Underfloor Heating Layout

Mmark · 8 Mar 2011

My builders are about to fit my UFH and have provided the layout found below from their designers. The floor area is about 36M2:

I added the external doors, and external walls text and lines myself - sorry for sketchyness.

I've done a fair bit of research on UFH and layouts and this one seems sub-optimal. It uses a single serpentine to cover the entire room.

My understanding is that the design should try to ensure the pipes run along external walls and windows.

For that to happen C1 would need to be a triple serpentine. And I'd probably need a double serpentine in the top right corner, against the external wall and bi-folding doors.

I rang the design company with my comment, their answer was "we've been doing this for 25 years and it'll give you an even temperature throughout". Which wasn't really the helpful technical response I was hoping for, as I was hoping they would give me a technical reason as to why I'm worried about nothing.

So my question is. Does the layout really matter that much? Is their's fine or is their's suboptimal? i'm really hoping i'm worrying about nothing.

Mark

RichieHoneybucket · 8 Mar 2011

I agree with you & you've certainly done your research. However, with well insulated Walls it's really not that important now. Many UFH companies do fancy drawings & try to sell you lots of controls, just to cover the fact they're just selling pipes & fittings.

180mm centres is a bit odd though! But I'm sure it'll work just fine. Is the Plumber not fitting the system, I mean some hairy ar.ed Builder will not have a clue!!!

Mmark · 8 Mar 2011

RichieHoneybucket said:
I agree with you & you've certainly done your research. However, with well insulated Walls it's really not that important now. Many UFH companies do fancy drawings & try to sell you lots of controls, just to cover the fact they're just selling pipes & fittings.

180mm centres is a bit odd though! But I'm sure it'll work just fine. Is the Plumber not fitting the system, I mean some hairy ar.ed Builder will not have a clue!!!

The supplier and designer is florad, http://www.florad.co.uk/. I think they have reduced the space from 200mm to 180mm, as they are using 10mm pipe instead of 15mm pipe. But I'm not sure.

The builders are laying the pipes and doing the screeding. The plumber, who I assigned, is connecting the pipes to the manifold and pressure testing them.

My main worry was that we have these huge set of bi-folding doors, with a u-value of 1.6. they will be about 5M in length and 2.4M in height. I expected the pipes to run along them. The external walls I'm less worried about, as they are extremely well insulated. Building control are making us insulate the inside of the walls, as well as between the walls, due to the bi-folding doors.

Florad's answer was that we have a large room and their design will ensure a comfortable 21C throughout the room. When I pushed him on the issue of a design to ensure the pipes run along the bi-folding doors and whether it's necessary or not, he just got iritated and effectivey closed the conversation down.

Things have already been a little contentious with the builders with the UFH - who fell out with the plumber last week, who then refused the work, I had to beg him to come back onsite (see //www.diynot.com/forums/viewtopic.php?t=266267&start=0&highlight=). So I'm trying to decide whether this is not worth fighting over and let them just get on with it, as the difference wouldn't be that noticable. Or do I need to push on this and find another designer as they are making a terrible mistake. I just don't know.

Mark

RichieHoneybucket · 9 Mar 2011

Mark I feel your pain, nothing worse than a bully Builder who's trying to call the shots.

10mm pipe? Hmmmmm....How far down the line are you with this UFH outfit? They are starting to sound a bit dodgy!! And any large glazed areas, should be given special attension. Normal practice is to close band the pipes in front of the glazed area for a 1/3 of the height of the glass. But hey their a UFH company, they'll know that???!!

Yes, their design will heat the room, but you'll have a bit heat loss at that glazed area and that needs to be addressed now!!

Mmark · 9 Mar 2011

RichieHoneybucket said:
Mark I feel your pain, nothing worse than a bully Builder who's trying to call the shots.

10mm pipe? Hmmmmm....How far down the line are you with this UFH outfit? They are starting to sound a bit dodgy!! And any large glazed areas, should be given special attension. Normal practice is to close band the pipes in front of the glazed area for a 1/3 of the height of the glass. But hey their a UFH company, they'll know that???!!

Yes, their design will heat the room, but you'll have a bit heat loss at that glazed area and that needs to be addressed now!!

The UFH company never got back to me on an updated design. AstraCad were very kind and did a free rough mock up of what it should be. Basically two serpentines, one going to the right to cover the bi-folding doors. And another to the bottom. The builders have said if I draw it up correctly they will fit it as I've requested.

I've also bought 15mm pipe and asked them to fit that. I rang 4 companies today, all said stay clear of 10mm pipe.

I have found companies that do 10mm solutions, but they always seem to be for those pre-fab chipboard panels used for wood floor area. And have 100mm centres. Are wooden floor installations more worried about height? Why is it more common there?

I'd be interested to hear the pros/cons of 10mm vs 15mm.

No one can give me an advantage to 10mm pipe, other than it's cheaper and can be easier to fit in tight spaces.

Others have said however it will need more eletricity to pump, as the water will hve to travel faster. And it will take longer to heat the room. And it simply won't give the same heat output- so why take the risk.

I just don't understand why a "reputable" company like floran would offer 10mm over 15mm, there seems no logic to it.

Mark

Mmark · 9 Mar 2011

Diggy a bit depair, florad offer those prefab boards - where 10mm seems to be more common:
http://www.florad.co.uk/design-and-technical/floor-heating-products

I don't know why 10mm is more common for prefabbed, where as 15mm for standard lay. But i suspect as this "profoil" is their main product, all their pipe is for that. so they just use the same product for all solutions.....

Mark

RichieHoneybucket · 9 Mar 2011

Certainly 15mm is better than 10mm. In fact I've never seen 10mm used where it was not in a board or the likes. 15mm has a bigger surface area, that's the simple difference. As a 22mm pipe would replace 15mm if the area, heat-loss or mean water temperature required it.

If your are now doing your own design, then there's many factors to consider.

bengasman · 10 Mar 2011

Probably best to ignore RichieHoneybucket, he is a known troll who has been barred a number of times, and this is his latest alias.
He has never worked in the trade in any way shape or form.

bengasman · 10 Mar 2011

The lay out of the pipes in itself has little or no influence on the presence of the doors; the ufh will do the job, or not whatever way you lay them. The question is: will the ufh be sufficient to heat a room with that much heatloss, and will the correct controls be installed in the appropriate way?

If the installer has done his measurements right and applied these correctly in his design, all should be well.

RichieHoneybucket · 10 Mar 2011

Sorry about Ben, he's trying to discredit me, not sure why?? Perhaps he's bitter & twisted as he has not worked for ages & never away from this forum. I think he may be a career change chancer(CCC), that has spent a fortune on a cowboy course & is now sitting at home waiting for the phone to ring. Hope the phone rings soon Ben!!

Certainly with the poor U value glazed area, you'll have a big heat loss there. So normal practice is to do as I stated above.

ajrobb · 10 Mar 2011

I thought the preferred method of laying pipes is to lay the flow and return next to each other all the way round the room. So taking a cross-section across the floor, the pipes will alternate flow, return, flow, return etc. That way the heating is more uniform.

Is the maximum heat from UFH supposed to be 100 W/m²?

RichieHoneybucket · 10 Mar 2011

ajrobb said:
I thought the preferred method of laying pipes is to lay the flow and return next to each other all the way round the room. So taking a cross-section across the floor, the pipes will alternate flow, return, flow, return etc. That way the heating is more uniform.

Is the maximum heat from UFH supposed to be 100 W/m²?

The object of the install is to get the hottest pipes to the biggest heat loss, so if you have the flow going around the perimeter or running along outside walls. But it's not that important. However, in the OPs case he has a large heat loss through the large glazed area to contend with!

You can have a high floor surface temperature, even above 29degC, if there's no traffic in that part of the room.

mointainwalker · 10 Mar 2011

How much pipe are you planning to use per circuit and how many circuits ?

What is the calculated heat-loss for this room ?

bengasman · 10 Mar 2011

ajrobb said:
Is the maximum heat from UFH supposed to be 100 W/m²?

Whatever figure you want to use here is even more theoretical than normal heatloss calculations, because there are even more variables.
The effective output depends for a large part on the differential temperature, which is far from set. As this differential is a lot lower than with rads, the variation of the differential is a lot higher. Add to that the unknown quantities that the designer does not know, and can also vary, and you have a rather arbitrary figure.

RichieHoneybucket · 10 Mar 2011

Rubbish Ben, you've clearly never done any UFH design. Of course you can give a wattM2 of any floor, as long as you know the floor construction, pipe size, centres & floor covering. There's also other factors, like it's radiant heat with little or no convection, so the room air changed are vastly reduced.

There's many things to be considered when doing UFH design. And it's not something any gas monkey could do.

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Underfloor Heating Layout

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