bobh

Any thoughts on my floor make up We have a raft foundation with DPM below, as we are in a radon area we need a radon barrier above the slab and below the insulation. We're planning on taping the insulation joints to form the vapour control layer, this means we can't pin the underfloor pipes directly to the insulation without compromising the VCL The architect has specified a wire mesh over the insulation to fix the pipe to which sounds a dreadful idea to me 🤣 We already have several hundred clips to pin the pipes to the insulation and this would be my preferred method So my question would be does the radon barrier double as a VCL? If not can anyone suggest a solution

Thanks so much for everyone's advise. I'm going to look long and hard again at ashp

Air tightness presumably will come from our attention to detail during the build, it's sips panels and we will be looking to achieve a good standard. Thermal bridges have hopefully been designed to a minimum, we are having to go with the architects experience on this but I can't see any obvious issues in the design That's a very cheap ashp and changes the possibilities, that said is it too cheap? Has anyone actually fitted a had good results from one of these units? Fitting 2 Willis in a system would seem the best option especially as they are so cheap, if we end up using them I would probably consider have a spare on the shelf in case of failures as getting spares delivered to a Scottish island can sometimes take a while. We are very hands on and will be doing the great part of the build ourselves.

@TerryE we hit most of those specs, just outside on the walls at 0.16 but floor and door are 0.14 and 0.13 respectively. Triple glazed with average u value of 1.3 I'm just waiting to try and get the local mean temperatures then I can finish the heat loss calculations and hopefully try and answer your 2 questions

@TerryE I'd not considered an air to air unit, all I've ever read, heard or experienced of them was quite poor from a whole house point of view. Quite good for an open plan type but not so good at getting heat into various rooms I'm going to run through the spreadsheet that @LA3222 linked above so I've got something to base calculation on

@LA3222 many thanks

@TerryE as usual it comes down to budget, and well in our case location Quite simply an ashp is beyond our budget and gas isnt available as we are on a Scottish island. How does one predict the energy requirements on a theoretical build innorderto do the sums though?

Thanks @TerryE sound like the system coped admirably I'm seriously contemplating this system for our new build which isn't up to passive house standards but hopefully as it's only 106m² single storey a coup!e of Willis will cope

@oranjeboom how did this system cope with the cold weather we had recently? Did the second pump solve the issue?

Drainage layout was designed by our engineers along with the foundations. I've found a company that will supply a 0.4l/s restrictor which is essentially a silt trap with a cap on the exit pipe with an appropriately sized hole in it and then a filter fitted to it. I'm pretty sure I could make the same myself but don't know if building inspector would ok it. Scotland based if that makes a diffrrence

The total roof cover is 136m² The system has been designed with 150mm pipe rather than 110 to include a 10 m filter trench as well

Our SW drainage requires a 0.4l/s flow restriction before the outfall. Now to my mind this is as simple as a capped pipe exiting a silt trap chamber with an appropriately sized hole drilled in it to give the required flow. Do we think this would be suitable or do I need to spend a few hundred pounds on a ready made product?

Hi folks Can anyone suggest an alternative to IdealCombi windows. I particularly liked the idea of the PUR thermal break in the wet zone, replacing wood for an imperrishable material in the area most liable to rot seemed a great idea. Unfortunately IdealCombi have informed me they won't consider delivering to Scotland so I'm looking for an alternative, anyone seen anything similar in a wood/Ali composite?