Flooring over UFH decisions, advice please

[Grian]

My mum and I are both building houses with wet UFH (using an air-source heat pump). Choosing tiles is proving difficult (blood is coming out of our ears), we dismissed engineered wood because it would transfer heat less efficiently but now are wondering, how much difference does it actually make - are we looking at a noticeable difference in heating bills to achieve a given temperature, or just slower heating up if we alter temperature? Any advice welcome as I can list the entire catalogue of several tile outlets and that is not healthy!

 

Also, travertine and slate, are they really onerous to maintain, are they worth considering? Like we need more options!

 

Thanks

Kirsty

[ProDave]

Nothing wrong with engineered wood over UFH.  Our last house had Maple, and this one has Oak.

 

And if anything, I find the heat transfer to the rooms downstairs with UFH pipes in pug mix and wooden floors is better than in the bathrooms that use spreader plates and tiles.

 

UFH is never a "quick heat" system, it works best at a low level but on for a lot of the time.  Just make SURE you have a LOT of insulation under the floor.

[Ferdinand]

I do not think that tiles or engineered wood will make a huge difference.

 

You need to worry more about insulators like carpet and maybe if you use a thicker than usual underlay under your tiles if they are click fit.

 

Have you considered tiles made to look like wood, and Vinyl Tiles? They are both good choices ?.

 

Start from the other end for the covering, and decide what characteristics * you want for your floor, weight for importance and prioritise. Then rate each finish on each thing, and multiply by the weighting’s, and look at the top two. May help.

 

Ferdinand

 

* eg hard or soft feel, required lifetime, installed cost per sqm, is it cat proof, will grandma go arse over tip, does it show mud etc.

 

 

 

Edited September 13, 2019 by Ferdinand

[Jeremy Harris]

There isn't much difference between different hard floor coverings, the major issue that determines efficiency (how much it costs to run) is the amount of insulation underneath the floor.  All UFH systems lose more heat to the ground than other heating systems, typically around 10% for a reasonably well insulated floor, but if the insulation under the floor isn't that good then the losses can be quite high.

 

We have a mix of bamboo flooring (very like engineered timber) and travertine, and there's no noticeable difference between the two areas.  Carpets and rugs do tend to slow down the heat transfer a bit, though.

 

In terms of care, we find the travertine easy enough to look after.  I sealed it with the special sealant after it was laid, and before it was grouted, then again after it was grouted, and since then have just swept it and washed it with a normal (non-acidic) floor cleaner.  

[Bitpipe]

Our ground floor is suspended timber (over basement) - build up is UFH in alu spreader plates - 18mm OSB - 12mm ply - 9 mm ply - 6-7mm Sika resin comfort floor.

 

Nice and warm underfoot year round, whether the UFH is on or not.

 

Remember tiles etc are good at conducting heat away from your feet so will feel cold unless warmed up via UFH (i.e. in summer). Wood, resin etc is a poorer conductor so will feel warmer underfoot. 

[Ed Davies]

Engineering toolbox gives thermal conductivities of likely [¹] woods ranging from 0.12 to 0.17 W/m·K. This page says 0.22 W/m·K along the grain and 0.14 W/m·K across the grain for pine. Skip reading this article gives mostly higher conductivities for engineered bamboos.

 

Taking the worst-case (i.e., lowest) plausible value of 0.12 W/m·K and assuming a thickness of 12mm that would give a thermal conductance of 0.12/0.012 = 10 W/m²·K. That's about the same as the conductance from the surface of the floor to the air (by both conduction/convection and radiation) so the effect of a wooden floor would be to no more than double the temperature difference needed between the top of the substrate (screed, concrete, whatever) and the room.

 

Since in a well-insulated house that's only a degree or two anyway and any other flooring will have some thermal resistance of its own the effect of the amount of extra insulation provided by the wood would be tiny.

 

As @Bitpipe points out, if you're likely to walk around in bare feet much then the reduced conductivity of the wood allowing the floor to feel comfortable at a lower temperature might be a more significant effect.

 

[¹] Balsa's probably an unlikely wood for floors.

[Bitpipe]

3 minutes ago, Ed Davies said:

As @Bitpipe points out, if you're likely to walk around in bare feet much then the reduced conductivity of the wood allowing the floor to feel comfortable at a lower temperature might be a more significant effect.

 

We enforce a canadian /european style no-shoe rule in the house for everyone (visitors etc) as for the first year we had an unmade driveway so wanted to minimise grit etc.

 

Much more hygenic and everyone gets to enjoy the soft & warm resin floor underfoot. 

[Ferdinand]

37 minutes ago, Bitpipe said:

Much more hygenic and everyone gets to enjoy the soft & warm resin floor underfoot. 

I feel more relaxed already ? by internet osmosis.

 

[Grian]

Well this is encouraging, I think. What a lot of good info, thank you. Engineered wood is definitely an option then.

 

We are no-shoe households but there are dogs and with my current Karndean I mop regularly, I will look into how well it withstands a bit of moisture.

 

The UFH is embedded in the concrete slab laid before building begins, if that makes any odds. Good point about when heating might be off completely in summer.

 

Thank you again for responses. Now to browse all the wood floor options

[nod]

4 hours ago, Grian said:

My mum and I are both building houses with wet UFH (using an air-source heat pump). Choosing tiles is proving difficult (blood is coming out of our ears), we dismissed engineered wood because it would transfer heat less efficiently but now are wondering, how much difference does it actually make - are we looking at a noticeable difference in heating bills to achieve a given temperature, or just slower heating up if we alter temperature? Any advice welcome as I can list the entire catalogue of several tile outlets and that is not healthy!

 

Also, travertine and slate, are they really onerous to maintain, are they worth considering? Like we need more options!

 

Thanks

Kirsty

You won’t get a better conductor than porcelain 

Also extremely hard waring  

[Jeremy Harris]

Here's a guide as to typical thermal conductivities of materials that might be used for flooring (the higher the number the more thermally conductive it is):

 

Carpet - ~0.1 W/m·K

 

Oak - 0.16 to 0.17 W/m·K

 

Bamboo - 0.2 to 0.35 W/m·K

 

Travertine - 1.26 to 1.33 W/m·K

 

Porcelain floor tiles - 1.5 W/m·K

 

Concrete (typical floor density) - 1.0 to 1.8 W/m·K

 

Slate - 2.01 W/m·K

 

I doubt that thin layers of any of the hard materials will make any detectable difference to performance, but it's worth bearing in mind that, as mentioned above, the higher the thermal conductivity the colder the floor may feel in bare feet when the heating isn't on.  Even with the heating on in our house we find that the travertine feels cooler underfoot than the bamboo, as the heating rarely heats the floor much above 22°C to 23°C, so it's still well below body temperature.

[bobberjob]

we are looking at this just now and trying to decide whether to have engineered wood or tile or vinyl.

 

Wood always looks nice but all these options add extra layer of finish and therefore cost.

 

Has anyone polished their concrete screed to achieve a finished surface or I am being stupid?

 

What are the downsides of polished concrete?

 

[Jeremy Harris]

1 minute ago, bobberjob said:

we are looking at this just now and trying to decide whether to have engineered wood or tile or vinyl.

 

Wood always looks nice but all these options add extra layer of finish and therefore cost.

 

Has anyone polished their concrete screed to achieve a finished surface or I am being stupid?

 

What are the downsides of polished concrete?

 

 

 

@jack has a polished concrete floor.  Looks very nice indeed.

[PeterW]

29 minutes ago, bobberjob said:

What are the downsides of polished concrete?

 

 

A number ..! It has to be laid to be polished, so is slightly higher to allow for material removal. There are also a number of other things you need to understand as the aggregate finish can be “patchy” depending on how the mix is laid. You also cannot use fibre reinforcing so you have to use a standard reinforcement if needed. 

 

I would have loved to use it but it does need to be planned in advance, polished and then protected when the rest of the build proceeds. 

[Grian]

I think polished concrete is expensive too... budget is a constraint so I'm looking for tiles or engineered wood in the £40/sqm range. 

[jack]

20 hours ago, bobberjob said:

What are the downsides of polished concrete?

 

Even with a sealant, you have to be religious about wiping up spills to avoid staining. We have a large permanent mark in our kitchen where my wife took a rubbish bag out of the bin, put it on the floor, then went off and did something else. It wasn't picked up again until the next morning, and by then whatever had leaked out of the bag was well and truly soaked into the concrete.

 

Oh, and stuff tends to break when you drop it onto concrete, but that's an issue with tile as well.

 

It very fast to clean though - a large microfibre broom lets you cover a lot of space quickly. It's also heavenly in the middle of a heatwave when you walk in from a stinky hot day and the concrete sucks the heat out of your feet when you take your shoes off (the kids sometimes lie down on it when they come in). Underfloor cooling helps, and again, you'd get the same effects with tile.

[Jeremy Harris]

I've just cleaned the house, so thought I'd time how long it took to clean the floors.  First was a whizz around with the Dyson, took 12 minutes to do the whole house (130m²), and just about completely filled the dust bin.  I then wet cleaned the travertine (roughly 65m²) with a microfibre mop, a bucket of Flash in hot water and a handheld cloth for the awkward bits.  Took me 16 minutes to give the floors a thorough clean, clean up the mop, bucket etc and put everything away.  Sitting here with a cup of tea it looks like the floor's dry already, which is surprising as, although  its a sunny day, the floor cooling has been on for a couple of hours or so.

 

PS:  As @jack mentions, walking around in bare feet on a cooled floor is very pleasant on a day like this, especially after a little bit of work.

[Declan52]

I have a mixture of carpet, porcelain tiles and engineered Oak on my floors. When the heating is on you can feel the warmth on your bare feet through the tiles and Oak flooring after around 90 mins. Carpet is totally different as it doesn't really warm up to your touch but you can still feel warmth. If you choose carpet then you must get the lowest tog rating for the carpet and under felt or you will block any heat from getting through. 

I actually prefer the engineered flooring under foot. It just feels nicer to walk on than my tiles.

[Temp]

We have a similar mix but stone floors in some rooms. Great as its warm in winter and cool in summer.

 

They reckon you should keep the TOG value of carpet and underlay to around 2.0-2.5 in total. There are special low TOG underlays with  TOG of 0.6-0.7. Beware, some carpets come in two versions, Hessian backed and foam rubber backed. Some shops reserve the right to deliver either version in the small print. You probably  want the Hessian backed as the foam rubber no doubt increases the TOG a lot. In which case get the shop to write something on the order.

 

Edited September 13, 2019 by Temp

[Ed Davies]

1 hour ago, Temp said:

They reckon you should keep the TOG value of carpet and underlay to around 2.0-2.5 in total.

 

That sounds about right. 1 tog = 0.1 m²K/W which is equivalent to a U-value of 10 W/m²·K which, in turn, is about the conductance from a floor to the surroundings above it. So 1 tog of carpet halves the heat flow upwards or doubles the temperature difference needed for a given heat flow. 2.5 tog would multiply the temperature difference  by 3.5 which seems like about the point when a simple control strategy of keeping the slab at a constant temperature would break down.

[Grian]

Well mum is probably going to choose engineered wood, other than in the utility and bathroom, result! Since her kitchen is coming from Howdens and we have looked at their flooring I expect that's where she will source it, unless anyone can advise differently. I'm going to do the same, but not necessarily source from Howdens as I will be buying a used kitchen. 

 

Thanks for the help this has moved things on hugely.

[Temp]

During our build i picked up a load of samples of engineered oak at a self build show. When I got home and put them in natural light I found a very wide difference. They all looked good at the show but some were virtually orange at home. Shop around for appearance as well as price. Perhaps even buy one pack to lay out in the room. You can buy it ready finished or unfinished for you to paint yourself. We got ours prefinished but if you do the latter I recommend Osmo hard wax oil. Also consider the orientation carefully (across or along the room).