full-time attendance, and a heavy insurance premium

Not good. The width appears to be cut very neatly, so why not the length as well? I consider expanding foam to be for emergency use (and window fitting) only. it is uncontrollable and will expand from where you want it into other voids. In this case it will likely link the PIR to the sarking: not that anyone will see it but it is not meant to be there and could cause problems.. Meanwhile in a steading in the highlands this has been happening. Self-built with time and care, but there are unavoidable tiny gaps. The cut-outs for the ties will be filled with mineral wool. I will start a new thread on thoughts and progress.

Thanks to your comments I now revise my counting to 15 for and 9 against. Some of the 'againsts' could be legitimate vetoes depending on circumstances. Contrary to that is the over-riding expectation of a wood-burner in a forested rural area. On the draught and heat-loss that will occur without much control, through the flues, my attitude is that 1. there is a pragmatic approach that 'very good' will suffice. 2. insulation and airtightness first, then add controlled (or reasonably controlled) ventilation. 3. How much heat loss through a flue compared to doors opening?....I especially value porches for this. 4. As the power was off for 80,000 people for 8 hours yesterday, how much should we depend on electricity?

Simplest yes, but not the long term solution. Silicon degenerates and goes hard. Then you will have to scrape it out and replace it. The boss of a good window company will despair at this (and be glad you told them), and get it remade at their own expense.

I don't agree. They are avoidable and it might take weeks to dry out. If this is new build then it is unacceptable and should be remedied, and not by patching. What does the design say the slope should be? Whatever, the fact appears to be that part of your roof has negative slope, and cannot drain until the water is 15mm deep.

can we see the trial hole results please?

Some sort of cowl or cover is essential to keep out birds and rain. We have 3 woodburners in a different place. The first is an old inefficient burner from 20 years ago and just ducts up an old-fashioned chimney. On top is a wire insert to keep the crows out. It is the least efficient but perhaps that is the fire and brick chimney. The second is also up a chimney which has a rainproof masonry capping. Sparrows loved it but are now kept out by expanded metal (chicken wire not small enough!. This works nicely with the occasional backdraught when cold, never when hot. The build-up of resin on the wire is interesting.....if the holes are too small it blocks the fumes...if big enough it coats the wire but leaves enough vent area....so that must be to do with hot resin hitting cold metal. The stove itself is modern and efficient. The third fire has this rotating thing. It turns with the slightest breeze and whizzes in the wind. I wonder how long until the bearings fail. This is the easiest to light. perhaps too much forced ventilation when not wanted though? Isn't the OH clever but also intensely ugly? I have seen them one-sided perhaps called an OJ ?? These stove cowls are very much cheaper outside the UK. ( I mean a third). the twirly one cost me E30 and it appears to be £100 online.

Let me tidy a few points up. It is not a fiasco, and it would be unwise to suggest that to your Engineer. I foresee a solution 1. Trees will the the issue here. 2.4m depth is normal enough if the trees are, or will be be tall, with high water demand, and the ground is liable to shrinkage. 2. Clay is the worst*. It expands and shrinks seasonally. If the ground was sandy, or the trees were pine or bushes really, the requirement would not be for 2.4m 3. The foundations are designed for the eventual heights of the trees not the current. 4. the depth is less elsewhere because it is further from the trees, and nothing to do with the building size. Now, you say the trees will be 'knocked down'. Does the Engineer know this? Even if he does, the trees' effect on the ground will continue. They could grow again if the stumps remain. For at least the next year after the trees are removed, the ground will move as the conditions have changed. the likelihood is that the ground will slowly get wetter, to many metres, and the clay will swell, and the ground will rise. Discuss this with the Engineer and ask for confirmation. then don't build your foundations for a while. The trees should then be removed asap, to let the winter water seep slowly into the ground (again clay is the worst for this, and will take time to wetten. BTW underpinning has to be done in 1m lengths or there is no support and the wall falls down. * Clay is made of millions of layers of silt washed into a lake a very long time ago. These layers allow water between them and expand. Then trees suck the water out and it shrinks again. At 2.4m down the tree does not drink the water, hence taking the foundations down to there.

Yes but the balls would be influenced. I did an indoor bowling centre once with 4 lanes. the concrete was in tolerance but did veer off at one corner by a few mm. This became home advantage. Once the concrete is dry, roll a golf ball and see how it swerves.

I think that will be fine. An inspiring boss once dealt with this by chucking a pound coin into the puddle, and asking the client if he was now ok with it. He later explained that the water was deeper than the coin but that this always works up to 3mm, which is the tolerance. Remember that the slab will be a bit high and a bit low variously so this can exaggerate the effect. You will not notice this in real life and does not need an overscreed, If you ever see a leak in the fanciest of retail sheds, you will see just the same. The official test is a 3m long straight-edge (or an unusually straight piece of wood). Lay it anywhere and look for a 3mm or more gap. I suspect you will not have that. The water is good for your concrete anyway.

Adsibob, that is a very good point and I had simultaneously picked it up from jack on the ongoing string elsewhere particulates in your house than if you didn't have a fire. You are right , and I will add it to the list later. I got smoke back into the room tonight from a wood burner..not immediately when lighting it but when opening the door to add wood for the first time.

What do you think of cowls. Keeping birds out, keeping the rain out, preventing downdraught, and the rotating ones sucking air up? I have had enough of sparrows finding their way in to chimneys through the tiniest gap, or onto the tiniest ledge. Then the young not getting out and falling into the stove: dead ones to dispose of and live ones to assist outside.

I was intending to install a duct to an adjacent position, and with a grille on it. Then we have control and, an additional air vent if wanted (stack effectively), and without the capital. Yes, downward smoke is not nice. I have always (no, learnt how to) overcome this with a lot of effort, just as with the first fire with a cold, damp brick chimney. A small hot fire to start with (paper and kindling, and then it is ok. Once you have mastered an Inglenook, a stove is a doddle......or is Inverness weather different?

There are rules about how gas pipes are carried through a building. Ducts have to be ventilated in case there is any gas leak and build-up. I had this on a project where the highly professional M and Contractor didn't know it but the building inspector pointed it out. Or to be fair, perhaps we built the box-out with out discussing it. Could have been a big issue. Probably applies to any void that the pipe goes through. There will be more, to do with the risk of damage/ differential movement. So yes, it really needs looking at early.

My response became so long that I have put it in a new thread rather than hijack this discussion.

I was about to reply on another thread, and realised I was hijacking it, so here is a new thread. We are putting 2 log burners into our highland conversion, and I consider myself eco considerate (got a badge for it). I'd be interested to hear if you disagree with any or all of these. FOR 1. It is very rural so it is not going to annoy or harm anyone nearby. 2. For the first 2 years there will be demolition timber, which would otherwise go where? A big bonfire probably. 3. They will provide quick heat whenever UFH is going to struggle, and allow us to keep the background heat down. A surprise change in the weather is readily dealt with. 4. Lots of surplus wood in the commercial forests around. Not the best and will require work, but otherwise it will probably be piled and burnt at some stage. 5. Aesthetically it is very attractive 6. We have an area of woods....rather lovely primitive, soggy woodland, but some can be harvested. I also favour planting some timber for pollarding. 7. The burners we are intending (Spanish) are 82% efficient. This is realistic as we have one already and it burns 30 big logs to every tiny ashpan. It has air inlets at the back to burn the fumes and you can see this working. This compares with.....what? isn't electricity 25% efficient by the time it reaches us? 8. In a well-insulated house it won't be a very big burner, or used much. 9. Other local houses have them too, and it doesn't seem to be causing any issues. 10.The flues create air flow and ventilation by stack effect, even when 'closed'. 11. There are are umpteen mills around, all with waste to get rid of. They seem to sell it even though the price doesn't seem that great to me. Otherwise it goes where? 12. If selling, they would be expected by most people. 13. We don't have to use the fires. AGAINST 1. Burning is burning, and makes fumes. 2. The air is so incredibly pure around, and there is lichen on the trees that depends on clean air. 3, Perhaps the smoke will hang around and be a nuisance. 4. The flues create air flow and heat loss when not in use. 5. Capital cost. 6. Holes in the roof. 12 against 6 isn't the issue as the weightings could be different.

Yes get this too. They are seldom used on commercial sites as the book says use a helmet. But they are practical especially when you know that nothing can fall on you. It keeps the muck out of your hair, the hair and sun out of your eyes. Safety-wise, they are great at protecting your head from nails sticking through roofs, and the odd bump from a batten or sheet of plasterboard that might overturn. I have trusted a small plasterboard sheet to stay in place while reaching for something, and been grateful for the cap spreading the thump. You will wear this when a helmet would be a pain. Get a red one and it doubles for a MAGA cap at any fancy dress.

As a newby Site Engineer I sought a red helmet but it wasn't allowed. Similarly we lusted after a tartan lined donkey jacket, but that required 2 years service. Helmets mostly used when it was raining or to hold nails back then.

One of the big questions in construction. Wrong to have colours according to hierarchy, but sensible to mark out a banksman for easy recognition. It should be a bright colour, and so yellow, orange or white depending on which will show up best on your site. Red and blue don't show up so well, and black is lunacy (for managers determined to have a different colour)