Underfloor Heating In an old Victorian House - will it work?

[PurpleFox]

Hi All

I am refurbishing an old Victorian house and cannot make a decision as to whether to go for regular radiators or underfloor heating (or both). I have flip flopped between the two so many times and now I need to make a final decision to move on with the project........

I have had a number of quotes for supply only from various UFH companies who all say it will work fine, which they would as they want to sell me the products.

Please can anyone share their experiences with UFH - I know it is ideal for new builds / concrete floors and the like but certain things I cannot change, its an old, large, Victorian semi detached house with high ceilings, large double glazed windows and wooden joisted floors.

I want to put UFH in majority but not all of the ground floor (Kitchen, hallway, Lounge, sitting room, approx 110m2). There are rooms below in the basement and above.

Having researched the different methods (overlay, spreader plates, biscuit screeds etc) I think I would do the following:
- Rip up old floor boards
- Batton and insulate with 75ish mm celotex
- Lay aluminium spreader plates
- Cover with 18mm ply and Karndean
- or cover with 21mm engineered wood straight to joists / plates

I wouldn't be happy with the additional weight of the biscuit screeds between joists (9") method.

Taking the lounge as an example, an online heat loss calculator gives a loss of 2700 watts.

The floor area is 22m2. An optimistic figure for UFH seems to be 60w/m2 which gives 1320 , less than half the loss.......

Hallway is 11m2 so optimistic UFH output is 660 watts. Heat loss calculator suggests 1100 watts

Similar for kitchen (8.5m x 4m and 3.6m ceiling)

The figures suggest UFH would not be suitable but is that because I am using calculation methods for radiators which consider the room height? Have been told that UFH does not heat the top of the room so needs less power.

Just looking for some real world examples please and any other advice.......

Thanks in advance.

 

[Dan Robinson]

I never trust the online calculators, but prefer to do it properly. You should squeeze more w/m out of the floor. Most important thing is to eliminate drafts.

 

[Agile]

In theory, properly designed it would work. Although on older properties much higher heat outputs are needed which rather stretches the heat output normally obtained with UFH.

But the advantage of rads is that its easy to make subsequent adjustments.

With UFH once its bought and laid that's it and you cannot do much about it.

Although you can do a mixed system which does have some advantages because the rads help a rapid heat up and the TRVs can be set to close when the room is almost up to temperature and let the UFH continue to provide the heat loss.

Tony

 

[TheVictorian]

If you are going to that much trouble then I personally would insulate the inside of the external walls with 50mm Celotex or similar. I have done this on the top two floors of my place and it's amazing how little heat the rooms lose now, small cast iron radiators keep it warm and it holds the temperature well over night when the heating is off.

I do have underfloor heating in my ensuite and it works very well, but that is a 3.5sq/m space with no window!

 

[Agile]

A friend insulated the whole house with 50 mm in the walls.

That brought the heat loss down to less than 10 kW for a large house with six bedrooms and seven toilets.

He has put in a total of 26 different UFH zones.

Tony

 

[muggles]

What is your sub-floor construction, suspended timber or solid? Try NuHeat for size, they will give you a guarantee that whatever system they spec will heat your home adequately, will give you advice on the best system, and will even refuse to quote if they think that your house just isn't suitable. They're also a good company to deal with. You should get much more than 60w/m² out of UFH - their LoProMax, for example, has achieved 190w/m² in testing, although in service it's limited to around 140w/m²

As above though, increasing insulation and draught-proofing would be very cost-efficient first steps

 

[Agile]

And without increasing insulation could well be unsuitable for UFH.

Also forget about insulating the top of the floor with shag pile carpets!

Tony