BartW

Thanks guys. How do the TF suppliers manage to back their back up their claims as to uValue then? And is there a more accurate tool I could use to calculate my target U? (PS. mac user here).

sounds and looks good My target is 0.15. The plan is to get the TF company to fabricate and erect the structure, lay osb and vcl externally, and then take over from there. Would I do inner layer of earthwool, then inner vcl, then service cavity? I did a quick calculation in a piece of simple ios app, but when I add the “air” layer it reduces the U by quite a bit. All well and good, but timber battens add quite a bit being a cold bridge. see below for comment please:

With that view in mind, what would you swap the inner PIR anti cold bridge layer with? More rockwool slab, perhaps cross layered and packed as part of the service cavity?

Thanks. Trouble is the 32 seems to command double premium compared. I need 210m2 for external walls, and been working out price difference between TF manufacturer supplied insulation vs PIR (GA4120) vs variables of rockwool, and between PIR and dri35 there was roughly £1500 difference. Let alone, floors, internal partitions, roof, intermediate floors, inner face of external, etc.

Thanks Peter, good point. I have checked again and 140mm Frametherm 35 roll would be available with the same level of savings, whilst providing better R value. Happy days

Hi, Quickly borrowing the thread to ask how packing oversized rock wool into the TF frame would stack up as a practice. I mean 150mm rock wool into a 140mm Timber Frame. I have been doing all sorts of calculations, and somehow a 150mm Knauf Dritherm 37 works out cheaper than Dritherm 32 125mm, whilst providing similar uValue performance. I appreciate packing the whole thing would be a bit more of a faff, but insulation cost difference would be around a £1000 for just the external walls. Any opinions please? Bart

Hi, Resurecting the thread. Andy, did you get anywhere with Solo? I am awaiting a quote from them. They seem a friendly bunch.

I would save a grand for something else

Yes, X is the surface induction, so a massive continuous surface able to heat wherever you put the pan, whereas the standard Pure has 4 individual zones.

Pure X recirculating is £2720 + VAT, and Pure is £1890 + VAT. All Bora range is going up in price as of Jan, and the above will be £2990 + VAT, and £2180 + VAT. Date of your order will secure a price, i.e. although not deliverable until March, you can benefit from 2020 prices if paid before end of December 2020 Oh, and they come with filters, etc so you would not be venting fats back into the MVHR system. Naturally, if you only want to use MVHR to vent the cooking, then perhaps that is not a good idea, and would (almost certainly) not pass Building Regs.

Hi Steve, We are (soon to be) going to be building at Graven Hill too congrats! Bart

Would you mind sharing who you "interviewed"? And what was the scope of prices between the cheapest to the most expensive one? I have a preliminary price from MBC, but waiting to even hear back from most others. So, curious what they are even likely to entertain.

I think the running cost would be comparable. As for the big combi with the house size, and potential number of occupants in the future, I would probably feel better if it has got a sizeable tank for when the demand is there. And the whole thing between gas vs ashp probably boils down to preference, and what one believes in. The latter being cleaner energy has got some appeal to me.

Another interesting advice that has been provided by one of the TF suppliers was that the I-beams have less deflection than pozi over the same span. What are your thoughts guys?

The build is in Graven Hill, OX25 so South East. The max air exchange rate is 3Pa/h. Not looked at that fully yet. Started off with open panel TF from likes of MBC or Fleming, went Durisol, but now giving the TF “a second look”. all slightly confusing. Or perhaps adding up, otherwise I would just have everything ?

£2k connection is something I could avoid by not having gas. Another £2k would come from not having a tank and boiler, and another £600 for commissioning. Now take the cost of a said ashp and tank and I am virtually back to zero difference which would be keen. the property is 2/3 storey (gym on top floor) with 180sq m GIA. 3/4 bedroom with UFH on all floors, and below 0.15uValue for the entire envelope. About 80sq m of glazing double or triple. 7kW unit too much, but 4kW not enough probably. So aiming between 5 and 7kW but care about 250L water tank for 4 showers in the morn (for when the kids come), with everyone getting equal share of hot water. those are my credentials.

Which would borderline warrant me installing it myself, and getting the Gas Safe engineer to commission and certify the whole thing? I am weighing up the savings of the ASHP vs Gas boiler + £2k connection to the grid. I am not far off!

I know a Gas Safe engineer that might be able to help, so would I need to ensure he is MCS registered for the RHI to be utilised? A bit of a daytime pisstake... Make something twice as expensive for the 50% of the premium to be written off over 7 years. I mean, what is the point of the government trying to sway people to become carbon neutral?

Hi, I am looking into the choices between different ASHP units available, and have found that half decent units start from £3k + VAT onwards. In summary, VAillant aroTherm 5kW would start shade over £3k, but would need a tank bought separately. LG do a mono block that is around the same, but tad more and also needs a tank. Mitsu Ecodan do a monoblock with a tank here https://www.orionairsales.co.uk/mitsubishi-electric-ecodan-quhz-w40va--ehpt20q-vm2ea-air-source-heat-pump-with-thermal-store-4kw-a-10965-p.asp and that @ just under £4k seems good value. Now from the technical point of view, is the thermal store an equivalent to a megaflo tank? If so, would one of the stronger units from LG or Vaillant be a better option for sizing, and flexibility to add a bigger tank? One can get a 250L tank from Main or similar for around £500 - £600. Is that the right thought process? And if so, assuming that installation is not much more involving than that of a Gas boiler, why is an average quoted cost of ASHP for a typical detached dwelling oscillating between £8k and £12k? (or more?). Sorry for all the rather blunt questions, but it is my first attempt at ASHP having learned from an earlier post (thank you so much!) that the RHI has been extended until 2022. Regards Bart

Great, thanks!

I agree, the wall plates will have a job and a half over that open plan there. As for the timber on the upper floor, perhaps I could do a timber construction only over that open area where the overhang is... Although the point of the build was a well built monolithic construction initially.

Yes they gave me a contact for SE practice. I have just not had them do any work as yet, whilst I have been finalising the design and resolving the obvious oversights that would otherwise lead to over-specifying of connection details that would later be changed or followed. Both usually at cost. Velox do an intermediate floor system that in theory might be able to deal with the overhang on its own, but I am not sure if mixing the two would be a good idea.

Yes, that is all very relevant what you are saying, thanks Perhaps I panicked thinking I might suddenly end up with 421mm high joists otherwise Probably best if I stipulate the cost difference of taller single length joists vs RSJ half way through the middle + shorter joists of a smaller height. Then the handling of the latter, which could be (arguably) a simpler task as well. Anyone could share some knowledge on the cantilevers at the front please? I hope overcomplicated steel structures may not be necessary.

that’s not bad then. I guesstimated similar budget for my 80m2 of cover. Admittedly, much higher joist profile. Are you saying much higher joist profile due to weight per m2?

hi, mine is going to be weighted down by Lewis + screed, so will probably make it a bit more rigid, and quiet. Sound transfer between my floors is my paranoia, having seen some new developments recently. I didn’t understand the 17M run. Was it 17m2? If so, I might be quicker and cheaper to consider steels to break things up. The downside then is running of services that becomes particularly inconvenient. Water and electricity being the easy ones...