Underfloor heating in a workshop

[solexious]

Has anyone done underfloor heating in their workshop? I'm currently planning a build for when we move, my old workshop was a large one car garage size space on a small industrial estate (thats sadly been bulldozed to make deliveroo kitchens). The 2 main annoyances with it (other than the leaking roof) was the uneven concrete floor and the lack of heating. So I thought I would combine both in having a nice smooth level concrete floor and combine in underfloor heating. From what I see its the best way to make use of heatpumps and I plan to have solar panels on the roof too. My only worry is how thick you need to have the concrete between the pipes and the top surface for if I have any big heavy bits of kit, like an old lathe or something?

Thank thoughts, advice or tips welcome.

Cheers

 

[Doug B]

I used to work in a workshop that had under flooring heating, the pipes were in a standard screed which was covered in a floating floor of t&g chipboard.
It had a large Felder combination machine in the middle of the workshop & there was no issue with the weight.
The heating made it a really nice place to work in the winter, I only wish I could afford the same set up in my own shop.

 

[Sachakins]

Normally when planning underfloor heating layout, like say in a kitchen, you only lay it in open spaces, so you don't layit where fitted units and appliances go, avoids heating unnecessary covered space and avoids being placed under heavy appliances, especially the likes of heavy aga ranges etc.

Maybe if had a layout plan for your heavy and fixed machines you could avoid.heating in that area.
Also if you lay out heating on entire floor, then don't try and bolt anything down later, sods law you'll hit a pipe!

 

[NormanB]

This ‘problem’ begs more questions the answers.

1. How big is the new workshop?
2. Is the underfloor heating likely to be supplied from the house and its ASHP?
3. Are you able to design the layout of the machinery and benches with certainty?
4. What is the useage profile of workshop?

Some general comments:

1. Consider designing a super insulated building (Sips panels) with a well insulated slab to reduce the heating requirement.

2. If a stand alone heat input is envisaged and point 1 addressed then an air to air solution will be less capital intensive, reduces the floor loading issue (of UFH) and the difference in running costs with UFH and ASHP not material.

3. UFH will require detailed and less flexible floor plan as UFH should not be laid under machinery and benches.

4. UFH really demands a long and slow heating operation, response time is slow until the slab warms up. Air to Air is more responsive and can be used as air conditioning on the few days when that may be useful.

5. There is no correct answer, budget, building usage profile and personal preferences all influence.

6. The one universal truth is the money spent on reducing heat loss (by super insulating) will pay dividends down the line whatever heating solution is implemented.

 

[Ollie78]

Not sure how effective it would be once you put machinery on it. If you don`t have an exact layout in mind you may waste some underneath stuff, the other thing is making sure it doesn`t make the floor weaker for heavy stuff.

If you are having solar/ battery then you could have the electric underfloor heating, its very thin in comparison to the pipes. My brother had some installed under the tiles in the bathroom and really likes it, it was laid first into a layer of tile adhesive and left to set then the tiles were laid as normal the next day on top.

If its well insulated enough then you need very little to get it up to temparature so a little fan heater might be adequate.
I have seen quite a bit about air source heat pumps actually not being all they are cracked up to be regarding energy efficiency, I am also suspicious because the government are trying to push them so it must be dodgy, lol.

Ollie

 

[Herr Nilsson]

In a small to medium sized garage/workshop I would consider an air-to-air heat pump = rapid space heating and 1/3 the price of an air-to-water installation.

Sounds like you might be a professional woodworker, therefore traditional wet underfloor heating could work well *if* you/others occupy the workshop all week, but I would be looking at something more “on demand” as domestic heating requirements are quite different to commercial. A lot of messaging in the media at the moment is aimed at the domestic market, which among other things, looks at the fact we’re all occupying our homes a minimum 50% of the time (more if you now work from home post-pandemic or are retired!). In contrast, a small (30-50m2), well-insulated workshop only occupied approx 25%* of the week (*discounting weekends), obviously has a lower heat demand than an average family sized home (75-125m2).

Optimum sized ufh slabs (70-100mm) have low heat inertia, so not ideal for 25% usage rate. For example, 1-2 days to reach room temp of 20*C from cold start, but not an issue if “constantly on”. However, there are more expensive specialist poured screed ufh solutions with fibre reinforcing and clipped pipe systems on special panels that are designed for low build up (I think down to around below 30mm, including 16mm ø pipe coverage), which provide a quicker heating response, but due to having less thermal mass will need to be heated more frequently and/or at a higher (less efficient) temperature? Commercial floors can be around 40mm, but there are other factors to consider such as if bonded/unbonded to subfloor. Therefore you may be looking at a minimum of 40mm (with a specialist screed), but you would have to investigate what the heating “lag time” would be and temperature you would need to run the heat pump at, in order to maintain the desired climate. There is quite a lot of engineering involved!

Bare in mind, if you’re used to working in a converted garage (I.e., solid walls/floor, no insulation etc) then a building with only double skin walls and 150mm rock wool cavities (I.e., *new* minimum building standard: new builds) it is going to feel like total luxury … even with a plug-in 2kw electric heater, which would probably cover you to at least -5*C external temperature, if space is not too big!

Try to approximately calculate the heat loss of the new space, specifying different insulation levels to find out what your heat demand is likely to be and then work out if you’re prepared to run it 24/7, if going the wet ufh route.

However, if you’re considering incorporating the new workshop into a new domestic dwelling, then that’s a different matter entirely.

 

[solexious]

Thank you everyone for your reply's, the different viewpoints have helped a lot. Apologies for the slow response.

To fill in the missing info from me, I would be using this as my main workplace, so most days of the week and using it for hobby time on off days too. So I don't think I will suffer from it having to heat/cool cycle from me not using the heating, or heating it when I'm not there too much.

Since my original post we have found a property and have been working on completing on, its the first time we have been in the buying process, I thought moving rental properties was stressful, but this is on another level.

Luckily, this place does have a barn, though it is wooden and in need of a lot of love. It's just over 200^2m in the main barn and ~100^2m in lean to's to each side. It's also 3m to the eves and 4.6m to the peak, so lots of lovely head room. Sadly its seen better days and has a fair few holes in the cladding, a few broken window pains and a split wooden upright that's been kept up by an acroprop. So currently I'm looking into either making repairs to it and insulating the barn, or getting rid of it and replacing it with a metal framed barn with insulated panels. If the latter, there would be the option of also replacing the concrete slab and building insulation & ufh into that. (and I would like to be able to hang stuff from the frame, the wooden one I wouldn't trust!)

So thanks again for all the input, will use it when planning if we go down the replace rather than repair route.

Cheers

Sol

 

[Phil Pascoe]

3. UFH will require detailed and less flexible floor plan as UFH should not be laid under machinery and benches.

Surely it's only electric UFH that shouldn't be laid under stuff?

 

[Jacob]

Underfloor heating could make sense if you have a low temperature heat source like heat pumps which need a large surface area to radiate from. All that wiring/piping would be a bogger though, if anything failed.
Otherwise much simpler and cheaper, in fact obvious, is an insulated floor such as chipboard laid over rigid foam insulation. This would also make it quicker and cheaper to heat the room from whatever source as there would be less "thermal mass" to get up to temperature. Also zero maintenance and independent of heat source.
I often wonder about the "hypocaust" idea. You'd have an insulated slab with suspended floor above with hot air circulating in the void. Depends on your heat source.
Ultimately reducing heat loss is the big issue, including reducing "thermal mass" by placing insulation as near to all internal surfaces as possible e.g. insulation backed plaster board, insulation tight up under floorboards etc.

 

[Sachakins]

Underfloor heating could make sense if you have a low temperature heat source like heat pumps which need a large surface area to radiate from. All that wiring/piping would be a bogger though, if anything failed.
Otherwise much simpler and cheaper, in fact obvious, is an insulated floor such as chipboard laid over rigid foam insulation. This would also make it quicker and cheaper to heat the room from whatever source as there would be less "thermal mass" to get up to temperature. Also zero maintenance and independent of heat source.
I often wonder about the "hypocaust" idea. You'd have an insulated slab with suspended floor above with hot air circulating in the void. Depends on your heat source.
Ultimately reducing heat loss is the big issue, including reducing "thermal mass" by placing insulation as near to all internal surfaces as possible e.g. insulation backed plaster board, insulation tight up under floorboards etc.

However, once a thermal mass has warmed up, it retains a lot of thermal heat energy, therefore reducing the on going heating required of just insulated floors, which cool quicker, so require more energy to get them warm again.

 

[Jacob]

However, once a thermal mass has warmed up, it retains a lot of thermal heat energy, therefore reducing the on going heating required of just insulated floors, which cool quicker, so require more energy to get them warm again.

Takes more energy to heat up thermal mass at start up, which when no longer needed is then wasted as it cools down slowly.
Lots of insulation and minimum thermal mass is cheaper and faster to heat up and less is lost as it cools down.
OTOH if you want continuous steady heat then thermal mass helps as a buffer and heat store - perfect for a long Russian winter. Russian stove - Wikipedia

 

[Cabinetman]

Thanks Jacob, that was interesting about the Russian stove, I had heard of them but didn’t know that much about them, they were /are a lifesaver. When you think about all the wasted heat going straight out of the chimney from most combustion here in the West we have a lot to learn really.
My workshop (65 sqm ) is well insulated but could be better and uses a single oil filled radiator, barely on at all.

 

[deema]

I’m presently having a new workshop built with UFH. The floor is designed to withstand machines up to around 3.5 tonnes. It’s a concrete substrate, followed by DPM, then insulation, DPM and finally 75mm of self levelling over the wet pipes. You needcto select insulation with the compression strength you need, it’s specified in KPa. Then talk to the screed manufacturers, they are extremely helpful and will advise what product and what thickness you need. Avoid products based on calcium sulphate as the top coat of resin or what ever wear surface of your choice is as it makes bonding to it very difficult. I have a thread running in the build.