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Thought I'd do a short blog on the Polycarbonate tunnel we built. Our big field suffered with no storage, and location meant containers were very expensive to transport. so one option was to build a polytunnel, which we have planning permission for. again due to location, 500m from the coast 73M AMSL I wanted something sturdy. so looked at off the shelf packages. in the Highlands and Islands the PolyCrub is seen as the mecca. Designed in the Shetland isles, guaranteed to withstand 100MPH winds etc etc. due to the ability to get CROFT grant assistance on these, the price is, IMHO, artificially high CIRC 6K for 4M *6M.. this wasn't going to happen, so after looking at many photos I designed my own.. Basic principle is hoops of MDPE pipe secured to posts in the ground, then 3*2 timber used as horizontal support, with Polycarbonate sheets secured to this timber. the bottom sides are then clad. My design was to use 65mm Black MDPE pipe, and secure the timber with coach bolts and penny washers through the pipe. this way I get a guaranteed fixing that won't pull out , and it still allows for flex in the whole structure. 4m wide x 6M long, but this can be extended. My ground has bed rock close to the surface, 300-500mm below ground, so just knocking in post wasn't going to be secure enough to withstand the winds, also where I was sighting the tunnel its on sloping ground, so I couldn't get it level. I cleared the area to removed the top vegetation and a bit of the top soil. and dug 14 holes. then due to rock levels I then core drilled the rock to allow for the post to be deeper. We then set these in concrete, (at the same time as doing the slabs for the cabins.) The next day we had a look and I wasn't too happy with the security of the posts, so slight change of plan, we created a plinth. basically I used some 6x2 either side of the posts, with a slight angle, then filled this with concrete (again we used ready mix at the same time as back filling the treatment plant) this added about 300kg of concrete to each side, and joined all the posts together, and gave us a solid plinth at the side. No Photos of the next stage but we cut 7M lengths of 63mm pipe, this when placed over the posts gives approx. 500mm dwarf walls and a 6M polycarbonate sheet, giving a head height of around 2.3M. we used a plumb bob to get the centre line on each hoop and drilled an 8mm hole through the pipe and secured the top 3x2 treated timber to al the hoops. One thing we found was that the MDPE did not bend uniformly, this may have been due to slight errors with the posts being plumb. The resultant timber (which was not very straight), snaked from hoop to hoop. after head scratching and re thinking. I decided it was a poly tunnel and to get on with it. we used 7 lengths of timber jointed with half lap joints to extend the length to 6.5M. if using a clock analogy the timber was placed at 9,10,11,12,1,2,3 positions, with the 9 & 3 o'clock being 500mm off the ground, also ensuring the 9 & 3 o'clock timbers were approx. 5.8M apart circumferentially. Then it was a case of securing the polycarbonate sheets to the timber. each sheet is joined with some soffit H joint strip. (you can buy a clear joining strip for the sheets but for a 6M length it was around £65. the H strips proved extremely difficult to connect the two sheets together, or should I say impossible. so I cut off the back edge on one side and used some glazing sealant. this way we could attach the strip to the polycarbonate prior to bending over the tunnel. and each sheet 'H' strip basically lapped over the previously installed sheet. day 2 we had the basic structure. It was noticeable that the curve was not symmetrical, so putting the door frame header in by securing to timbers at 11 and 1 o'clock was not level. I overcome this by using a ratchet strap attached to the 11, and 3 o'clock timbers and tightening until timbers at 11&1 o'clock were level. I then put the two door jambs in (concreted at the base) and cut to the length required and secured to the header. This worked and the tunnel was now more cylindrical. I framed the rear by baring 3x2's off the horizontal timbers. Last steps were to clad the base, I used 4*1 treated timbers that were screwed into the MDPE pipe and wooden posts. then used strips of visqueen to create a more sealed dwarf wall, this will help prevent driven rain from the winds getting inside. over this I used Larch timber backs* to create a vertical cladding All in with hardware, polycarbonate, timber, concrete the project cost £1200. not cheap, but its solid as a rock. It withstood the first Autumnal storms this week with winds hitting 50MPH. Its also very warm inside, even now as the temperature is falling. Larch timber backs are the offcuts from the saw mills and are reasonably priced as scrap. we purchased a pack of timber backs, approx.40 lengths of larch timber with bark in 4.8M lengths for £100. these are not uniform and taper etc, but as i only needed 500mm lengths it was straight forward to make it work.

Speaking of foam guns I’ve just found mine in the garage with a can still attached to it. For long term storage I normally remove the can and thoroughly flush out with gun cleaner however this time I must’ve forgotten or assumed I was going to use it again imminently but 18 months have gone by and that didn’t happen. So… I was assuming I’d need a new gun but I gave it a squirt and after a brief moment where nothing happened out it came and it worked as good as always!

Pumps upside down, so it’s a train-wreck. No way the MI’s ever said to fit it this way. Clearly been Frankenstein’d for convenience to the installer.

I think that says it all really, if it were higher then “overlooking” may be a problem, methinks your neighbour is a nosy b@stard with nothing better to do! Who is waiting on who? Are the planners waiting to hear from you or are you waiting for the planners to contact/enforce with you?

Not like my house I hope. The light switch is not near the main door, but on the opposite wall. Probably designed that way by an architect, who knew he would never live in the place.

CT1 will work well as it remains flexible. Gripfil is good but dries too hard for threshold strips

Keep both roof “cold” and put in ventilation.

Hello Everyone, My name is Mike and I'm supposed to be retired. However, that soon got boring so I bought a house and refurbished it, new kitchen, fitted bedrooms, underfloor heating etc then sold it and bought a small holding on the edge of Dartmoor national park that was pretty derelict with the exception of the house. I'm a reasonably competent DIY type of guy and will turn my hand to most things. Projects completed to date are numerous, but the highlights are:- Heat Recovery and Ventilation system fitted to my bungalow. Now I have two wood burners heating the whole house. LPG usage has fallen by 66% and the gas boiler now only occasionally heats the water. Fitted PV and use excess power generated to heat the water (I hate exporting KWh at 4.3p and buying it at 35p!) Super insulated the bungalow, with 80mm Kingspan on the inside of all external walls and the flat roof ceiling and 300mm in the loft. 175 meters of trenching to link all outbuildings with the house and laying water, armoured cable (10mm) and a ground source heat loop (for future use). Future projects include getting off grid for electricity and water, building a timber and glass conservatory and using the stream that runs the length of the property for a micro hydro system. A post about this will follow. Mike

I used Visqueen behind the larch and lapped this onto the ground, so instead of guttering I will use some more Visqueen and create a french drain and collect from there..but it means breaking up rock so it will have to wait.

NOPE! Stop hoping for a quick fix please. The pump needs to be the right way around, the flow and return need to be plumbed to drop down and come in at the level of the lower rail, and the thermostatic valve will, ergo, be at the bottom level too. Sleep well, for tomorrow you will find a new plumber and heating happiness. There is absolutely nothing you can do the the existing arrangement by rubbing some hope ointment into it. Needs a full re-work, prob 2 days work at least for a conscientious plumber.

Ah, OK. Just so you know, written posts on the internet / by folk on here, much as mine do also, can be seen a bit blunt or as if we’re having a bit of a dig. For clarity, any dig is at your installer and absolutely not at you. We will of course help you as much as we can You don’t need any replacement kit btw, just the whole lot needs to be reinstalled / reconfigured. Then you’ll be back up and running in no time. The kit here stands zero chance as it’s simply all installed arse over tit. Do you know a good plumber with some patience? Hopefully the wiring side will need little or no intervention, as long as the actuator cables will all reach the manifold locations after the shuffle.

“ I'll try a sloppy one “ is that a technical term?

Thanks for the reply Conor, only just seen, valuable info. Luckily enough I bought some straps this morning and they are 90 degrees. I have a vice so hopefully can bend them ok, they are substantial- a good thing so long as I can bend them! Thanks again. Also thanks for the reply @markcsorry for not replying before, just liked your reply as it was exactly the info I was after. Ended up spending £220 on straps this morning. They are eyewateringly expensive for what they are!

It will have an insulated door over it. It will only get used very occasionally if painting for example

All the photos of Reliance manifolds I can find on the web show flow meters on the top flow rail and actuators on the bottom return rail. Example..

So, due to day storage heaters using only excess PV power we still have not turned on the ASHP yet. Works well through diverter. Set to hot water until temp met, then on to day storage heaters.

You could easily lose your neighbour in 900mm if you do end up having to back fill.....

sorry if this is a sucking eggs comment but if going for gravel “chuckies” (as they call them where I’m from), get a quote direct from quarries in particular independent ones. I paid £22 per tonne, including VAT & delivery, for a lorry load of loose tipped 20mm granite a couple of months ago . Avoid 1 tonne bags from builders merchants unless you only need a small quantity.

There is also absolutely ZERO way they your pump should be upside down!! This is a mess and I expect the pump / thermostatic valve orientations have been set up in confusion to make a left hand installation suit a right hand arrangement as far as plumbing / pipework is concerned. This needs a major removal and refitting. Stop tweaking, get a plumber, or the person who fitted this badly to come back and do it the right ( correct ) way.

My point is he would have to have been well versed in exactly what was happening by scrutinising the plans. A casual onlooking neighbour wouldn’t spot it.

@Pta Would be good to have a photo of the pump end of each manifold. Eg Framed to show one actuator and one flow meter, the pump, the isolation valve and the mixer. Some parts like the pump and mixer may have arrows or letters on them like F and R. If these arent visible in the photos can you mark up the photos in MS paint or similar. Eg like this photo without the bottom cut off..

Single zone with weather compensation. With night time setback of a couple of degrees. Have the thermostats set slightly higher than the target room temp of 20, to keep the UFH manifold pump on. Bedrooms temps are 18, set by slowing the flow rate to those rooms. Last year I worked out the how long the floor takes to heat up and set start time and end time of the day time temp around it, so starts at 0230 and at 1830. My current flow temps are around 23 degrees. According to the boiler datasheet, I should be getting around 110% efficiency. Not sure how true that is. Gas usage including DHW is averaging around 15/16kWh a day over the last 10 days in NE Scotland.

We have 7x loops and had 3x zones. Over summer I changed that a single zone. I haven't notice any obvious difference in efficiency. I had to increase the pump speed to get the flow rates set correctly as it was having to serve all loops at the same time, which it previously might not have had to do. I've also started playing with the temp differential (i.e how low below the target temp before the stat calls for heat). For some reason my stat was set to 0.5c (even though the manual says the default is 1c) and I found the boiler to be turning on every 30 mins. I've dropped it to 1c and it's now coming one once an hour, so a difference but I'll need to wait a couple of days to see whether it's actually made it more efficient to run...

We're very open plan.The company that set up my system said they have found that simplifying to a single zone, or as few as possible gives the best efficiency. We have a single zone that includes the UFH downstairs and the four rads upstairs.

There’s a whole section of electrical building design dedicated to this. Based on the rolling sphere method usually but can be directly assessed for more vulnerable buildings. Always interesting designing LPS schemes for ammo dumps. Or AA missile batteries on tall buildings in South Korea. It’s a whole section of risks multiplied together to give a final risk factor. If you live on top of a hill with no surrounding trees or buildings, you may be at a slightly elevated risk level. But it’s usually designed for prevention of loss of life rather than property as any direct strike is going to melt whatever conduction measures you have and probably make a big hole in the roof anyway. Check your insurance doesn’t omit it as an ‘act of god’ but I don’t think I’ve ever seen an LPS for a private resi scheme.

Metal building is a conductor from roof to ground. A metal roof is top of a building that is generally a conductor on top of and insulator, so the risks are different No ideal if it makes a real difference. Ask your electrician he may know?

Ahh yes. I built about 300 steel sheds, about 30,000m2. Over 30 years. Lightning strikes nil. Our supplier has made 30,000 sheds around Europe. Lightning strikes that they had heard of...nil. My theory is that if lightning hits your metal building then it earths through columns to bolts to ground, like a Faraday shield. If it doesn't then it doesn't. Either way, no harm done. BUT. When the buildings were for a local authority, they insisted on a risk assessment by a specialist...who always advised that they install protection. This was a copper strap from the bottom of a column to a spike adjacent. If you have a metal roof on a non metal building I don't anticipate any increased likelihood of the lightning choosing your building....it will head for another building with greater conductivity, of steel, or with a lightning conductor. The risk is different for hospitals and churches. Always provide protection for them.

LED strips are CV, the other things are all CC. EItherway, the luminaires all connect directly to the (unswitched) +24V supply but the negative terminal returns back via a dimmer (in the central-cabinet next to the PS). The dimmers all apply the PWM on the negative supply (so "common anode" right?). Mostly DMX driven LED drivers e.g. CV: https://www.aliexpress.us/item/32824271209.html CC: https://www.aliexpress.us/item/4000473275297.html

Love it! You've inspired me.

Yes

This also helps reduce annoying squeaks and ticks with expansion and contraction of the pipe.

Hopefully this helps BH folk get a further insight into the ins and outs. Here a few extra of my own thoughts. Take two cases. Case 1.. a simple ground beam spanning over a drain resting on a couple of pads at each end. Case 2.. say an ICF basement, raft slab with a waterproofing system. In both cases SE say works out the loads and designs the concrete and sizes the rebar. Then often produces a basic reinforcement layout drawing showing bar sizes, concrete cover, durability etc and a few important details; say the lap length, key corners and so on. The SE will usually carry out a review to make sure that what they have designed can be built "somehow?? " (I hear some of you laughing) and markup up the drawings with some CDM notes and so on. This is then passed to the "lucky" Contractor who has to get on with it. The temporary works are delegated to the Contractor as are all the other problems that go with this type of work. The SE may then be engaged to come to site to check the rebar sizes, spacing and so on just before it is all ready to pour. Now that can work ok on large projects where the Contractor maybe has their own in house Engineers who can do all the temporary works design, carefully check the rebar type, spacing, that the bars are all in the right place and has lots of experience. On small domestic projects this often causes problems as smaller contractors / general domestic builders just don't have the breadth and depth of experience or maybe the resources in house. They often need to get someone else in to do the rebar schedule / provide a price so they can tender properly and so on and this comes at a hidden cost, then the need to install all the bars and shuttering and hope for the best. In summary when things don't fit up on site and the concrete is ordered a lot of money can be lost (tempers fray..) usually by the self builder / domestic client. Designing rebar so it fits and the schedule. Once you have done your "SE" bit the next step is look at the bars in detail and start by thinking "what can go wrong here". Extra long bars or bars that are not basically off the shelf at local stockists could come distorted due to bad handling or may be on a longer lead time.. important later if one or two get damaged on site. Cutting and bending rebar is not an exact science, even with modern machinery. All bars have a length cutting tolerance and when you are setting up the bender the first bar may not be quite right, but still in code tolerance. The ones made on a Friday afternoon may not be quite the same as the ones made on a Wednesday at 10.00am. Some can be over bent, some underbent. Also you get what is called spring back, steel is springy so when you put a bend on a bar all bends won't be the same and this can result in quite a difference and this causes problems at corners as for example. You can reduce the concrete cover to the bars. Remember that the bars when they go into the bender may not be perfectly straight to begin with. If that is not bad enough you have to allow for a tolerance on the shuttering. A shutter that is leaning in coupled with a sprung out bar can leave the bar with little of no concrete cover, and as @saveasteading says in cases they just won't fit at all. Bars that lean in can cause bar conjestion and that means that you can have zones where the concrete is not able to be properly compacted.. to be avoided. Often you say to yourself. Hey if I put laps here I can avoid problems with bars fitting over a wide length between two shutter faces. If I'm using cranked bars in say a basement slab with top and bottom bars can I allow the contractor to move the bars a little in case the cranked bars are a little off. If so, how do I convey this "get out of jail free card" to the contractor. Once you have figured this out you go back and check that the SE design has not been compromised. The bar bending schedule is then relatively easy to produce as you have done all the hard work. Then you check it all again! It's not just burning it's white hot! Take case 1. A simple beam. I'll do the schedule just working off my 2D cad drawing. Often I'll do this for a nominal sum (fee) especially if it's for a contractor I work with regularly or just "good" for the job. If I make a pigs ear of it then I would expect to foot the bill, but that is a commercial risk I take and is lumped in with the rest of the SE design. Case 2. Ah! Quite happy to do the schedule.. here I say to myself.. 2D is not enough, the risk is greater. What I do is to use say Tekla detailing and model the rebar in 3D and put in the shuttering lines. Now I can really visualise where the problems lie and work your way round the model fixing problems, thinking about buildability, pour sequence and size, the weather / time of year etc.. while all the time asking.. have I compromised the SE design. Another aspect here is to make sure you have all the other information you need to coodinate any service penetrations, water bar details etc. Once all that is done then the schedule is the easy bit especially as the software does a lot of the hard work. But again once you have the output from the software I would spend at least a day checking it, just counting bars and so on and a few other things. Lastly you need to check you rebar spec and so on. Quite happy to do this, put my head above the parapet.. someone has to so why not me? If I get it wrong the bill will land on my door step. However I charge accordingly to carry this risk and am careful about the contract terms. Am I just liable for the bars that don't fit or am I liable for any project delay for example. One claim could be a few hundred, the other many tens of thousands. That is something I discuss with the client about what level of risk they want to take on and how much I will charge for the various risk levels. Usually a sensible agreement can be reached where the risk is shared in an equitable way. The main thing is to have the discussion: Is my fee going to result in an overall saving to the client and deliver what they think they are paying the contractor for in terms of build quality and so on. If yes.. then cart on. Another option is where the Client novates you to the Contractor to do this. Basically the Contractor employs the SE directly and carries the risk. But on self build this is complex contractually especially when you are trying to nail down prices to get say funding for the build. In summary. If you are self building then the above is worth a look at as an approach. It's a balance. The more you spend on the design information the easier (we hope) it is for builders to deliver. Also less risk at tender stage as contractors if they are unsure at tender stage about something will just add on a big number and think to themselves.. if I get the job I can afford to worry later about how I'm going to do it as I have a big profitable lump sum built into my figures.

Sure but worth a try. Explain your situation including the health challenges.

I'm afraid it's unlikely even CEO intervention will fix this, as you have the right to shop around for export contracts, there's no way for them to know retrospectively whether you spent the last year being paid by some other provider. Plus there's a bundle of paperwork to provide before they would start payments. It's pretty atrocious they didn't provide an initial bill for a year despite your chasing though

Email Greg Jackson (Octopus CEO) I did and my problem got resolved.

It may have that capability, does not mean it is used. Hate to say it @patp, but I suspect you missed the boat on the last year's exports. Just bite the bullet and get a proper contract with them, they seem to be offering the best rates. There is ideology and there is pragmatism. Go for the latter when money is involved.

You could rip them down to 150mm at the thin end removing the requirement for separate furring strips and making the most of your ceiling height. This is the root cause of your issues. I'd be tempted to put all tools back in the van until this was really sorted. Have the roof trusses been ordered?

Did you have another thread about the install of this system?? I thought that some/all 3 phase meters did net metering so if you export on one phase and import on another, the units exported would offset those imported. Net result is youd only pay for any units imported that were more than those exported.

Yes, if you don't have an export contract they won't pay for exported power.

Well done. I looked at the Polycrub Opyl as a shed but was put off by the price and the fact the walls weren't vertical. You've done a good job, bet you're pleased with that.

Feeling very encouraged! Thanks for responses, loads of good information. It is absolutely true, this needs to work but it certainly doesn't have to be perfect. @Thedreamerthat is a great looking shed. @andyscotlandI very much appreciate the detail about screws v nails, for this it seems screws have a lot going for them, especially as the bits won't jump around.

Looks great. We drove the NC500 this year and saw quite a few of those polytunnels you mentioned and got up close inside one to see how it was done. Yours looks great just like those but at a fraction of the cost. next project for you is half cut drain pipes along the 2 long sides to collect all that rain and and an IBC for storage. So jealous, if we ever get planning my veg plot becomes the house and garden and I have to start fresh further in to the field. I’m at the opposite end of the country but high up near the coast and also suffer from the storms so currently have a walled plot and a netted tunnel to keep the birds and butterflies out. I’d love to suggest this to HWMBO but I know the answer ‘by the time the homes built the last thing you’ll want to do is garden well be too old’

If you're after volume and efficiency it's chest freezer. Ease of access, go for an upright. Chest freezers tend to be colder and quieter. Most people I know around here have one in the garage for meat.

Knowing how much you can loose: Partner Children Friends Dignity Time Body Parts Tools . . . . . .

Do you need to freeze apples to preserve them. I though wrap in paper (discard bruised ones), put in box, put in a dark cool corner, was the way to do it. Certainly was the way to do it when I was growing up (a long time ago)

Keep the floor plan/building shape as simple as possible. Don't go 1.5 storey unless you choose attic trusses. Avoid valleys and structural steelwork. Insulate, insulate and insulate some more. Naturally ventilate. Avoid air-conditioning if you can. Orientate the house to maximise natural light and heat. Consider renewable energy sources. Establish a budget and stick to it. Use an architect-a real one! - one who you can work with to deliver what you want.

First - the process overall should be enjoyable Don't get carried away with room sizes - you can end up with a huge houses. Decide things early and documented on the drawings, ideally before getting any pricing. Any change after the contractor has priced is a cost added - in many cases even a simplification of their scope. The more decisions you can make ahead of starting the build, the less stress during the build. Once you make a decision, don't change - it will cause lots of other hidden changes and snow ball, to more cost and delays Keep it simple, often things get way to complex and can ramp up costly quickly. Don't ask forums questions with open questions, as you will get 1001 answers all different, many not relevant. Do insulate way better than you think you need. Consider thermal bridging early on. Go as airtight as possible. Consider cooling if you have large windows, this can be direct aircon or solar shading externally. Question any large windows on the north face of the building as these are just heat losses - min 4x the heat loss of a wall (high performance triple glazed), generally more. Keep heating system as simple as possible. Do not zone the heating system, 1 zone ideally, a max of 2 zones. This will give your heat source an easy time and work better overall. Well insulated houses have very low heat requirements, many builders and heating companies will use generic formulas to size boilers radiators etc, none of which work with low energy housing. So check things yourself and be aware of your requirements, ask for help when needed.

Bar bending and reinforcement quantities! Have written this as I hope it helps all who are doing everything from ICF, piled extensions or just using rebar. I often do these on small domestic projects. I sell this as an extra to the Client by discussing first what type of builder they may want to employ. Take two cases: 1/ A house extension.. a few piles with a ring beam. Here your local builder (or you) could maybe get a piling contractor that leaves the pile heads. These are commonly designed at SE stage to be up to 75mm out of alignment and still be code compliant. Next the builder has to figure out how to connect the piles to the ring beam, the shuttering to say get the concrete cover right and all the bars in the right place. Now your local builder may find this a challenge. I say.. hey I'll do the schedule and a shuttering detail. Your builder can then send my schedule to the benders for pricing, make the shuttering and I'll nip by and check it before you pour the concrete. If you want the builder to sort it all out it will probably cost you more than getting me to lay it all information wise out on a plate for the builder. All they need to do is send my schedule out for pricing.. no hassle for them and if no hassle less tends to be added to the price. Or you can get a ground worker that will sub out the piling and do the ring beam.. but someone has to coordinate all this and that is something that comes at a hidden cost.. and you have to take a leap of faith that they are doing it correctly. Better to spend more on good pragmatic design info than have a bad day when it comes to the concrete pour or worse.. once the concrete has been poured and you discover all is not as you expected. Stepping up to say an ICF basement. Here I would push the Client to pay me to do the steel (bar bending) schedule. In fact I would be reluctant to do the job unless I had sufficient design control over it and be able to check on site. What folk don't realise is that when you bend rebar it is not an exact science (bends vary a lot!) and that you need to be very careful to maintain concrete cover, the correct lap length and make sure the concrete can be well compacted at particularly the corners and junctions as that is where you often get leaks. The folk that provide the ICF stuff don't cut you much slack if your bars and in particular the bend radius is a little off. The steel fixer will use what they are provided with and while they will often do their best they can't make a purse out of a pigs ear. Remember that rebar is very heavy and if a rebar cage falls over it could kill someone. I want to make sure that the tying of the bars and temporary stability bracing will be sufficient for it to stand safely during the construction phase. ICF suppliers.. their interests / priorities are not the same as yours when it comes to rebar and so on. Yes some SE's don't do schedules.. years ago it was part of an Engineers training to design a concete beam / slab and produce the bending schedule.. I still remember learning how to do it. The main thing for me is that if I do it say for a basement or say ICF, a retaining wall I have to really look and draw/ model how it is going to fit and if it can be built /poured. It's almost like a last design safety check as when you have to sit down and do the schedule / shuttering you can spot things that you may have missed. It's like another design review/ safety check. If it can't be built as per the design then it's not safe. I could pass design responsibility to say.. well who is going to carry the can.. that is what you need to ask. The sad reality these days is that few designers want to carry the overall design responsibility as modern Clients are often not willing to pay for what they percieve as an extra. Why.. because modern professionals often don't explain (and have often not been taught how to) to a client how they can make savings at the end of the day. I minded to blame the telly.. too much Sarah Beany, Homes under the hammer and Grand designs etc .. well I'm not going to blame myself? If you have the skill to convey to a Client that your way is the most cost effective, efficient and delivers and the Client is not of like mind then you need to walk away from that Client, let them get on with on it. Projects like that often only lead to disappointment on all sides.

Can't comment on your specific question, but its easier to bend a 90degree strap to 30degrees or whatever than it is a straight strap.

Right then... I've ignored all advice, and we've specified a full fill rigid insulation (well 15mm residual cavity) using Kingspan Kooltherm for our build. I'm aware this is going to be tricky to get right, but we didn't really have the option of going much wider with the cavity, certainly not wide enough to get the same nominal U values with other options. Of course the actual U value depends on how good the installation is - it's now crunch time and we're about to begin! We have some good brickies who seem to have a good eye for detail, and our plan is to work around them doing the really time consuming bits and spending the extra time to improve their best efforts. So any tips? Specifically: How best to cut the rigid boards, particularly around intricate details like our periscope vents? Inevitably there'll be some gaps between boards in some places, can these be filled with an expanding foam?