MCS requirements for whole home UFH

[Nick Laslett]

11 hours ago, Gus Potter said:

The reason I often challenge is that folk are desinging the pipes in the floor with no redundancy, or recognising that what gets built on site may not actually be what is shown on loop cad for example.

I’ve mentioned this before, but my ground floor UFH was installed with every pipe run being about 10m shorter than the loopCAD design, essentially missing at least one loop in each room. 
 

Unfortunately, even though I diligently took many photos of the install, I didn’t actually notice the shorter runs until many years after the foundation had been poured. 
 

One room is particularly bad. Don’t know what the installer was thinking. If you compare the picture to the design it makes no sense. Wrong loop pattern too. I was still very green at this stage of the build. 
 

 

 

 

Edited November 8, 2025 by Nick Laslett

[saveasteading]

57 minutes ago, Nick Laslett said:

I was still very green at this stage of the

Such a good example of incompetence.

I get your point.

As a newbie you don't contemplate for a moment that supposed experts can be so incompetent.

Can't read a drawing. Don't understand what they are doing or why it matters.

Don't know how little they know.

 

You don't dare question them or you get abuse, condescension or simply ignored.

And now you deal with it how?

 

[saveasteading]

Just after the above, I read this about tacit knowledge. Very relevant.

 

What is tacit knowledge

It's sponsored (ad at the end) but interesting.

 

https://www.independent.co.uk/life-style/tacit-knowledge-further-education-teaching-careers-skills-learning-b2825537.html

[SimonD]

On 04/11/2025 at 20:38, cmdrawesome said:

MCS are saying that in order to qualify for the £7500 grant the UFH needs to be in every room. Is this really the case?

 

Take it from someone working in the industry that if anyone, and I mean anyone, including a person from MCS, say MCS says this, ask them specifically where it says that in the library of standards they've got. 99.9% of the time they'll go silent a crawl back to their hole.

 

For example, in the last month I've had an MCS umbrella dictate installation requirements that MCS publish. I lifted exactly what MCS says - in fact - to tell the umbrella they're wrong. the umbrella immediately changed their mind. I've also just had to submit a complaint to a competent person scheme because they refused to certify an installation of mine because of what 'MCS requires.' I then quoted exactly what MCS requires and it's the opposite of what the competent persons scheme assessment people told me. Funnily enough they've gone completely quiet since my complaint.

 

Unfortunately there are a lot of people in this industry who haven't got a clue what they're talking about ☹️

Edited November 8, 2025 by SimonD

[Bornagain]

On 04/11/2025 at 20:38, cmdrawesome said:

Ok, so in my 4 bed, 2-storey self build I'm having wet UFH installed at the bottom of the concrete slab, which sits on top of an isoquick passive slab. Walls are passive spec, roof is almost passive spec, ICF construction so airtightness will hopefully be <1. UFH and DHW all powered by an ASHP. Yay for acronyms!

 

I was planning to put aircon in the upstairs bedrooms, electric UFH / towel rads in the upstairs bathrooms, and leave it at that.

MCS are saying that in order to qualify for the £7500 grant the UFH needs to be in every room. Is this really the case? the aircon will be able to provide a small amount of top-up heating if required.

 

 

We live in our self build that we did in 2011, the house is ICF with all the normal bells and whistles. It has UFH downstairs with no heating upstairs, the UFH being powered by E7 electricity.

 

This summer we have taken advantage of the BUS and have had an ASHP fitted which heats the existing UFH and thermal store which then provides DHW.

 

We had three firms in to provide quotes and all of them were happy that we would be eligible for the BUS grant without adding any heating upstairs, the work has been carried out and the grant has been paid to the firm.

 

The slab that our UFH heats is a combination of 100mm of concrete and around 170mm of screed, this all sit on top of 300mm of EPS - we have a very low heat curve and the heating is working with a COP in excess of 5, there is almost no cycling.

 

 

 

 

 

 

[JohnMo]

On 08/11/2025 at 07:36, JohnMo said:

For me I have done glycol, pumping losses were huge, then changed it out and did VDI 2035, but decided normal water with an appropriate corrosion inhibitotor was easy to fill, easy to maintain. So now use Adey MC1+.

Should of added if low temp system and/or you do cooling you also add biocide and chemistry should match your inhibitor.

[cmdrawesome]

On 08/11/2025 at 10:28, SimonD said:

 

Take it from someone working in the industry that if anyone, and I mean anyone, including a person from MCS, say MCS says this, ask them specifically where it says that in the library of standards they've got. 99.9% of the time they'll go silent a crawl back to their hole.

 

For example, in the last month I've had an MCS umbrella dictate installation requirements that MCS publish. I lifted exactly what MCS says - in fact - to tell the umbrella they're wrong. the umbrella immediately changed their mind. I've also just had to submit a complaint to a competent person scheme because they refused to certify an installation of mine because of what 'MCS requires.' I then quoted exactly what MCS requires and it's the opposite of what the competent persons scheme assessment people told me. Funnily enough they've gone completely quiet since my complaint.

 

Unfortunately there are a lot of people in this industry who haven't got a clue what they're talking about ☹️

 

@SimonD That's a really helpful response - thank you. Unfortunately my installers have responded with this:
"As with regard to the heating on the first floor have your acquaintances any further details of the library of standards as I have spoken to Ofgem and MCS as well as our umbrella scheme and they are all saying each habitable room needs to have a heat emitter. Happy to get our umbrella scheme manager to give you a call to discuss further and she is also happy to speak to your acquaintance if necessary.

 

This is what I have been given:" ..see attached.

 

[JohnMo]

13 minutes ago, cmdrawesome said:

 

@SimonD That's a really helpful response - thank you. Unfortunately my installers have responded with this:
"As with regard to the heating on the first floor have your acquaintances any further details of the library of standards as I have spoken to Ofgem and MCS as well as our umbrella scheme and they are all saying each habitable room needs to have a heat emitter. Happy to get our umbrella scheme manager to give you a call to discuss further and she is also happy to speak to your acquaintance if necessary.

 

This is what I have been given:" ..see attached.

 

Either find an installer that will play ball or just cut out the middle man and DIY the install. R290 Haier heat pump 4kW or 6kW from Wolesely are £2100 and £2300 including vat.

 

Do a direct cylinder for DHW heat via immersion on cheap rate and a simple time switch. About £500.

 

Connect ASHP directly to UFH and run WC. Two pipes, strainer on return (supplied with ASHP), couple flex hoses and isolation valves, job done.  £200.

[cmdrawesome]

1 hour ago, JohnMo said:

Either find an installer that will play ball or just cut out the middle man and DIY the install. R290 Haier heat pump 4kW or 6kW from Wolesely are £2100 and £2300 including vat.

 

Do a direct cylinder for DHW heat via immersion on cheap rate and a simple time switch. About £500.

 

Connect ASHP directly to UFH and run WC. Two pipes, strainer on return (supplied with ASHP), couple flex hoses and isolation valves, job done.  £200.

Tempting, but if I've learned anything in my self build adventure so far, it's not to be too ambitious about what I take on myself vs what I ask a responsible adult to help with.

[SimonD]

1 hour ago, cmdrawesome said:

As with regard to the heating on the first floor have your acquaintances any further details of the library of standards

 

It's ironic isn't it? They ask for reference to the standards, but don't seem to know them. But the big warning bell that's ringing for me is that they're using an umbrella company. I assume you have a separate contract directly with the umbrella company too?

 

So the actual MCS Design Standard (both current and redeveloped schemes) say this:
 

Quote

3.4.1 The following procedure shall be followed for systems where the heat pump is to supply
100% of the space heating load with or without a supplementary electric heater to
ensure the correct sizing and selection of a heat pump and related components for each
installation:

a) A heat load calculation should be performed on the building using internal
temperatures not less than those specified in Table 1 and external temperatures
specified in Table 2 column A or B, according to the MCS Contractor's assessment
of the building location. If column B is selected, no uplift factor for intermittent
heating is required. Heat load calculations shall in other respects comply with BS EN
12831-12017.

b) Any supplementary electric heater shall be designed to not operate above the
external temperatures in Table 2.

c) When calculating the heat loss through a solid floor in contact with the ground, the
temperature difference to be used is the internal design room temperature (Table 1)
minus the local annual average external air temperature (see MGD 007 Section 5).
d) When calculating the heat loss through a suspended floor, the temperature
difference to be used is the internal design room temperature (Table 1) minus the
design external air temperature (Table 2).

e) A heat pump shall be selected that will provide at least 100% of the heat load as per
the calculation in a), taking into consideration the flow temperature at the heat pump
and without input from any supplementary electric heater. Performance data from
both the heat pump manufacturer and the emitter system designer should be
provided to support the heat pump selection.

f) An air source heat pump system should be able to maintain the internal design
temperatures across multiple defrost cycles

 

As you can see, this does not stipulate that you have to have an emitter in each room. It is just assumed by the designer and installer, probably because they have no experience dealing with low or ultra-low energy buildings and therefore don't understand how a passivhaus would perform thermally.

 

I'd recommend you have a good think about using these people as this is not a good start. But also, have a think about your design - at some point you may want additional heat and be able to have cooling, in which case you can use fan coils or UFH to provide this. I saw some very neat fan coils by Panasonic today. Very unobtrusive.

 

I think definitely try to find a good designer and installer who can discuss the options with you.

 

Plenty of help on here should you want help to diy instead.

 

 

[cmdrawesome]

Thanks @SimonD - appreciated.

I have spent part of the afternoon reading the standard and yeah - it seems to me that you need to be able to heat all the rooms to the figures in Table 1 (18C for bedrooms and hallways). It does not require a heat emitter in every room.

Edited 2 hours ago by cmdrawesome