Sparrowhawk

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.

Thanks John, that was what I was hoping. The transfer fan is something I can't add though as due to the nature of our work clients need privacy, and I think that fan would break soundproofing. A separate supply to the 6.8m2 office is the best alternative? Oh good, I thought I had to balance each floor. Great to see what a coanda nozzle looks like, that will blend in nicely with what's planned for that lounge wall.

I've gone over this a lot, and there's 4 reasons I've headed to MVHR The location. We're in an exposed coastal location and when the wind hits, it wind-washes the house by finding a path between any openings. I want to avoid trickle vents on new windows and remove existing extractor fans. AFAICT dMEV/dMVHR cannot prevent this wind washing, because the openings are on different aspects of the building. With MVHR, with the intake and exhaust on the same aspect the pressure should equalise Avoiding adding trickle vents to the new windows Air filtration. We have bad hay fever which meds don't fully combat, and the idea of keeping pollen out of the house for much of the year sounds wonderful. High internal humidity. We've had a dehumidifier running 24/7 this winter which has made a big difference. While many systems help (the standard solution around here is PIV) I figured a flow through the house is going to be important, not just room by room and we need ventilation no matter if it's windy or calm outside. This is complicated as external humidity is often high (both RH and absolute). But, autumn-spring, should be lower than indoors As an aside on 1) our kitchen extractor fan stops extracting in bad weather if the wind's from the south west. Better than it was 4 years ago The home made blower door has done great work, and sealing first floor joist penetrations this winter has made one room airtight and a big difference in the others. When it's not windy outside, the rooms I've worked most on get stuffy and need a window opening. This year we're replacing all external doors and double glazing which - after extractor fans - are the leakiest part of the house. I'm lifting the suspended floors this summer and adding airtightness and insulation. EPS cavity fill is coming, and the chimney was removed this winter and will be draft free once we remove the fireplace and seal it up. All of which is to say I don't have a figure, but I have an ongoing programme to make it better.

So I don't derail @Omnibuswoman's thread any further I've posted the plans and TMI in a new thread:

After my last ask, we've negotiated with the neighbours to redirect their boiler flue so we can put the MVHR in the most logical place: the garage. I've also compromised by putting upstairs ducting in the cold loft. This has simplified things: A few notes (or skip to the calculations below) Upstairs I've compromised by putting ducts in the cold loft outside the thermal envelope, as my wife is 100% against any boxing in The loft is well ventilated at all eaves (anywhere there is a fat wall on the plan) Positioning supply away from doors makes the pipes run close to vented eaves, so more exposed to cold air in winter. Best compromise is to keep pipes warmer and put near doors? Between floors I've gone for separate distribution boxes on each floor, to minimise number of penetrations into cold loft (airtightness). This is open to negotiation. The chimney breast has wood frame round it supporting floor joists, so cannot drill straight through in ceiling void - has to be within the downstairs room Downstairs Got permission to lower part of the ceiling in the dining room & hall to hide ducting Need to sort route to downstairs cloakroom - an annoying run to the other side of the house Have to get the ducts through an external wall + chimney breast into main house No duct to dining room - assuming the flow through from the office & lounge will be enough ventilation MVHR Compromised by putting outside thermal envelope in unheated garage Will build insulated "plant room" around it with 100mm PIR to protect from temperature fluctuations Fire safety requirements? Can mitigate with 2x plasterboard boxing in the MVHR and ducts? Calculations There's 2 of us in the house but as it's 4 bed I'm calculating based on 4-5 people. I started with the rule of thumb for 0.3ACH by @Iceverge which gave me great hope - I didn't need massive supply/extract between floors or through solid walls! Then I looked at Part F and the Passivhaus recommendations (which seem v sensible, thanks @JohnMo) and came to a halt. Here's my rooms, displayed based on @jayc89's spreadsheet. The final column is me trying to get supply and extract volumes to match. Editable spreadsheet attached. Questions Downstairs has v little supply, despite people being down there 15 hours/day. Bedrooms having more seems wrong? The utility room and kitchen are effectively a single room (no door between them). Worth reducing utility room extract so the kitchen clears more easily? I am stuck with how to treat duct length for pressure drop figures - do I calculate it from the MVHR to each plenum, or do MVHR to first splitter / splitter to distribution box / distribution box to plenum? Correctly sizing the ducts between ground floor and loft distribution box, and to the Dining room distribution box, is going to be crucial. Does 2x 90mm OD for each of these seem right? How do I best make the loft penetrations airtight? Sealing multiple circular ducts to the ceiling so there are no leaks looks a challenge MVHR calculations for BuildHub.xlsx

Thanks John. I am stuck on the PH bedroom guideline figures as this puts a lot of supply upstairs. Ours is a 4 bed house (2 live here, but assuming 4-5 person occupancy). If I use the PH bedroom supply rates, upstairs is well ventilated - but upstairs is almost the whole house min fresh air requirement for 5 people. Downstairs at 0.3ACH gets v little; bedrooms are 1ACH+. Did you use the bedroom figures of 20m3/hr and 40m3/hr?

@Iceverge that's the clearest explanation I've seen on the forum, thank you. I spent last weekend messing around with spreadsheets trying to calculate flow rates and resistance and reached the point of giving up and admitting I'll have to pay £1000 to get someone to design the system. Now, I'll give it another go...

How are you rejoining the ducts at each cut? An additional metal joiner with 2 O-rings?

Sounds like this PH architect has designed to the letter of the certification and not to the spirit. Unless the clients have imposed limitations that make it impossible to design out the overheating.

It the lime vs cement one here about flexibility, or breathibility?

The popular online answer is "when it's converted", but that's not very specific! The last owners built a utility room in the back third of the garage. The remaining space is too short for a car. I'm now thinking of taking another chunk as a plant room for the MVHR. At what point is the remaining space no longer considered a garage, and so the fire regulations for a garage don't apply? It would be handy not to have to add fire dampers to the MVHR ducts where they pass through the stud wall and into the utility room.

Is there a standard way to compare airtightness of windows across suppliers? I've seen BS EN 1026:2016 and BS EN 12207:2016 so do we request their certification for each design of window / patio door? I want to make sure we end up with something substantially more airtight - and watertight in driving rain - and guess it's an area some suppliers will cut corners.

Having got stuck with how to route the MVHR ducting for my retrofit, I've spent the last few months sourcing design quotes as it's getting beyond me and I wanted to get a pro's input. After being quoted £750-£1000 for design-only without them even glancing at the brief or plans I submitted, and then warning that "If it's more complex than we expect that'll increase" I'm back to trying to sort the blockers myself. Through false ceilings in the landing, a side room and part of the dining room I've managed to keep the ducts out of the cold loft and within the thermal envelope. I've got access to almost all rooms without little visible boxing in. But I have 3 remaining problems: First floor: how to get ducts from the landing to bedroom 2 / en-suite /wardrobe. There's a disused chimney breast in the way, plus the ceilings in the extension are lower. This is where I gave up last time and went looking for an expert. If it was 1-2 ducts I'd say core drilling, but there's 3, or 4 if the en-suite needs doubling up. Swiss cheese anyone? Linking the ground and first floors. My current idea is to take down the lathe and plaster wall between the landing and bedroom 4 and build a new wider wall with the ducting inside it. The 70cm wide loft hatch (not shown on plan) is smack bang in the middle of the landing corridor and I overlooked it. Short of making it narrower not sure how to get the ducts past it. What do you think? I'm also uncertain about the supply/extract vent positions. Upstairs they'll have to be in the wall not ceiling so I don't break through into the cold loft; and few are at the correct point in the room. Will coanda effect vents do enough to circulate the air when wall mounted? MVHR plans anonymised.pdf

According to an earlier thread it's a "water based acrylic" not that that tells us much. I'm picturing acrylic sealant in droplet form, pushed into gaps.

I like the sound of this though I'm not the target market. Have you looked at having a presence at https://www.nsbrc.co.uk/? You get good exposure at their shows and it gives you visibility and I'd say credibility-by-association in the UK market.

Depending how big an area you need to touch up, mixing the colour match by yourself can work. I did this in a rental property to cover over damage when their "magnolia" matched no shade from the shops. I did it with a mix of emulsion testers plus artists acrylics and got a close enough finish. Getting the same matte finish as the rest of the wall was harder and took abrading + a bit of talc rubbed in to blend it together.

My wife's started working in the room above my office, and we can hear every word the other says. The makeup between us is plasterboard - solid timber joists - 22mm chipboard. I've sealed any cracks so there's no direct route of transmission for the sound. Is the next logical step to add rockwool or similar between the joists? If so does the density of it matter or like in a stud wall that there's just "something" there?

I've had good success with Tikkurila's matching service, and their paint is nicer to use than Valspar. But if Valspar was that far out there may be an issue with the sample. Brewers decorating centres have also been decent.