williamlincs

Have had a search through old threads on a similar topic, and wanted to check I’ve understood correctly - apologies for rehashing old questions! House is 170 sqm, 3 bed. UFH has been installed in 50 sqm of the property with 150mm PIR under screed. Rest of property is heated w rads. Boiler is a 32kw Grant Combi, occupants 2 adults 2 teenagers. Will a 120 ish litre buffer tank suffice for the UFH? Mains pressure is good, flow a little on low side, around 15 l/m, we are on a spur off the main feeding 3 properties, have spoken to salamander technical, wondering if we need an accumulator? many thanks

Thanks all for contributing to this thread, I’ve learned masses and thankfully it’s stopped me doing something stupid. I’ve read BS5250. Little confusing as it seems to me insulation infill between rafters is classified as warm roof in the paper? anyhow, the PIR is coming off the roof tomorrow. This is my plan to insulate the space now. 1. 50mm PIR in between rafters up to collar height. A further 50mm PIR below this, I.e on underside face of rafters. AVCL. Held on with 25mm battens. Plasterboard. 2. Frame between collars and put 100mm PIR on underside face. AVCL and 25mm battens. Plasterboard. this gives me 50mm gap between top of PIR and top face of rafter to allow for membrane drape. 5250 says about vent tiles, I’m using concrete double pantiles, VISTA membrane. Do I need vent tiles or will I get sufficient flow into roof void without? Again, my thanks for all your help!

@Iceverge I suspected bad idea hence question, thanks for confirming such. current roof build up is bitumen felt and then tiles, no insulation. 4” rafters with a high collar. Plasterboard goes up rafters and across collar. on stuff I’ve done before it’s been PIR cut between rafters. I hate doing this job. I’ve got the PIR on externally, counterbattened/battened. I wasn’t sure if I should have put the membrane in between counterbattens and battens, but I see from response above I’ve done correct build up. Presumably I now have to fill in between the rafters. Does it have to be PIR or can I use a mineral wool? And then put a Moisture barrier underneath. How would you approach this? Thanks all for your help.

@Temp Many thanks. Looking at a refurb of one of our properties - can i put further PIR 50mm insulation on ceiling, with then the roof void above open, or will i get issues with moisture in the void? Ill have 100mm PIR outside rafters, and i dont want to cut and fill spaces between rafters with PIR, if i cant help it. Ceilings are high and so i thought i could put insulation under ceiling joists, counterbatten and then plasterboard.

To check I am correct of buildup using PIR on topside (i.e external) of rafters 1.Rafters 2.PIR 3.Membrane laying on top surface of PIR 4. 25mm tile lat counterbattened 5. 25mm Battens for roof tiles Many thanks!

@IanR I see now, the beams i was looking at were the z sections in between the steel portals! One thing that keeps cropping up with my design being single storey is the form factor issue, and Passivhaus standards being easier to meet with 2 storeys. How did you you mitigate this with an expansive ground floor plan?

@IanRThats a big house! Were all the i-joists pre-cut or are they delivered in standard lengths and cut to size on site? What is the purpose of the beams located outside the upper face of the trusses running perpendicular? Would you mind giving an indication of cost p/m2 of the Warmcel for your build?

Thank you all so much for the warm welcome! @PeterW Floods of 1952 came dangerously close to where my site is. Its a real worry for everyone in Tourism/Agriculture here. So much land, particularly south of Skegness relies on the internal drainage boards to mechanically pump water out to sea. @Donegalsd Thank you for that tip @IanR Wow, this is a great list, many thanks. What was the build up of your roof construction? Same as walls? By racking you mean bracing between the verticals?Does the DHF then preclude the need for an additional permeable membrane? battened and then counterbattened and your cladding on top? No tape sounds excellent. I had been looking at Hempcrete, simply because Warmcel seems to be 3rd party installation. I suppose doing it as a similar way as you have done would make off site not feasible. @Iceverge Old Holloway is exactly what i had in mind! Thank you!!!!

Hi there, house will be 5 miles west of Skegness!

Hello all, Have been browsing the forum for a few days, time to introduce myself. Im looking to self build a 4 bed single storey house, approx 150 sqm. I have renovated a couple of properties, and built extensions, but never a full new build. What id like to do is to build a house myself, to passivhaus standards. Current thinking is to borrow for several designs in like in terms of layout / elevations, adapt for my site, have a timber frame designed and manage the construction myself. EPS Raft foundation and Ibeam with natural insulation is current thinking, timber clad exterior. I am undecided whether to attempt some level of modularity, I have a big shed i could use to construct sections before moving to site and i like the idea of insulation preinstalled. What im struggling with is knowing how to manage the design in terms of orientation / glazing to make it work to passivhaus standards, and i dont know who to use for the design work - im not trying for architectural identity, more performance of the fabric. Any recommendations welcome!