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I've not had a detailed quote yet, we should be get the steels design from the structral engineer this week and then the builder will complete his quote with a better degree of accuracy. I will ask the builder to price up demolition and rebuld of the existing exterior wall. FYI there is 23m of wall standing 2.5m high that we had intended to keep. So 57.5 sqm. Having done a quick google I've average price suggestion from £150 to £230 per sqm for a builder to errect a brick and block wall (finish internally as well). So somewhere between £ 8,625 and £13,225 plus we'd also have to pay for the demolition and disposal. So perhaps ball park £15k - £20k in total. What am I looking at for EWI, not including the rendered finish (since I am going to have to pay for that either)?

The structural work will all be done by a builder.

Would love to hear some more thoughts on this. We are really struggling to make a decision and are perhaps leaning towards doing nothing at all.

Thanks for your input. Yes we gave strong consideration to a full rebuild waay back at the start of our journey but it wasn't going to be cost effective from our own calculations. When you say a 50mm cavity is useless, presumably you mean from a cavity wall insulation perspective? Approx 100mm of EWI with silicone render certainly looks like good option, thanks for the reassurance. Does air flow need any consideration? Would I need to remove the existing CWI? etc For the insulation type, I was eye-ing up mineral wool for its accoustic properties, I don't think there's a major u-value difference or other benefits if going with EPS/XPS?

We're about to embark on a significant renovation of our 1970's bungalow and are considering options for improving the insulation of the existing exterior walls that will ultimately make up about 50% of the final external walls. The existing walls are 115mm facing brick, 50mm cavity, 100m block. The cavity was filled with "Megafoam" (Urea formaldehyde) in 1977 but I suspect that's largely useless now due to age and ideally needs removing, although I've not yet had a survey in that regard. We will be... - replacing the entire roof (giving us access to top of the cavity) - replacing all windows and services (so an expansion of the exterior wouldn't be a problem, were we to install EWI) - rendering practically the whole facade (so no concerns about retaining existing brick) We're not looking specifically to achieve eco or passive haus standards. The new walls and new roof will be built to latest regs only (walls will be typical brick and block to match existing unless someone is able to convince us and the builder of something better) Presumably we would ideally bring the existing walls to regs standards to match the new walls, otherwise heat is going to leak out of the poorer half of the exterior? Is my thinking correct here? Originally we were thinking of just replacing the CWI, this is obviously an affordable approach but I doubt this will cut it. IWI is a possibility but we'd rather not lose any floor space. So I suspect EWI is the way to go but I'm a little in the dark on pricing and also have some concerns about about condensation, dew point issues etc. We do love the fact EWI might provide an acoustic barrier and the contained thermal mass will help keep things cool in the summer, so that might make any additional cost more bearable. Would love to hear your thoughts, opinions and/or experiences. What would you do if you were in our shoes?

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Hi all 👋🏼, I wanted to introduce myself and our project as I anticipate I'll be in hot pursuit of the forums thoughts, opinions and experiences in the forthcoming months. We purchased a 3-bedroom 1970's bungalow in August 2022 but had some planing complications due to a parish council policy that attempted to dictate that "a bungalow must stay a bungalow". 15 months later our planning application was finally granted, albeit with some compromises. Here's a few points on what we're attempting... Replace existing roof (& ceilings) entirely, building up the walls ~80cm, adding a new roof with 1.2m increased ridge height and steeper pitch Upstairs will accomodate two bedrooms, bathroom and "breakout area" overlooking hallway void Large single-storey flat roof side and back extension out to locate 65sqm kitchen/diner Complete re-configuration of downstairs layout Complete replacement of heating system (gas will be cut off entirely) New ASHP (current thinking Valliant Arotherm Plus, one-zone, no buffer) UFH all-round on ground floor (retrofit lo-profile UFH on top of the existing slab (Wunda?), insulated/screeded in new extension). Possibly fan convectors in bed-rooms upstairs Complete rewire I would assume MVHR (current thinking is a radial system installed through new posi-joists, manufacturer TBH but will get BCF to design) New solar panels, and battery (current thinking GivEnergy to unlock Octopus Intelligent Flux) New double-glazing all round (Residence R7 probably) also 2.7m high, ~8m wide sliding doors at rear (either Corteso Cor-vision or Minima) The biggest grey-area for us at the moment is how much to focus on/invest in improving the insulation and air-tightness of the existing exterior walls. I'll raise a separate thread for this in due course. Fortunately we were able to leverage a second mortgage and keep our existing home so we don't intend to live in the place whilst the majority of the work is taking place. The properties are only 0.5 mile apart so I am hoping I'll be able to keep a close eye on the build whilst I work from home. We are also intending to do a little of the work our-selves as possible (i.e. fitting MVHR, UFH, painting & decorating, airtightness membrane?, etc). Thanks for having me and in advance for any advice, Ollie Fleet, Hampshire Plans 24 OD - Amendments Combined.pdf Concept Images Existing Images