Sparrowhawk

Welcome @Mash! You are sensible doing it all at once (and I assume moving out while the work's ongoing?). We're doing a smaller renovation of an extended 1920s house while living and working in it, which has slowed progress a lot.

I shoved a layer of plasterboard offcuts between the rafters. Today's assessment is it's made the sound problem worse not better 😂 I haven't added any fluffy stuff yet as waiting for heating engineer to do his stuff, as I don't want to risk it getting wet as he moves the cylinder.

Welcome Graham. I hope you'll share your build here as it goes. There's a lot of skepticism about straw bales on this forum; me I'd build a straw house if I could for the carbon footprint, but mostly as I like the aesthetic they end up with. Fingers crossed that the warrant doesn't take as long as planning did.

"P = Length of the exposed perimeter (m)." Clarifying that the exposed perimiter isn't 36m (the length) but we involve the thickness too? I hadn't taken that into account before, which would explain some odd numbers I was getting 🤡

It is, the options on the Kingspan calculator are very limited (only this material, only 450mm joist centres) so it's going to come out better than the other. But - I was hoping to verify on 2 calculators that 100mm PIR plus flooring would at least get me to 0.25?

You're so lucky with that joist depth. My entire joist + void depth is around 200mm.

It is German, and I can't see what they're using for permiter/area, if anything. Kingspan by contrast required those two values before calculating the results. They only have an option for "floor", not ground floor. I can choose the space at the bottom to have air or earth in it, but AFAICT restricting what's at the bottom to those two settings is the main change vs modelling as a "wall" or "roof".

No they're not. I lifted some 1920s floor downstairs to see how much space is available, and I have a 100mm floor joist with 100mm-130mm void under it. Right now I'm trying to see if I can even meet ADL for existing floors (0.25m–2 K–1) if I put some insulation in, given the void is shallower than it's meant to be.

@IGP that looks excellent! And thanks for sharing your experience, as I've been eyeing up their method too. How deep are your joists and the void underneath, and what U-value have you aimed for?

This is doing my head in. I've done a suspended floor build up accurately in Ubakus and get a U-value of over 0.3W m–2 K–1 which seemed high; then did the same in Kingspan's calculator and got 0.19W m–2 K–1 . Is there some obvious error I've made? Trying to work out if I can comply with Part L for upgrading existing floors...

I'll be able to do qualitative testing, but havent' got anything to meaure sound levels with (unless an iPhone will do a good enough job, hmmm)

Thanks for that. I have got plasterboard sheets ready to go to the tip. This looks like a cheaper way to dispose of them. So, from top down: Chipboard floor (for now) 50mm of fluffy stuff like Rockwool Sound Insulation Slab (35kg/m2) 1-2 layers of platerboard offcuts between rafters, as tight fitting as I can (or sand along the edges if I'm feeling obsessive) Current 12.5mm plasterboard ceiling Air paths are sealed through the ceiling, but not the chipboard floor as I keep lifting it for stuff. It's funny you mention sand, I came across Quietex which is crushed limestone to pour into ceiling voids to improve acoustic performance. I thought it weird but as it's mass it makes sense. I have enough headroom in my office that resilience bars are a good shout. Ditto for putting rubber above the joists to cushion impact onto the chipboard. I didn't know any of that, so many thanks. This site's an education every time!

I need to block the sound of me talking and my laugh going from my ground floor office to the room above. My plan is to add another layer of plasterboard to my ceiling, stick some dense material between the floors, and then mastic gaps between chipboard sheets before relaying the floor covering. At the moment 100mm batts of 036 Steico Flex (60kg/m2) is working out cheaper per m2 than Rockwool RWA45 (45kg/m2) or RW3 (60kg/m2) which is unavailable except by the pallet load. Knauf's Rocksilk products are likewise hard to find. Has anyone experience of using this for acoustic insulation?

I've updated my spreadsheet, and it looks like 90mm single/double runs will cover all, while double 75mm would break the 2.5m/s rule for the kitchen and en suite extracts. To connect downstairs to upstairs I think something larger than 2x90mm is going to be needed, given those speeds for the full supply and extract volume.

That's my bad, downstairs I've got permission to lower ceilings as the ceilings are higher to begin with / the rooms don't have sloping ceilings cutting into their height. I do need to find out if in the 30cm side of chimney breast I can drill 2x 9cm holes for the ducting (as drawn above) without weakening it. If not then I need a big rethink for how to get from the garage to the dining room.