Vijay Posted June 27, 2016 Share Posted June 27, 2016 I'm having a beam and block floor on the ground floor (apart from the garage) and this is my floor makeup from top down: 75mm screed 500 gauge vapour barrier 75mm Celotex FF4000 150mm Celotex XR4000 1200 gauge visqueen radon barrier/dpm on blinding sand 150-225mm beam and 100mm Celcon blocks. My question is can I replace the Celcon blocks with an insulated block like Tetris or Jetfloor (or the beam suppliers own thermal block) but keep the other layers, so I'm basically increasing the floor insulation? I've yet to price it up but wondered if it's a good idea or will the difference be negligible? Cheers Vijay 1 Link to comment Share on other sites More sharing options...
PeterW Posted June 27, 2016 Share Posted June 27, 2016 225mm of PIR is a lot of insulation - what is your target uValue for the floor..? You could use Jetfloor and combine the insulation and beams, lose the blocks and the screed and make your life a lot easier. It would also be substantially thinner. Link to comment Share on other sites More sharing options...
RandAbuild Posted June 27, 2016 Share Posted June 27, 2016 We are using Jetfloor - the blocks between the beams are 485 or 295 wide and 150 deep. Then 80mm grey EPS goes over the top with 70mm reinforced screed/underfloor heating, so the total floor depth is 300mm. Link to comment Share on other sites More sharing options...
Vijay Posted June 27, 2016 Author Share Posted June 27, 2016 5 hours ago, PeterW said: 225mm of PIR is a lot of insulation - what is your target uValue for the floor..? You could use Jetfloor and combine the insulation and beams, lose the blocks and the screed and make your life a lot easier. It would also be substantially thinner. We were working to 0.11 but I'd like to get as low as possible if it makes sense (I'm just thinking of getting the house fabric as good as I can). Link to comment Share on other sites More sharing options...
PeterW Posted June 27, 2016 Share Posted June 27, 2016 Youre in the law of diminishing returns there as you will be better off getting the walls and roof to the same level and air tight. 0.11 to 0.10 is negligible Link to comment Share on other sites More sharing options...
AliG Posted June 28, 2016 Share Posted June 28, 2016 Hi Vijay, The Celotex U-Value calculator gives 0.09 U-Value for 200mm of XR4000. Using 2 layers of insulation will considerably increase the cost due to extra labour for little benefit. Are you using 2 layers as FF4000 is the insulation that Celotex recommend for UFH? As I understand it, it is fine to put UFH on the XR4000 insulation. The FF4000 is harder so it is easier to install the UFH but I don't think it is necessary. Link to comment Share on other sites More sharing options...
DeeJunFan Posted June 28, 2016 Share Posted June 28, 2016 If it were me, id just go with standard blocks (should be much cheaper, but you guys get screwed on block prices) and the cheapest version of the PIR. You shouldn't have any issues with the UFH, just get the longer clips, as @Nickfromwales suggests. Link to comment Share on other sites More sharing options...
Vijay Posted June 28, 2016 Author Share Posted June 28, 2016 Thanks guys. I'm actually happy to hear that it would be pointless. It was just an idea anyway and haven't had any prices yet. There's 225m2 of flooring to do, so a lot of blocks to get in place - but I'm happy to do it. Link to comment Share on other sites More sharing options...
Vijay Posted June 28, 2016 Author Share Posted June 28, 2016 15 hours ago, AliG said: Hi Vijay, The Celotex U-Value calculator gives 0.09 U-Value for 200mm of XR4000. Using 2 layers of insulation will considerably increase the cost due to extra labour for little benefit. Are you using 2 layers as FF4000 is the insulation that Celotex recommend for UFH? As I understand it, it is fine to put UFH on the XR4000 insulation. The FF4000 is harder so it is easier to install the UFH but I don't think it is necessary. I'm not sure to be honest, it's just the insulation that's been speced on my working drawings Link to comment Share on other sites More sharing options...
AliG Posted June 29, 2016 Share Posted June 29, 2016 Unless there is a specific reason for it, it seems like an unnecessarily expensive solution. You may be stuck with it now though as it would alter the levels. I told my architect that i wanted a well insulated house and he specified the most expensive insulation solutions. I then went through and changed many of them as often reducing the U-Value by 0.01 or 0.02 resulted in a saving of thousands of pounds and the specification was not cost effective. For example he had specified Kingspan K8 which is almost twice the price of Celotex CW4000 for roughly 5% better U-Value. Link to comment Share on other sites More sharing options...
Vijay Posted June 30, 2016 Author Share Posted June 30, 2016 I think I need to look into this a lot more as I didn't expect my architect to get the best solution but I just assumed (wrongly on my behalf cos I didn't think about it until AliG's post) that floor levels would be what they are and insulation thicknesses would be pretty standard. I've yet to start to things can be changed. Link to comment Share on other sites More sharing options...
DeeJunFan Posted June 30, 2016 Share Posted June 30, 2016 yeah its a common thing. PIR Thermal conductivity - 0.022 PUR Thermal conductivity - 0.021 So if you do the calculations you might be lucky to get a 5% improvement and it will be double the price for PUR over PIR. 1 Link to comment Share on other sites More sharing options...
CC45 Posted June 30, 2016 Share Posted June 30, 2016 Hi Vijay, your floor make up is virtually the same as ours (now down & screeded). 2 layers of PIR is fine. Use sand to remove any rocking. Tape seams on both layers. Easy DIY job for me. We used 'normal' blocks for the B&B. I'm happy with it. CC Link to comment Share on other sites More sharing options...
AliG Posted June 30, 2016 Share Posted June 30, 2016 Just today I noticed that my architect had specified Celotex FF4000 floor insulation instead of GA4000. The U-Value is the same, the FF4000 has slightly better compressive strength than GA4000 and supposedly a different structure to make UFH clips stick into it better. However, the GA4000 can be used just fine for UFH. I thought I had already changed it to GA4000 and had missed it. Across my 500sq metre ground floor the price difference is close to £4000. In the initial costings for my house, Kingspan insulation was the most expensive component of the entire build! By changing to Celotex, PIR vs PUR etc I have cut the cost by tens of thousands of pounds, whilst the insulation levels are barely changed. CC, two layers of PIR is fine, however, if you are paying a builder to do the job they will charge you twice for labour. In fairness the labour to lay floor insulation is pretty low , but still you'd get much better value for money using a single layer solution. Link to comment Share on other sites More sharing options...
Oz07 Posted July 1, 2016 Share Posted July 1, 2016 You will lay 2 layers across the same area pretty quickly. In reality it probably wouldn't take you twice the time of 1 layer Link to comment Share on other sites More sharing options...
CC45 Posted July 2, 2016 Share Posted July 2, 2016 PIR doesn't come 225mm thick so you're stuck with 2 layers. I put 75mm down first (with the sand to reduce rocking), taped it & then 150mm. GA sheets used for the lot, UFH was put down with 60mm staples & no issues at all. The second layer is quicker than the first. Our timber framed house insulation has come in substantially less than £8k (246m2) - PIR in walls & floors with fluffy in roof. U values are ~ 0.1 floor & ceiling with walls at 0.16. We will roast with the log burning stove on! CC Link to comment Share on other sites More sharing options...
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