Leaderboard

So after a month or so in the house, the time has provided us with an opportunity to reflect on what we have achieved and what if anything, we would change or could have done differently. In truth there is very little if anything that we would change. The rooms flow, the doors open in the right direction and the lights can be switched on and off in the appropriate places. Even the WBS has proven to be a worry that wasn't worth worrying about, as it's position within the hearth is no longer an issue due to it being vented through the back as opposed to the top. Some jobs have been completed such as the down pipes and a few jobs remain outstanding but nothing that has an impact upon our daily lives. One such job is the porch that needs to be slated. Thankfully I still have some financial leverage over those various trades so I know they will return. Our satisfaction I suppose, has to be routed in the preparation work, the research and being a member of this superb forum. None of these elements should be underestimated. Therefore I would like to sign off this blog with a heartfelt thanks to all those who have contributed, not only to my issues over the past couple of years, but to all the other threads, as they too are just as relevant / enlightening. I have also attached some images which complete the project, namely the WBS chimney installation and the erection of the much mentioned porch. For a final time, thanks for reading, and given the date, seasons greetings to you all. Paul.

If you have a narrow gap under a door then the air will move faster and it is possible to have a slight draught for that reason. I think a minimum gap of 10mm is usual. The air from the supply vents will always be a degree or two cooler than the air in the room so will always feel cooler. You can fit a small post heater to overcome the heat loss if you find it uncomfortable. Setting it up correctly will probably result in reduced air flow. I put a section in my blog about commissioning my MVHR system. Some cross posting with Russell.

Is it meant to be all different colours? What an appalling mish-mash of "styles" though there's nothing stylish about it. Looks like they took the scaffolding down before it was rendered.

(Puts on highbrow helmet) Ask a dentist...

I prob just have bad taste......I think that looks shite.

Check this out, bit chuffed with this, never used a bender before.

@tanneja yep, it's the Ubbink 180mm insulated duct and both runs have a slight fall from inside to out.

Paragraph 55 is now Paragraph 79 ?. They should have called it Appendix 1, then it wouldn't get changed every time the NPPF is redone. Planning to do a short blog piece about the planning factors that aligned to get it through - a lot of them.

@Crofter From SG website: The Control Area Regulations will allow planning authorities to designate all or part(s) of their area as a control area. Within such a designated area, the use of a dwellinghouse for secondary letting is always deemed to involve a material change of use and requires planning permission. Outside such areas, the current case-by-case consideration would continue to apply. The requirement to seek planning permission in a control area would not, of itself, imply any predisposition to refuse consent. However, as planning applications are required to be determined in accordance with local development plans, it would be open to individual planning authorities to consider the inclusion of policies relating to short-term lets in their relevant local plans. Whether or not the various adverse impacts that have been cited are material planning matters in respect of any individual application, and what weight to attach to them in considering the application, would continue to be assessed on a case-by-case basis within a control area. As a primary purpose of control areas is to help manage high concentrations of secondary letting, we are proposing that, in a manner similar to advertising hoardings, any planning permission which is granted would be valid for a default period of ten years (unless a longer or shorter period is set by the authority) but that local authorities should have the power to revoke planning permission after that time. Without such a mechanism, the granting of planning permission for use of residential property for secondary letting is a one-way ratchet, in which the number of properties which can be used for this purpose would only ever increase. My reading of that is that local authorities can if they wish, designate areas as a control area (similar I suppose to Conservation Areas in that there has to be justification), which then allow them to apply planning legislation, and in particular specific policies to control the number of lets. I suspect this is primarily aimed at certain city centre locations where residents (or those that are left) face misery on a daily basis as whole flats are let out to groups of people who consume copious amounts of alcohol and the fall out that follows. PP would normally specify the period of time it is valid, i.e. time from date of approval to commence development. The general principle in planning is one of 'use' rather than simply being - you could have a little cabin in your garden and use it for purposes incidental to the enjoyment of your dwelling with no PP req, but rent it out as holiday accommodation and it's use has changed. The cabin is the same, but the use is different and would require PP. Equally you could have planning granted and then decide not to implement it. Ultimately it will all depend on your local authority view on the planning side of these measures. They may be quite content with status quo and just implement the registration side.

Fibber. pipes look to straight

Nah

Should be but it is not a vapour barrier. If it exists it is a vapour control layer at best. Probably loft hatch, pipes, wires and ducts penetrating. VCL is probably not contiguous with the outer leaf. The roof needs low and high level ventilation. Soffit and ridge.

No - it’s my (expletive deleted)ing house

Is that at wentworth i worked on a few in there and they had that sort of look.

I am very pleased with it. My biggest fear was that I would wrongly order something, I just allowed for the cabinets to be a few mm shorter than the space available. Would be much cheaper without doors. Drawers also add considerably to the cost. Use wider units if possible, a 1200mm wide unit is much less than 2x the price of a 600m wide unit. They are very flexible, the website allows you to adjust sizes. I ordered 680mm deep units as I think the standard 580 is a little skimpy, also 2400mm tall so I had lots of room for double hanging.

No draughts from ours at normal rate unless you stand on a stool right by a vent. Full boost mode when showering is a different matter, quite noisy and I can feel a draught on my (bald) head in places.

Are you feeling it at low level due to the gap under a door close to you, my extract system in another house sucks air under a door that you could fly a kite in the draft, open the door and you would never notice it, it just seems concentrated on that 10mm gap so feels more powerful than it is.

I've not noticed drafts arising as a result of our MVHR, but then of course there has to be some air movement between rooms as that is required for it to properly function so it may just a case of me not having noticed it (perhaps by virtue of the fact ours might not be running as fast as yours). Regarding the temperature of the outlets do remember it is not a heating system and so any moving air below body temperature has the potential to have a cooling effect when felt immediately after exit (it'd soon mix with the ambient air at ceiling level). Furthermore, with it not operating at 100% (not far off though - ours seems to generally hover at >90%) the air it pumps in will always be slightly cooler than the air it sucks out. The limited volume and heat capacity of air though means it shouldn't be noticeably cooling the house down much (and certainly nowhere near what a trickle vent admitting untempered outside air in would).

Hideous extensions. 'outstanding architectural merit'? - pah!!!!!!!!!!!!!!

Think it was mentioned in the program that it is limestone?

(expletive deleted)ing amateurs !

In theory the roof membrane should be breather membrane, however you could put some small wedges in the laps to increase ventilation. I suspect moisture is coming through the ceiling into the loft and the membrane simply can’t disperse it fast enough, so it simply condenses and then drips. remember not all breather membrane is created equally, so try some methods such as the simple one I’ve suggested to increase airflow

You're not the only one.

You might consider linking some to sign off by Building Control. Groundworks - Foundations and drains completed and approved by Building Control. Walls - Completed to roof level and approved by Building Control Roof - Structure complete and tiled and approved by Building Control. Completion etc

Have you asked him why ..? And how about offering to pay the supplier invoices direct to manage the cash flow. Also means you’re the owner of the goods outright.

Please read this independent of ecological considerations, habitat loss, species extinction etc. That's an different topic. I considered the Carbon offsetting and have come to the notion that it's bogus and an excuse to continue the status quo. In @SteamyTeas article the $300 million over 3 years spent by Shell is only 0.028% of their revenue per year (2019). $1 out of every $3450 that goes through the company. They don't care, it's literally half of what they spend on ads. Climate change is a result of us digging up coal, oil, gas, peat and burning it. We are considering the idea of carbon sequestration as a way to reverse this but the process involves sucking carbon (CO2) form the atmosphere. Plants and trees and algae etc do this and over their lifespans die and fall to the forest/ocean floor. Some of the carbon they contain gets trapped in the earth but much gets released into the atmosphere again as greenhouse gasses. Left to it's own devices this process would eventually trap all the carbon we have released in the last 300 years into oil coal gas and peat again but it would take millions and millions of years. It's an incredibly inefficient process as only a fraction of the dead living thing gets permanently trapped in the ground and helps to slow climate change. The tree you plant today will only make a useful immediate difference to capturing any carbon if you cut it down and dry store it permanently. If you let it fall and rot on the forest floor only a small fraction gets permanently trapped. That's assuming that the land isn't turned back to farmland in a hundred years and the carbon ploughed out again from the top layers. To this end, purely in terms of capturing carbon, you'd be as well off investing in commercial forestry and finding somewhere to store the lumber (like a house!). There is nothing and I mean absolutely nothing which slows carbon caused climate change more than leaving fossil fuels in the bloody ground! Anything else misses the mark by orders of magnitude. To this end if you really want to build low carbon 1.Keep embedded energy low. Despite what the concrete+oil industry says you don't need energy intensive materials to have a superbly performing house. 2.Don't use oil based products ( ICF and SIPS have plenty). Leave them in the ground. 3.Lock up as much carbon as possible using plant based building materials. You can't control bought in energy, so reduce your use as much as possible. Generate as much onsite via solar as you can and send the excess back to the grid to offset someone else's fossil fuel use. I went off ICF because of the cost. That and ICF is the Dime bar of wall construction when what you want is an Armadillo! The soft bit on the inside! Timber is massively nicer to work with and does away with concrete which creates 99% of the suffering and mess on a build. I chased the walls of ours with a 9" grinder. It is the worst job I've ever done. I'm timber framing the garage myself and enjoying every moment. It was difficult to find a builder comfortable with anything other than cavity walls. The common builders manual is full of pictures like this. I suppose the reality is climate change is a generational thing, I'm mid thirties and I say the right words and believe the problem but I'm probably too selfish and lazy to really do much about it. I didn't really understand the issues and still don't with many. Until I learned to calculate the numbers myself I haven't appreciated how much BS there is put out by manufacturers of various products. There is an absolute sea of it. With the external blind option consider whether you want 1:half a window you can see out all the time or 2:all of a window you can see out half the time. It will cost quadruple, need triple maintenance, and loose twice as much heat. I'd be interested to see where your table comes back when you add a timber frame option to the list along with the sips and the ICF. Jonathan

Knocked out 57m2 of the old concrete, excavated the sub floor then sand, dpm, 100mm of PIR and more dpm. Then approx 400m of UFH pipe. 25mm of PIR upstand along with expansion strip foam and 75mm of free flow screed (laid by contractor)....... kept me fit over the summer doing the project and is now keeping us toasty warm over Christmas..... probably the most enjoyed end product ive ever done!! i echo the above comment in that it is easier to install than radiators etc. one thing to remember- keep the pipes under pressure when you have the screed laid. You dont need to hire or buy an expensive pressure tester, i bought one from ebay for £11 and it works fine.

For you I’ll do it for £59.50 as they are a doddle ..! They need a good set of eyes to see the terminals and a small screwdriver so I tend to make them up on the kitchen table with some tails on and use Wagos to connect them. Make a power fly lead using a plug and you can test and programme on the bench first as they keep their memory for ages. The main issue I found was getting it to recognize on the phone app, so use an Android tablet or laptop - also worth adding your phone hotspot as a secondary internet provider so if you lose the internet signal you can still access the unit. Monitoring is good too - I’ve got a couple (one is a 1PM with the sensor header) and it gives me the outputs of the sensors over a period of time and you can download the data too. Nice touch is the override switch - if you go for a retractive switch it means it can never be left “On” and lock out the controls from the app or the timer.

Shelly 1 could do it - bypass the live to the feed (unless it’s a Nv switch ..?) and can do by pressing a button or phone / app etc. Cheap and easy for about £10. You could go all the way and replace the whole of the system with a Shelly with a thermostatic head, you can programme them and they will also communicate with other MQTT devices.

Roof integrated PV can work out cheaper than tiling, and it reduces the thermal energy by up to 20%. A mate of mine did a report about 15 years ago about carbon sequestration schemes though forestation. Found out that many were double counting i.e. the reforestation was going to happen anyway, so no net gain, and a few were just scams. The best way to reforest is to let nature do it i.e. just put a area aside and the trees will appear. Now that the UK has left the CAP, only time will tell if all the new environmental schemes will actually happen (pulse fishing has been banned already, but this may lead to over fishing). I am always dubious about the tonnes CO2 stored by trees, one has to be careful as there are different methods of measurement used around the world. How everyone decided trees will save the planet – and why they won’t Everyone seems to agree trees are a major solution to climate change, but there is a danger that mass reforestation could see us to continue pumping carbon into the atmosphere EARTH 26 February 2020 By Adam Vaughan De Agostini editorial/Getty Images TREE planting doesn’t usually feature in US presidents’ speeches, UK general election battles or the business pitches of oil companies. Yet in the past year, pledges to embark on reforestation efforts have become a popular way to show you are committed to fighting climate change. There are several initiatives to plant or protect a trillion trees, to add to the 3 trillion we have today. So how did we get here, with humble tree planting taking centre stage among the tools to stave off extreme warming? Can we really plant the numbers needed to lock up enough carbon to make a difference? Perhaps most importantly, is all this talk of trees just a big distraction? “Fossil fuel industries can say they are harnessing nature to address their emissions” “Suddenly, this last year there’s been an explosion of interest,” says Fred Stolle at Global Forest Watch, a US initiative from the University of Maryland and other groups. Rising public concerns seem to be making governments and corporations realise they need to do more on climate action, or at least be seen to do more. “I think there’s massive concern about climate change now and people genuinely want to do something about it. I think they are reaching for what are easy solutions,” says Joanna House, a lead author of a UN Intergovernmental Panel on Climate Change (IPCC) report on land use published last year. Planting trees is popular, usually uncontroversial and brings benefits beyond storing carbon, from our mental well-being to habitats for wildlife. “People love trees,” says House. The spotlight on tree planting may have its roots in the 2015 Paris agreement, in which governments committed to try to hold global temperature rises to 1.5°C, rather than the 2°C many had expected. This led to a 2018 IPCC report, which made it clear that to hit 1.5°C, global greenhouse gas emissions need to fall to net zero by 2050. There was much debate about “negative emissions” technology, such as machines to capture carbon dioxide from the air. But with these in their infancy, the focus fell on trees as the only proven option. “I think a lot of the talk around the new ambition for 1.5°C was one of the biggest driving forces for putting negative emissions – and particularly nature-based negative emissions – on the stage,” says Stephanie Roe at the University of Virginia. But tree mania accelerated last year, when Tom Crowther at ETH Zurich in Switzerland and his colleagues published a paper that said Earth has room for nearly a billion hectares of extra trees, which could lock up several years’ worth of humanity’s carbon emissions. The research has been criticised as an overestimate, but was influential and made global headlines. “I think that played a key role in re-legitimising reforestation,” says Mark Hirons at the University of Oxford. A few months later, political parties campaigning in the run up to the UK general election competed on who promised to plant the most trees. Last month marked peak tree planting fever, when the World Economic Forum launched 1t.org, a plan to plant a trillion trees (other plans launched three years ago). Even US president Donald Trump, who has withdrawn the US from the Paris agreement, backed the initiative. Douglas Gimesy/Getty Images But even if we start planting vast areas tomorrow, can trees store enough carbon to buy us time to act on climate change? The Crowther paper said 0.9 billion hectares could lock up 205 gigatonnes of CO2. Including land-use change, such as forests being cleared for farming, humanity’s annual emissions are about 41 gigatonnes. But House says many researchers were shocked by the paper. “It’s quite harmful because it makes it seem like trees can do more than they can,” she says. Several experts took to scientific journals to explain why they felt it exaggerated the amount of usable land and how much carbon could be stored. In response, Crowther says a lot of the criticism is well-founded, but it is important to get a global perspective on what it is possible, in order to set meaningful restoration targets. Based on Roe’s review of the literature, reforestation has the potential to lock up between 1 and 10 gigatonnes of CO2 a year. “In terms of what is feasible, we came to 3 to 4 gigatonnes [a year],” she says. More research is under way on calculating the carbon storage potential of tree planting. In the meantime, it seems large enough to be attracting big business. Last year, Shell announced that it would spend $300 million over three years on reforestation projects to generate carbon credits for itself and others. On Crowther’s analysis, Duncan van Bergen at Shell says: “Even those people who have challenged it, have not challenged the fact that it is really, really big. It’s on the margins between really big and huge.” He says the numbers presented “resonated” with Shell’s own researchers. Such interest in reforestation from oil companies has set alarm bells ringing in some quarters. “Fossil-fuel industries can say they’re harnessing nature to address their emissions, which is dubious I think, in terms of the scientific case for this significantly having an impact on climate change,” says Hirons. There is a risk that we plant trillions of trees without firms and countries also deeply cutting their emissions. Shell says that isn’t the case. “We are definitely not doing this instead of other tough things and changes we need to make. This very much comes on top,” says van Bergen. Even if mass reforestation happens in parallel with decarbonisation of economies, Stolle warns that trees must be planted at the right place and time. As well as picking suitable species for the climate and the soil where they are planted, it will be crucial to plant trees that help rather than hinder biodiversity. Biodiversity warning Take the UK, where the government’s climate advisers have called for a tripling of tree planting to hit carbon goals. Jane Memmott at the British Ecological Society says there are huge differences in biodiversity levels between trees you might pick for the UK. “Something like oak and birch is fantastic – there are literally hundreds of species associated with them, whereas something like sycamore has pretty much a single aphid on it,” she says. Then there are the people who live in and around the places where reforestation might take place, often in developing countries. Restored forests won’t thrive or remain intact long enough to lock up CO2 for centuries if local people aren’t invested in them, says Stolle. “In developing countries, people very much understand the value of trees,” he says, but only when they play a role in deciding when and where they are planted. Hirons fears that the urgency of tackling climate change could see the wishes of local communities being ignored. “I think there’s a massive risk of social harm being caused by widespread reforestation. There is an idea that there is lots of underused land, which is a myth.” While there are international guidelines on how best to do reforestation, set by the Society for Ecological Restoration, there is no requirement to follow them. Lastly, if the CO2 locked away is to be counted properly, we will need to monitor reforestation for a long time. That is surprisingly tricky. Deforestation is easy to spot – satellites show areas turning from green to brown. But they find it hard to detect new trees, which for the first few years will be tiny saplings hard to discern from space. Higher resolution images may help. Perhaps the biggest thing missing from today’s focus on reforestation is the great number of trees being lost to deforestation, which is getting worse. The world lost forests the size of the UK every year between 2014 and 2018. Deforestation in the Amazon rainforest has spiralled to the highest level in a decade. Recent bushfires in Australia burned 64,000 square kilometres in Victoria and New South Wales, most of it forests. “It’s an eternal debate,” says Stolle. “Is [reforestation] a distraction because we really need to stop deforestation? On the other hand, if you look at the IPCC, we need those negative emissions. We can’t wait until we’ve done one before we do the other.” Revenge of the tree-hugger Trees have long been at the heart of environmental issues. Three centuries ago, in a bid to stop local trees being cleared, villagers in India put themselves in front of loggers’ axes, with some literally hugging the trees. Several were brutally killed, says Alice Bell at UK climate charity Possible, who is writing a book on the history of climate change. The actual term “tree-hugger” wasn’t coined until the 1960s, though, she says, and became pejorative in the 1970s. Bell says the “save the trees” movements of the 1990s and 2000s weren’t dissimilar to today’s debate. “It was about climate change but without mentioning it. Now it’s climate first,” she says.

Hi @AdamJ, Excellent posts. You're well on the route to building an excellent house the way you're thinking. FWIW I started my journey at ICF too and ended up with a wide cavity wall after considering almost everything. (If I was to do it again I'd opt for timberframe) A couple of points I noted from your posts. 0.6W/m2K is probably a bit optimistic for whole window performance including frames. I'd put 0.8 to 1w/m2K probably. Overheating seems to be your prime differentiation for energy use with the different build methods. It can be all but eliminated at design phase. I'll try to summarise. Heat added internally (body heat, cooking, radiators etc) and is either fixed or easily controllable ( assuming you don't do anything silly like install an AGA!) Heat added externally is from the Sun and enters through the windows or soaks through the walls/roof. ( more on this later) Windows transfer the bulk of the sun's energy and this can be limited when we don't want it via external shading. This is easy to do on the south as overhangs or brise soleil just sit there passively and block the high midsummers sun while letting the low winter sun in. East and West is more of an issue as the low morning and evening sun can't be shaded without blocking views. Motorised blinds can take care of this but are expensive and require manual intervention or complex software. @tonyshouse has a great blog and discusses his I think. As mentioned solar glass can be used but the real trick is to limit the size of E-W openings. The wall and especially roof buildups can in certain circumstances cause overheating problems and I think this is what is causing your SIPS house to overheat. There are a few names for it but phase-shift and decrement delay are two of the most correct ( i think! ) . In layman's terms it's the amount of time a change of temperature on one face of a wall/roof takes to be noticed on the other face. A hot roof could be above 60deg in the sun and in a lightweight construction like SIPs will transfer heat to the inner surface quickly as there is not much energy taken up to heat the insulation itself. The inside of your roof will then be radiating heat into your house causing overheating. With a high decrement delay roof, by the time the heat had soaked through to the inside it would be nighttime and the heat flow would have already reversed due to the drop in outside temperature therefore never allowing the interior to be exposed to the extreme summer heat. Decrement Delay should be over 12hrs. More doesn't make any difference. 150mm concrete with external insulation to 400mm concrete with external insulation perform identically in heat protection. Overheating is taken care of in the following ways but they have issues. Its better and cheaper not to have it in the first place. 1. Ventilation - Requires manual intervention, creates a security risk with open window, bugs can get in, noise and dust are issues. Only effective when the outside temperature is less than the internal. Relies on air as the cooling medium and it is pretty lousy at transferring heat. 2. Active cooling via aircon - Extra plant required to be installed although can be relatively cheap and if the unit is correct can be used for efficient heating in winter. Low ability to cool large volumes of air unless very large unit installed. Can be run for free from solar PV as @ProDave said. 3. Active cooling via UFH- Niche idea in the mainsteam althought several buildhubbers have used it to great effect. Effective way of cooling quickly and if you're planning UFH not much cost involved either. Finally there is the heat storage capacity of a house. It is the amount of heat you have to add or take away to alter the temperature of the house internals. A house of high heat storage capacity or specific capacity will take much more energy to heat up the structure and will slow the temperature rise but also slow the temperature fall later on. Having a house of very heavy construction (high specific capacity) will do nothing to remove heat, only dampen its onset and retreat. It will help to level peaks during variable weather but do little during a prolonged heatwave. Remember all the other items in your house like furniture, books, floor coverings etc add to this specific capability too. Low specific capacity is never the primary reason for overheating. TLDR. Solve overheating at the design phase by 1. Adjust window sizes to reduce East and West glazed areas and add shading to the south. 2. Build the walls and roof from a material with high Decrement Delay (Phase Shift) ( woodfiber, cellulose, concrete are examples) 3. Don't get hung up on adding too much mass to the interior. It'll only help buffer heat swings, not solve overheating. 4. Allow for provision to add active cooling via solar PV if you think it's needed. Separately on the carbon issue look up MBC timberframes twinwall package with blown cellulose insulation. It is a good example of low/negative carbon construction but many are available.

Just for a heads up, if you fit some solar PV then you will have plenty of generation in the summer, so you can pretty much ignore energy consumption in the summer for cooling as that will be free.

Yes, timber frame, with cellulose insulation. Not got the time at the moment to look at all the charts. Couple of thoughts, reducing East/West window area may reduce overheating. Reflective films will also help. Adding PV will also reduce overheating. The Exeter climate model does not take into account changes in cloud cover (as far as I know, it didn't when I was there), so not the ultimate guide. And, just a little bugbear with some of us, tell us the SI units for 'Thermal Mass', or use the proper term.

The creation of new dwellings have a far more rigorous Planning process than extensions or additions to provide certain uses, especially within the Green Belt. Only in situations where Very Special Circumstances can be provided will help get you there.

Why make the choice between solar thermal OR MVHR. they are both entirely different things for different purposes. Many of us on here are using an ASHP to heat our DHW. The two key things seem to be use an unvented hot water cyilinder, NOT a thermal store, and heat the DHW to about 48 degrees which is plenty hot enough and well within the capabilities of an ASHP. You will probably want a larger HW tank because it is not at "gas boiler" temperature, 300L seems a popular choice. MVHR is worthwhile in a well insulated well sealed house to reduce heating bills by reducing ventilation heat loss. This is quite separate to the heating and HW system. Solar Thermal is effective at heating your DHW in the summer but no so in the winter. Many of us preferred instead solar PV which can be used for DHW heating as well as a whole host of other things. Is budget limitation forcing you down the one or the other route?

That's what I am doing upstairs. Up through floor and into built-in w/r and then out through a top panel of the w/r. You could also just encase it in an exposed false beam (glulam-look rather than mock tudor!) or box the pipe in a corner of the room (if you have any). You could also just not hide it and have it exposed in some steel/aluminium pipe if the look is okay for you.

Agree with Russell, counter battening gets rid of the requirement to leave a gap within the insulation layer, you can full fill.

Oh god, made a cock up read your post to quickly, i had assumed your insulation was a rockwool type fluffy bat when it is actually pir board. In that case I would change that duct to the oval stuff and chop it into the second layer of pir under the plasterboard. Having removed 50mm of insulation in a small strip will not make any difference to heat loss. Its the lack of vapour control that is the issue.

Where is the airtightness layer in that roof build up? The MVHR room ducting is best kept entirely within that

Having thought a bit more, you wouldn’t need to cut out the pir to fit the duct, just push the duct into the other insulation. I would still up the other insulation to 200mm and check what you are doing for a vapour control layer.

I’m not 100% sold on your roof build up. 1.. I don’t believe you need to leave the 50mm void between insulation and your sarking board. As you have a ventilation gap above the boards. I’m happy to be told I’m wrong. 2. What is providing your vapour control layer ? so why not use standard pir under the rafters instead of insulated plaster in the area of the duct and bring the duct closer to the surface so it has full insulation behind it and only a strip of pir missing where the duct is.

I'd keep it out of the insulation if it was me. Will there be any built in wardrobes or such like that it can be hiden behind?

Could you not look to use the rectangular style ducting which is flatter and wider? Failing that, you have a 50mm cavity, then 150mm of insulation, so you would in theory only need to reduce insulation by 25mm to allow for ducting

Agree - accept that things will go wrong and focus on prevention and solution but not blame. Many trades have their 'way' of doing things and unless explicitly instructed to do otherwise, will default to the usual. If you expect different then make sure they are aware of this and that it's detailed and costed. I remember finding half of the Velux insulation kit in the skip as the roofer 'didn't bother with it' but then again I assumed that what was in the box would be installed and we never explicitly discussed it. You learn as you go.

Hi Oldkettle. It's a matter of preferance really as to whether an SE is local or not and at what stage you get one on board. For work that is below ground.. basements, retaining walls etc then a local SE will have a reasonable idea of what may work vs the risk the Client wants to take. At one end some don't want to spend any money on say site investigations or exploring the options of cut and fill, drainage etc. This increase the risk that you will encounter the unforseen. At the other you can spend more, too much, well not often, on investigation and this provides greater certainty. They (local SE) will probably be familiar with the area. Also, they may well have a good rapport with local BC and be sharing knowledge about what is encountered under the ground locally and so on. One thing that can be really useful though is just being able to have a chat with an SE, call it a brain picking excercise. There are some SE's who will come out to site in an informal manner with a pad of paper and pencil, walk you through the various principles of design, do the odd sketch to demonstrate the principles and "chew the fat" with you. At the same time they will give you pointers as to what you need to investigate and how you go about it, who to approach and how you ask (technical jargon) for your particular site. This can pay dividends later on. You can find SE's who take this approach. It can work well as you start to build a relationship, which you can if you wish formalise later on. Try asking some SE's if they will come out on this basis to give some informal advice. Some will be delighted to do so as for an SE it is often much more interesting to be involved all through a project, offer to pay for their time, say by the hour and you may well be pleasantly surprised at the outcome. All the best with the project.

KISS I wouldn't bother.

50 sounds achievable (provided scaffolding is up). We came in below £50 m2 using JUB rendering system last June. The materials/labour cost were 40/60. The rendering company we used were recommended by JUB and did a first rate job (ejl.plastering@gmail.com). They were not fans of pump systems, preferring to mix and trowel. It's very weather dependant work and our job took three weeks elapse to complete. There was no "roughing up" of the ICF it's not required, well at least not using the products we used. It was also good to use materials from a single manufacturer.

As promised I’m back to stop you all getting bored one of the main high usage taps will be a distance of 20m from the cylinder is this getting crazy , am I looking at needing a hot return oh god my heads hurting again, all I need now are some smart Alec comments from @AnonymousBosch and it might push me over the edge.

Ok, quick reply’s you must all be sitting at home bored hang on and I will come back with some measurements. Cheers all.