Can you help me finalise my UFH heating zones and manifold positions?

[Adsibob]

Screed is being poured in 4 days' time and I need to finalise my UFH heating zones and manifold position for my ground floor. Originally we were going to have three zones, as shown in the three different colours on this drawing, with:

• Zone 1 being the kitchen area/dining area/utility room
• Zone 2 being the lounge area where we have our wood burning stove and also the hallway and guest WC area
• Zone 3 being the front room (which apart from the WC and the utility room is the only area of the ground floor which is not open plan).

But because there are two steps in between the hallway and the lounge area, my builder's plumber prefer to have two manifolds, one for the hallway/WC area and the front room and one for the lounge and the kitchen/dining/utility. I know a couple of people here have said that one manifold would be enough for the whole of the ground floor, even though it is split level, but there are other advantages of having a separate manifold for the front room and hallway/WC, in that those areas have a much thicker floor finish (14mm engineered wood in front room and 20mm terrazzo in hallway and WC) whereas the rest of the floor is just 3.5mm of microcement.
So my question is do i have a fourth underfloor heating zone just for the WC and hallway, or do I keep it on the same zone as the front room? If I had it separate it would create four zones, which for just one floor seems excessive, but I also don't want to combine the kitchen dining area (where there is a lot of solar gain) with the lounge area where there is going to be a wood burning stove. When we don't have the stove on we'll want UFH on, but when we do have the stove on we might to turn the UFH off there, but not in the kitchen/dining area.

 

Other question is where to put the second manifold for what is currently shown as Zone 01 and Zone 02. I was going to put it in the utility room, but not actually a huge deal of space for it. Didn't realise they were 750mm wide.  

[joth]

Have you had a loop design done? I requested 4 zones but the design came back with 9 loops, to my surprise, so spending time debating 3 vs 4 zones maybe moot if they'll split it to more than 4 loops anyway.

Also, it took us several weeks to iterate and finalize design, then more time to get parts, and several days to install the loops, so I have to say if you're pouring screed this week you need to get a proper wriggle on. Good luck!

Edited October 2, 2021 by joth

[Adsibob]

1 minute ago, joth said:

Have you had a loop design done? I requested 4 zones but the design came back with 9 loops, to my surprise, so spending time debating 3 vs 4 zones maybe moot if they'll split it to more than 4 loops anyway.

Also, it took us several weeks to iterate and finalize design, then more time to get parts, and several days to install the loops, so I have to say if you're pouring screed this week you need to get a proper wriggle on. Good luck!

The builder/plumber are taking care of the loops layout. I hadn't really considered designing that. Not sure I understand how differently designed loops would affect performance. What are the pitfalls we should be avoiding?

[joth]

4 minutes ago, Adsibob said:

The builder/plumber are taking care of the loops layout. I hadn't really considered designing that. Not sure I understand how differently designed loops would affect performance. What are the pitfalls we should be avoiding?

We had Wunda do all the design and supply, so I personally have no idea! There's loads of discussion on this forum about it, I've seen links to software packages that will do it, but it was one area I was happy to keep my nose right out of. 

Hopefully someone else will chime in with more useful guidance.

 

Edited October 2, 2021 by joth

[Adsibob]

1 minute ago, joth said:

We had Wunda do all the design and supply, so I personally have no idea! There's loads of discussion on this forum about it, I've seen links to software packages that will do it, but it was one area I was happy to keep my nose right out of. 

Hopefully someone else will chime in with more useful guidance.

 

ditto, hence i thought i would leave it to the builder/plumber to sort.

[joth]

Main thing you do need to decide is exactly where you do and don't want the UFH to go. 

For example, we decided to leave a cold spot where the cat litter tray goes, and damn I'm grateful will did every time the nightfurry drops a stink bomb. 

Edited October 2, 2021 by joth

[joth]

Going back to your original question, why do you think 3 zones is okay but 4 excessive? Maybe that's the detail I'm missing.

 

[Adsibob]

1 hour ago, joth said:

Going back to your original question, why do you think 3 zones is okay but 4 excessive? Maybe that's the detail I'm missing.

 

I guess because another plumber (not the one we are using) told me that UFH works best if you leave it on all the time at a low temp, rather than have it multi zoned. Something to do with response times being much slower than radiators and so if you are too hot, switching the UFH off will take at least an hour, possibly longer before you cool down. 

[joth]

1 hour ago, Adsibob said:

I guess because another plumber (not the one we are using) told me that UFH works best if you leave it on all the time at a low temp, rather than have it multi zoned. Something to do with response times being much slower than radiators and so if you are too hot, switching the UFH off will take at least an hour, possibly longer before you cool down. 

 

Yes, but keep in mind you can run many zone system as one big zone, but the reverse is not true. You only get one shot at laying out the pipes so you may as well split the loops up into as many zones as you (sensibly) think you could ever need, just in case you do ever need the control.

I have 9 loops arranged in 5 logical zones (despite me originally only asking for 4 zones..) however I don't have any actuators on the manifold and just use it as one big zone which has worked great so far. But If I do want more control (e.g. if we convert the snug to a bedroom for elderly relative that wants that room HOT) it's just a case of adding actuators and some wiring. Much easier than pulling up flooring, screed, and moving the loops!

 

[Adsibob]

All helpful stuff, thanks @joth.

I think the only areas we are unsure about is:

1. whether to put it under the kitchen island and
2. how far, if at all, to go under the kitchen units which are along the external walls.

As for the kitchen island, I know there's one school of thought which is to not heat under this on the basis that you won't really feel the benefit and it might not do the kitchen units all that good. But I've also read on this site that some people say that with a screed based UFH system, if one doesn't heat under the kitchen units, the screed alongside that area will loss heat to the cold bit of screed under the island. Is that right? Surely if heat moves mostly upwards, and with 100mm of foil backed PIR underneath the screed, this won't be a massive issue?

I know 150mm or even 200mm of PIR would have been better, but there was no way of fitting this as this is a renovation not a new build. Our Island base is 2600mm long by 700mm wide, although 600 by 600 of that is a wine fridge where obviously I won't run the loops. 

 

As for the space under the units that run along the walls, 90% of those external walls are brand new built to comply with current building regs for extensions, so we have breeze blocks, then cavity insulation, then facing bricks. Not sure what exact U value is, but you get the idea. I'm tempted to let the heating loop run under these but only to a depth of 15cm, which is about a quarter of the total depth available. Does this sound sensible, or would you run it a bit more depth than that?

Edited October 3, 2021 by Adsibob

[Rob99]

The loop design is important and you shouldn’t leave it completely up to your builder/plumber. In my experience they will do a good job of calculating heat requirements, loop lengths etc but can easily overlook obvious things. We had our loop design done by Wunda and, although it was suitable at first glance, if we had followed it completely we’d have ended up with some horrendous cold spots. I adapted the loop design and added in a few bits and it all worked out fine. You only have one chance to get the UFH right.

 

On kitchen islands, don’t heat underneath. Yes, you’ll get some heat transfer through the screed underneath but it will be minimal. Same for under other kitchen units, I wouldn’t run pipes behind the plinths as you’re just heating dead space (and whatever is in your cupboards!) nor any appliance spaces either.

 

On the manifold question, for your layout one should be adequate. I would only think you might need two if you are likely to run them at different temperatures to suit the different floor finishes and honestly I can’t see why you’d want to do that with such an open layout.

[Olf]

12 hours ago, Adsibob said:

Surely if heat moves mostly upwards

It is hot air that due to lower density moves upwards, carrying heat (convection) .

In case of screed, the energy will travel radially from the pipe through the volume, identically in each direction (conduction). 

The island itself will act as as insulator, so if you were to put UFH underneath, it will not be able to pass a lot of the heat out, and so it gives little benefit. By the same measure, any losses from the loops around not heated island will be negligible, as the island itself will insulate. 

Considering you're likely have collisions with other services going to the island, not having UFH pipes only helps