Underfloor Heating - Help needed!

[PullerGas]

Thanks for all the comments.

The clipper plates are circa £5 each plus screws/fixings and we need 300+ so obviously we wanted to look for other solutions to have a couple of grand!

Would it be possible to clip the piping to the underside of the chipboard (from below) & then 150mm mineral wool insulation underneath. Feed the pipes through the metal webs. Joists are spaced at 600mm.

Problem fitting from above is we would have to cross batten the deck which raises the floor height as we cannot drill/notch the metal web joists unlike traditional joists.

Yes very labour intensive but fitting ourselves. Any problems with this method?

Thanks to those who genuinely tried to help

Fixing to the underside of the flooring means you're heating air & not a thermal mass. Sorry mate, I've just noticed you have web joists.
If the joists can take the weight, I'd lay 12mm OSB on top of the joists, then 50x25mm battens, pipes between the battens & screed. Thermal mass is king!!

 

[dilalio]

+1.
It needs to work like a storage heater.

 

[Sunshine12]

Thanks for the advice.

The problem we're facing is we really can't afford to lose anymore head height (long story - roof height & planning) & we can't drill/notch the easi joists.

Hence looking to fit the piping under the deck.

How do the metal clippa plates work in terms of thermal mass? Do they transmit much extra heat compared to just having pipes?

The clippa plates can be fitted from underneath but it's quite a substantial cost which I'm starting to think we may have to pay after all?

What are you thoughts to run the piping up & down the boards 100-150mm spaced and feed the loop through the metal web at each loop.

Basically pipes run North & South - joists run East to West.

Followed by 200mm mineral wool or possibly upgrade to a rigid board eg Celotex if you think it makes much difference.

Thanks again

 

[Agile]

Tony[/QUOTE]

How would you use a spreader plate system and then screed it? Or more importantly why would you do that?

[/QUOTE]

This is not standard spreader plates but a special type designed to support pipes and a thin screed.

The metal conducts the heat to spread it.

Sorry don't have any brand names but should be easy to search for one.

The price of the one I saw was reasonable enough for me to consider it for my own house extension.

Tony

 

[DP]

This is not standard spreader plates but a special type designed to support pipes and a thin screed.

LoPro or similar trade name comes to mind, have used it, but it is not metallic. Perhaps you could say what it is called

 

[PullerGas]

Well, why not fix 12mm OSB onto the underside of the battens at the top of the web joists, what will that give you, 30-40mm? And fix pipes etc as I've already stated. Ofcourse you do need to double check the joists will take the additional weight.

 

[dilalio]

OP: you gotta do, what you gotta do!

Can you not speak to one of the UFH pipe manufacturers and explain your predicament and ask their advice? They will have technical data coming out their ears and should be able to provide a compromise!

You could indeed thread the loops though the web of the joists, it's not ideal but would still give you a practical solution. I take it that there are timber 'rails' to the top and bottom of the webbed joists? Can you not still screwfix cheeks to the sides of these, made of strips of 60x12mm OSB, with another wider strip joined to the bottom of them to form a 'tray' between the joists. You could then clip your pipe (evenly spaced in two runs per bay) to the floor of these 'trays'. At the end of each bay the pipe could 'dive' through the OSB, pass through the web of the joist and come back up through the floor of the next 'tray'. It would be fiddly to run, but doable! You could then screed the 40mm 'trays' flush with the top of the joists and then cover as normal with t&g deck board. From underneath, you could then stick 20/30/40mm celotex up below the OSB tray bottoms and mineral wool or foil tape over any of the loops at each end that are visible from below!

 

[dilalio]

Well, why not fix 12mm OSB onto the underside of the battens at the top of the web joists, what will that give you, 30-40mm? And fix pipes etc as I've already stated. Ofcourse you do need to double check the joists will take the additional weight.

Haha PG... You posted that while I was still writing

 

[Steelmasons]

This is not standard spreader plates but a special type designed to support pipes and a thin screed.

LoPro or similar trade name comes to mind, have used it, but it is not metallic. Perhaps you could say what it is called

Don't hold yer breath DP..

 

[denso13]

Ofcourse you do need to double check the joists will take the additional weight

This is critical. A 40mm screed will weigh nearly 14 tons and new builds nowadays aren't guilty of overspecifying on things like joists.

 

[roboughton]

Thanks for the advice.

The problem we're facing is we really can't afford to lose anymore head height (long story - roof height & planning) & we can't drill/notch the easi joists.

Hence looking to fit the piping under the deck.

How do the metal clippa plates work in terms of thermal mass? Do they transmit much extra heat compared to just having pipes?

The clippa plates can be fitted from underneath but it's quite a substantial cost which I'm starting to think we may have to pay after all?

What are you thoughts to run the piping up & down the boards 100-150mm spaced and feed the loop through the metal web at each loop.

Basically pipes run North & South - joists run East to West.

Followed by 200mm mineral wool or possibly upgrade to a rigid board eg Celotex if you think it makes much difference.

Thanks again

I was in this dilemma with floor height too, you either have to bite the bullet and go with the trays or not have UFH upstairs. The problem with the trays is you still don't have the thermal mass for the UFH to work well. In the end I went with a few rads upstairs and it works fine. If you do go with the tray I would use rigid board insulation to push the heat upwards.

EDIT; both the main manufacturers I contacted advised against me using UFH upstairs if I couldn't get the screed in which is why I didn't do it in the end. I didn't use either manufacturer as they were so terrible on pricing giving me prices and advising I go to a local agent who could do it better I just went with someone else downstairs. I am happy to disclose who they are if you require. They aren't a big name but they use Reliance manifolds and a decent pump.

 

[Agile]

I still think the metal spreader system is useable providing you don't have grand ideas for thick engineered wood and thick carpets.

After all that's what they are sold for.

They work by spreading the heat from the pipes over the full area of the underside of the flooring.

But to be effective the flooring has to be pretty thin so it does not kill the heat transmission.


The system I saw was a formed metal tray which would carry a thin screed of about 25 mm containing the tubes.