Underfloor heating as main source

movilogo

So may be I'll be better off with just extending standard wall mounted gas radiators from my existing combi boiler?

vacheron

movilogo said:

So may be I'll be better off with just extending standard wall mounted gas radiators from my existing combi boiler?

The issue would be that to properly insulate the concrete you would usually put at least 70mm of insulation on top and then the pipes and screed / flooring would add another 50-70mm, so unless you wanted a 120-150mm step up into the room with UFH, the existing concrete floor would have to be broken out first. 

FYI, I've added a couple of photos below showing our partially laid insulation (ours was 100mm thick) which the pipes are then laid on top of before being covered with about 65-70mm screed + the underlay / carpet / flooring of your choice.

gzoom

movilogo said:

How difficult/expensive to install gas underfloor heating in concrete floor? I guess it requires significant amount of digging. 

Others have answered this, but it's not an DIY or none disruptive job. You have to insulated, than lay the pipes, than pour screed and finally finish the top.

My wife deicide she wanted radiators in half of the downstairs despite us having the opportunity to make the whole downstairs run with UFH. She now wishes we had done that, radiators work fine, but UFH gives nicer 'warmth' and feels very nice under foot.

FreeBear

movilogo said:

So may be I'll be better off with just extending standard wall mounted gas radiators from my existing combi boiler?

Replacing (or adding extra) radiators would probably work out a lot cheaper. For kitchens, I like plinth heaters plumbed in to the CH system - These take up zero wall space and direct warm air out at floor level. Not cheap, and they do require a convenient power point.

movilogo

OK, looks like I need to decide between conventional gas radiators vs wet underfloor heating. Disruption is not an issue as I have to re-do the ground floor anyway. Need to get actual quotes and then decide. 

Albermarle

movilogo said:

OK, looks like I need to decide between conventional gas hot water radiators vs hot water/wet underfloor heating. Disruption is not an issue as I have to re-do the ground floor anyway. Need to get actual quotes and then decide. 

In many ways they operate the same way, by having hot water supplied by the gas boiler pumped around the system.
However the underfloor hot water has to be at a lower temperature than you would normally have the radiators.
So you would need extra temperature controls for the underfloor, as you already have existing radiators.
Also as said the part of the house with underfloor heating would heat up and cool down a lot more slowly than the part with radiators, so you would have to have two different timing schedules.

moneysaver1978

What prompted you to consider under floor heating rather than radiators? If it is the space or visuals, is it worth considering a skirting board heating system?

ComicGeek

If you retrofit wet UFH, then you would install a profilled panel which is just installed over the existing concrete floor - something like https://www.underfloorheating.co.uk/profi-panel/. This is an insulation board with foiled grooves, within which the UFH pipework is placed. Depending on the product you then either use a thin latex screed to level for floor finish, or install plywood and floor finish over.

The benefit is that the floor heats up quicker, and doesn't have the slow responsive times that full screeded systems do - the disadvantage is that more heat is lost down through the floor as the insulation isn't very thick.

ThisIsWeird

movilogo said:

How difficult/expensive to install gas underfloor heating in concrete floor? I guess it requires significant amount of digging. 

Yes.
Are you sure that is something you are happy/prepared to do? 
As explained by others, to fit any form of UFH, you need to insulate under it, so that would require a significant amount of concrete floor removal. 
What do you mean by 'have to redo the ground floor'? If you mean that the concrete slab needs digging up and relaying in any case, then you'd be installing a thick insulation layer in the replacement floor, so - yes - I'm sure the consensus would be to fit 'wet' UFH over this, supplied by your new boiler. 
Wet UFH is probably the best overall heating system. It has big plusses, including comfort (it is the best!), it works on low water temps (so is ideal for the most efficient forms of heating, and perfect for a future ASHP), and it looks great (because you cannot see it).
It has one drawback - the lack of fast control. It's really a set-and-forget system, and it's barely worth even trying to reduce the temp overnight as the response time is so large, tho' it can be done for more energy savings if you want - you just need to factor in the lag time.
Where its lack of control can sometimes show itself is with, say, a room receiving sunshine and resulting solar gain. Mil has UFH, and it's absolutely ideal for her - a constant, comfortable temperature. However, when the sun beats in the window, the set 20oC quickly rises to a stuffy 23, 24+, and windows need to be opened. Of course, the 'heating' goes off as soon as it exceeds 20oC, but the large floor mass continues to provide the stored 20oC for hours, which is why the additional effect of the sun is so great.
Other than that, tho', the few places I've been with UFH have undoubtedly been the most cosy-feeling, as the floor is not cold!
So, if you have to remove the concrete slab in any case, or if the quotes for doing so aren't excessive, then seriously consider wet UFH run from your boiler - it's the best. If the cost is prohibitive, tho', then normal water-filled radiators are you next best choice - but still add some insulation on top of the concrete under whatever flooring you intend to use. (Floor insulation isn't as important with normal heating, since the air above the floor is the coolest, so less heat is lost in that direction, but all insulation is good!)
If you go 'radiators', then seriously consider 'over-sizing' them so that they can provide the required heat output with a lower water temperature. The lower the temp, the greater the efficiency, and the better the future-proofing.
When you think about it, UFH is just a giant radiators, so that's why it can heat a room with such low water temp.

vacheron

ThisIsWeird said:

movilogo said:

How difficult/expensive to install gas underfloor heating in concrete floor? I guess it requires significant amount of digging. 

Yes.
Are you sure that is something you are happy/prepared to do? 
As explained by others, to fit any form of UFH, you need to insulate under it, so that would require a significant amount of concrete floor removal. 
What do you mean by 'have to redo the ground floor'? If you mean that the concrete slab needs digging up and relaying in any case, then you'd be installing a thick insulation layer in the replacement floor, so - yes - I'm sure the consensus would be to fit 'wet' UFH over this, supplied by your new boiler. 
Wet UFH is probably the best overall heating system. It has big plusses, including comfort (it is the best!), it works on low water temps (so is ideal for the most efficient forms of heating, and perfect for a future ASHP), and it looks great (because you cannot see it).
It has one drawback - the lack of fast control. It's really a set-and-forget system, and it's barely worth even trying to reduce the temp overnight as the response time is so large, tho' it can be done for more energy savings if you want - you just need to factor in the lag time.
Where its lack of control can sometimes show itself is with, say, a room receiving sunshine and resulting solar gain. Mil has UFH, and it's absolutely ideal for her - a constant, comfortable temperature. However, when the sun beats in the window, the set 20oC quickly rises to a stuffy 23, 24+, and windows need to be opened. Of course, the 'heating' goes off as soon as it exceeds 20oC, but the large floor mass continues to provide the stored 20oC for hours, which is why the additional effect of the sun is so great.
Other than that, tho', the few places I've been with UFH have undoubtedly been the most cosy-feeling, as the floor is not cold!
So, if you have to remove the concrete slab in any case, or if the quotes for doing so aren't excessive, then seriously consider wet UFH run from your boiler - it's the best. If the cost is prohibitive, tho', then normal water-filled radiators are you next best choice - but still add some insulation on top of the concrete under whatever flooring you intend to use. (Floor insulation isn't as important with normal heating, since the air above the floor is the coolest, so less heat is lost in that direction, but all insulation is good!)
If you go 'radiators', then seriously consider 'over-sizing' them so that they can provide the required heat output with a lower water temperature. The lower the temp, the greater the efficiency, and the better the future-proofing.
When you think about it, UFH is just a giant radiators, so that's why it can heat a room with such low water temp.

Great response!   

We chose UFH for our extension as it was going to be built from scratch, so an easy choice, however this area also incorporated the original kitchen area, but fortunately, this consisted of a suspended timber floor over a concrete sub floor, so the concrete was already about 150mm below the finished floor level and nice and solid and level.

This suspended timber floor construction also continues across the whole downstairs area, making retrofitting UFH "relatively" simple. However we still considered this to be too much disruption for now, as the floors were already nicely finished throughouth the house, but it is good to know that the option remains for the future.