lizzieuk1

So, PaulHeat have calculated as below, I think that means we need a unit(s) to do 438 m3/hr max. They suggest either 2 x zehender 450 or 1 x 600 - I'm not sure why if we need 438m3/hr, we can't have 1 x 450, is it to do with the l/s do you think? Anyway, if we need one or other of those options any opinions on 1 or 2 units? (We may go for the Ventaxia units but undecided, same Q re 1 or 2 units though) Initially I thought is it easier to have 2 units so that we have less logistical issues ducting from 2nd floor plant room to gf (we could put the 2nd unit in the utility room on the gf) but, I'm not sure if that's reason enough to buy 2 units! Any thoughts?

No need to panic! They are definitely going to do room by room calcs, all mcs certified. We're just at the initial design phase so once everything is firmed up on that will proceed to final design with full calcs. I was reading about your program and it looks really good - once I get time I will have a go with it for our design and give any feedback I can.

It's a valid point Nick, I suppose there could be some short term variation room by room and, perhaps more so floor by floor with insulation between floors having an effect, but I guess overall the temps will balance fairly quickly with flow round the house via the mvhr anyway.

Thanks Simon. I've not had any contact with Panasonic, I've left that up to the person who doing the install - he seems to be struggling with a fan coil system design, initially it was a spec for the ducting but now seems the more complex issue of whole design for pressure drops etc if we went for a multi room fancoil. I think we've almost ditched that option now as seems far too complex to sort out so, looking to do individual fcu in each room instead, obv more pipework needed but I guess it's swings and roundabouts compared to the multiroom option.

This sounds sensible, thanks JohnMo. The ashp will be set up for wc and we're going with a single zone for ufh in the gf. Not sure about the ff/sf though, the Aquarea allows 2 zones so we could keep the bedrooms a little cooler I guess, not sure it's needed though 🤷‍♀️

I've only done the whole house calcs via Jeremy's spreadsheet. I will set to work with a room by room calc and see how the rooms compare. Our part O was fine so no issues with overheating but, we'd like the option to cool anyway.

So, I'm going round in circles trying to sort this out. It is seriously stressing my nerves! Plan was to have an ashp with ufh on gf then use fancoils on ff&sf so we can have top up heating & some Cooling if needed in warm summers. Sounds simple but, No! I'm still not sure we will need any extra heating upstairs (ICF build, aiming for very good air tightness etc etc) but too unsure to not put any in and would also like the option to cool if needed. The installer we've been working with is very comfortable with ashp and ufh, he is keen on the Panasonic aquarea as is a registered Panasonic supplier and thinks they will fit our scenario well. Fair enough, I know they are more expensive than some but also reputed to be a good ashp and, Panasonic do make multi room fancoils which would go well with our design for ff&sf. However, he seems to be struggling to get a design solution for the fancoil units. I'm not sure why! His latest email has said that, having spoken to Oceanair (i contacted them to see if they could help and pointed him to them to see if he could get a design sorted as Panasonic werent being very helpful!) the response he's had is that they're not ideal for heat/cool as require a much larger power input for cooling, I've not got the detail on why yet but will once I speak to him. Surely that's what fancoils do well?? Or, maybe its the ashp supply to them for cooling that's the issue as we have a heat loss of around 4kw for heating requirement 🤔 Can anyone please help me find someone who can offer a solution? I'm going round in circles here! None of the options are cheap but if we're spending large amounts we want a really good system that does everything we need! Maybe we should get a separate A2A system for ff&sf to run aircon but seems nuts if we can use the ashp. 🤯😩

I was thinking the same Nick re the use of AB before boarding, am assuming also better to do 1st fix before to allow the AB to seal everything up? Think we will also have to use something like parge or poss some membrane behind our pole plates as they will obv go in before and not sure the AB will penetrate behind those once they're in. We were graduating towards float and set plaster as think it would go well with the woodcrete but, a. I'm not sure we will easily find a plasterer who's skilled in that, as d&d has been the preferred for so long now, and b. feels a bit like overkill using that and the AB. Still so many choices to make.....

We are certainly going to do that Nick. I haven’t forgotten our previous exchange on here about it 👍 I wasn't sure if we should parge coat as well but, from your comment, seems unnecessary?

No panic we're running at 1:60

Update on this : I spoke to the raft supplier today (had a few other bits to discuss) and they confirmed there is no issue with point loading so, all fine to run foul drains wherever we need. Onwards & upwards!

Can I add, I really appreciate comments & advice here. It's all taken on board and I'm always learning. I realise many of you are specialists in certain areas and some have vastly more experience of new build. However, this isn't our 'first rodeo' we've built 2 before so do have reasonable understanding but, it's our first one using an insulated raft & icf so plenty to learn & understand on that level. Apologies if my questions may come across a bit 'novice like' I'm a bit of a belt and braces person so, when I ask its not necessarily that I've no idea, (though sometimes it is the case!) it's just my way of cross checking my thinking/understanding!

Yes, we're installing a new STP so not too fixed with invert level. My original Q was really whether we had any issues with starting depth under the raft - whether there was a minimum we needed to adhere to. From the answers of others (including yourself Nick - many thanks) it looks like there's no set minimum.

Guys I think we've gone off topic here. We have had the whole build specified by a SE, raft is by AFT so fully designed out. And the rest has been specified by a SE with experience in our construction choice. We're not going it alone in that respect! My initial Q was only regards bringing the (2) drain runs out from under the raft.

It's an AFT raft so all designed by their SE, our build is in Ecobrix, again all designed by an SE. We've only got 2 drain runs out, one is app.9m straight out the other app.4m straight out. Neither are under an internal load bearing wall both obv exit under the external walls.

We're putting in a new treatment plant so have flexibility for the inverter level.

I hear you Gus but I'm not sure a SE is necessary here, shouldn't really be any point loads in an insulated raft - obv the external walls & load bearing internal walls will have the most loading but by design that should be spread throughout the raft.

Yes, the architect has specified ICs on the regs drawings but he has one that is right in our paving under the portico which isn't ideal aesthetically. I cant understand why your bc wouldn't allow greater than 8m, isn't it far greater in part H, 22m or 45m?

'Groundworkers' are me and OH! We also have a 'digger man' with plenty of experience but obv need to set out the runs etc for him. We've not got a sand blinding just peagravel for the insulation to sit on so may just fill with that above the pipe runs in the slab area. Good thinking re the IC positioning, as you say far better to get them centrally in the paving. Yes, have considered services, ours is actually quite straightforward, both water & electric coming into the utility just inside the outside wall and will be perpendicular to the drains so a simple cross over. I need to calculate the falls so I know what levels the drains are at to accommodate the water/electric incoming but nothing too complex.

Have you topped the pipe with pea grit then mot on top? Thinking in the 150 layer there's not much room for both!

Thanks 👍 sounds like we are OK to be in or just below the MOT then.

Thankyou 😊 do you know if there's a reason the Chambers needed to be so far out? Or was it just 'on the way' to the mains connection?

Many thanks Nick, that's really helpful. 👍

We're prepping to dig foundation and drainage out and wondering about depths for the (approx 5m) run that is going to be under the insulated raft and how low to set the foot for the main stack which exits straight out. Any idea what that depth needs to be? Is it 600mm below the mot 1? Also, how far out from the edge of the raft do the drains need to run - I'm reading 1m min is the part H requirement if pipe is below foundation but, as our raft is only 450mm into the ground makes interpreting the regs a bit tricky as, pretty much any drain will be below the raft level. I'm not sure if it's interpreted the same as obv the weight is spread over the raft rather than down through strip foundations so, does this make a difference? Or, do I just ask BC?!

Have you also asked the water board? They may have minimum distance requirements along with max build over distances (I'd try to avoid that though!) We are having an insulated raft and have a min of 600mm hardcore beyond the footprint (with integral drainage) all round if that helps.