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  1. Hello, Does anybody know the U-Value required when retrofitting / renovating underfloor heating? There seems to be plenty of resources talking about new builds but finding it hard to find any definitive information for retrofit. For my specific property, I have a ground and first floor. Both having a concrete slab floor with screed over it. I will remove the screed, then add insulation, then UFH pipes, then concrete poured over. Trying to work out how much insulation I need. I'm assuming less required for the first floor. Once I determine the maximum U-value permissible for building regulations, I can use various services such as this U-Value calculator to work out how much of what insulation I need. Any help appreciated!
  2. Hi, I'm currently renovating a house on Skye, typically in Scotland, the window recesses have check reveals. I'm looking at getting Nordan Alu-Clad Windows. Problem - there are check reveals. I want to get rid of the old timber in the recesses, the house built mid 70's I think the original Windows (long gone) attempted (badly) to close the cavities. I want to install the new windows the way the house was originally built - front face of window frame tight up to inner face of external block leaf. Problem would arise where window fixing straps/brackets are used. They'd either have to be bent a lot to reach the checked reveal thereby making it difficult to install Insulation on the reveal, or could I pack out the inner reveal with something like compacfoam and fix the brackets/straps through that and into the edge of the inner block leaf. We get some wild weather now an then so like the Windows to be recessed nicely. If I can use something like compacfoam, could I continue it into the Cavity to the inner face of the outer block leaf in order to close the cavity? Or do I make a timber frame to fit the inner block leaf window recess, fix that into the reveal then fix Windows to that? So many different ways of doing this, I'd really appreciate input as to what's the best course of action. TIA
  3. Hi, I'm currently renovating a house on Skye, typically in Scotland, the window recesses have check reveals. I'm looking at getting Nordan Alu-Clad Windows. Problem - there are check reveals. I want to get rid of the old timber in the recesses, the house built mid 70's I think the original Windows (long gone) attempted (badly) to close the cavities. I want to install the new windows the way the house was originally built - front face of window frame tight up to inner face of external block leaf. Problem would arise where window fixing straps/brackets are used. They'd either have to be bent a lot to reach the checked reveal thereby making it difficult to install Insulation on the reveal, or could I pack out the inner reveal with something like compacfoam and fix the brackets/straps through that and into the edge of the inner block leaf. We get some wild weather now an then so like the Windows to be recessed nicely. If I can use something like compacfoam, could I continue it into the Cavity to the inner face of the outer block leaf in order to close the cavity? Or do I make a timber frame to fit the inner block leaf window recess, fix that into the reveal then fix Windows to that? So many different ways of doing this, I'd really appreciate input as to what's the best course of action. TIA
  4. Hi all!, I'm new to buildhub and hoping someone can help or point me in the right direction! I'm in the process of installing a floor. It's a block and beam floor. I'm now at the point of installing the xps insulation over the top before ufh (water) and a screed. The insulation I have received is danosa danopren xps pr-p. Their website states this is for the wall with a compressive strength of ≥ 200 kPa . They make a floor insulation with a compressive strength of ≥ 300 kPa. I have looked at Celotex insulation as a reference who state their insulation is 140-150 kPa. I will be installing rebar mesh on top of the insulation to hold the ufh pipes down. Does anyone know if this will be ok? I have already done this to another floor before I realised! I'm not going to dig it up unless something happens but would like to know for sure with this next floor. Many thanks in advance. Jason
  5. Hi all, we are nearing completion and have about 8 rolls of Pavatape left over. Brand new, unopened. This is aluminium laminated butyl rubber tape in 15m lengths at 150mm wide. £29.40 + VAT per roll each when bought new. We are open to offers! Please share. Thanks. Joanna
  6. Anybody come across this before? It claims to be equal to 25mm polystyrene , and at £4/m2 could be a contender when looking for just a bit more. It is just bubblewrap with foil.
  7. Would anyone care to crit this preliminary design please? 2 drawings below. Of course these will be submitted in cad form. The building is a Scottish farm steading. The walls and roof are substantially intact, and there is a concrete floor. The building regulations requirement is for 'reasonable effort' to be made re insulation, and that includes cost. As there is only 4.5m wall to wall, the wall lining has to be kept skinny. There is also a headroom issue in some locations, but I may increase the floor insulation where feasible, if steps can be avoided. Of course we want good insulation too, and I have come up with this compromise. The 1m of bitumen sheet lining shown at the bottom of the wall is cribbed from another steading's blog, and seems clever, but I don't know if it is expected or standard. The dpm may have to be radon spec. It is marginal and I will check. All existing timber will be sprayed. I am quite pleased with my idea of having a 25mm cavity batt between stone and stud, as it will provide a thermal break and also allow tolerance in verticality. As it is waterproof, I don't think we need vapour barrier. Which then makes me think, do we need that bitumen tanking barrier: it is there to keep the wettest part of the wall away from the inner materials, but the insulation can do that, as in any cavity wall. At £15/m this comes to a lot of money but may be worth it for peace of mind. I have shown a 25mm air gap between sarking and insulation, because it is required with PIR. Not quite sure why PIR needs it but Batts don't. Actually more is stated but it is guidance only, and we have sarking boards with gaps, which is much better for ventilation than whole OSB sheets would be. However, I think there will be much less waste in cutting PIR between the rafters, than batts. Adding a 4mm insulating strip to timbers before boarding is just a thought. I will calculate the effect on the U value and suspect it is trivial. theoretically it also provides a gap between insulation and board, and hence a surface, but i think that would be nonsense to allow unless cynically chasing a specific U value target. Cost-wise, I have to assume that availability and prices will settle down by the time of doing the work. What else might you want to know? Underfloor wet heating, air source. Mostly single storey with highish ceilings. Some existing upper floor, with very tight headroom below ties. Most of the roof soffit will be boarded over, perhaps exposing some ties. It is mostly in good condition but not pretty. Obviously we don't want to take off the roof and rebuild, so working underneath is the only option. All comments are welcome as are ideas, especially proven, but also wild, and do ask if anything is unclear.
  8. I want to improve the insulation of my old barn. I have underfloor heating but the external walls let out all the heat. It has featherboard cladding on the outside which has shrunk so there are gaps on the sides in lots of places. Behind the featherboard is about 50cm of celotex and some black membrane in places then plasterboard. From the inside, you can also feel the cold air in the holes in the wooden beams. What is the best way to improve it? My builders says I should remove the existing featherboard, batten and then put some sort of insulation material and then put new featherboard back on. The council will only let me use wood as I am in a conservation area. Any suggestions for the best type of insulation? I would prefer not to do any work on the inside if possible but that may be the best way to do it.
  9. I have a couple of box gutters that are draining internally through a cavity wall space. I know that isn’t ideal but had to be done because of various party wall conditions with the neighbour. I want to insulate this pipework to protect against acoustic potential and also to stop any potential condensation that maybe produced because of it being located in a cavity space. Has anyone used Rocklap before or an alternative product or maybe a different idea to insulate it quickly and easily? It’s soil pipe size. I attach some details on the Rocklap.
  10. Any recommendations for decent sound insulation between stud wall partitions? Or are they all about the same? Any tips most gratefully appreciated. Already planning to use soundbloc 15mm plasterboard everywhere. Would anyone recommend sticking 20mm PIR on one side of the stud walls as well or is that overkill?
  11. Hi all. Am finally underway on a renovation I've been planning and overthinking for a couple years now! We've just finished demolition on the bathroom, which is now this: The room is located on the first (top floor), with lath and plaster walls and ground floor ceilings (under the now removed floorboards), solid brick external walls and timber sash windows. I'm having the window rebuilt and reglazed with double-glazing. We need to re-frame and build the ceiling in this bathroom as the original was about 1" taller than I am with some nasty styrofoam tiles (now gone). I'm wavering on what to put on the external wall and non-wet wall to the right where sink and toilet will be located. The house is 1880-1910 era (with extensions added on variously), with solid brick external walls, 40mm lime plaster on internal walls, and lath+plaster for ceilings and newer walls (like here in the bathroom). There are some damp issues with the house (of course) but wherever I find a problem with dampness or water damage, but I'm growing increasingly skeptical about whether this is actually due to any fundamental issues with the house build - it seems that as soon as I remove wall covering to sort out damp, I find evidence of someone bodging on some anachronistic tech to quickly fix a problem (e.g. a patio outside with bricks blocking the air bricks for the cellar, cheap MDF cabinets in front of brick walls in kitchen, etc.). So, I'm thinking I prioritise draughtproofing and insulation, with good heat-recovery where possible, but also make sure that the building envelope is breatheable as much as possible. Obviously this is a bit tricky in a bathroom. The bathroom is inbetween guest room and MBR, so I'm planning to prioritise sound insulation for internal walls: rockwool sound insulation slabs in the floor and internal walls, and foam tape on the floor joists. Once I have insulation in, I'll put down 18mm plywood, install toilet/sink/bathtub/shower, with a beadboard/tile box around the bathtub and then tile on the floors. The bathtub will be installed on the left side of the room (shown in the photo) against the wall, with shower up overhead. Given the way that my children take baths (e.g. water thrown exuberantly all over the place), I need to put up some seriously hardy boarding on the walls adjacent to the bath. I'm thinking something like schluter kerdiboard (or an equivalent) as I'm hoping for a simple install I can do myself. But what should I put on the back wall? I considered PIR board for a bit of insulation with an air gap and moisture-resistant plasterboard in front, but I'm not sure this will be effective with the space I've got in the joists on that wall (70-90mm) and I'm worried about breathability of that system. So now I'm leaning towards 80mm or so of sheepwool batting, perhaps with woodwool boarding on it, then lime plastered and painted. Has anyone done something like this on a bathroom? Right side walls could just be rockwool acoustic insulation slabs (I gather that sound dampening is much strong than sheepwool with these) and plasterboard in front, but am now wondering if I should just do woodwool board there too? Happy to hear any/all suggestions! Especially if you've tried to do something similar. Floors:
  12. Good morning All! We bought an1960's semi detached house in Stockport a year ago now. I am already insulated the loft area with 200mm rockwool, added OSB boards, make a new cutout and installed a loft ladder. Now we need to upgrade and insulate the ground floor. Ground floor is a suspended timber floor with no insulation at all. Currently there is carpet, 22mm T&G floorboards (most of them have no T&G due it was lifted up by previous owner/builder) on 2x4 joists. Under the joists there is a 300-320mm air gap for ventillation. Roughly 400mm distance between centre of joist. The whole floor area (including kitchen, chimney in the middle and understairs area) is 35m² (7m deep 5m wide) The joists running along 7m front to back. I do not see any wet/dry rot when inspected in a few paces when lifted floorboards and the area under it is fully dry. No sign of wet areas or mould. Since we moved in the floor is a bit springy, and most of thr floorboards are creaking. When we moved in, i was lifted the carpet and removed the nails from few of the 22mmx140mm floorboards and add some screws to stop creaking. What we planning/have in mind: -We want to insulate it. And make additional slepper walls. This is 100% and here comes the things that would be good to do: -Change the 2x4 joists to 2x6 -Add new floorboards to subfloor -Upgrade the groun floo to UFH And now here comes a all my questions: Sleeper walls: I made some research and as far ask I know i need to make a honeycomb structure to do not block wentillation (what is quite obvious) How it need to be done? I mean first make a 100-150mm trench perpendicularly to the joists, fill it with concrete, let it harden, add DPM and then brickwork (class 2 engineering bricks)? As there is no guarantee that the height of the brickwork will be exactly at the bottom of the joists, what do I need to use to fill the gap between the bricks and joists? I have another method in mind as well: Same trench and concrete like above, but instead of brickwork use some adjustable metal joist support like in the picture? Joists: I think it would be beneficial to change it, bcs all of them as old as the house (i think) and I am not sure that it can handle the load of the new floor/UFH/ tiles. Plus it will be a peace of mind that all theese joists are new ones, so i do not need to touch it for a long time. I was make a lot of research on the internet in the last past months, and I don't get straight answers to my questions: Is it a good idea to change the existing 2x4 joists to 2x6 and how should it be done? I mean as i know (but maybe I am wrong) where the joists attached to the wall there is a cut-out in the bricks. Should I make a bigger hole to fit the 2x6 or reduce end of the joist with 2 inches in the deph of the hole in the wall and strengthen the joist after the cut? (See pic#1) Or just replace with the original size? Or it is a wasted time and money and just leave it as it is if there is no dry or wet rot on it Insulation: Which insulation is more beneficial? 100mm PIR, earthwool or sheepwool? I am thinking on PIR or Sheepwool. But there is a lot of different application processes on the internet. Everyone say different how it need to be done. Some of them says a windproof breath membrane MUST be added first and then the PIR or sheepwool insulation. (See PIC) The others says that will make the joist rot on the surface it is covered with it. Others sas the membrane should attached straight under the joists. Others say not any type of membrane needed. Just insulation and floor boards. With the PIR should I need to apply expanding foam between the wall and the insulation. Or (as few of them says) MUST leave 10-15mm gap between the insulation and the wall? Which for my opinion makes the insulation as useful as an ashtray on a motorbike... Do i need to cover the ground with any kind of membrane? If yes which is the one that i need to run with? Floorboards: Which boards to choose? PAR 22x140, chipboard, OSB, plywood, NoMorePly? Some of them says 22mm chipboard become like weetabix after a few years. some of them says 18mm ply is the best and few of them say NoMorePly is the best. And what structure is the best prior to UFH? I have one in my mind which is: Floorboard then pre trenched hard board for the UFH pipes, then a thin layer (1-2mm) of membrane, and the tiles/hardwood floor on the top. In this case how thick the different type of floor boards need to be? Or it is much more better and efficient to install the aluminium plate for the pipes onto the insulation and then ue the floor boards and tiles/hardwood floor? A few details to get a bigger picture: I can not stand that the floor is moving under us as we walking on it and all the contents of the cupboards moving like glassware, flowers pictures etc... The other thing is that if we will have UFH, we would like to have tiles on it. And if the floor is moving I think all of you can imagine the comsequence.... The main thing is that when it will be all done, I don't want/ I can't lift tiles, UFH, floorboard to change/repair insulation/joists/floor boards. But I guess you all think the same. currently have a carpet which we would like to change to tiles or hardwood floor. We still not deceided yet. 3 of us (my wife, our 3 yrs old daughter and myself) living in the house and there is no option for us to move out while the work carried out. I know it will be kind of a pain this way, but this is the only option we have. I would like to do DIY because this way I can save £1200-£1500 on labour only to make the sleeper walls, and/or replace bad/all joists... And i really like to DIY as much as I can. I am already made big built in upboards, decking with roof on it, isulate the loft and boarded, insulate and reroof garage, etc... And i am keen for woodwirking/woodturning. Because of that I am feling quite confident to do it I am plannimg to do it in around 2 weeks excluding the heating. Until the UFH i will put the carpet back temporarily. I think this is doable. Any advice, comment or help is greatly appriciated. And please feel free to correct me if you think something above i wrong. And as I am living here only 10 yrs ago also let me to apologise for any grammar mistakes that I made above. Thank You in advance! Joe
  13. I stumbled on this site while researching MVHR and saw some great discussions and expertise. I have a 112 m2 top floor flat part of a mill converted in 1995. I am looking at sensible upgrades for the next 10-15 years. Presently I have Electrical heating (1995 storage heaters) 12000 kWh pa , aluminium double glazing from 2010 (3 x 6 panel windows 2.3mx1.6m), have heard mention that frames are not thermally efficient, thick solid stone walls (580mm window returns) insulation status unknown, 3.5m high ceilings lounge hallway and bedrooms, observed 200mm loft insulation. Lounge and bedrooms are long and narrow and perhaps not well suited to present (lack of ventilation) Perhaps the biggest immediate concern for next winter is high CO2 levels (measured by Awair sensor) in the flat unless windows are opened. It also gets very stuffy in summer and I suffer from hay fever. There is no vent fan (apart from cooker hood with activated carbon filter) in the kitchen. Its been blocked up probably because the flexible trunking collapsed(a neighbour experienced this). The only connections to the outside are two 95mm?(100 nominal?) holes through the stone work which are connected through boxed in trunking along the floor (wouldn't mind moving it up to reclaim floor space) to kitchen (originally) on one, and 2 bathrooms on the other. The bathroom fans suck but no perceptible flow at outside of building. Maybe disconnected by previous owner and routed into loft space (on the other side of a fire division - not good) I am thinking that PIV system might be best rather than MVHR due to forum mentions on air leakage, although a lot of it might be beneficial in terms of heat input... The available 95mm openings are in bedrooms and I need to minimise cold piping, Can I use one opening for fresh air and one to take kitchen and 2 bathrooms out. Or is there a way to alternate (breathe in, breathe out, like ....lungs...) For moisture control, I tend to finish the timed laundry for when I can use the dehumidifier on Economy 7 for a couple of hours in the morning (early riser). I see the dehumidifier as effectively free to run as I have electric heating anyway. Seeking expert commentary, please, especially on whether I can get good ventilation with the two 95mm openings to the outside. Can I anyone recommend an approach and contacts for HVAC design?
  14. Victorian detached house with a footprint of about 11m x 8m. Roof constructed with three king post trusses. Around 125mm rockwool insulation laid maybe 30 years ago? Want to retain as a cold roof, but just lay some boarding to provide storage space. Boards will sit on top of the kink post lower chords, about 200mm higher than the ceiling, so that all works OK. BUT here's the thing: there is a huge quantity of mouse shit on top of the existing insulation and I mean huge. It is everywhere - truly gross. So it just doesn't seem right to ignore this issue, and lock the problem in So am sorely tempted to start again - remove all the shitty (sic) old insulation and relay new. But what would others do?
  15. We should hopefully getting our EWI and render in the next couple of weeks thank the bl00dy heating gods because we are hoping this will improve the bills! You'll know from the original layout of our bungalow that part of the bungalow is stepped inside (to the bedroom/dressing room) as it is higher. This means the DPC is at a different level. This is going to look really odd as we have our DPC at different levels. The builder was speaking to the different reps about the render and if there was any solution because it's going to look a bit messy with the render coming lower on some parts and higher on others. It's days like today when I wish we would have knocked the whole thing down...... Pic below is our bedroom and dressing room and the bungalow is higher here as we step up two steps to access this part of the bungalow. This pic below probably demonstrates it better and you can see how it steps up. The scaffolding is in front of the living room/snug and the wall window is the middle hall. Ignore the garden walls and any paving etc... And then this is close to our front door where we have the existing part on the left which is pretty much where it is stepped inside and then our extension. We had picked Krend pure white but I've just had an email from the builder with the spec for the EWl and render and it's something called Ecorend and Jablite. Is Ecorend similar to Krend? And Jablite - is this a suitable EWI? Feeling slightly overwhelmed again! EcoRend_Spec.pdf Jablite Spec.pdf
  16. Ages ago I wrote a spreadsheet for doing what-if comparisons to see whether it was better to invest in more insulation in the walls, roof, floor, fit better windows and doors, or fit a better MVHR system. Others have found it useful and I've been reminded that I've not re-posted it over here, so here's the latest version. It should be self-explanatory, you fill in the cells with your wall, roof/ceiling and floor areas, add the areas of each door and window, put in the U values for each and, if you can, get hold of the met data from the met office for your area (the data in there is for West Wiltshire, right on the border with Dorset). This isn't a thorough modelling tool, it just looks at heat loss fairly accurately but doesn't take into account heat gains, although there is a crude way of doing that by drawing a line across the seasonal plot at the point where you don't use heating and you can very roughly assume that anything above that line will be heating. Please feel free to ask any questions, but bear in mind I wrote it back when I was designing our house and haven't used it for a couple of years. so I may be a bit rusty. Heat loss calculator - Master.xls [edited to add latest version of the spreadsheet]
  17. Hi, I live in a 1930s top floor apartment with a flat roof above me. I’ve been considering getting new double glazing but I think my main issue is the roof is really poorly insulated which means the apartment gets freezing in winter and boiling in summer(31c at 1am and 26c at 7am). Is there a specific type that works best for residential? My brief searching seems to be that it’s mostly meant for commercial use and would make my apartment look a bit office like. Not sure if battening some type of lightweight insulation board against the roof and plastering over it would be a better solution? thanks
  18. I have my SAP calculation for my forthcoming bungalow and all generally looks good. The roof and floor have U-values of 0.08 W/m².k. However, the walls are a bit low, about 0.18 W/m².k. I did this on-purpose to maximise floor-space but it has turned-out a bit lower than I expected so I am thinking of adding an additional layer of insulation inside the the airtightness layer of say 25mm or 50mm of PIR. I was planning a 25mm service void anyhow. My questions: Could I just fill that service void with sheet PIR everywhere except where services run? That would do the job without stealing more floor area. I am aware that electrical cables may need de-rating if they are insulated. To counter this, could I just leave, say, 50mm air-gap each side of a cable run? Are there any other problems with largely doing-away with a service void by filling it with insulation? (For service runs, as a bungalow with a warm roof I will have 200mm of open space between the metal-web joists in the flat roof). (The external walls will be 240mm I-beams at 600m centres full-filled with blown-cellulose/Warmcel.) (The airtightness layer is Pro-Passiv Smartply.) (I am aware of condensation-risk analysis and I am confident that adding such a small amount of extra insulation won't cause a problem).
  19. I'm trying to find out what insulation options on a solid walls I have and which ill choose so advise or suggestion's insight in any way would be welcome i have been told they are grants for this work this could even be a factor when making my choice
  20. Hello all, I'm after some help understanding if the following drawing is correct for a timber frame building to sit on. The building is a two-story extension and is to be clad with timber feathered edge, not a brick cavity wall. Any help would be greatly appreciated, Cheers.
  21. Evening all, New person here 👋 Myself and my husband have just bought our first ever house and business. Two Scandinavian Style A-Frame Lodges, One to Live in and one as a self catering rental property. Both in need of renovation in all shapes and forms! Look forward to getting stuck in and picking brains on here 👍😁🤯
  22. Hey, would really appreciate your views on this one! Looking for thoughts on structural support for block and beam on a new build with basement and the various preferences from my designers Basement: 300mm concrete walls, internal cavity with insulation, inner leaf block, plasterboard Ground floor upwards: outer leaf brickwork, cavity with insulation, inner leaf blockwork My Architect wants an unbroken insulation zone from the basement to the roof, and to make this happen the block and beam to ground floor will sit on the inner leaf blockwork built up from the basement 300mm slab. We will also have block and beam on the 1st floor, so again the block and beam will sit to the inner leaf blockwork. Architect's request: My SE instead wants to shift over the block and beam so that the inner section of the 300mm basement walls provide structural support for the floors, rather than the blockwork as shown above. This is going to introduce a bridge to the insulation layer. The SE said if we use the above approach he wants to install steel posts and beams to support the floors above. SE Preference: If we didnt have a basement, and still planned to use block and beam, the beams for the floor would sit on the inner leaf of the block wall anyway. Just because we place a basement wall in does not mean it then has to be used to support the beam/hollow core floor? When we get to the 1st floor we have another block and beam, and for this we have no option but to sit the beams on the inner leaf block work. Which option should we go with? Thank you
  23. Just getting my head around wall construction and the balance of vapour, heat and draught resistance and how they work together. I'm planning to renovate my walls (internal, as neighbours in the terrace aren't necessarily enthusiastic) house-wide - the solid double-brick victorian design (basically just bricks with plaster on it) has some significant room for improvement. But there are a dizzying array of options and configurations for internal wall insulation and it seems like information "out there" hasn't quite kept up with our developing understanding of water vapour and airtightness. Here's my current understanding, am hoping folks can correct me where I'm wrong (from outside to inside): 1. The air outside: The weather here in the UK is rarely on average over 21C, so the inside of the house will almost always be warmer. So the design needs to address water vapour that is *leaving* the house, getting cold and turning to condensation at some stage during its exit from the inside rooms. Not much reason to worry about water vapour coming in from outside. 2. The outer structural layer, that is in my case a solid double brick layer has a Vapor Resistivity, N s/(kg m) of 45 - 70 (got that from here: from here: https://www.engineeringtoolbox.com/vapour-resistance-d_1807.html). This means that it is "semi-permeable" 2b. Leaving on plaster (or not): Most of my walls have plaster (in some cases lime plaster, but haven't done an exhaustive survey), which I gather is straight-up "permeable". I can't see a consensus as to whether it's better to remove or not remove plaster, but I gather it may be necessary to remove (a) so that one can assess damp problems in case they aren't fully permeating the plaster to the inside layer of the wall (to show on paint etc.) and (b) so as to install some sort of membrane, or (c) obviously to address where there has been damage, and it seems to make more sense to leave it off if it's already off. But it seems like some folks like to save time and energy by leaving it on if there aren't mitigating situations. I'm about 70/30 leaning towards removing paint and plaster to expose the brick and check things out properly. 3. Air gap (or not): I've noticed some disagreement as to whether an air gap is now necessary. I gather an air gap is needed so that air can circulate vapour so that it can evaporate or vent out through the brick wall rather than condensing as it might in a tighter space without air. For the air gap, I can do battens over walls - and it seems that wood and stainless steel are the likely options here, nailed or screwed. Steel is more expensive, but will avoid rotting better than wooden battens (though damp proofing should ensure this isn't happenning!). Seems like Damp Proof Membranes are also an alternative, but a bit of overkill for my purposes here as it's not a cellar and all walls are above ground. But then the 4. PIR boards. I'll get these with foil backing, as this has an astronomical Vapor Resistivity value (4000), putting it on the very high end of "vapor impermeable". But it seems that some folks prefer the more labour intensive but easier-on-battens-long-term "warm battens" approach, where a insulation is split into two layers (a) a membrane is put down with half or more in layer of foil-backed insulation and then (b) an inner layer of battens with more insulation boards inbetween. This keeps warmth around the battens and ensures that moisture will condense further out in the wall. This seems reasonable to me - and I don't mind the more challenging job if there's an efficiency to be gained. What I'm not sure about is whether to use a membrane or foil-backed insulation boards for the vapour membrane at this stage. And if I use a membrane can I skip the air gap? 5. Plasterboard. "semi-permeable" here, skim on some plaster and ready to go. With regards to thermal transfer and insulation performance, here's what I've got: 1. Air = cold 2. Brick wall has u-value of 2 W/m²K or so 3. Air gap will reduce this slightly 4. PIR boards have a very low U value, which is why they'd be preferrable in walls to various wolls, cellulose, or other good options. I'm aiming for 70mm PIR or more (if possible) to try and get as close to or lower than my target U-value of 0.30. 5. Plasterboard adds a bit here too, but not much. Compliments of diydoctor, here's a diagram of what I'm doing: Option 1 (keep plaster, cold battens): Option 2 (warm battens - ignore blocks in picture): Option 3 (with service void): So questions are: (1) Is there a way of adding internal wall insulation on a solid double brick wall using new "tech" which will enable me to skip the air gap? (2) Should I strip plaster off the wall? (3) What's the best material for battens? (4) Any tips on how/whether to do a service void? I'm going to wire the whole house with ethernet and rewire electrical, so this wouldn't be out of place. (5) I've noticed comments elsewhere by @Jeremy Harris regarding a need to do graded vapour permeability, starting with (as he suggests): "the least vapour permeable and the outermost layer is most vapour permeable". This approach seems to be pretty difficult with internal wall insulation. Or am I allowed to ignore the plasterboard for the purposes of this kind of calculation? Would love to be enlightened. Note: this was quite helpful: https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/658604/BEIS_-_SWI_Innovation_Final_Report_-_FINAL_Approved.pdf
  24. Hi, walls are all done, roof on, windows all fitted and I've just realised the brickies didn't carry the cavity wall insulation (PIR board) 150mm below the DPC. Stressing out a bit as too late to change it but about to put down floor insulation in prep for UFH and screed. I'll be putting perimeter insulation before the screed but very concerned about cold bridging now. Are there any options for blown insulation into the bottom of the cavity? I still have access in spots where door and window cils not yet installed. Am I worried over nothing or is this a big oversight and will leak heat unless resolved? Thanks.
  25. Hi, I spotted an opportunity to save money a while back and in areas where we are not using the space all the way to the roof I changed from PIR insulation between the rafters to rockwool above the ceiling. What I did not realise though was that the MVHR ducting has to be in an insulated space. So now we need to insulate the MCHR which loses almost the entire saving. The installers have recommended using 50mm foil backed insulation wrapped around the ducts. This is fine, but I wondered if in areas where the ducts are installed just above the roof trusses and the loft insulation was pushed under the duct work could be just add another layer of rockwool that covers the duct work? This would be a lot faster and cheaper, but there is more risk that bits of the duct aren't covered.