Why Zoning of heating is Bad Practice

[Dave Jones]

all the math....

 

 

 

 

 

[PeterW]

Someone want to tell UK Gov and BRE.. and most of the other researchers that input into the updates to Part L when they changed it to make zoning mandatory for the saving of fuel..??

 

 

[Dave Jones]

in reality, for the majority of buildings with UFH there will be 'zoned' runs of piping as a single snake would be too long. Be interesting to see BCO position on the fact that these are all treated as a single zone on the manifold.

 

 

[JohnMo]

51 minutes ago, Dave Jones said:

UFH there will be 'zoned' runs of piping as a single snake would be too long.

Or they would be termed as loops not zones.  The zone would be how a single or group of loops are controlled.

 

Zoning

Per regs

Heating zone - A conditioned area of a building which is on a single floor and has the same thermal characteristics and temperature control requirements throughout.

 

There are plenty of get out clauses within the regs on how you zone or don't. Even not installing room thermostats is allowed.

 

High thermal mass (so lots of UFH systems), heat demand below 10W/m2, these don't need thermostats.  Floor area below 150m2 can a single zone. But you basically need a zone per floor, which makes sense.  Your room thermostats if needed don't have to control temp they can be limit stops, nothing is explicitly stated.

Edited March 14, 2023 by JohnMo
Lots of details changed

[crispy_wafer]

Thanks for posting that, quite insightful for a newbie like me wants to know a bit more without overloading the grey cells.

 

I dont have an ASHP installed yet.  But have the UFH in.  So when the ASHP is installed, I'm getting the message that I should chuck out the not yet installed loop actuators, set the loops to the design flow rates.  Just have a single thermostat to monitor air temp to trigger the ASHP?  Anything that causes on & off's in quick succession is bad? 

 

I've got a bit to learn on this subject but we all have to start somewhere... 

 

[Adsibob]

We have about 12 zones in our UFH heating system and I find the zones to be very useful. The front of the house is East facing whereas the rear is West facing, so quite different solar gain patterns. We also have quite variable usage, plus one zone has a wood burning stove in it, so not sure how I'd survive with just one zone per floor.

[Iceverge]

1 hour ago, Adsibob said:

We have about 12 zones in our UFH heating system and I find the zones to be very useful. The front of the house is East facing whereas the rear is West facing, so quite different solar gain patterns. We also have quite variable usage, plus one zone has a wood burning stove in it, so not sure how I'd survive with just one zone per floor.

 

I think the idea that if you design it well and insulate it sufficiently then you can run it at very low flow temps. 

 

That means that if the floor is at 25⁰ and the room is already at 25⁰ due to sunlight/woodburner whatever then the water passes through the UFH in that area without actually emitting any energy. 

 

It'll give proportionately more energy to colder rooms than warmer ones. Hence no zones. 

 

This won't work with high temp rads at 70⁰ for example as they'll still emit heat as the room will always be colder. 

 

 

 

[joth]

12 minutes ago, Iceverge said:

That means that if the floor is at 25⁰ and the room is already at 25⁰ due to sunlight/woodburner whatever then the water passes through the UFH in that area without actually emitting any energy. 

Problem with this is that 25° is far too hot for a small fairly sealed bedroom, but you may want to keep the UFH running for a large open plan area that vents up through several floors.

Indeed this is exactly the situation in our house and why I've spent the last couple weeks implementing zoning. By large I have all zones run at once, but when needed I can cap off the max temperature that the snug/guest room will heat up to. (it also has SW facing glazing so gets solar gains too) 

[Alan Ambrose]

Yeah, the other half likes v cold bedrooms - windows open even in the winter - and I like warm bathrooms. Also, I think there's something to feeling some temperature variation rather than living in a hermetically sealed box.

 

Alan

[Adsibob]

1 hour ago, Iceverge said:

 

I think the idea that if you design it well and insulate it sufficiently then you can run it at very low flow temps. 

 

That means that if the floor is at 25⁰ and the room is already at 25⁰ due to sunlight/woodburner whatever then the water passes through the UFH in that area without actually emitting any energy. 

 

It'll give proportionately more energy to colder rooms than warmer ones. Hence no zones. 

 

This won't work with high temp rads at 70⁰ for example as they'll still emit heat as the room will always be colder. 

 

 

 

That makes sense. My house isn't sufficiently well insulated for that though, and there are some rooms, like the guest room and the study which get used very infrequently (guest room a couple of days a month at most; study a couple of days a week) such that it wouldn't make sense to heat them above their natural "resting point" in winter of about 17C much of the time.

 

[SteamyTea]

There is nothing to stop people varying the power output in different rooms, while still being on the same zone.

Changing the UFH pipe spacing is just the same as having different output radiators.

[joth]

4 hours ago, SteamyTea said:

There is nothing to stop people varying the power output in different rooms, while still being on the same zone.

Changing the UFH pipe spacing is just the same as having different output radiators.

So if more guests stay in the room some days, or it's a particularly sunny day I should dig up the pipes and adjust the spacing 😂

 

[JohnMo]

No just have a well insulated floor and house job sorted.  My floor is currently 22 deg, room is 23 degrees from solar gain, floor therefore absorbs heat instead of outputting heat - no digging required. Just design right before you start.

[joth]

18 hours ago, JohnMo said:

Just design right before you start.

That's even more funny. Given 0.1% of UK houses are designed right for whole house heating strategy, it explains why  building regs require room by room control. As even with PH  certified architect, ME designer and builder, we still have two bedrooms overheat, and guests complain of it being too warm hence retrofitting zone controls. 

Kodus to the geniuses that gets this right first time, but for the rest of us what's the alternative. 

[JohnMo]

1 hour ago, joth said:

building regs require room by room control

Not completely correct. They actually state

 

NOTE: Installing thermostatic room controls may not be technically feasible in some cases. These may include the following.

 

a. Dwellings with very low heat demand (e.g. less than 10W/m2).

b. Dwelling with buffer zones for heat absorption or dissipation with high thermal mass.

 

The regs don't define b. in any details, so thick screed UFH could comply and not require room thermostats 

 

5.21 It may be justified to control a heating zone rather than individual rooms in either of the following cases.

a. In single-storey open-plan dwellings in which the living area is greater than 70% of the total floor area. In such cases, the dwelling should be considered as a single heating zone.

b. Where two adjacent rooms have a similar function and heating requirements (e.g. kitchen and utility room). In such cases, the adjacent rooms should be considered as a single heating zone.

[joth]

7 hours ago, JohnMo said:

Not completely correct. They actually state

 

NOTE: Installing thermostatic room controls may not be technically feasible in some cases. These may include the following.

 

a. Dwellings with very low heat demand (e.g. less than 10W/m2).

b. Dwelling with buffer zones for heat absorption or dissipation with high thermal mass.

 

The regs don't define b. in any details, so thick screed UFH could comply and not require room thermostats 

 

5.21 It may be justified to control a heating zone rather than individual rooms in either of the following cases.

a. In single-storey open-plan dwellings in which the living area is greater than 70% of the total floor area. In such cases, the dwelling should be considered as a single heating zone.

b. Where two adjacent rooms have a similar function and heating requirements (e.g. kitchen and utility room). In such cases, the adjacent rooms should be considered as a single heating zone.

Thanks for this. I guess it was updated since 2019? Back then our M&E guy told us we had to have room controls (and though didn't need them) due to part L, and I read it up that was the case....  except for retrofits, so I pushed back on that basis. But we did design it to be easy to retrofit at least.

 

Just continuing this thought. We have a room that is sometimes a spare guest bedroom, sometimes a music room, and sometimes a massage studio. Desirable temperature range from 17-23 °C depending on the guest / customer.

How can this be achieved without messing with the whole house temperature, and without room specific controls?

[JohnMo]

49 minutes ago, joth said:

17-23 °C depending on the guest / customer.

How can this be achieved without messing with the whole house temperature, and without room specific controls

That may be difficult 

[Nickfromwales]

11 hours ago, JohnMo said:

That may be difficult 

You mean impossible, surely?

[JohnMo]

5 minutes ago, Nickfromwales said:

You mean impossible, surely?

Yep

[Iceverge]

Easy with rads and TMV I assume?

 

 

[Dave Jones]

On 15/03/2023 at 19:54, joth said:

Thanks for this. I guess it was updated since 2019? Back then our M&E guy told us we had to have room controls (and though didn't need them) due to part L, and I read it up that was the case....  except for retrofits, so I pushed back on that basis. But we did design it to be easy to retrofit at least.

 

Just continuing this thought. We have a room that is sometimes a spare guest bedroom, sometimes a music room, and sometimes a massage studio. Desirable temperature range from 17-23 °C depending on the guest / customer.

How can this be achieved without messing with the whole house temperature, and without room specific controls?

 

a2a air con unit ?

 

Designing for 2 different temperatures within a sealed insulated box isn't very desirable. it means you will be running both the heating and cooling very inefficiently.

 

Edited May 20, 2023 by Dave Jones