sgt_woulds

Sorry, I missed your reply... It depends on the specification of the woodfibre sheathing. Some are available with a hydrophobic coating that allows any moisture that gets behind a properly ventilated rainscreen to run off and additional membranes would not be required in most parts of the UK. If you are in an exposed location where rain could force its way into the cavity, or if the rainscreen has less ventilation (due to firestops, or behind a brick or stone skin) then it will require a waterproof breathable membrane fitted, before the battens and rainscreen go on. Ideally, a nail-sealing tape should be used between the battens and the membrane to ensure that no water can run down the wall and find its way into the insulation zone. At least one manufacturer makes a woodfibre board that is pre-bonded with membrane to make this task easier and quicker (although slightly more expensive in material terms, you save on labour costs and install time, and reach a weather-tight stage, sooner) REI60 should be possible with the correct cavity closers and detailing. The aluminium skin would reduce the spread of flame, and woodfibre - although a class E product - smoulders and self-extinguishes (unlike plastic insulations which melt and ignite, spreading fire), so you are unlikely to have a Grenfell situation. The woodfibre manufacturer should be able to advise on this, and it is better to have e-mail evidence from a manufacturer to show building control if needed.

3 to 5mm. Just big enough to allow a dropped credit card to disappear - ask me how I know... 🙂 But thankfully, easy enough to lift and replace without the homeowner noticing any changes!

Papers on legs?

I should add that I only used this construction for my garage. The main house extension used SIPs (Never, ever, again!), again with direct rendered woodfibre externally to prove a fire-rated finish.

I'd ask the Architect on what basis they specified that build-up? Did they consider moisture at any stage? WUFI assessment? With a non-permeable sheathing board, your internal VCL and sealing would have to be immaculate to prevent damp issues with the frame - that is practically impossible to achieve on site with your average Great British Builder. For my own timber walls, I used a system that allows fully open moisture transport and easy sealing. Uses fewer components, zero membranes, and is less critical on detailing if Bob the Builder is having a bad day or there is a football match they need to watch... 😉 Inside to out: Plasterboard 25mm battens (with woodfibre or hemp flex between to help moderate internal moisture levels) 15mm OSB3 such as Smartply or equivalent with air and moisture tightness. Taped and sealed, this forms both the racking and airtightness in. Easy sealing and hard to damage. TF (I-joist studs for better u-value) with Woodfibre or hemp flexible insulation - mineral wools work, but I like to maximise the decrement delay for future heatwaves T&G Woodfibre sheathing - provides additional airtightness and reduces cold bridging. Breathable render Wood fibre used in a certified system behind a render or plaster system achieves a B-s1,d0 classification for both internal and external use. This is a classification of the render system; depending on which system is used, the manufacturer can provide the relevant data. Approved document B asks for external cladding within 1m of the boundary to be Euroclass B, so rendered woodfibre is fine as long as the height of the building does not exceed 11m. If the aluminium cladding is a must, this could be used over the woodfibre (without render, but with additional breathable membrane), but you'll need to speak to the woodfibre manufacturers to confirm the build-up for ventilation and fire rating.

I'll bow to your knowledge with suitable evidence. PU resins (at least those I've had experience with in industrial cement repairs) generally contain solvents to liquify them to allow pouring and shaping. The solvents off-gas as it hardens. Adding warmth generally speeds up this process. Do the resins used in modern flooring use a different process?

I agree, using SIPs was the worst decision I ever made! If I could do it again, I would use Kithurst NIPPS or Ecocon panels or other similar products, that not have nasty PIR and have better structural flexibility than PU SIPs. Also better for the environment and internal healthy air. Also, consider accoustics - SIPs are awful for noises resonating through the drum-like skins. If you live under a flight path you'll regret SIPs. Also consider decrement delay - SIPs are good at keeping internal heat in, but are rubbish at keeping external heat out. I used woodfibre externally to counter this to some extent, but a build-up with decrement delay is probably going to be more important than ultimate u-values for the short winter months in the coming decades. MVHR - great, but expensive for what it is. Best with passiv house levels of airtightness. If you are self-building, you should always aim for Passivhouse, even if you don't plan to have it certified. Pick your builders and specifiers well to achieve this. UFH - wet underfloor any day. But if my house was passivhouse, it probably wouldn't need it except in bathrooms where it works a treat I wouldn't have PU resin in any house that I intended to breath in. Too many VoCs - especially when heated by UFH.

No, just stating a known fact 🙂 I may have been getting the wrong end of the stick, but I felt the inference from Andehh's comment was that TF and rubble trenches were inferior. I not stating that such a building would definitely last for thousands of years, merely that it could, based on extant evidence. As could any structure built with care, and with proper design and maintenance. Not something we can apply to most mass housebuilder efforts, nor the ego-boosting glass and concrete towers littering most major cities. I suspect most of these will be torn down or require a substantial rebuild in the next 50 years.

True, and the oldest man-made structures on earth are made of mud bricks or cob on rubble trench foundations 🙂 There are also plenty of timber frame buildings in this country dating back more than 800 years. Combining the best features of all of these structures that will last the test of time is the ideal, as long-term savings in running costs and maintenance can then ameliorate any initial up-front carbon costs. So-called 'energy-efficient' monstrosities built using tonnes of concrete and bricks, but with a practical life measured in decades, is where we are at today, unfortunately. At least as a self-builder, you have the chance to build something better. Put your name on a little commemorative brick like the Victorians did, and someone can praise your efforts in 100 years...

If you really want to save upfront carbon, then changing to natural stone will save much more than the mortar alone - and it will look lovely as shown above. Changing to engineered timber rather than sawn will save more - (less timber section required for the same strength, and more of the tree can be used for structural components versus traditional sawn timber). The smaller cross-section allows more insulation and reduces cold bridging as a useful side effect. This works well with a woodfibre external sheathing board and flexible insulation between the studs - hemp flex for preference to reduce upfront carbon even more. TF can work well with a brick skin as long as you allow adequate ventilation and effective protection for the insulation. Probably the best area to save UFC is in the foundations. These don't need to be concrete - a rubble trench foundation is as green as it gets and is perfectly acceptable to building control with a structural engineer's sign-off. As a plus, it is the quickest foundation type to make, and also act like a French drain to keep your walls bone dry.

Not necessarily large sections! Some, like 'We Build Eco' provide pre-cut and numbered timbers to allow swift build on sites with limited access for lorries/cranes. Essentially a rapid and accurate stick build with very tight tolerances. With or without all insulation and finishing boards included. House 'kit' content will vary according to manufacturer - most end with the basic shell ready for fitting out, but some include all items required for finish (e.g. Huf Haus) Essentially one step down from pre-fab

I briefly worked in a car insurance call centre. The line managers' commissions were based on the value of our sales so were always pushing us to upsell unnecessary extras. In most cases that involved screaming and spitting at those members of the team they could get away with, and generally being as objectionable as they could be to the rest of us without actually expecting a knuckle sandwich. The entire call staff quit on the same day, just after we got our payslips. Would have been one of my best days ever - a real 'self-respect' moment - but one of the scumbags sexually assaulted one of the girls after she went to collect something from the toilets. I was in the pub with the team when she came in crying. I never met any of them again, but I heard later week that some of the guys had tracked the scumbag down and 'sorted him out'. They all got done for GBH but he was never convicted as the poor lass was too scared of him.

But back to the OP's question: Alongside the alarm you should really consider a smokescreen system. If they can't see it they cant steal it

Personally, I think introducing a little public shame back into society might work wonders - bring back the stocks and televise the rotten tomato throwing. There is so much open lawlessness on the streets we could never throw enough people in prison to curb it. There are gangs marauding pavements on stolen mopeds and people openly shooting up on the bench outside our local police training station. As the police pull out in their vehicles they deliberately look the other way. The decline in morals and public order is shocking. The increasing apathy in policing is even more so.

Isn't it strange how the bad bosses seem to have all the luck? I had one, who used to call us all 'see you next tuesday' every other word. Vile man, but he could turn on the charm when he wanted to and most people who didn't work with him thought he was just a 'rough diamond'. He always got away with things that would see the rest of us in hospital or prison. Typical example: Overloaded van Torrential rain No seat belt Holding phone to ear with a shoulder Because he was rolling a fag with his hands and steering with his knees Over 90 mph (Me with my head in a book trying not to see what the idiot was doing and silently praying as he swerved in and out of lanes...) We get pulled over by a jam sandwich and he comes on with the cheeky-chappie cockney sparrow routine. Much laughter all around. Then they ask his date of birth and realise it's his birthday. 'So which one of these offences would you like us to charge you for then...?' The fact that it was hissing down with pets and they wanted to go off shift probably helped. Only got done for using a phone.

Yes, when I first got on roofs this was how my then boss expected us to work. 'That's just how everyone does it...' He also liked to make 'ladders' out of any bits of timber that were lying about. I politely told him to do it himself and I would watch from the van and take photos for the H&S investigation. Pretty cocky for a 20 year old rookie I know, but we were both in the TA and he knew that one day I might be standing next to him with a rifle and I'm sure he'd like to know which way I'd point it when it counted. Even back then a roof ladder cost peanuts; he bought a Youngmans ladder the same day for less than £200 and it saved his life a couple of days later when he was overreaching and the slate he was standing on slipped. He only just managed to grab the ladder, but it held, and so did he.

You should never rely solely on what you read on the interwebs... 🙂 Plus my knowledge doesn't extend to WUFI software, unfortunately. I have fitted solar panels to an externally insulated roof in the past. From memory, the screws were 280mm long and even though the timbers were over 100mm wide we were extremely nervous about hitting centres. We had a jig made that would hold the screws vertical to the face of the roof as they went in, and hired a pull-out rig, (used for testing 'man safe' systems) to ensure that each screw had hit its mark. We also used extra fixings on the frames' outer edges for additional insurance. It worked, but it was a total PITA and took an age to complete. Nothing is impossible, but all options should be weighed up and thought through. I'd be interested to know how you resolve this.

Too true, but you get where I'm coming from - to the layman, (our Landlord could not be more 'Lay') BS stands for something else! They only care about what the government has 'suggested' and that BC are familiar with. @Benpointer always good to get an expert viewpoint. I look at the fold-down rail to the right-hand side of the toilet and think, 'If a wheelchair user is expected to use that on their own without sustaining a concussion, then a toilet seat lid will be child's play!' Personally, I think the lack of lid is more to do with its use in public facilities - cheaper to buy, easier for cleaners to see if the last dirty scrote has left them a message, quicker to clean, and less likely to be damaged or ripped off by the animals that use these spaces.

Thanks, but BS 8300 is not mandatory. We only need to comply with building control Part M, (or possibly Part T if the building use changes). Really, I just need to know if there is some section or amendment to Part M that I haven't seen that precludes the lid. Otherwise, it appears to me, that manufacturers who sell Part M 'approved' toilet seats are talking out of their derrière 🙂

The only time we ever had PV panels come off was with a zinc standing seam roof. To be fair, the panels didn't come off the roof, the whole roof detached from the building and landed in a field about a quarter of a mile away. [Wish I'd seen it happen - the roof was about 4 football fields in size and it landed in one, (rather twisted) piece]. It seems that the roofers hadn't used the correct number of fixings per metre specified by the structural engineer to counter the PV uplift. In any contract, always ask for photos of the completion of any key stage to prove that instructions have been followed. And ensure that a structural engineer confirms the roof design. Don't rely on an architect for this aspect - they know next to nothing about how a building is put together.

Can anyone point out to me where it states in either approved documents T or M that the toilet seats can't have a lid? The only specific mention regarding the seat I can see is height from the floor, (between 480-500mm). However, the only available part M-approved seats I can find come without lids, and our landlord refuses to fit anything else. As this is a commercial - rather than a publicly accessible building - I think we should decide based on a risk assessment that includes a balance of risks. We have a one ambulatory-access female toilet and one wheelchair accessible universal toilet, (the de facto Male toilet). We do not have any employees in a wheelchair, (or with any mobility issue) and only see visitors in a blue moon. The likelihood of any accident caused by having a lid is extremely low - especially regarding the number of times this facility will be used for disabled access purposes, (in our case next to never). The risk to health from the spread of bacteria and disease is much higher without the toilet bowl being enclosed during a flush. (There is publicly available evidence to show that flushing with no lid or with the lid up creates an aerosol of water and ‘other things’ which coats every surface in the room – flushing with the lid down reduces the toilet plume by between 30% and 60% ) Balance of risk therefore confirms that the health risk from flushing outweighs any difficulty caused by lifting a lid. I have suggested fitting a toilet seat with a handle as a compromise. If in the future, we employ somebody with additional needs, we can create an employee-specific risk assessment. Is there anything in either document or some other standard that I am unaware of to dispute this argument?

It may be possible to use all insulation above the rafters - with a WUFI assessment to confirm that it works. I cannot stress that enough. Also, using woodfibre above the rafters would require a significant depth of insulation to achieve similar U-values to the example shown above - you would be using dense insulation boards throughout and these do not provide as good a U-value as the flexible woodfibre used between the rafters. Shown below is a build-up with U-value of 0.248 W/m2K: Here, the 18mm OSB3 is used without a VCL membrane and a UDB breathable membrane is used above the insulation. Ubakus doesn't have the TLX Batsafe listed, but this should provide a similar performance. Two layers of woodfibre are shown, 100mm of better U-value, and a layer of 40mm which has a hydrophobic coating to provide additional weatherproofing. In this case, the breather membrane is used as protection from the bats, otherwise it would not be required. If you can find the correct quality of OSB3, (unfortunately, not easy in the UK) it can be taped and sealed to provide both airtightness and vapour control. You could also use a VCL over the ply if required. Points to consider: Fixing Length – with this thickness of build-up the fixings would be a minimum of 220mm long. The fixing process needs to be exact to make sure that the fixing penetrates the centre of the supporting rafters. This can be difficult to achieve consistently with such long lengths. If a lower U-value is required then the overall build-up increases as does the screw length. Counter batten size – the counter batten and screw hold all the insulation in place and need to be designed to withstand any wind & snow loads and carry the weight of the external finishes. The counter batten width needs to be sufficient so that when the fixings pull into the structural frame, the batten doesn’t pull into the insulation layer; the woodfibre is relatively dense but this needs to be accounted for. Hence the fixing manufacturer, (e.g. HECO Topix Screws) must design a fixing methodology to consider all the following factors – wind load, snow load, exposure, insulation type, batten size etc. The same build-up using F1 felt and a V-VCL membrane will show moisture issues in Ubakus, but again, if you have it assessed by a WUFI expert you may find this is within acceptable levels. I suggest speaking to 'Mike Wye' or 'Back to Earth' as they have more real-world experience in their technical teams and will be able to advise accordingly.

TLX has been on the market for decades now - I'd be very surprised if it was not up to the job. When I spoke to the bat expert on our roof replacement job, TLX was still fairly new and the manufacturer had only just come up with an approved testing method to confirm performance. Her objection was that it hadn't been proven safe in the real world; obviously, they couldn't test it on real bats and used a spinning apparatus with lots of little hooks (like a wool carding board) to simulate bat claws scrabbling against the fibres. I'm not quite sure what she actually expected them to do to prove it! I'm sure TLX must have that real-world evidence by now, but if it is still killing bats I'm sure there would be more horror stories on the interwebs. As to your other questions: Yes, 35mm woodfibre sarking - labels removed as this is not the place for company adverts and I'm not answering 'officially'... 'Simple' U-value calculators such as UBAKUS will always show a moisture risk as they can't accurately model the sorbative properties of natural insulation. The fact is, there will be some moisture forming on the very outside layer of the insulation, and it is imperative when you design for a moisture-restricted system, that you allow for a path. to transport it back inside the building when conditions allow. To be effective, this drying path, (driven by sorption and breathability) must remove more moisture long-term than it accumulates over short periods. The only way to confirm if this will work in each situation is to have a WUFI assessment interpreted by an experienced assessor. We don't generally advise vapour-restricted constructions with natural materials and It won't work in all situations - but we should never let perfect get in the way of good enough! If WUFI confirms that the moisture load is not excessive long-term, then it is a solution that can be weighed up in this particularly tricky circumstance. I'm not against combining natural and unnatural materials, but again this should be modelled carefully; I'd be driven by the WUFI expert's advice on this. Moisture will get past gaps in the PIR and condense into water between the PIR and felt. As PIR is not sorbative, this moisture will not easily transport back inside and will build up. Freeze/thaw at this junction could cause damage to the felt and PIR. Another thing is that PIR insulation shrinks - especially when subjected to a high-heat location under tiles - and this would increase moisture issues and reduce thermal performance. Open rafters are not a solution, you need a moisture vapour-variable membrane, that will restrict moisture entering the insulation but still allow it to return inside when conditions allow. Most moisture issues are caused by poor airtightness rather than the type of insulation material. It is, (theoretically) possible to create a fully airtight roof insulated with unnatural materials but it is not likely in reality. This is where the vapour open and sorbative, (active moisture movement) of natural materials wins out - but it still requires very careful taping and sealing of the V-VCL to make it work. This will also make your building more airtight which is just as important as increasing the U-value. I'd fit this membrane myself - I'd never trust the average builder to take the time to do it properly.

I work for one of the woodfibre insulation manufacturers we’ve had a couple of similar questions regarding bats in the last few months – hopefully, this means there is an uptick in bat population, but it is awkward to specify a suitable breathable build-up. Below I have copied the relevant parts of some previous conversations FYI: Firstly, unlike spun fibre insulation, such as fibreglass or Rockwool, woodfibre insulation does not pose a direct threat to bats due to entanglement. However, speaking as an ex-roofer - and having seen what guano can do to structural elements, membranes, insulation and electrical cables - I’d recommend keeping them separate wherever practicable. There is a fundamental contradiction when considering the building fabric's breathability and ensuring a safe environment for bats. Breathability is critical for the building fabric, and the only way to achieve this in a risk-free scenario is to use an external layer that ensures water vapour can escape. So a breather membrane or vapour open board. However, the risks associated with long-term exposure to guano should not be underestimated. In volume, it can also pose a significant risk to the wood fibre and the structural timber. The use of a bituminous felt is therefore the recommended approach when roofing to ensure no potential trapping of the bats and to protect the structure. Of course, bituminous felt is non-breathable and hence not ideal for the building fabric. Creating a fully vented cavity below the felt can solve the breathability issues but you also need to vent this at the eaves, and ridge which is not straightforward when trying to ensure that bats can’t access this ventilation space. You could use TLX ‘Bat Safe’ breathable membrane as an alternative to Bitumen F1, but I’d be guided by the bat experts on this. I remember speaking to an ecologist on a job 15-20 years ago and they were critical of the testing procedures used to validate the membranes. This is not a fault of TLX, more that it is hard to test without using real bats! Hopefully, they’ve resolved any issues by now and I'd hope that they have some long-term monitoring data to confirm it's real world performance. You certainly shouldn’t use a standard breather membrane -I’ve stripped it off a roof where it was killing bats that got tangled in the threads and it was a sad sight. I’d still rather use the felt though. My gut feeling is it will stand up to the acid in the droppings better, but I only have personal experience to go on. I have, (unfortunately) dealt with many pigeon infestations where good old F1 felt stood up well to the muck, but on the job I had with bats and the breather membrane you could poke your finger through the membrane where the guano was removed. Going down the ventilated void route would sort breathability, but reduce available insulation depth. In addition, we always recommend a secondary water removal layer below felt as it can degrade over time, which makes the build-up more complicated. A more holistic approach may be to consider a non-vented build-up which allows breathability back to the inside. In this scenario, external ventilation is not critical, but overall performance should always be justified by a long-term hygrothermal analysis of the fabric, (via software such as WUFI which also considers external exposure, rain, shading, occupation and use, etc on a project-specific basis). As an example of a vapour closed approach, please see the build-up below, which may be an option with suitable analysis. This uses a woodfibre sarking board externally and woodfibre flex insulation between the rafters: In this simplified example, the U-value, based on an existing 120mm rafter, is 0.26W/m2K. You will see that there is condensation shown by the software, (U-bakus) - but, with full WUFI analysis, this may well be at a level that is not critical. SIGA, (and other manufacturers who produce moisture vapour-variable control membranes) will undertake a WUFI assessment if their membrane is used, so we have shown their Majrex 200 and would recommend this as an alternative approach which addresses some of the factors discussed above. [not shown in the diagram is the lime or clay plaster on the woodwool panels] Felt does degrade over time, (so do breather membranes) but in my experience, this is exacerbated by their own weight stretching the reinforcing fibres over time and under summer heat. Fully supported over a sarking board this should be less of an issue. Even if the felt does fail in 50-odd years time, then, (if you choose the right product) the woodfibre sarking can act as an additional weatherproofing layer with its hydrophobic surface coating. Using an external sarking board and counter battens as in this example will only raise the overall roof by 60mm which really only shows at the gable ends, and can again be ameliorated with architectural detailing. A conservation officer probably wouldn't even notice it on the finished roof from the ground unless you pointed it out to them. A practicable modification to the existing roof profile that allows for lowering CO2 emissions, protects the building structure, and allows a safe habitat for wildlife it is a compelling argument to use with planning and conservation officers, and ensures the building will be fit for use for many more years with minimal visual difference. Surely this is all they can ask for. In terms of ultimate U-values, this isn't the be-all and end-all in terms of thermal comfort, and building regs with older properties. For existing elements in existing buildings, Part L of the Building regs defines a threshold value of 0.35W/m2K for Roofs in certain conditions where it's not practical to achieve the modern requirements. Worth discussing with your BCO; for an older building, most BCOs are now sympathetic to the argument that breathability is more important than the insulation value. Woodfibre will also provide more decrement delay than unnatural insulations; summer heat protection is probably just as important these days as keeping warm in the short winter months. I suggest speaking to advisors at: Home | spab.org.uk and Historic England - Championing England's heritage | Historic England as they have experience with upgrading the thermal performance of old buildings whilst maintaining their architectural features and may have some case studies you can use. Can you provide links to the information about Batsafe membrane being unsafe for bats? I can only find historic 'concerns'.

Have you measured the local grid voltage? In parts of the UK, (Cambridge, Norfolk, Suffolk) grid voltage can be quite high. Back in 1999/2000 before feed-in-tariff and DNO limits came in we had to manually program the SMA inverters to allow them to work outside of normal grid voltage ranges (at the time, a very narrow range which did not reflect reality). There were also a lot of arguments with DNO at the time as they were essentially caught out for having defective regulation of the grid. We found that voltages in Cambridge normally 'floated' at about 250 volts, but in some areas (end of transmission lines) grid voltage could be well over 260volts/ Highest variance I ever recorded was in a cottage in the middle of a field in Devon. Having done 3 return visits from London I eventually persuaded my company to allow me to sit there for two entire days monitoring the grid voltages. At various times of the day, voltage spiked to a constant 278 - 280 volts then dropped down to 230-238 volts the rest of the time. There were specific times of the day that these occurred. TCALST: The cottage was at the end of a very long transmission line, immediately after a clay works. Every time they stopped for a planned break, machines and furnaces turned off and voltages spiked. The homeowner told me she was always having to replace electrical appliances - she thought it was just due to poor build quality and bad luck! Perhaps you have a similar situation in France that is being exaggerated by daisy-chained inverters?