Wooden floors + UFH + Geotherm

smadger

Hi all,

I'm in the start of the planning process for a house build. I've got my eye on a geothermal heat pump which implies underfloor heating.

I read that wooden floors aren't suitable for use with UFH since wood is such a good insulator. Is this true? Are there certain types of wood floor that are more suitable? Or does it really matter since UFH has to be on a long time and isn't used for instant heat?

Thanks in advance

yop

Welcome to the DIY section.

One point, it is said that UFH is more suitable for use with GEO as the rads will supposidly shorten the lifespan of your HP but you can use rads.

There are various arguements on the issue on whether or not to use solid wood or semi-solid floors with UFH.
I know people who have used solid wood flooring with their UFH BUT in saying that from what I have read it is more suitable to use semi-solid. Go to a dedicated floor store and have a talk with them.
Don't know who told you that wood was an insulator but go back and give them a slap on the ear arse their through talking are.

Or does it really matter since UFH has to be on a long time and isn't used for instant heat?

Not sure what you mean here?? It is that you suggest that UFH takes longer to warm up?

gregos

Wood is a better insulator than a lot of materials. Not arse completely talking are through they.

smadger

yop wrote:

Not sure what you mean here?? It is that you suggest that UFH takes longer to warm up?

Since it has to heat up the screed first, does that not mean it'll take longer than rads to heat a room, regardless of whether wood is involved?

But now you've set me thinking about how little I know . If I have wooden floors, does the UFH need a screed at all or is some other mechanism used?

Thanks for the input guys. BTW, I think I'd prefer UFH to rads for aestethic purposes as much as anything.

yop

Wood is a better insulator than a lot of materials. Not arse completely talking are through they.

I know what you mean but I think he means that it will block the heat from coming up through to the rooms.


Admittedly (sp!) screed does take longer to heat up but then again it takes longer to lose the heat then also.
if you put in screed you get better heat coverage in the room as it is a good heat retainer and conductor.

Have a look here http://www.underfloordirect.co.uk/html/floor_types.html

And choose the FloorTypes menu on the left to see the ways of doing it

patrido

there are a few things to take account of when using UFH with wood floors.

1: R value, or how much is resists the transfer of heat. Tiles are best with an r value of about 0.011 m2KW, wood laminate is about 0.050 and 22mm solid wood is 0.125. By comparison carpet (which most people discourage with UFH) is 0.150. In general narrow plank boards are better than wide plank boards. Though I think admont claim to have a wide plank board suitable for UFH.

2: room for expansion. In the heating season, the wood dries out, and small gaps appear between the boards. In the summer, the wood contains more moisture and expands a little. So there has to be room for expansion at the boundaries. Make sure the installer knows this. The wood manufacturer should have a recommendation on how much space for expansion should be left, based on the floor area.

Also, if the floor is nailed, it restricts the natural expansion and contraction of the wood. Many people are glueing the wood directly to the screed. The glue must be approved for use with UFH. Junckers have a very clever clip system, so the floor just lies on the screed, and the clips hold it all together. The clips allow for expansion, and when the wood becomes drier, it pulls the boards together, reducing any gaps that might otherwise appear.

3: moisture content. It is crucial that the moisture content of the wood is low (i think 8 percent is the benchmark). This means that the wood will be more dimensionally stable when the heating is turned on. Some wood floor manufacturers guarantee their products for use with underfloor heating. Junckers is one. I think admont is another. They don't guarantee thermal efficiency or anything - just that if you follow their instructions (regarding acclimatisation, surface temperature, screed moisture content, etc) that they will not warp.

4: Acclimatisation: as with the screed, you must allow it to acclimatise before installation, and before ramping up the heat. The floor manufacturer will have a guideline, but I think you generally leave the wood in the house for 2 weeks before installing it. After installation, you can turn on the heating at a quite low setting, and every few days notch it up a degree or two.

5: surface temperature. The maximum surface temperature, which should be specified by your UFH engineer, cannot exceed a certain value - the figure 29 degrees comes to mind.

6: air gap. you can't put battens on the screed and then nail the boards to the battens in the traditional way, because there will be an air gap that will resist the transfer of heat. I already mentioned gluing and clip systems. Some ufh suppliers provide battens that can be embedded in the screed. they have some kind of a rubber bottom on them to allow you to level them, and you can drive nails into them. This allows you to nail the boards to the floor, without leaving an air gap.

You could also have a suspended wooded floor. Some ufh suppliers, sell aluminium diffuser plates. The plates sit on the joists, and have a channel in the middle to hold the pipe just below the top of the joist. The floor boards can then be nailed to the joists. No air gap here either. This system has 2 advantages - you have a much higher response, almost as quick as a radiator, so it's good if you have an intermittent heating cycle during the day. You also dont have the pipes set in concrete. Though you could easily drive a nail through the floor boards into the pipes!

www.junckers.com have some good information on using UFH with wooden floors.

Hope this helps

pd

patrido

yop wrote:

Admittedly (sp!) screed does take longer to heat up but then again it takes longer to lose the heat then also.

Dead right.

The key to managing this is having a good control system. If you want 20 degrees from 6 pm till 12 midnight, the system should be clever enough to turn on the heating at 4pm and turn it off at 10pm to allow for the thermal mass of the screed. Some controllers take the outside temp into account too, so it comes on earlier and stays on longer in colder weather.

Many people who are unhappy with ufh, treat ufh like a traditional central heating system. I.e. they turn on the heat when they want heat.

There are ways of increasing the response time if that's important (i.e. when you have intermittent heating cycles) You could use a thinner screed - using a flow screed, you could get it as thin as 35mm. Or use a suspended floor with diffuser plates.

Also, using setback controls, rather than letting the system cool down completely when it's off.

With setback, when the system is "off" according to the timer, it is instead set back by about 7-10 degrees. So when the "on" cycle is called, it responds much more quickly. I've read that this is more efficient too. Does anyone know if this is actually the case?

yop

Excellent post RP - very informative


patroido - flow screed, is this a special screed you can purchase from the likes of roadstone?

Setback info
http://www.ippec.co.uk/contfaq2.htm

patrido

yop wrote:

patroido - flow screed, is this a special screed you can purchase from the likes of roadstone?

Roadstone don't do it as far as I know - I asked their Slane branch and they knew nothing about it. Jerry Beades Concrete (in Fairview, I think) is the only place I know that does it - their product is called Easy Screed. I'm still trying to get info on it, so I don't know the full story.

Basically, it's liquid, and flows through a pipe, so it's dead easy to pour and to level. No wheel barrows, and no "screeding" with long planks.

It's based on anhydrite/calcium sulfate, it's sposed to be more efficient for ufh, and can be applied (according to my UFH supplier) in a thinner screed than a sand/cement screed.

If anyone knows anything about it, I'd be interested in hearing their opinion.

pd

smadger

Thanks guys. I'm learning a lot today!

Patrido, did you get someone local to do your UFH? I'm in Louth so if it's someone you would recommend, I might give them a shout when the time comes.

yop

That sounds like a good screed

patrido

mine isn't installed yet

I'm still putting on the roof, so it will be a while yet. I'm planning to do the UFH myself, so I don't know of any local installers.

One company (unipipe) who sent me a quote recently recommended an installer in Cavan - I will look up the name this evening and post here tomorrow.

Heatmerchants (and probably all the major suppliers) have lists of plumbers that can do it. I don't know if there's a heatmerchants in Drogheda, but there's one in Navan. Also, Chadwicks are agents for Quality Plastics, so they might have a list.

If I was you I'd get lots of quotes from suppliers, pick one you like, and then find someone to install it.

I'm probably going to buy from Heatmerchants (Rehau). Quality plastics are also quite good. The systems by Polytherm and Nu-heat also look very good, though they haven't sent me any quotes yet.

yop

Patrido - Have you tried warmfloor in Tyrone and www.underfloordirect.co.uk in Belfast??
Found warmfloor cheapest for install and supply, underfloordirect are the best and cheapest for supply only

patrido

I've just checked and I did send both an email with my plans attached, and they never got back to me. I've just contacted them again now, so they'll send some info on.

Did you install the underfloordirect system? Was it their single tube or triple tube system?

Any idea why they are cheaper than everyone else?

bmm

patrido wrote:

1: R value, or how much is resists the transfer of heat. Tiles are best with an r value of about 0.011 m2KW, wood laminate is about 0.050 and 22mm solid wood is 0.125. By comparison carpet (which most people discourage with UFH) is 0.150. In general narrow plank boards are better than wide plank boards. Though I think admont claim to have a wide plank board suitable for UFH.

Nice post patrido, it's mind bogling the number of ways to put down ufh, it's certainly not for the faint hearted, every builder and plumber i met tried to put me off but that was mostly due to their ignorance.

One point that hasn't been made is that ufh pipes can go down at foundation stage, this is probably cheaper as the proper depth of floor insulation can be installed at an early stage . Also there are fewer circuits, fewer costly thermostats, smaller manifold etc. (although a circuit should not be longer than 100m)

I'm at the floor laying stage, used a standard concrete mix as screed. I can't afford Junkers (i used up all my money on the ufh ). I want to know why all the laminates say "not suitable" for ufh. Has anyone ignored this and had a good result? Also has anyone found that glueing the laminate to the screed has given a better performance than laying it onto the screed? thanks,

bmm

yop

Not sure why UnderFloorDirect are cheaper to be honest, I was speaking to 3 local UFH installers and they now have switched to these guys as they are much cheaper,.

Single tubing is what I am installing.

patrido

bmm wrote:

One point that hasn't been made is that ufh pipes can go down at foundation stage, this is probably cheaper as the proper depth of floor insulation can be installed at an early stage . Also there are fewer circuits, fewer costly thermostats, smaller manifold etc. (although a circuit should not be longer than 100m)

I was going to put mine in at foundations stage, but decided against it for a few reasons. One of the major reasons is protection for the protruding pipes/manifold - I did most of the blocklaying myself, so I know exactly how often trowels, half blocks, etc fall If you get builders in, will they treat your pricey components with enough care and respect?

It's also very difficult to keep the floor in that nice smooth "just poured" condition, which is important for gluing or laying wood. There is a spec somewhere of no more than 5mm variation in height over any 3metres in length.

I think individual room zoning and thermostats are probably worth paying for... most houses these days are empty during the large parts of the day (if the missus wasn't working too, how could we pay for all our heating gadgets ), and different rooms have different occupancy patterns. Though you could easily designate 2 or 3 zones for eating, living and sleeping, and control them seperately. A 2 or 4 port manifold is *much* cheaper than a 12 port one

Systems with only one thermostat are really taking a sample of the house temperature, and different rooms will naturally have variations in temperature due to aspect, number and type of windows, number of external walls, insulation, etc. UFH engineers do take heat loss due to walls, windows and doors into account, but I don't think they go to the extend of factoring in the U-values of your choice of window, insulation, or the effect of passive solar heating in south facing rooms, etc. Some rooms may end up being too warm or too cold.

I think the 100m limit is because of the drop in water temperature over the circuit. The max drop is usually about 10 degrees, and your UFH engineer should work this out for you. I think you could get over that limit by using a faster flow rate and/or a slightly larger pipe.

Systemlink and Nu-Heat have a gadget to reduce the length and hence temp drop of individual pipe runs...
http://www.systemlink.ie/details.asp?l=2&lone=1&two=138
http://www.nu-heat.com/index.cfm?fuseaction=home.whatYouGetFastFlo

bmm wrote:

I'm at the floor laying stage, used a standard concrete mix as screed. I can't afford Junkers (i used up all my money on the ufh ). I want to know why all the laminates say "not suitable" for ufh. Has anyone ignored this and had a good result? Also has anyone found that glueing the laminate to the screed has given a better performance than laying it onto the screed?

Don't know... do you want to take the risk ? Any of the major floor sellers should be able to advise - Brooks, Noyeks, Tubs & Tiles, etc.

pd

patrido

fyi... beades got back to me, and the flow screed seems the business. but whoa it's pricey. over 4k PLUS VAT (at 13.5%) for 175m2 to a depth of 40mm. that works out at almost 700 bills per cubic metre.

it self levels, is installed in about 3 hours, and can be walked on the next day.

and it's strong enough to avoid the need for steel reinforcement. I think she said about 25N?

yop

anyone else get quotes on these guys or is there even an alternative!!

Can you rent out these machines where it pumps in the screed by any chance?

zep

Guys,
Seen this flow screed a couple of times on Discovery...
Is defo recommended for UFH over sand/cement on these progs. It is supposed to eliminate all air bubbles because it flows so easily.
Yop, don't think that the pumps can be rented out seperatly as any time I seen them they are just part of the lorry. Could be wrong and these progs were all based in the UK.

Wobs

I got info a while back from those guys, they sent out a promo DVD, the stuff looks the business, would like to see the finished product in person though. I belive they come and pump it in for you straight off their truck. Didn't get a price at the time but that is steep.

Doper Than U

We've had this screed done (I think!). We got Amtico flooring in our kitchen, and they layed a very liquid screed and then used a vibrating machine (nearly wrote vibrator :rolleyes: ) to level it. I have no earthly idea who did the screed, but there may some information on Amtico's site?

CJhaughey

Amtico? nice stuff but v pricey.where did you get it from?