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Hi everyone I'm stuck with my construction method and insulation... Please can you help me with the pros and cons? I'm getting a lot of mixed reports from the things I'm reading and the people I'm speaking to! Background: I have just bought a 1950s house in Hertfordshire, cavity wall construction, completely uninsulated. It's in pretty good condition structurally, but hasn't been touched since it was built. Project: I will be completely renovating and modernising the property, taking it back to brick, moving a lot of internal walls, new plumbing, wiring, windows, doors, floors, ceilings, etc. Oh, and getting rid of the asbestos! I will also be adding a 4x10m double storey extension on the back. The back of the house is South-facing. Externally, I want to finish the house in a combination of brick slips and render. (I don't like the colour of the current brick that is used). I will also be retiling the roof, and adding a couple of gables over the rear extension. I want to take a fabric first approach to the build to make it as energy efficient as possible (within reason and budget constraints). I am not trying to take it to PassiveHaus or EnerPHTT standards at all, but I would like to try and achieve the best I can afford to do that makes sense and isn't over engineering it at large costs for the sake of small incremental gains. I also really want to install MVHR. Where I'm at: My plans are still awaiting approval, but I want to crack on with structural calcs and BC drawings. However, unless I tell them otherwise, the extension will be specified to built in cavity wall construction, and the specifications & details will just be to satisfy normal building regs. My thoughts were that I would full fill the existing cavities in the existing house, then wrap the whole house in EWI. Insulation material for both the cavity fill and EWI is TBC. Questions: What should I build the rear extension in, and how should I insulate? Brick & Block with cavity? I assume this would be easier to tie in with the original house, as it is the same construction method as the original, and would be easier to find tradesman for this as it is the most common. If I do this, I assume I would then continue the same full-fill of the cavity and EWI as per what I plan on the original house? Single Block with EWI? Given that I want to use EWI on the existing house, perhaps it doens't make sense to build the extension in cavity brick and block, and instead I could use a single blockwork and continue the EWI on that? A different monolithic single block construction method? E.g. the JUWO evolved SmartWall? (https://evolvedsupplies.co.uk/juwo-evolved-smartwall). The sales materials sound convincing (obviously!) as it seems it would be cheaper and quicker to build the brick and block, provides a slimmer finished wall, has better thermal properties and means I wouldn't need to use EWI on the extension as well. But don't know if that is just all hot air (pardon the pun) and also don't know if that might give me an issue in the future with lenders and insurers? Timber Frame? I've been told that this could be cheaper and quicker to build, and could be more thermally efficient? But it could be difficult to tie in, and I'm unclear if just insulating the frame is enough or if you would also wrap EWI over the outer leaf before finishing with the brick slips and render? I'm also getting confused re thermal mass, and whether it is good or not to have!! My original thinking was that a solid wall from e.g. bricks, blocks, concrete, etc has a great thermal mass and therefore will store the heat generated inside and outside and release it slowly during the day, keeping it warm in winter and cool in summer, and creating a cosier environment etc. i.e. construction using materials with a higher thermal mass is a good thing. However, when researching timber frame construction, I'm reading that their lower thermal mass is a good thing, and is more likely to create a better living environment than with a solid-wall construction method! Argh!! Regarding insulation, I'm also getting mixed reports re products, so any advice there is appreciated! Looking forward to hearing your views! Thanks in advance

Hi it seems that if you have a passiv-esque house you will not need UFH upstairs and maybe no heating at all. My build is is more traditional, it won’t be insulated to that level or airtightness, for this reason I think I need to consider the upstairs heating as a must. Im reluctant to opt for radiators, one because it will waste space and two because I think they need to be run at a higher temperature. So with that in mind, I was considering UFH not only on the ground floor, but the 1st and 2nd floor too. Although I’m concerned about this set up too as there will be little room for insulation and I think the efficiency will be poor. Especially if I have wood flooring. Stone flooring upstairs doesn’t seem right some how. Another option is skirting board heating, but it looks *relatively* untested and also runs at a higher temperature. It is however neater and you don’t lose any space. Any thoughts would be welcome