ICF all plumbing in passive slab

[ultramods]

Hi,

I have been investigating building a house with ICF and now looking at how to run the pipes for the plumbing. The house will be all one one level around 250 sqm with 3-4 bathrooms and separate utility room. Also sink in kitchen will be on an island. I am planning on putting in UFH pipes (for potentially cooling the house).

I know that it's normal for the waste and UFH pipes to be in the slab, is it also ok to put the hot and cold water pipes in the slab? I ask this as I think it would be easier to do it this way rather than cut chases into the ICF internal foam.

Thanks in advance for any help

[Jeremy Harris]

Usually the soil pipe(s) will run below the slab, rather than through it, because of the need to put a slow swept (rest) bend between the vertical and sloping run, and these are pretty deep.

If you're using plastic plumbing, to avoid joints in inaccessible locations, then you could look at running pipes in ducts, with slow bends at the ends, or you could put the pipes in the slab, although there is a potential problem in doing either of these, as the slab will be at room temperature, so warming the cold water supply and in turn drawing cold water will take heat out of the slab locally.  The same applies in reverse for the hot pipes. 

Concrete conducts heat reasonably well, so a directly encased hot or cold pipe is going to either take heat from the slab or conduct heat into it, and could waste a bit of energy.   You can get pre-insulated plastic pipe that is intended to be buried (I'm not sure if it's rated for potable water - it would need a check, as it's intended for things like ASHP underground flow and return pipes) and that could be a solution.  In effect it's pipe within a duct with insulation around the inner pipe.

Our current house (not the new one we've nearly finished) has all the hot water piping for the radiators in the floor slab, running right around the edge.  I can say it wastes a lot of heat into the slab, as whenever it snows the snow melts for around a foot away from the house walls, which I think is largely heat loss from the heating pipework.  Mind you, it has no floor insulation, so is far from being energy efficient, anyway. 

[ultramods]

Thanks Jeremy.

Could the cold water pipes run below the slab, to keep the water cold? Also is there any reason that it would need to be cold, rather than room temp? I know for brushing teeth in the bathrooms i want cold. But apart from that I don't know when I need cold water, apart from the kitchen. In the kitchen we would need to put the cold water pipe in the floor anyway as the sink will be on an island. We are planning one of the instant hot water taps (apart from island there will be no other worktops for a kettle), which I think also make the water cold.

When you say ducting, do you mean running the pipes in the ceiling (will be using posi joists)? 

[Jeremy Harris]

You could run the cold runs under the insulation, that would be no different to the way our water pipe runs into the house (it runs along under the whole length of the house).  I don't think there's any real risk in keeping cold water at room temperature as that happens in all houses anyway - the water in any pipe, insulated or not will eventually end up the same temperature as its surroundings.  The only issue with putting pipes in concrete is that concrete is a very much better conductor of heat than air or insulation, so the pipes will warm/cool very much more quickly.

I meant ducting in or under the slab.  You can pull plastic water pipe through flexible ducting easily, if there are slow bends at the ends, we have a few 25mm MDPE runs in 100mm ducts around outside.  I ran a duct in our slab to bring a fat cable to the island, it could easily have been a bigger duct and had a couple of pipes in it instead (you're not supposed to run water pipes and cable in the same duct though).

You'd need to check the regs re: pipe insulation, it may well be that you have to run pre-insulated pipe anyway.

[ultramods]

Thanks.

[Stones]

We are running the main runs of our pipework and wiring in the roof space, dropping down into a service void created using battens onto ICF exterior walls, or through internal partitions as appropriate.  My contractor certainly believes battening out to create a service void is far quicker than chasing out the ICF block.  We also have a kitchen island, and as suggested above, we have run two ducts in the under slab insulation to get electricity and water to the island.  The water duct is a length of drainage pipe so should be big enough to take both hot and cold water pipes that have been insulated with armaflex or similar.  You can see the two ducts sitting in the underslab insulation ducts in the picture below.

[ultramods]

Thanks Jason. Do you have any photos of the service voids?

Edited July 7, 2016 by ultramods

[Stones]

No, not at that stage yet, however it isn't especially complicated.  Battens will be fixed through the polystyrene insulation into the plastic ties that form the core of the ICF block.  My contractor is going to be using 25mm tile battens.

 

 

[ultramods]

ah OK, ta.

[PeterW]

I was talking to one of the suppliers at a show and they said they had a modified gun type soldering iron that they used to cut simple grooves into the ICF blocks up to about 25mm deep. 

Surely that makes more sense than battening out ..? 

[Stones]

Could do, although I suppose it comes down to preference.  Both will take time to do.  I suppose the main advantage of battens is there is then something easy to put fixings into, and makes screwing on plasterboard easier?

[PeterW]

I thought the PB was screwed to the same plastic bits as the battens would be..?? That seemed to be the way with Nudura (??) or whatever it was !

Who's system is it btw..?

[Stones]

Our build uses the Amvic system.  Don't see why you couldn't screw direct into the plastic ties (albeit longer PB screws needed) if you wanted.  I'm guessing my contractor has stuck with battens and a service void as it is easier / more cost effective (as he believes strongly in both!) from his perspective.