Ferdinand

TLC Direct can be good, especially if you are near a store. https://www.tlc-direct.co.uk/

100-150mm gap should be fine. 8mm glass may be surprisingly cheap - remember how inexpensive large shower screens can be. Try a little local glazing man if you have one. Whatever you use, check the safety requirements. Might plastic get too dusty? We had secondary glazing (for draughts in a listed building with original Georgian sash windows) which was just sized and edge polished sheets of toughened glass, which we fixed up with mirror hinges for the winter then took down again. We just used a circuit of foam to block the draughts and cushion.

Yes - it would help. You need 2 things - a wide air gap and a good seal around the edge. It will not cut other noise routes, however.

It's all discussed in the pinned discount thread. Have a dig here. For Wickes it should stack with the Trade Discount. Quite often via employer card discount schemes - I get one with my health cash plan scheme. The mechanism is that you have a reusable cash card, load it up on the website at a discount to cash value you are loading, then use it to pay at Wickes or where-ever. They come as a perk with all sorts of employee schemes, memberships and similar. And many just don't know the value.

There's an optimist at the Estate Agent. That per sqm price on the theoretical house is 50% more than the local ones that are finished. What happened?

Always remember that at Wickes -10% is always possible as they hand out trade accounts like confetti. And that they participate in discount card schemes for a further -10%, which takes it to roughly their staff discount level (last time I checked, which is not very recent). Plus good discounts for eg NHS staff or Blue Light card. Presumably all that is within margin. F

Having explained the history of the whole thing above, also to get my thinking in order - to address the direct questions. Basically if you store it it then it depends on whether you use it yourself later from your storage, or export it later from your storage (aiui at a 20-25% round trip efficiency loss). The storage just does a time shift, you get to use your solar electricity later and import less, or export it if you have that level of control and potentially get export payments. If you don't export it when generated or later (if you time shift it using your battery), then of course you won't be paid the Export payments - as you have not exported anything. Although you may still get "deemed" export payments, as discussed above. But on an Agile Tariff you could get paid more or less for your exports depending on how you time the export. Plus - and this is the one you have wrong I think - only a small fraction of that 56p is Export Payments (Contract 2 as I referred to it). Your FIT payments (Contract 1) are not dependent on exporting electricity.

That's not quite right. Let me explain my understanding, also to clarify in my own head - I'm have moved my tariff to Octopus Export Agile. This is how it operates: Under the FIT scheme you have TWO contracts: Contract 1 with your FIT provider that will pay you for everything you generate. This is basically a subsidy to help you pay for the cost of your solar equipment to get the ball rolling for the country, which reduced over time as the cost of kit fell. This was 60p per generated unit at the start for installs from 2009 (?) or so, and fell to about 11-12p by 2015 for contracts started then, and was then significantly reduced as it was deemed to have basically done it's job. It was usage based to make sure that people would install solar arrays to actually produce energy. I did mine in late 2015, and paid around £1k per kWp to get the solar installed. You may have paid 4x that, which is why you get the big FIT payments. Contract 2 would also be with your FIT provider (afaik) and would pay you a minimal amount for lecky you actually export to the grid. If you have an export meter, that would be on the amount you export. If no export meter, they "deem" half to be export and pay you on that basis. This is why there is an incentive to use 'divert devices' which prevent export and divert it all to a local load, such as electric ufh, a hot water tank or a Sunamp. The "deeming" process means that you get paid for an assumed half, and get all the electricity as well. Back then some people thought this a bit ethically dodgy, but everyone is now cheerfully cynical. The Smart Export Guarantee (SEG) is a minimum guaranteed payment per unit of export, which I think is aligned with the base payments under Contract 2. The Octopus Outgoing tariffs replace the Contract 2 with a new contract with Octopus (other companies do similar but are less innovative aiui), where they pay you either a fixed amount (normal version) which is higher than the (SEG) which was 7.5p per unit and has recently jumped to 15p per unit, or they pay you an amount ('Agile' tariffs) based on the futures market price for tomorrow's electricity minus admin expenses and I think a small margin. Outgoing tariffs require an Export Meter, which is part of the gubbins in a SMETS 2 Smartmeter, which is why they require that. The currently innovative bit aiui is that Octopus let you keep your existing normal import tariff (ie import = your normal supply) which avoids the risk of being shafted by the market at times of high demand when they used to make you have an Agile import tariff as well. That makes it nearly a one way bet, upwards. They also seem to let you timeshift your house battery output if you have a house battery and a means of controlling it. The current capital cost per kWh of charge stored over the lifecycle do not make this a cost-effective single reason to get a house battery even at current prices. You need more justification, such as if it reduces your lecky bills enough to cover the difference. That is one reason I say keep it simple. On the battery aspects, obviously if you stick lecky into your battery you can't export the same lecky. That's one of the things you get to use your skill and judgement on, within the controls that you have over your battery and your current export limits and what it is you have chosen to maximise. Whilst it is I think technically possible to feed the current export price into an automatic controller which will switch your setup between export and import by the minute, you'll have to programme (or use simulated data) for your own control system *. At the moment it seems that the better option is to keep it simple and either tune your house / life around times when it generates solar, and accept that Agile Export is a pretty good lazy way of sort-of-maximising your benefit if you do not have a house battery (perhaps 60-70% as good - guessing), or have a house battery (or base load) and a divert device to use everything you generate (in which case getting Agile may be an irrelevance). Octopus also have various tariffs for cheap-overnight, Tesla cars etc. At present it's a very flexible environment in which you can innovate. But therefore also you could end up dazed by the 27 different options, like the proverbial centipede **, and end up doing nothing. So doing *something* beneficial is perhaps more important than getting analysis-paralysed. You pays your money, and takes your choice. I'd say start simple. In your position it will be imo advantageous to move your Exports (Contract 2) to an export tariff, but hang on to your FIT payments (which are guaranteed at 50- 60p per unit until 203x) like a limpet. Make damned sure that you track any change process - which is a bit like the Children of Israel and their 40 years in the wilderness - closely enough that you do not lose your FITs (Contract 1) by mistake. I have not known it happen, but it is a drawn out process, and you need all of your paperwork to hand. HTH Ferdinand * We discussed these control and programming aspects here last year: ** The centipede was happy, quite until the frog, in fun, said: "pray which leg goes after which?" He worked her mind to such a pitch she lay distracted in a ditch ... considering how to run. *** One further complication is that part of SSE (my FIT provider) have been bought out by Ovo, and now use Ovo for their FIT meter (solar generation meter) reading service, but will still tell you to talk to SSE about the export contract. I am still hacking through this last bit of undergrowth, because Octopus need my confirmation email from SSE that my final meter reading has been accepted before they give me any Agile Export money, and the computo-email from the meter reading service says it will be processed "in the next quarter".

Yes - that all seems well expressed, @Gus Potter. This is the comment from the linked FAQ page, which a - specifies that a person accessing the loft shall temporarily be supportable, and b - is 1996 building regs, so earlier lofts need to be considered separately (and Wickes quotes 50kg). I'd do a couple of joist dimension and spacing measurements and span calculations and compare with load and span tables making conservativer assumptions eg *: https://www.timberbeamcalculator.co.uk/en-gb/span-table/floor-joists?load=1.5&class=C24 (Notes: 1 - a sensible assumption will need to be made about timber grade. 2 - a 1kg load imposes about 0.01 kN ) British Standards BS6399-1:1996 for new build homes installed with a loft hatch require trusses to be designed to carry a 25Kg per square metre storage load plus the temporary load of a person moving around in the loft. Some homes may have been designed to exceed this but if you want to exceed 25Kg per square metre we would recommend consulting a structural engineer. One tactic is deliberately to board only near the hatch so no large people climb into the loft. As for putting things like boilers and batteries in lofts - not something I like. I have one in a loft in a rental, and it is a bit of a sod. I boarded out a walkway to the boiler in 2ft wide OSB over the bottom layer of insulation, then put the top layer of insulation in the same direction so that removal of one stripe would clear the walkway, and put a sign next to the loft hatch. I would not put a potential fire hazard or weight like a battery anywhere near a loft. They go in the garage or in a fireproof booth. F

Add glass to the list of energy intensive materials. My 2G man has told me to hold off replacing units unless it is urgent. As a perhaps typical data point, Wickes 2.4m 3x2 CLS is about 15% below 5-6 months ago, which was when I think I bought some and what I paid.

I had a sheet of toughened naked secondary glazing (full height, half width of a Georgian sash window) approx 1600 high x 600 wide explode on me when I held it about 30 degrees off the vertical face (not edge) up gripped too close to lower end. No impacts - just the tension in a weak dimension by holding at the wrong angle. Quite an education.

If you care concerned about floor loadings then I would do some general load and point load calcs, as the weight will more be in your supplementary wood and the boarding than in a 50kg tent. I used loft legs when a T needed storage space, and they soon add up once your need a decent area. Depending how you intend to load it, the loft legs may allow you to dispense with your extra lengths of wood. Wickes say 50kg per sqm, and have a short vid hjere:

Revisiting this thread briefly, I am delighted I ran away at post 4 on page 1. Play nicely, peeps. 😉

You need to check carefully whether you need PP and Bulding Regs Approval, and what will apply in your circs. The requirements for insulation etc just hiked upwards quite seriously in June. I'd ask them "what is it in planning terms?" eg extension not needing Building Regs approval, porch etc. There are also factors such as closeness to the boundary that they do not seem to mention. Given that they seem strangely backward in coming forward with details of the insulation - eg material, u-value etc - even on the "specification" page, I'd speculate that you might possibly be better off with a second hand 'panel' (rather than 'dwarf-wall') type conservatory. You might still get quite toasted, so I'd suggest an install on the shaded side if you can. Careful research needed, I think. I'd certainly recommend going to see a couple in situ. ATB F

The one I'm thinking of had a huge feature stone wall bisecting the house, and iirc it had a GSHP heating it up. But I am not at all sure without finding it.

There was a Grand Designs project that used a full height inside wall as a massive storage heater on the similar "chimney in the middle of the house to heat all directions idea". It may have been slate or stone. A quick search and I can't locate the exact project.

OK, breakfast having gone down and teeth polished, it is time to earn the full value of the money I am not being paid 🙂. This is a bit of a brain dump, so pull things out. Let me first be sure I understand the problem. The core problem here is 1 how inexpensively to insulate a 300-350 sqm roof on an ~4-4.5m sloping up to 5.5m 'tin' roof, with a subsidiary of 2 how the duck to attach insulation to steel joists, and 3 how to be sure of an ability to manage humidity. All for not very many £££. I think one thing not mentioned that needs a passing thought is potential fire hazard. Another is whether particular activities need particular temperatures or RHs (eg does doing X to a car require the temperature to be Y for the process to work? - you know about that), and do T and RH therefore need to be controllable? Also it is not clear where you are on aesthetics - can it be ugly? I think that Rockwool is the correct material if possible, or something similar but less prone to releasing fibres. I had not met the space blanket water bubble issue, though it does obvs prevent fibre shedding, but I have never used space blanket. I also note that unwrapped rockwool is ~1/2 (?) the cost of space blanket. Now - analogies. In the past the cheapest insulated roof I did was for a conservatory (with 7" deep wooden joists) repurposed as a lounge, where I put a tin roof on top of the joists (over the existing polycarb), and staple-gunned 100mm rockwool just above the bottom level of the joists to leave a ventilated 25-50mm gap, with routes for air circulation in and out. Then wiring was done along the joists, and it was clad with white shiplap (at about £5 per sqm). I would not use plastic shiplap now, as I am unhappy about gases it would potentially put out in a fire situation, but risk is managed. Nearly ten years later it is still solid. The other thing that strikes me as similar is putting insulation under a suspended floor. Again my standard inexpensive was is as much rockwool as possible stapled in place, which comes in at about £1 - £1.50 per sqm per 100mm of thickness. The other one I have been involved in has been renovation of a 6000 sqft mid-height (20m by 30m ish, prob. 5.5m high walls and a 8-9m ridge height) former warehouse into a gym. We did not try and insulate; we did repaint. Possibilities A How to support rockwool on the pitch? The one that jumps to mind is something like sheep netting (metal or plastic) or even wire mesh. Very inexpensive. Though roofing laths every 1m or so may be more practical. But that leaves... B How to attach to steel . Are those modest depth I-beams * or simple rectangular cross-section? If I-beams, can you just wedge roofing laths or something a bit stronger across each ~2m inter-rafter gap, and secure with spray foam? If rectangular section, can you just attach laths using spray foam to keep the rockwool up there? Will it support it? Perhaps a test? Is such a light structure an issue if bits fall down (I'm guessing potentially yes 🙂) ? Or is there a kind of punch nailer that will go into the steels, or bolt through every 2m or so across those 2 to 2.2m inter-joist gaps, or attach clamps and attach roofing laths across? Those feel more tricky except the last, but structural metal-work is not my thing. C How to be sure of an ability to manage humidity I'm with those who say ventilate above the insulation, and making sure there are inlets / outlets at top and bottom, or both ends. I'd say do it by putting rockwool depth in 75-100mm shallower than the depth of your beams, aligned to the bottom, and seal within reason around the edges. With dehumidification as an available Plan B when required. I wonder, is there something to be said for a workshop version of a lowish volume PIV fan as a humidity control, as these are heroically cheap to run. Triggered by humidistat? D Make it a cold loft. @Onoff touched on this. What about a mezzanine or similar structure, or putting sub-buildings inside it? My wild thought is that could you use a mezzanine partial mezzanine of 3m scaffolding? It's structural, gives you the chance to subdivide cells when you need it, on 2.5m or 3m cells or with larger bridged cells probably suitable for cars, and you can just roll out the insulation on top. I make it about 6 x 10 max cells, so is that doable? Plus you get a structure to subdivide if needed. With scaff you get to take it down and sell it in 20 years, plus the rockwool, and the building is unchanged. Needs a detailed think check, and probably a bankrupt sale. It feels like quite a big chunk to spend, perhaps. But can you build your scaff framework, roll out fencing mesh on top (attached with zip ties), then roll out rockwool on top of that? Needs thought about access - perhaps a run of scaff planks along an edge of each cell? E Make it beautiful I think this should be criteria 27 on the list, and that criteria 1 through 26 should be cost and practicality, but in at least one comment above you imply it matters at least slightly. I think that in that case you are looking more at a modest renovation, and may need to be looking at things like internal cladding beneath your insulation. On that I cannot do better than the plastic shiplap I mentioned, unless you put box section tin on the inside. That's my random thoughts - I hope there is a spark there somewhere. F (Update: I realised that I have missed the suggestion of using glue to secure the insulation supports to the roof joists, which is really in the same type of idea as supporting it using spray foam. Are there suitable glues around? Which may be expensive - when we glued down 4500 sqft of rubber matting to our gym floor we used £900 worth of the strongest glue from B&Q. But 4 years later the matting is still firmly attached, and the only thing that pulled it up was when the ^&*(())_ landlord insisted on bringing a mini digger or a forklift or something in to do maintenance. But if it does the job satisfactorily, it would be worth it.)

Might a dehumidifier be a suitable solution to any humidity problems - personally I would ventilate the roof / seal the insulation as well as practicable (rockwool is good for that), and then see. I've been putting my thinking cap on on this project, and will do a separate post. F

What are the dimensions of the roof? Is it a simple oblong building?

How are you going to warm it if you have a 1m diameter hole to the outside with a fan in it?

It's 3 feet. That's waist deep. IMO anyone would spot it. Is the bit by the house still at the same level? One concern I would check by email with the architect is whether there is any loss of lateral support to the structure of the house. Is there a change of level wrt to your neighbour. If you are lower on your side, are they sufficiently supporter? As an N, that would be a concern for me.

OT. I'm interested in that road, and the mandatory * cycle lane. That cycling lane looks dangerous, how wide is it? Given that the standard bus lane in ROI is 3m, I'd say it is perhaps 1m wide - not very adequate imo for a parent with their toddler in a trailer with 2.5-2.6m wide buses tearing past about 0.3m away. Is there a 30kph speed limit on that road? Cheers Ferdinand (* Mandatory cycle lane in ROI is one that motor traffic is not allowed to enter - basically the same as UK, but ROI is better where parked vehicles can't block cycle lanes freely. Up until 2012-2015 plus a bit - because the reform was botched - people on bikes were also required to use even dangerous cycling facilities in ROI.)

A clear explanation - great. My questions are: 1 - How did you affix the larch offcuts at the bottom, given no wallplate? 2 - How long do round wooden posts in concrete last in that situation? In my area, that would be a recipe for post rot I suspect. Does the wind blow all the rain away 🙂 ? F

I'd support the letter to the CEO. Octopus trade on good customer service and being nice - TBF they have achieved a Which top rated assessment 5 years in a row - so perhaps it may work. F

Welcome. He means pics of the building, just in case you are an exhibitionist 🙃 . I like your mix of projects, and willingness to take tactical advantage of one for the next one in the future. I'd quibble slightly on your definition of "superinsulated" - to me 80mm of wall insulation is normal, though pretty good for a reno. I'd start superinsulated in a wall at about 125mm of Kingspan these days. It's interesting that the new building regs have just somewhat caught up, and now require a wall u-value of 0.18, which is something like 90mm of Kingspan. On the export energy price, you might have a look at an agile tariff such as Octopus Outgoing Agile, which pays you the wholesale price per unit, at present averaging 20-25p per unit (their fixed outgoing alternative is paying 15p). I've just switched. There are various threads about this on the forum.