UFH In Ground Floor Extension - thoughts?

[Steveham]

Gents, please be gentle - I have had planning permission granted for an extension and am in the process of getting building regs so now is the time for choosing the design and the kit. A kitchen extension with a separate bathroom is being built, with stone floors, a total of 35m2 - to ensure I don't spend every winter freezing in there and wishing I hadn't wasted my hard earned has anyone any advice on wet UFH systems please?

So far I have asked for quotes for the equipment from Nu-Heat, Speedfit, Thermoboard and floorheatingonline, as well as asking my plumber for an installation quote.

I would like to think I have the bases covered but if there are any hints or advice that you could give I'd gratefully receive it.

My plumber is properly registered, has previously removed our old back boiler and installed a new WB 30CDi in the loft, all good work and no problems so I trust him, I just like to do the research before spending money, naturally tight I guess.

 

[dcawkwell]

The underfloor would need to be on a separate zone to the rest of
the house as underfloor needs to be on for long periods no on and off.
So it will mean another set of flow and return pipes from the boiler down
to your extension. There will therefore need to be a separate timer
and thermostat for the extension.
It is very slooowww to respond a complaint I get regularly.

The only time I come across it is when people are unhappy with it
or it isn't working.

I don't like tiled/solid floors myself a little hard and cold in this country.
I much prefer wood and suspended floors.

 

[Steveham]

I know what you mean, but it's what the missus wants. Our heating is on all the time anyway, only goes to 18 at night, two babies and wife is of irish descent so always cold, so I don't think the long warm up time will be too much trouble.

It is expensive to install though.

 

[dcawkwell]

I know what you mean, but it's what the missus wants. Our heating is on all the time anyway, only goes to 18 at night, two babies and wife is of irish descent so always cold, so I don't think the long warm up time will be too much trouble.

It is expensive to install though.

Yes the problem with underfloor is if people suddenly feed cold or want
heat there and then.
Normal radiators turn up the thermostat a couple of degrees and 15-30 minutes later it will be there.
Underfloor it will still be getting there 2 hours later.
Similarly the problem is if people start feeling hot. You have built
up a large heat store in the screed, turn the thermostat down and nothings
going to happen for a couple of hours that heat has to be released.
So people end up opening windows.

 

[Dan Robinson]

Our heating is on all the time anyway, only goes to 18 at night, two babies and wife is of irish descent so always cold,

Àaaaaaaaaaaarrrrrrrrrrgggggggghhhhhhhhhh

 

[Steveham]

Ha, scared of the heating bill or the wife? TBH we live in an old Victorain house so the ground floor has airbricks to combat damp - we don't get any now, but as we have the floorbaords exposed and high ceilingsa it takes some heating. The range is 18 as a min and 20 as a max on the heating. And it's off all summer. Still crippling bills though, hoping that UFH will mean less draughts through the airbricks and will not allow damp to rise as it will dry out the joists.

 

[Dan Robinson]

UFH + drafts = big bills.

I was screaming at the "two kids" bit. Kids really don't give a monkeys as long as the temp is above 16 or 17. They should be moving or sleeping IMHO.

Women are women and will moan either way. So there is no point worrying.

 

[Steveham]

I concur wholeheartedly! The tiles over the joists will banish the draughts, but not the damp, the UFH should cure that. I am trying to think about the whole house eco syatem, if I block the airbricks and install radiators I risk damp, with UFH and plenty of insulation underneath I mitigate that risk.

 

[Agile]

You say you are currently waiting for Build Regs approvasl.

That should have shown at least the insulation for the UFH.

Whilst UFH does have its place and if she never goes out thenj perhaps that for you.

I would always prefer rads or warm air heaters because of the fast warm up and the ability to switch it off when out to save costs.

Tony

 

[Steveham]

Planning approved, building regs drawing will be completed and sent in the next week. Insualtion will be noted in the extension, but where it is the current kitchen this is on wooden joists and as it's the existing house does not need drawing or approval.

However, if I tile over this existing floor I block air from underneath, Victorian houses need air to prevent damp, but if I have UFH my Victorian damp specialist, who doesn't sell UFH btw, says it will not be a problem.

If I tile and have rads it might be. I would prefer not to have the cost of installing and running but it may lead to costs to combat the damp. Hmmm.

House is occupied a fair bit, two kids under 4 yrs old. And probably more to come.

 

[Agile]

Any UFH needs at least 80-100 mm of insulation underneath.

I think that UHF is mad in a proper kitchen because cooking causes the temp to vary widely. Rads and warm air can respond quickly but UFH cannot !

As long as the underfloor is ventilated properly I dont see why you should have any particular damp problems. They arise in solid floors with no dpc.

Tony

 

[ALEC1]

with correctly set up UFH floor temp is just a bit higher than air temp.

Have a read of this:

doc

• ALEC1
• 20 Jan 2012
• 2

its also worth bearing in mind that the controls that are the UK norm for UFH require very high flow temperatures to ensure that blending valves work as designed.

Its also why the consume far more gas than necessary

 

[Agile]

That is primarily extolling the feel good aspects of UFH which is nice in a lounge. Only applied to mostly 24 hr operation though.

The main problem that occurs is the 40 C circulating water and the usual UK 28 C floor temp.

As the floor is warming up there comes a time when the heat input ( flow temp ) needs to be reduced in anticipation of the forthcoming room temp. That needs an intelligent controller.

Its interesting that in Europe its very common for the boiler to directly supply the UFH at the required ( low ) circulating temperature.

You also ideally need predictive weather forcast information but that is not available in a usable format yet and is somewhat localised too.

Tony

 

[Steveham]

The damp we had when we moved in was a corner of the property where the outside rarely gets sunshine, not bad but stopped a replastered wall drying, and this was above the floor level damp. The addition of an airbrick fixed it.

I am concerned that tiling the floor might interrupt the airflow, but I guess underneath will still be well ventilated. I like the idea of UFH but am worried it will be more trouble than it's worth. I also like the idea of being able to put kitchen untis wherever without worrying about rads, we would have to put big cast iron jobs in to fit the rest of the house. The cost of these things also makes UFH seem less expensive.

Food for thought.

 

[TicklyT]

Have you considered kickspace heaters fitted under the kitchen units?