MoDo

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'.

For a SIPS building with brick skin. Walls/roof aiming for 0.12 u-value - so fairly decent thermal performance and MVHR. Trying to decide between uPVC and alu-clad. We are fairly desperate to reduce cost (thanks to budget overruns at the foundation stage) but for such an integral part of the building not sure if this is a compromise worth making. A trusted local window firm can produce (and fit) the Eurocell Modus which claims u-values as low as 0.7. I asked Eurocell whether this refers to the glass or the glass/frame combo but only received the attached as a reply. I admit to being unable to determine from the document whether this profile would be a match for the 0.8 alu-clad products at more than double the cost. If someone interpret the attached - I'd be very grateful. M75-207 Calculation Summary.pdf

One more question please: Filling out the TP1 - I found a covenant on here that fits with our situation perfectly - ie to protect my parents retained house and garden going forwards after we split off half. However I'm not sure if I've entered it in the correct box or in the correct format. Any one able to advise? EDIT: Just to clarify - the covenant I'm referring to, is the one I've entered into 'Restrictive covenants by the transferor' - but need advice if this is the correct place for it and whether I need anything entered in addition in 'Definitions'?