Help! £1000 for Underfloor Heating, need to decide by 8am!

[trish1400]

The short story:

I've recently realised that my open plan kitchen + living extension floor is suitable for underfloor heating. I was previously happy enough with the idea of 2 radiators + a plinth heater but given how much people rave about underfloor heating I'm thinking I would be foolish to pass up the opportunity. The builder said it's not something he would do personally but he spoke to his plumber for me and said the plumber thought it was a good idea and it'd be around £1000 extra to do. I'm meeting them both on site tomorrow morning (Monday) at 8am and I'll need to make a decision then. I hoping for some advance guidance and opinions - so I'm not going in to the conversation completely wet behind the ears. Thoughts please?

The long story:

I'm building a lean-to extension on my post war semi - creating an open plan (approx 6m x 6m) room - which will be a kitchen / diner living space. There will be a lot of glass and the extension will have a lofted roof.

Proposed Floorplan:

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• trish1400
• 12 Apr 2015
• 1

Proposed front of the house:

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• trish1400
• 12 Apr 2015
• 1

Proposed back of the house:

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• trish1400
• 12 Apr 2015
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The existing room which is being opened up was part concrete with quarry tiles and part suspended floor but the structural engineer specified a lot of steel had to be put through the floor so the whole floor has come up and the whole sub-floor will be concreted. The builder and the plumber agree this would be a suitable base for wet underfloor heating.

This is the kitchen plan showing the proposed radiators if I don't do the underfloor heating - there will be one radiator under the back window (existing location), a little one next to door and a plinth heater under the sink:

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• trish1400
• 12 Apr 2015
• 1

When I first asked the builder about the underfloor heating his reasons against were:
1) he'd never seen it done in one room only (it's normally the whole ground floor)
2) you have to find somewhere to put the manifold which can be quite big
3) he, personally, is out of the house for 12 hours a day so, as the idea of underfloor heating is to have it on constantly, it would be a waste.

After he spoke to the plumber he came back and said the plumber has installed it in one room only (and it's fine) and that the manifold for a single circuit is smaller and can therefore fit in a kitchen cabinet. It would be about £1000 more to install than the radiator setup - which is an amount I can stretch too if I could convince myself it's the right way to go.

So my questions - if you can help with any of these in advance of tomorrow that would be great:

1) If I did go for underfloor heating - would it work in that room? As in, would it actually heat it enough (especially with the lofted ceiling and all that glass). Would I need a radiator as well? I can calculate BTUs for radiators but there doesn't seem to be any guide for UFH.

2) Would UFH be better than the radiator / plinth heater set up? Particularly with the open plan space (I'm worried with radiators if you were in the middle of the room it would be cold).

3) I was planning on putting a vinyl floor (Karndean) down - it says that it's suitable as long as the surface temperate doesn't go above 27 degrees centigrade. Is that within the normal range? If you have to insulate the underfloor heating to reduce the temperature it's a bit counter intuitive.

4) I'm also out of the house for about 10 hours a day, 5 days a week - does that make UFH inefficient?

5) I was planning on getting a Nest thermostat - with UFH I realise it would be a separate zone so therefore I would need to get two. This extra thermostat won't be included in the £1000 but I'm wondering if the Nest thermostat negates the need for the UFH at all. Edit: as Dan pointed out in comment 3 this question makes no sense - I've tried to explain better in comment 4.

6) Generally - what do you reckon? I've read all the pros and cons but I still don't really know, I think I'd be happy enough with the two radiators and one plinth heater - but UFH is so much the 'done thing' that going against the trend feels like the bigger gamble.

Sorry for the long post - thanks for reading if you got this far!

 

[picasso]

I would go with the ufh, it would be £1000 well spent.

 

[Dan Robinson]

For a grand, and as long as it is done properly, then it is a no brainer in that space.

Not sure why you think a nest thermostat would mean you don't need a heat source? . There are better thermostats out there too. . Honeywell Evohome will let you control multiple zones from a single controller and app as well as the hot water.

The fact that you are out 10 hours just needs to be taken into account when you programme the schedule.



BTW, never take a builders advice on anything other than bricks.

 

[trish1400]

Thanks guys - good to have your opinions

Sorry Dan, that really wasn't very clear about the Nest bit - I meant with Nest combined with radiators.

To be honest, it's hard to express what I meant, I think what I was trying to say was - the advantages of the Nest thermostat is that it can sense when I'm home, it can learn my behaviour patterns and I can control it remotely. If I can have a heating system which is so responsive - is there any need for a slow burn / always on solution like UFH?

Having thought about it more now - it's actually the other way around, the UFH negates the need for the Nest (in that zone anyway).

Thanks for the tips on the other thermostats - I'll go check them out. I think what attracts me to the Nest is the 'learning' (a long time ago I got a degree in Artificial Intelligence but never see it in practice). Nest are interfacing with more and more other companies to build the 'internet of things' which appeals to my geeky heart and as they are now owned by Google it's hard to imagine they won't just make all other competitors' technologies obsolete.

As for the 'builder', I'm calling him that as he's project managing but he's actually a time served joiner so he doesn't know much about bricks either (I've asked)! Give him his due though, as seen in this example, anything he's unsure about - he goes finds out and retracts his comments if necessary.

 

[Agile]

You seem to be someone with more money than logic.

Assuming you have read up on UFH then you will know it takes two hours to worm up ( and cool down. ). Rads take 20 min.

For a single room it becomes very expensive bcause of the complete set of controls that you need to time it separately.

Depending of floor covering you will also have read that a typical heat output is only about 100W per m².

You will have compared that with the heat loss of the room to see if its adequate, perhaps not.

By careful design of the UFH and the right floor finish then you can usually get about 150W per m².

UFH in my view is only a better choice for a property occupied 24 hrs a day like a nursing home or for retired people who don't go out much or non working women with babies or young children.

Although I am a Nest accredited installer, the general view is that they don't seem to do much of what they claim. They do control via the web but there are other makes that do that too, and perhaps better, for a lower cost like the Salus for example.

Tony

 

[Nige F]

I agree with Agile

 

[Biggles..]

And agile seems to be someone with more to say that he has training/knowledge and experience on.

150w/m².......why would you, considering that it takes no more than 70w/m² to give a floor temperature in excess of what the British satndards for UFH recommend at 27degC.

 

[Dan Robinson]

Problem with Tony's advice on ufh, it's largely inaccurate or too generalised to be useful. . 150w/m?

 

[roguetrader]

Ufh would be great in that area, the extension will be well insulated and it will provide a nice even temperature.
Make sure you know your kitchen layout as well as any island or peninsulas as its best not to lay any pipework under units.
You will need to be prepared to keep this area heated at all times during the heating season with an overnight setback of no more than 4 degrees or so.

 

[trish1400]

You seem to be someone with more money than logic.

I'm stunned that you would make this comment - what exactly does insulting me achieve? I fail to see what relevance 'logic' has here - the recognised idiom is 'more money than sense', generally meaning someone is profligate. If anything, the opposite is true with me - I've overly careful with money and have a tendency to be tight-fisted when a little expenditure to increase my quality of life would be money well spent, hence this very question.

And yet, as well as insult, you give me give information and advice. What's that about? Was it just so you could use that patronising tone?

I didn't know the heat output. As I stated in my post - I couldn't find any guidance on this, probably because I thought that it would be measured like radiators in BTUs, so was searching for the wrong thing. Apparently 1w = 3.4BTUs so at 100w/m2 there would be more than enough output but there wouldn't be enough at 70w/m2.

Well, thank you all (and I do mean all) for your comments - I'm still not sure what I'll do but you've given me a lot of food for thought (and not just about underfloor heating).

Cheers!

 

[Dan Robinson]

Don't worry about Tony. . He means no malice, is great at repairs and is an all round good egg. . Just very eccentric . I've known him for many years and am grateful for it. . Even if I do think his installation advice is lacking.


The heat requirements for the room are the same regardless of what is heating it.

It is the control strategy that is key. . Paramount in fact. . The only thing more important is the amount of insulation.


In that regard, if it means trimming a few hundred or even a few grand from the cosmetic budget to upgrade the insulation and control, then Crack on!!!!!!!!!


Every problem ufh system I come across has been down to builder's. . Either designing, limiting the design of, controlling the design of, or actually installing ufh.


Thankfully the chap I deal with most has been trained (which considering the cost of the floor covering is double the average annual income) so I pretty much leave him to it until the wiring stage. (his sparky is also well trained. ).


You have the advantage of a builder who seems happy to admit his ignorance and, ironically enough, that is a very good thing.


Moving on to floor covering. . Tiles are a much better option all round. Karndean in my experience looks great for a while. . But needs replacing sooner. Refer to what I said about budgets, and perhaps do as I did and put a floor down that, if needed, wouldn't be the end of the world to replace in 5 - 10 years. . If it lasts longer, then great.


I went for engineered wood (not laminate). . 70m was £2500 fitted with the rest of the build. . Heat output for the last 32 months or so has been bob on with plenty of capacity left (central Bedfordshire with mild winters) in my mid 80's house and the extension that comprised 30ish metres of the 70. . Roguetrader and Lee do some pretty big installs, and the mine can be upwards of 2500m per floor. . I know Tony works on a few big existing installations; but don't know what he has installed.


Not taking sides. . Just passing on my experience.

 

[trish1400]

Thanks Dan - I may have over-reacted to Tony's comments, I was a bit shocked.

Web based calculators said I'd need somewhere between 10,000 and 13,000 BTUs. If 1w = 3.4BTUs and the floor area without the kitchen units is around 30m2 - using the 70w/m2 figure it'll only output 7140 BTUs. So unless I've got the figures mixed up somewhere - I don't think UFH is going to fly. My previously planned two radiators and plinth heater would output 14,523 BTUs.

The insulation is spec'd on the building regs plans (I had no plans to ask for more) - I think these are the relevant parts:

• 
  Ground bearing Slab Floor to be constructed as follows: 75mm screed, 75mm thick Xtratherm Floorboard insulation or similar approved rigid insulation, with 25mm perimiter rigid insulation, minimum 150mm thick concrete floor slab with approved dustproofer/hardener.
  On 1200 gauge Visqueen DPM, on 50mm sand blinding and 150mm minimum well consolidated hardcore fill. DPM to be taken up sides of slab and lapped with horizontal DPC to all walls, to be Ruberoid Hi-Load or similar approved positioned a minimum of 150mm above ground level. Floor construction to achieve a minimum U-Value of 0.25 in compliance with Part L1 Building Regulations 2009.
  
  150mm Kingspan Kooltherm insulation between rafters and underdrawn with 50mm Kingspan insulation and 12.5 foil backed insulation skim and plaster finish, to achieve a minimum U-Value of 0.20W/mk to comply with the requirement of Part L1 Building Regulations 2009. 50mm air gap maintained between insulation & roof felt/underside of boards to be maintained.
  
  Windows will have a U-Value of 1.7W/m2degC.

The Karndean I picked before the UFH idea came up, it's a discontinued pattern and the local carpet shop happen to have exactly the amount I need in stock - so most of the expense will be the installation. I did consider tiles but I was worried about the acoustics in that space - I frequently notice if a room is echoey and it would drive me nuts. Both engineered wood and laminate would be more expensive.

About the control though - here you've lost me. Is that the manifold? The thermostat? Or something different again?

Thanks!

 

[Biggles..]

Ignore the web based calculators, they're massively over spec''do

If the build is to completely modern building regs, then heat loss of such build is usually no more than 35w/m2.

 

[Dan Robinson]

My ground floor is almost open plan kitchen, living space. . Next to no soft furnishings other than than the leather sofa. . Acoustics are only a problem when kids are being "exuberant".

Can't look up my Heatloss calcs now, but things were close to the bone on paper. . On top of that I'm using 10mm tube in an overlay system. . So pretty much the worst if can get in terms of output.

 

[Dan Robinson]

Just found my calcs...... 94.3w/m.



Granite worktops too.