MoDo

Where is your boiler/heat source? You might want to simplify pipe runs by keeping radiators closer to this area. Also depends on your beams - we've go I-Joists which have strict rules about cutting holes in the web - so routes have to planned around this. If you have open webbed joists it'd be a different story. Our architect placed the radiators under the windows. However this isn't really necessary. A good option tends to be on the wall as your walk into a room as you aren't going to want to put furniture there.

Would really appreciate some help with finessing my radiator plan before I start drilling holes… Hopefully some clarity here will help others in similar situations. Heating will be provided by a heat pump supplied and installed by British Gas. However, they do not do first fix apparently, so that’s down to me. They have sized the radiators (almost all small type 11 – mostly 400mm or 500mm wide though the widest is 800mm). We have 10 in total including 3x towel rads. All radiators are for upstairs only. We have UFH in the ground floor slab with a few spare ways in the manifold (installers decided to leave out a few circuits – but it is what it is). So, I could potentially run a few rads off the spare ways in the UFH manifold – not sure if that is a good idea or not? I know many on here have used the UFH type manifolds with separate runs to each radiator. However, this isn't ideal as we have I-Joists and MVHR so I have to be careful to keep the necessary distance from existing holes drilled in the joists. Coupled with a number of impassable glulam beams, it isn’t really an option to run pipes from each individual radiator back to a central manifold. So as a compromise I’m planning on around 3 pairs of flow/return coming off separate push fit manifolds. I would locate each manifold in the area below the stairs (centrally located in the house - see blue/red rectangles on diagram) on the side closest to the rooms they are feeding. These would be linked with 22mm plastic and reduce to 15mm at the ports. (This central area under the stairs is where the heat pump primaries would enter the house and where the UVC will go.) I’d then run a maximum four radiators off each 15mm flow/return pair. ChatGPT has helped with calculating flow rates and losses over different lengths of pipe. It claims that by adding additional flow/return branches, flow rates will be improved – rather than running say all 10 rads off one 15mm flow return circuit – which of course makes sense. I’d tee off these flow/return pairs in the void between the joists or in the stud partitions for each radiator. Does this sound reasonable?! Thank you. Planned manifold type 2/3/4 port depending on how many flow/return feeds (pipe to be pert-al-pert 15mm):

No airtightness tape detailing that I can see on their Standard Details PDF. The system is designed to have plasterboard fixed directly to the OSB. Airtightness is taken care of by overlapping and sealed giant T&G joints of the SIPS panels themselves. PIR is just for higher u-values. A breather membrane is fitted to the outside.

Perhaps for this reason (moisture getting trapped in outer osb layer) Kingspan TEK systems are built with PIR installed internally. The supplier we used has the u-value data for different thicknesses of PIR on this page https://www.clays.com/sips-technical-data

Right yes 1m3 makes sense - I used a larger impervious area in case permeable paving isn't suitable for some reason so got the slightly higher figure. Perhaps I just need to accept that this amount of storage will be required. Can't use a pond or anything like that - just isn't the space, will probably have to be those crates or some underground tank. I'm still wondering if we could simply argue that 1 or 2m3 of storage can be mitigated (avoided) by using permeable paving or something along those lines. I guess no harm to draft some sort of report any try it. Has anyone written their own report? Assume it needs approving by the local water authority prior to submitting to planning?

Thanks, some interesting approaches. Yes the site slopes very gently so water likely already running off. However I get that we have to improve the situation not necessarily maintain it. I've done some calcs (well, the website tools do the calcs) using the Wavin and UKSUDS tools - both seem to indicate we'd need 2.5 - 3 m3 of storage which is minimal. I've no idea though if we'd get away with arguing that using permeable paving ought to be sufficient.

Thanks all for the responses. I was deliberately brief, perhaps overly. Cutting a very long story short, we are picking up the pieces (on a pathetically limited budget) from a contractor who overspent and erred at seemingly every opportunity. This submission of compliance with a condition of planning being one of them (which we just discovered had never been approved) - as no drainage improvement information was ever submitted. My understanding is that SuDs and attenuation are distinct - I may be wrong - but on this assumption… Soakaways won't be possible - the site is too small and ground likely unsuitable anyway - we're in Manchester - very urban - no streams etc. The site is small, only a few meters to the road and almost nothing on the sides. So SuDs are unlikely to be viable (besides for the budget issue). The planning officer did also mention that it might be “possible to argue why SuDS cannot be incorporated into the scheme. However, it will still be necessary to demonstrate how existing surface water drainage rates will be reduced to existing greenfield runoff rates or 2l/s, whichever is greater”. The former part (in bold) leads me to believe that attenuation is non-negotiable (where runoff is increased beyond 2l/s) but that SuDs can potentially be omitted. Hence I'm left trying to calculate if a) we must have attenuation and b) how much do we need. I’ve been trying to work it out - mostly from this document https://assets.publishing.service.gov.uk/media/602e7158d3bf7f7220fe109d/_Rainfall_Runoff_Management_for_Developments_-_Revision_E.pdf but although I can see various tables titled “Attenuation storage volume as a function of QBAR/A and PIMP” I can’t work out which table to use! Building footprint is approx 12x10m if that helps to calculate the roof size (and thus run-off)? I should add the site was previously a dilapidated residential garage so we aren't increasing runoff - however it seems this is irrelevant - we cannot exceed 2l/s regardless. Here is the main part of the land registry location plan. If anyone can help (short of the firms charging £1600+vat) I’m more than willing to make a donation to the forum (though also willing to pay a reasonable amount if someone on here can help professionally) and would be grateful to PM any further info.

Been told by our planning officer that we have to "demonstrate how existing surface water drainage rates will be reduced to existing greenfield runoff rates or 2l/s, whichever is greater". The greenfield runoff rate seems to be below 2l/s even for 1in200 year event: Trying to understand if attenuation is required here. It would seem the development would cover between 50%-70% of the plot - depending if we use permeable paving. Is attenuation always required? I know a firm that has been mentioned on here will calculate how much attenuation is required FOC when buying their products - but they might be adverse to admitting if it were not required at all. Would be really grateful if anyone can advise.

I saw it here (another thread). The website linked to is https://www.unitherm.co.uk/pages/mcs-design Downside is the £1.5k only gets you the grant, no physical installation work. Though as you say, it seems majority if not all MCS installers are whacking on significantly more than £1.5k with grant funded installations.

Thanks @Bramco. Might look into Cool Energy then as the £7.5k grant is quite a disincentive to self-install if it cannot be claimed (with a self-install). My understanding is the grant is only available with an MCS approved install. Seems there is a firm that will do the MCS paperwork for a self-install for about £1.5k so that could be an alternative option.

Did you install the Cool Energy heat pump yourself? Is the 'couple hundred' you refer to, the materials required to install or the additional cost over the grant after covering professional installation? Trying to make a decision on this myself as with a trade account a Valliant is actually cheaper than a Cool Energy R290 unit - but if I've understood your post correctly, Cool Energy were able to claim the grant (did they arrange installation)?

Doesn't the firestop have to go all the way around? Though it seems that any cavity closer could be surrounded by 38mm timber to make it compliant.

Seems the Kingspan guidance is to fit windows essentially in the cavity in a TEK SIPS build. I've seen others on here suggest this too. For example a thread from 2022 says to fit them "halfway in the panel or on the outer edge of the panel". However it would seem this position is worse from a thermal point of view fitting it entirely inside the SIPS reveal? Is it just from a practical point of view that the windows need to abut the brickwork (or cladding) for a weather safe fit that leads to this in-between position? Another question is in regard to insulated cavity closers. Project manager says timber builds don't typically have cavity closers but fire-stops. The product shown in the Kingspan suggested detail below is not fire rated so wouldn't likely be suitable anyway, though similar less insulating fire rated products do seem to be available.

That's interesting - I'll check with the supplier, but my understanding is that they do manufacture the frames in-house using the profiles. So hopefully they can mix-and-match glass like you say.

Thanks for that - so it would seem there are indeed budget uPVC options available that can indeed match the performance of the far more expensive alu-clad products. At least 'on paper'.