Thorfun

it's an interesting point of view and I will definitely bear it in mind when making a final decision on manufacturer. thank you.

they use glass wool within the stud work covered in PIR (which seems pretty standard) and so would be easier to fit without gaps. it seems that 140x38 are the stud of choice as all the quotes I've had are using that size timber stud. one company did offer a 184mm wide stud though as an option.

thanks all. it's very interesting and good to know that a 400mm centre walls/building feels more solid. from the online U-value calculator the 400mm studs adds 0.003 to the U-value which is so little it isn't really worth mentioning! for me this is another tick in the good box for this company. 👍

yep! I guess it could be as simple as that. 😊

this is interesting and seems to be what the guy was saying on the webinar. but that would mean that the timber frame company would have to come back to site at some variable time in the future after the roofer has been. which I doubt they would do. I'm confused (which is easily done!)

thanks for the response. but the quote is for 140x38 CLS (C16) kiln dried stud work and none of the other companies feel I need 400mm centres and are using the same sized studs. I'm just confused why this company would. I have asked them, btw, I'm waiting for a response.

I'll try and find something...even if it means attending the replay of the webinar and asking it on there.

Hello, can someone please explain to me the benefits or drawbacks of using 400mm centres for external walls in a timber frame? I've had a quote from a company that is using 400mm centres and it's the only one from the various quotes I've had. all other manufacturers are using 600mm centres. apart from the obvious worse U-value due to more timber in the walls. what are the other good/bad reasons for using the narrower centres? cheers. ps. after attending the NHBC webinar on timber frames I am now aware that if you're not using a double header plate on the wall panel then the ceiling joists need to be in line with the wall studs. so I guess this could be a reason as the suspended floors on the quote are specified to be 400mm centres as well. but I would've thought that from a manufacturing perspective it would be cheaper to use a double header plate than to use more studs in the wall. but, maybe I've just answered my own question and it's because the joists need to line up with the studs! 🤦‍♂️

I signed up to a couple of these. one of them was the Timber Frame construction webinar. one this that they said that I wanted to ask the community is that the internal first floor walls should not be installed until after the full load was put on the roof. i.e. the roof fully tiled. now I presume this is to do with load and shrinkage of the timber frame with the roof covering on and seems to make sense but from all the reading I've done every timber frame manufacturer will come to site and erect the timber frame including the internal walls and then leave with the roofer coming to site afterwards to fit the tiles. if NHBC say that fitting internal walls is a big no-no until after the roof has full load how/why do the timber frame companies get away with this?

Thanks @A_L I adjusted the calculator to 85% mineral wool and 15% timber stud and it worked. I also adjusted the internal services cavity to include 15% timber batons. I didn't even know you could do that so thank you very much. it makes my rough calculations just a little bit more accurate. what's interesting now is that the corrected U-value is now failing the test and is above the Max U-value of 0.16W/m2K. Also, what's interesting is this wall make up is the same as MBCs 0.14W/m2K wall apart from them using the VC Foil Ultra VCL/Airtight Membrane (see below) can you, or anyone, explain the differences in the U-values received? although I guess it's that they use a different type of insulation as if I change the lambda value of the mineral wool and PIR to 0.032 and 0.020 respectively then I get an uncorrected U-value of 0.144W/m2K so that must be it. so, I'm still a bit confused but I think I'm getting there!

Not tried this but will give it a go tomorrow. Thanks for the tip. Ok, cheers. Will take a read again as I must’ve misunderstood it fully.

thanks for the additional information on points 1, 2 and 3. the calculator does indeed allow custom values and I've changed the lamda value of the PIR and Mineral Wool Batts to reflect the chosen insulation (defaults are 0.023 and 0.038 respectively). if I'm reading this correct, the timber frame itself has a massive impact on the overall U-value of the wall! I would assume that increasing the thickness of the PIR would reduce the impact the timber frame has as there is more insulation reducing cold bridging? I read somewhere (apologies but I can't remember where!) that the timber cladding would add an amount of insulation even if it is outside of the ventilated cavity. is that not the case at all then?

thanks for the response. I'm not in a position to buy stuff at the moment and so I haven't asked the manufacturers yet but I will do so once I get to that stage. I'm really at the planning stage to see how much I can reduce my reliance on PIR. 1. corrected/uncorrected: ok, this makes sense. so I would use the 0.14W/m2K U-value in this instance? 2. I thought this was dew point as well. I'll ignore this for the time being then and wait until I get proper calculations from the manufacturers or architect. 3. this is what I thought and no airspace is required. I will stick with fully filling between the studs. other comments: 1. is this true if using something this http://www.protectmembranes.com/protect-vc-foil-ultra-insulating-avcl/p/12? or do you just mention it because I have just got a basic polythene layer in the example? my intention is to use something like the Protect VC foil VCL/Airtight membrane but I couldn't see a way to accommodate that in the u-value calculator. 2. I haven't a clue how to do that in this calculator!

Hi all, I've been going through an online U-Value calculator to try and figure out my external wall make-up to get an idea of what I need to get a U-value. I have a few questions on the output: my questions on the screenshot below are: 1. what is the U-value (uncorrected) and U-value (corrected) differences? i.e. what is corrected U-value and which one would the TF manufacturers use in their marketing materials. so would this be a 0.14W/m2K or a 0.15W/m2K external wall? 2. on the right there is an image of the make up of the wall with a cross denoting "DP" within the 40mm of PIR. can someone please explain what "DP" is and is it being in the PIR an issue? also, where should it ideally be? 3. I have specified 140mm of mineral wool/glass wool (e.g. Frametherm 35) on this calculation. my architect has said that you shouldn't fully fill the stud work and should leave an air gap between the PIR and the mineral wool. is that true? if so, why would you need that? as leaving an air gap will reduce the U-value. thanks in advance.

as @ProDave has alluded to above if you want to build for near to £1000/m2 (especially in the south of England) then it takes time. one of either quality or speed of build will have to give and from reading his blog it is definitely not quality that has suffered! remember the time, quality, cost triangle. you can only have 2 of those choices.