UFH

[Taff]

Anyone clever enough to explain! 

 

Just going through layout of out of the floors, before I go back to designer and sounding stupid, I thought I could ask a stupid question on here without  feeling embarrassed. Why are there multiple loops in some of the rooms? There are thermostats on each area so for instance, if I want the longe to be 20 degrees and the landing 18 degrees how the hell does that work, if half the loop is in another room? Full of stupid questions me 

[ProDave]

Multiple loops per room is normal for large rooms. the control centre is organised so that room thermostat opens 2 or 3 actuators together.

 

I don't see loops bridging more than one room, other than pipes passing through on their way.  e.g your downstairs hall by the stairs is never going to be cold.

 

From experience, you will NOT need an UFH loop on the landing. Delete that one.

[Taff]

Ah that explains it I thought as the loops were the same colour they belonged to a single connection, told you I was stupid! Will it save money getting rid of the landing as I’m told that the piping is pennies, or are you thinking workload of the pump?

[ProDave]

It will possibly enable a smaller cheaper manifold, save a few ££ in pipe and labour fitting the unneeded landing loop.

 

We had that in our previous house and I don't believe the landing thermostat ever turned on.

[LA3222]

Pipe lengths is probably a factor too - think they go up to 120m so will need more than one to do a room.

 

All my pipes are 80&100m.

[Taff]

Think I was confused I thought they were different loops but @ProDave has better eyesight than me ? 

[PeterW]

There are far too many thermostats in that design ..! Only works when all doors are closed and no air flow between rooms. 
 

I would reduce down to having one upstairs and one downstairs with the en-suite / bathrooms potentially on their own circuits just so you can run them for longer or slightly warmer. 

[Oz07]

I had that problem with suppliers wanting to design a system with too many different zones. Your not going to get massive temp differences in a well insulated house

[Taff]

And I thought they were the professionals in their line of work,  guessing they are just trying to sell me stuff that is not needed! Grrrrrrrrr. What ever happened to helpful people (apart from folk on this site that is). Remember when you could speak to a good old plumber and they would put a lot of effort in to helping you, to get the right product at the right costs, then the customer promoting their business. 

[Taff]

10 hours ago, PeterW said:

There are far too many thermostats in that design ..! Only works when all doors are closed and no air flow between rooms. 
 

I would reduce down to having one upstairs and one downstairs with the en-suite / bathrooms potentially on their own circuits just so you can run them for longer or slightly warmer. 

Think I’ll go back to the designer and tell him, the house hopefully will be well insulated, on reflection these seem pointless as you both point out ?

[PeterW]

@Taff What is supplying the heat to the system ..??? Just seen it says supply temp of 45c, and that means gas or oil. 
 

I would seriously question if they have used a standard set of details or your build spec - that looks like a big heat loss to counter and 45c flow in a timber floor (??) upstairs is going to be hot. 

[Jeremy Harris]

FWIW, we have all our UFH as a single zone, as we don't like keeping doors closed all the time.  Flow temperature on our system is typically about 26°C to 28°C.  UFH heat output averages about 6 W/m² of heated floor area, with a maximum in extremely cold weather of about 22 W/m², but that's for a well-insulated house that only needs a small amount of heating.

 

Changing the flow temperature increases the heat output per m², by raising the floor surface temperature.  For a room temperature of 21°C the approximate heat output per m² of heated floor area for a range of floor surface temperatures would be:

 

30°C floor surface temperature ~100 W/m²

29°C floor surface temperature ~87.9 W/m²

28°C floor surface temperature ~75.9 W/m²

27°C floor surface temperature ~64 W/m²

26°C floor surface temperature ~52.4 W/m²

25°C floor surface temperature ~41 W/m²

24°C floor surface temperature ~29.9 W/m²

23°C floor surface temperature ~19.1 W/m²

22°C floor surface temperature ~8.9 W/m²

 

You can work out how much heat each room can get from the above, just use the heated floor area for each room and multiply it by the floor surface temperature.  It's unlikely that you would need more than about 50 W/m² even in really cold weather, and most probably you may not need as much as this for a new build.

[Taff]

Supply will be ASHP, I’m beginning to think do we really need upstairs UFH, I’m going to have to go back through their design with a fine tooth comb I think.

[Jeremy Harris]

I'm very glad we didn't install upstairs UFH.  We find we don't need heating in the bedrooms at all, but then we also don't like the bedroom to be too warm.  We try and keep the bedroom below 20°C, something that needs a bit of cooling from time to time (like yesterday, for example).

[ProDave]

8 minutes ago, Taff said:

Supply will be ASHP, I’m beginning to think do we really need upstairs UFH, I’m going to have to go back through their design with a fine tooth comb I think.

Many of us with passive house or near passive house levels of insulation and air tightness find no upstairs heating is needed, even here in the Highlands.  We have UFH in the bathroom and en-suite more so you are not walking in bare feet on "cold tiles"

 

What sort of U values are you having in the walls, floor and roof, and what does your SAP assesment say about the heating input required?

 

Like many others I fitted electrical points in each bedroom to provide for a small panel heater if I had "got it wrong" and we found heating was needed.  Those are still sitting there, unused, with a blank plate on them.

[Taff]

We are hoping for 0.14 walls and roof, the downstairs floor is being talked about as we may have to go pile rather than raft. The windows/door etc 1.1 I believe without checking. So going on all of your experiences I’m wasting good money which now by the sounds of it will be needed for piles.

[Taff]

However, I’ve just thought we are putting our bedroom downstairs, and the sitting room will be upstairs so I think if I can remember that may have been part of the decision to have UFH upstairs. Gonna get all my stuff out later and go through it all again, a nice Sunday afternoon read

[Jeremy Harris]

3 minutes ago, Taff said:

However, I’ve just thought we are putting our bedroom downstairs, and the sitting room will be upstairs so I think if I can remember that may have been part of the decision to have UFH upstairs. Gonna get all my stuff out later and go through it all again, a nice Sunday afternoon read

 

 

If we'd had the option to build an "upside down house" then I think I'd have opted for it, and then only put heating upstairs.  A friend had an "upside down house" years ago, and I really liked the layout.  In his case it worked well because the house was built in to a bank, that sloped away below the level of the road, so the front door opened in to what was really the first floor.  This also meant that the bedrooms downstairs didn't have a view out to the road, just down the garden.

[ProDave]

Would heating only upstairs work in an upside down house?

 

I am convinced the upstairs gets enough heat by convection up the stairwell and leakage through the ceiling / floor void.  So if only upstairs had heating, how would very much heat get to the downstairs rooms?

 

I would love to hear from someone that has an upside down house to let us know how it works if you turn the downstairs heating off completely.

[Jeremy Harris]

4 minutes ago, ProDave said:

Would heating only upstairs work in an upside down house?

 

I am convinced the upstairs gets enough heat by convection up the stairwell and leakage through the ceiling / floor void.  So if only upstairs had heating, how would very much heat get to the downstairs rooms?

 

I would love to hear from someone that has an upside down house to let us know how it works if you turn the downstairs heating off completely.

 

 

Not sure, but @Bitpipe has a basement with no heating that seems to stay at a pleasant temperature.

[PeterW]

@Taff you will struggle to get 45c from an ASHP - 35c is your target temperature and they should factor that into the design. 
 

What is the ground floor / first floor construction ..?

[Taff]

We went for this layout as we were future proofing it, when we cannot get up the stairs we will have our bedroom etc on ground level

[Taff]

Without having the documents to hand I cannot remember what the targets re temperature was, I’ll get them out though to go through them again. Not quite a passive slab was the option however, there seems to be a mix of clay and sand like elements following excavation, this week we will be going back through the methods in the floor construction. Once the founds are sorted it will be a sips build.