SBMS

Yes - I think that one is a bit darker. Struggling to find one that matches that lightness, most reds are quite a bit darker

Anyone know what a good match to this brick is? I think it’s a light red multi? this is another similar one (less busy) - any ideas?

ChatGPT and other generative AIs (don’t get me started on the terrible misuse of the term) are simply stochastic language parrots, and unable to perform any actual maths calculations. So wouldn’t trust them to actually deduce anything!

Yes, it was more about the cycling that JohnMo mentioned that I was trying to understand.

For those of us not in the know, and who are setting out on UFH design with an ASHP can you summarise the point regarding centres and flow temp?

20%?? I’d be tempted to put it in the cavity if this was true.

Not that much of an impact. The engineer at Pasquill has over specified it and a 202mm joist will suffice. I think he specified it for a traditional soil + greens roof makeup whereas we are using a lighter tray system.

If you could reduce your joist depth to 202mm - 2 layers of super quilt plus 40mm PIR making 242mm yields 0.15 u value. All warm roof. We’ve got a 202mm posi joist with green roof loading… alternatively if it’s the Mbc detail then it’ll be a 300mm joist (0.14 u value with cellulose) which you could do with a 202mm with 1 layer super quilt and 80mm PIR.

With difficulty. It's possible but once I started looking into it, I realised that the detailing had to be exact and a warm roof was much easier. The detail you've posted looks like MBC's flat roof with cellulose. Are you sure the joists are 254mm and not 300? 254mm cellulose filled wouldn't be a great U Value.. probably 0.16 or something?

Is it the MBC flat roof detail (300mm joists achieving 0.14)?

What’s your current joist depth your cold roof is working to - or to put it another way, what’s your maximum height you’ve got for the warm roof make up and the u value you’re trying to achieve?

We’ve had this exact issue with our flat roof design. We are going with 304mm posi rafters with warmcell for our pitched roof. Originally we were going to do the same with the flat roof portion but then another BH member pointed out the need to ventilate this. Then came the issue that cross ventilation with a parapet wall around the top is incredibly difficult to detail successfully. I decided to switch to a much simpler warm roof design with PIR on top. Any reason you’re not going warm roof for the flat roof? Much easier to detail.

@Mr Punter in both details or just in detail 2? Is the second matrix block required in detail 1?

Is the thermal break just required across the cavity to outside brick junction (irrespective of the depth of the track), or should it extend past the inside edge of the track? My example scenario shown below with a 186mm deep track: Detail A looks much easier to construct?

Marmox block = 65mm width. Track depth = 186mm. So where under the track is the marmox block positioned?

@Dave Jones - would only one row (deep) of marmox across the cavity be required for a 186mm deep sliding door track? With your detail above most of the doors and track are bearing down on the PIR?

Hi @Dave Jones Is the below right? Detail 5 or Detail 6?

We also have a flush threshold - so our track is sitting so its flush with FFL/screed level (adjusted diagram below). You've got me thinking.. Is the majority of the thermal bridging from the 'back' of the door track, and would the following detail - which is a variation of detail 1, help reduce that bridging - effectively reduce the cavity to the known bearing width of the door track and then do detail 1 with a PIR upstand adjacent to the screed: I don't know where the majority of the bridging would occur.. obviously the track would still suck up heat from the concrete, but would transmission be limited with the PIR behind??

Detail 3? With the marmox blocks on top?

Thanks @JohnMo - got it. My challenge is that I need 150mm clear above the roof deck so will need to do a 150mm + 20mm compacfoam above, but that should be fine. The detail for my roof light needs a rebate in the compacfoam as below: This is where I am up to with my detailing: Two questions: 1. Does insulated plasterboard on the internal face of the aperture deal with my VCL as well, or would it be better to run the VCL up the face as well and then put regular plasterboard on? 2. Would GRP adhere to the outside face of the compacfoam, or would it need to have OSB screwed to it? Thanks Matt

Just detailing my fixed flat roof light upstand and following on from a conversation with @JohnMo (sorry for my persistent questioning John!). In that other thread John suggested a timber frame with compacfoam on top for the upstand. It's going to be made out of compacfoam for the upstand - the rooflight will sit on this. On a warm roof with 150mm PIR. Can I run the PIR right to the edge of the aperture, and then form a 150mm upstand on top of the PIR? Roof light will weigh about 250kg - Detail 1. Or do I need to do two layers of compacfoam as per detail 2?

Is this sufficient support for 9m of aluminium triple glazed sliding doors to sit on? The PIR/Screed won't cause undue deflection? Also, if building from scratch, can you not just finish the inner block at that height, rather than breaking it away?

I think this might have been done to death, very often with no good conclusions, but we've got a significant amount of door thresholds on our ground floor (quite a bit of glazing). I'm trying to solution the different options and have summarised three possible details (traditional brick and block with a 200mm cavity - blown EPS beads, not that that matters). Can anyone comment on whether any of these options are not recommended, or whether the additional effort/cost, say, of running marmox or compacfoam (Detail 3) outweighs the potential heat losses from thermal bridging? Does option 2 work (with the doors effectively bearing onto PIR and screed)? This is to allow bottom fixing and support for a 160mm triple track slider system, and also sitting into the cavity as much as possible.

I get you. Could I make the upstand out of two layers of 150mm compafoam instead of a timber frame?

@JohnMo this detail would be okay for non ground floor.. but on ground floor there won’t be cavity insulation under the door.. with a 200mm cavity and potentially a 160mm door track, what’s supporting the track over the cavity? Would you recommend a structural cavity closer? Or take the floor insulation and screed to the outer brick skin (dropping the inner block a course or so)? Is PIR and screed enough to carry the weight of the doors?