UFH BS?

[Pooneil]

I've posted this here as it's more of a rant than a question.

I'm having a nightmare getting an estimate, or any straight answers on specification, for underfloor heating. I've tried heating and underfloor companies and suppliers direct. All are keen to tell me how great their product / service is and assure me it's perfect for my project.

I've clearly explained that I've got a maximum total build up of 80mm over an uninsulated slab and I've stressed I want to achieve a U-value at least in line with current regs. One heating company quoted (a huge price) for a system with <110mm build up. Speedfit priced for a completely unsuitable regular screed system. Another underfloor floor heating specialist priced for a 50mm (plus 22mm deck) floating floor system at an okay price, but I can't get a straight answer on what U-value that will achieve or whether I'll need further insulation.

I'm wondering if I'm asking the impossible, but it's being ignored by sales 'enthusiasm'. They might advertise <50% saving over rads, but there's no way of comparing that once it's installed and by then it's not their problem if I'm heating the soil.

An example of what's confusing is this, a 17mm floating floor that claims a U-value of 0.0038 w/m², how can that be right if, for example, 100mm of celotex is 0.22 w/m² ?

Am I missing something?

[thescruff]

Have a Look at Roth. We used to be the UK partners.

http://www.roth-uk.com/30.htm

If you're tight for space look at the climacomfort.

Insulation is king and don't forget the perimeters

[Pooneil]

I know there are systems that will fit the space, the problem is getting anyone to say whether they are fit for purpose. Despite all that bumph there is nothing much said about insulation under the system, and as you say, insulation is king.

Surely part of the service should be clear honest advice about how the product will perform in any given situation. For example, if I was asked to thatch a house I wouldn't expect the customer to take responsibly for making sure the base coat is suitable.

If I go with rads we'll reinstate the floor with 50mm celotex because that's all we've got room for, but actually heating the floor makes the effectiveness of that 50mm all the more important. No doubt these slim systems will heat the room very well, but there is no point spending more on a system that doesn't offer any advantage in running cost.

Apart from the sheer incompetence of people pricing for solutions that don't meet the stated specification, I find the fact that no one seems to wants to confirm the effectiveness highly suspicious.

[thescruff]

The figures they publish is with their products including the insulation.

[Pooneil]

'They' as in Roth in particular?

As I say Speedfit did include insulation in their calculations; 75mm of it, with pipes buried in 75mm of screed... not much good for a maximum 80mm build up. One heating firm also specified insulation but also beyond our limited depth. Of the thinner floating floor systems (around 20mm) I've enquired about, none of them will say if 50mm of extra insulation is suffice to meet building regs.

You say 'figures they publish is with their products including the insulation'. Including what insulation? Minimum of 75mm under screed, or 50mm over slab, or less, or none?

As far as I can see all the information on that ClimaComfort system is based on existing insulation, screed and then the system. That's not what we have. There may be no discernible difference, 50mm insulation may be plenty... I don't know because it's not something I have any experience with and I don't understand the technical issues of heating and heat loss, that's why I've gone to the 'specialists'. At least half of the 'specialist' I've asked so far haven't even addressed my basic requirements (one company seemed to have trouble working out floor areas from scaled plans!)

My point is that so far (this my not be the case with Roth) I've not been able to find anyone who can look at what we have and say 'this is what is available in this situation – insulation, heating element and deck – and this is how efficient it will be compared to traditional alternatives'.