Solid wood options with Underfloor Heating?

iplogger1

First off I am considering the possibility of getting a geothermal underfloor heating system installed in the new house we plan to build in East Mayo.
Does anyone here know what the restrictions are in terms of the wood
flooring dimensions (eg, thickness) which are possible to co-exist with a geothermal system (without substantial decrease of efficiency or risk of short or long term damage to the wood via expansion, cracking,etc).

I know of one local chap who has installed this type of system but he went for semi-solid wood flooring for his house. We were originally contemplating solid hardwoods for all flooring areas in the house. However, I am going to look at this chaps thinner wood (hardwood laminate?...) as he says it is very hard wearing and convincing as a substitute for natural solid hardwood flooring. However, I'd also like to be educated as to the constraints that putting in an underfloor heating (using geothermal source) places on the types of wood surfaces and thicknesses allowable in such a design for a house.

Any pointers, comments, info appreciated.

~ipl

yop

Bit confused on your questions to be honest.

Do you want to know of what woods are suitable with UFH and is UFH suitable for Geo??

iplogger1

Yes in a nutshell I want to know what floor coverings are suitable for
UFH (assuming temperatures typically provided using a geothermal system).

As I understand it geothermal is almost exclusively provided as the heat
provider for UFH systems since it isn't really suited to being used to
harvest heat used to circulate in conventional wall rads. So my query
is really more to do with whether I might be limited in the floors we
can lay down.

I've seen another thread here where someone had a screed within
which the UFH elements/pipes are embedded and they were told
that fixing a solid wood floor above that would not make sense and
would restrict the amount of heat provided to the room above the
floor and that by turning up the temperature there are risks of
cracking/expansion due to different coeffs of expansion of the various
materials sandwiched between top floor covering and the concrete
or hollow core substrate.

~ipl

yop

Okily - Yes UFH is more suited to Geo than rads are to Geo due to the higher running temps required by the rads.
UFH can be used with any heat source though, oil, Geo, Air, solar, solid fuel anything really.

On what timbers you can use I have heard many varied comments on this, I know people who have semi-solid, solid and lamiate without issues.
Now I think there are recommended types of wood which are recommended such as oak but I would not honestly know enough about it to comment, we have semi-solid oak, with UFH and Geothermal in our new house.
My mate has solid canadian pine with UFH and an oil boiler with no issues.

But I heard Junkers are very suitable, but expensive, I think if you search the threads here you will find some good threads.

patrido

there are 2 main issues with wood and ufh.

the first is resistance to heat transfer and the second is expansion/twisting warping.

firstly heat resistance... carpet is the worst for heat transfer (but certain types can be used), tiles are the best. in between are wood and laminates. laminates are best, while 22mm thick wood is only just better than carpet (but again, if your system is designed with this in mind, it should be fine).

secondly, wood changes shape depending on the amount of moisture in the air. it dries out a lot during the heating season, and during the summer, it absorbs lots of moisture from the air. too much change in humidity can cause problems with warping/twisting. if you get a good quality wood, well installed over a well designed ufh system, you should have no problems. if you take shortcuts, you might have problems.

the main issues to take account of are...
- type of board... semi solids / engineered boards are more dimensionally stable (so less likely to warp/twist) than solids, because of the engineered layers underneath the solid surface layer but a good solid board will not be a problem.
- size of boards... wide boards are not really suitable. anything 120mm or less should be ok. thinner boards allow the heat through more easily. 22mm is the limit. 18mm might be more suitable.
- there should be no wood subfloor, and any underlay/soundproofing should be suitable for ufh. these will add to the heat resistance, making it harder to heat the floor.
- species... certain species expand and contract more - beech and maple are not as good as oak. though check with the manufacturer.
- floor temp - normally you're not allowed to have a surface temp in a living area of more than 29 degrees, but this should be lower (perhaps 27) with timber over ufh. your designer should take this into account
- installation method - with the annual expansion and contraction, the floor should be allowed to move freely. otherwise, after a few seasons there could be problems. nailing down is bad, floating is better. the best system is probably the junckers clip system.

iplogger1

Padrido,

V.useful summary.

From what I've read on the various threads one concern I have with solid woods is the fact that it seems that to be used with UFH it seems that to get best thermal efficiency of heat transfer upwards and minimal losses it is recommended by some to glue the solid wood planks to the concrete subfloor or screed.
This seems messy and more trouble than worth. I've read that the notable exception to this is to use the Junckers click system solid woods which I think will probably turn out to be prohibitively expensive and posssibly less choices in terms of types of woods.

We were recommended, ash for hallway, red oak for dining room, beech for living room and ash in one or two other rooms such as a reception room downstairs.

What I seemed to get from the threads was that semi solid or engineered woods were a better bet with UFH.

Any further insights based on my hackish conclusions above ?

Tobi2

Hi
Quick reply here but this is a subject "close" to our hearts at the moment.
You may have seen some of my ramblings on this a few pages back.
I would second what Yop and Patrido say above.
You are starting out on the right foot as the whole point of ufh and installing geo etc is that it is a whole system that is part/integrated into the house instead of part of the house build, if you know what I mean?
It is not a case of putting rads here and there and then deciding on the interior design, ie flooring.
Ufh forces you to think of your flooring options before you go ahead and build so that the whole thing works as a complete system.

Re timber flooring, it is a difficult one to decide now as you are getting info from all sorts of places, but if you want to go with ufh then I would stick with those in the business (of ufh/heating houses), as tbh in my experience those not, do not know anything/very little about ufh and how it is supposed to work. People still think in terms of radiators and heating up/draughts etc whereas ufh does not operate like that. So firstly get your own head around the system and what you want from it.
The world and it's mother now has an opinion on ufh etc but if you ask them if they have lived with it/seen it in action, majority have not, so imo it is a bit of a "new thing" at moment in this country...and getting very complicated as the market is flooding with timber flooring of all sorts, so the choices are growing...as is the info (or is it??).
If you look at Scandinavian countries they have been using ufh for years under timber floors, with great success. In fact any ufh I have seen/lived with has been under a timber floor, so I know it works.

Think about what you know about heat and how it is transferred, natural substances such as stone are probably best at transference, however not everyone wants stone floors. Manmade products, ie textiles are not good at heat transference; carpets are not good. Then there is timber, a natural insulator, so while it is not the most efficient at heat transfer it is not the worst either and does retain heat. (Look at all those log cabins in Finland with inches of snow on the roof..even though the building is toasty warm inside).
I have come to the conclusion that the gluing floor down thing is a money maker...the glue is exorbitant and even though there might be some argument for glue acting as a heat transfer mode, I would hazard a guess that the amount of heat not transferred without glue is negligible. Also I suppose it does allow for a "floating" floor of sorts where nails were the only option before.
Would you consider tiling at all or are you determined to use timber on all floors?
If you have a large area to floor and you are going for ufh, then this might work out more cost effective in the longer term, and you will have broad range of products to choose from. Also I notice you are getting advice re different flooring for each room/area..is this what you want? Would you consider using the same flooring througout the house? It can create an open plan space without actually being open plan, iykwim? To the eye the areas/house can feel very spacious but you don't loose the "different rooms" plan either. It is hard to explain without seeing it but I hope I am making some sense.

If you are definitely going for timber, then I would urge you to get the best you can afford. As you say Junckers are pricey, but they seem to be the only ones out there at the moment willing to "stand over" their products. I have come accross other floors that are also "recommended" for ufh, prices not too dissimilar to Junckers, (more for the floor I wanted!!), new to the Irish market. When I enquired where they come from, they are imported from China.
If you ring Junckers, email www.junckers.co.uk and ask for the no. of local rep/agent, you will find them most helpful. They do get involved in the planning stage and will work out with you and your ufh designer the best way to lay your system if you are opting for this type of floor. I discovered this two weeks ago..:o :rolleyes:

Again, you could consider getting same timber in all the rooms, same reasons as above, re tiles.

We came to the same conclusions re semi solids and engineered floors and would probably have gone for this if we had the whole house to floor, but as it was, we could not find one system/company who could advocate their product for ufh and tbh the info I was getting from shop reps did not inspire me, which to me is an indication of how much they acutally know about the product/or how much the supplier knows about the product..ie little or nothing. Plus the cost over the duration of the mortgage is negligible, hubby reasoned why cut a corner here when it is not something we want to change for a long long time, if ever.
As a matter of interest, is it interior design advice re different timbers in each room?

Finally of course, regardless of flooring/heating system you must do as much homework on insulation, and factor in your cost here. This is the most important area imo, regardless of what system you use and if you don't get this bit right, then the rest is money wasted I would think.

Sorry for going on and on, haven't said much really that you didn't know already.
Best of luck and welcome to the minefield and adventures of housebuilding.

Tobi

Carb

Well I'm expecting delivery shortly of 200 sqm of Ipe/Brazilian Walnut. The flooring is 3 inches wide and 18mm thick, and the recomended installation is complete adhesion. I'll be laying it over a concrete floor with UFH. It may be more messy to glue the floor down, but I wanted a solid floor, so I'm willing to pit up with that.

patrido

i would not use beech with ufh, unless the manufacturer provides a guarantee such as junckers. also, a true floating floor is better than a glued floor as the whole floor can expand and contract without restriction.

the thermal efficiency should be fine as long as the boards are not too thick, and you don't use too much or the wrong type of underlay. the manufacturer should be able to give you the thermal resistance of the floorboards and any underlay. add them up and they shouldn't exceed 0.150m2K/W.

for example a 22mm board should have a thermal resistance of 0.125m2k/w, which is fine. but if you add an underlay of 0.080m2k/w the total is probably too high.

it depends on the radiant intensity of the room in w/m2. divide the heat loss for the room by the net usable area.

if this is anything up to 95 W/m2 you can have a thermal resistance in the floor of 0.200 m2K/W. between 95 and 110, you are limited to 0.150. above 110, you can really only use tiles or possibly laminate.

iplogger1

Hi Padrido,

How do I calculate the radiant intensity for a given room assuming
I have the room dimensions from the plans and can estimate the
usable space,etc ?

~ipl

patrido

calculate the heat loss in watts and divide by the net floor area in square metres. if u want, send me the dimensions and i'll work it out for you.

iplogger1

OK. doh.
and physics once was my best subject until my head was numbed
with IT.

That's a no brainer for me to calculate - thanks padrido.

~ipl

iplogger1

Tobi2 - Thanks for your summary of what you have found and advice,etc.

The guy who has been advising us re: various woods in different rooms is a knowledgeable chap who does a lot of pre-site work/landscaping and also is a major wood enthusiast (he is also a wood turner in his spare time as it happens). So he is a real advocate of solid wood flooring.

The problem is that when he advised us about 2 weeks ago as to different floor timbers in the rooms his assumption (as was ours) that we would have conventional rads and not UFH. This was down to a misunderstanding by my wife of the geotherm system. She assumed and he followed suit that the geotherm system was some kind of backup heat supply to conventional oil fired burner rads. Now that assumption is out of the window and it looks like the whole flooring question is more complicated and a lot more factors need to be taken into account.

For sure it looks like beech (as suggested as a "calming" wood colour for certain rooms) is not a good option for UFH. According to something posted by Kadman (sp?) who is a wood guru here there was an informative chart which throws into question the choice of beech other than some proprietary solution by some specialist timber company who do give guarantees for their beech flooring used in conjunction with UFH.

By the way have you any concerns about the efficiency of the UFH and its return on investment (aside from timber floor and possible heat losses due to that)? I've heard from one guy who says his pump is costing 3.6-6 Euros per day. I know he put in a lot of insulation. Maybe it still is economic in the long run given rising oil prices .. but electricity prices will be hiking I assume at almost the same rate (although maybe if ESB/Airtricity switch more investment into air then maybe that will soften the escalation of electricity charges in the next decade or more ... )

~ipl