Before I pour my slab what needs to be done to set up my UFH to ensure I end up with 'an 'Active Slab'?

[oranjeboom]

Not sure whether 'active slab' is being used in the correct sense here - what I want to do essentially is to redistribute heat from my solar gain areas in the south of my house to the northern cooler end with minimal sun.

 

So all my UFH pipework is in and I'm hoping to get hold of a contractor to pour the slab in the next few weeks (If I can get hold of someone I have faith in!). Prior to the slab being poured, what do I need to do before? Obviously I need to pressure test all of the pipework and ensure there is no major drop, leaks etc. Anything else I need to do in the actual floor area before it gets covered?

 

I've read with interest Jeremy's Active slab option and also found TerryE's blog entry of use:

 

The figures are a bit over my head at this stage, but all I want to do right now is to have all gadgets and gizmo's in place before the concrete sets!

 

I have a 12 port manifold serving the entire ground floor which has a makeup of:

 

·         Concrete (to be done!)

·         UFH tied to mesh (150mm centres)

·         Elevated mesh

·         DPM/Radon barrier (under top layer of insulation)

·         circa 300mm EPS insulation

·         Compacted Hardcore

 

At this stage I will be fitting a gas boiler (ASHP may be an option in future years). I have a large southern glass facade which is fairly well shaded by the trees in summer, but in winter with less foliage and a lower sun, the slab in the lounge/diner and kitchen should pick up some decent solar gain that I am hoping to re-distribute to colder areas of the house. I will have EWI installed also in addition to the PVs and planned MHVR).

 

1) Where do I place the floor sensors? I was thinking to have one in the lounge/diner in a spot where I know the sun's going to hit or somewhere not directly in the sun and away from a pipe? I'll also place one in one of the bedrooms that will never see any sun (along Jeremy's method: "deliberately placed around 150mm to 200mm away from the nearest UFH pipe on the "cold" side of the house (the bit that never sees solar gain)." Is it worth placing a couple of spare sensors in the slab in case of malfunctions in coming years?

 

2) What do I need to do on the manifold side with regards to plumbing. Obviously I can do this after the concrete is poured but if I can save from having to do major changes later on?

 

 

TIA

 

Back to a bit more cable tying....

[Jeremy Harris]

In the light of experience, I'd say that floor sensors are a "nice to have" rather than in any way important.  Mine's only used for data logging now, and frankly I don't bother looking at the floor temperature at all most of the time.

 

All that's really needed is a way to be able to run the UFH pump when the heating/cooling system isn't running, to allow the redistribution of heat around the slab a bit faster than just letting it stabilise over a longer time period.  This depends very much on how much solar gain the sunny parts of the slab get.  Ours used to get a lot, but once we fitted the solar reflective film on the outside of the glazed gable that dropped a great deal, so there is far less of a requirement to redistribute heat around than there used to be.

[MikeSharp01]

Eh up Erwin. Looks great, remember if you need a hand that I am happy to return the favour you did us. Quick question, have you elevated the mesh or is that to be done, looks like it is resting on the insulation in the Pics.

 

[oranjeboom]

Thanks Jeremy. Seeing the floor sensor's don't cost a lot IIRC I'll put in a few...just in case I really need them in future.

 

14 hours ago, MikeSharp01 said:

Eh up Erwin. Looks great, remember if you need a hand that I am happy to return the favour you did us. Quick question, have you elevated the mesh or is that to be done, looks like it is resting on the insulation in the Pics.

 

Thanks Mike. I'll see how I go with my contractor hunt. Guy who I had lined up last year is now not responding to messages so I guess that's a 'not interested anymore'.

 

Mesh not elevated yet and still needs extra ties on most loops. I thought it was easiest to lay the pipework with the mesh laying on the floor rather than tripping up every other step, falling through the mesh etc. Just need to do a final measure up to see how high the pipework's going to end up within the 100mm of insulation. Think I decided on 40mm from surface, so with 16mm pipe and 16mm of (A142mesh) gives me approx 30mm to elevate beneath. So looking to get this type of spacer (http://www.lemon-gs.co.uk/shop/reinforcement-accessories/plastic-spacers/plate-spacers.html) as that will minimise risk of puncturing DPM in those areas that I have it. Expensive buggers for a bit of plastic! Hopefully I won't need too many per sqm!

 

Also need to create some kind of shower tray former for the bathroom as I want a slimline/low profile shower tray. A bit like the way you'd done it Mike!

[MikeSharp01]

1 hour ago, oranjeboom said:

Also need to create some kind of shower tray former for the bathroom as I want a slimline/low profile shower tray. A bit like the way you'd done it Mike!

Yes mine worked OK but there were some voids under it where the concrete did not get even though I had all those holes, suspect I lost concentration on it as well, and, although I have not got any cracking in the slab, I think I should have surrounded it with a ring, welded, of rebar as the slab is thinner there and so any stress will have a better chance of cracking the slab and I don't want them to get out.

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Edited August 19, 2017 by MikeSharp01
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