Heavy machine tools, workshop floor insulation and, thermal bridging?

[Jelly]

I'm well into dry-lining my workshop now, and as I think more about the thermal performance of the building I've hit an awkward problem.

I'd like to maintain it at a fairly constant temperature, ideally in the 16-20°C region by using oil-filled radiators and an AC unit linked to a PID controller, but to make that economic need to minimise sources of heat loss, and the floor is a bleedingly obvious one that's not addressed.

Once I have my small machines and surface table set up, I'm aiming to acquire a large lathe (in the 17" center height kind of region) in the next year or so and a medium size surface grinder and largish (Deckel FP3 size) mill after that... All of those have *very* significant floor loading involved.

Existing floor is a 6" concrete slab with rebar and 12" foundations around the edge, sat on good hardcore, so I'm comfortable that will be ok.

But there's zero info on acceptable floor loading in the technical data I can find on the various retro-fit floor insulation options, and without information to the contrary I would assume none will withstand tools weighing over a tonne without compressing enough to mess with the leveling of said tools.

At the same time if I have a large mass of cast iron sat directly on the concrete, I'm creating a huge thermal bridge which defeats the object of putting down insulation elsewhere.

Is there an established solution to this issue?

I was planning to grout the bigger machines in anyway, and figure that there would be an insulating additive/fill I can use with a vibration damping grout, although I'd like an alternative to mixing custom grouts if at all possible.

 

[mikej460]

Tricky one, but given the obvious value of the machinery I would ask an architect if a solution is available then pay a structural engineer to advise and calculate what you need.

good luck

Mike

 

[Sandyn]

Can you mount the machinery on wood and insulate around it, so the machinery isn't resting directly on the concrete. Wood is a pretty good insulator.

 

[Inspector]

You could look into digging around the outside the slab and insulate the perimeter several feet deep with styrofoam. That would reduce the heat loss from the slab.
Pete

 

[Jameshow]

As Sandyn says work out where you want your machinery to go and place spacers instead of insulation under the load points.

Only problem is you cannot easily reconfigure your workshop .

Also getting them in without damaging the flooring / insulation might be an issue. A sacrificial couple of plywood sheets might help.

Cheers James

 

[Jacob]

If it's worth the effort; dig up the floor and lay new over insulation. A reenforced slab will distribute the load even over softish stuff but get an architect to specify the details, maybe design in some footings for anything very heavy which will stay in one place. But how cost effective that would be is doubtful, if you have well insulated elsewhere.
The cheap way would be to lay chipboard direct on the concrete. Has more compressive strength than you might think, and some insulation value. Not just the weight but the size of the footprint, where it actually comes into contact, determines the floor load.

 

[Jelly]

You could look into digging around the outside the slab and insulate the perimeter several feet deep with styrofoam. That would reduce the heat loss from the slab.
Pete

This is an interesting idea, producing a much gentler thermal gradient between the inside and outside, and effectively making the slab plus a good chunk of earth into (relatively poor) insulation, but so thick as to still have a meaningful impact, l like the lateral thinking.

 

[RichardG]

This is an interesting idea, producing a much gentler thermal gradient between the inside and outside, and effectively making the slab plus a good chunk of earth into (relatively poor) insulation, but so thick as to still have a meaningful impact, l like the lateral thinking.

This works, a house I lived in had a solid concrete floor laid up to the inner 9 inch solid brick wall, the corners always had a cold problem which led to damp / mould on the carpet. I was given similar advice and I cut a 50mm channel in the floor on the outside walls and put in 20mm strip of insulation on the outer edge and then backfillled with concrete creating a thermal break. Problem went away and I felt the room was warmer but that may have been me imagining it...no idea how much warmer the overall slab was but the outside edge was much warmer.

The 50mm was simply a function of angle grinder dimensions and removing the waste. The 20mm was so so it was hidden behind the skirting boards so the carpet fitter has something to fix the grippers to.

 

[Jelly]

Can you mount the machinery on wood and insulate around it, so the machinery isn't resting directly on the concrete. Wood is a pretty good insulator.

This is a traditional option for lower precision machines but has limitations due to both the compressibility and movement of wood, I'd be aiming to get at least the grinder leveled to less than 21μm of deviation per meter (two tenths of a thou per foot).

However, I could attempt to level the machine onto a steel plate, or composite of steel plate on reinforced concrete which is sufficiently stiff to maintain the alignment and then mount that on wooden blocks.

 

[jimmy_s]

Most of the heat loss from a ground bearing slab is from the perimeter. Do you know the perimeter and the area of the slab roughly. I can run a couple of U value calcs if you want to see how it performs as it is and with perimeter edge insulation etc.

Jimmy

 

[Jelly]

Most of the heat loss from a ground bearing slab is from the perimeter. Do you know the perimeter and the area of the slab roughly. I can run a couple of U value calcs if you want to see how it performs as it is and with perimeter edge insulation etc.

Jimmy

That would be cracking if you could.

Perimeter is 21.6m, Area is 25.6m², and Slab depth is 300mm at the perimeter, 150mm across the middle.

 

[Jelly]

If it's worth the effort; dig up the floor and lay new over insulation. A reenforced slab will distribute the load even over softish stuff but get an architect to specify the details, maybe design in some footings for anything very heavy which will stay in one place. But how cost effective that would be is doubtful, if you have well insulated elsewhere.

It's probably worth it to me to get it right but completely re-laying the slab would see the expense get out of hand.

I'd come to the conclusion that if this was the only route, it would be cheaper to just accept the higher energy bills over the length of time I expect to be in that workshop.

 

[Spectric]

Have you thought of underfloor heating, a freind had this in a workshop and it performed better than mine with gas boiler and three large radiators.

 

[jimmy_s]

The U value of the slab at the moment is about 0.85w/sqmk so if its -2 outside and you are looking for say 18 deg C inside you would loose about 440 watts through the floor.

if you were to install something like styrofoam 150thick 600 deep the U value would drop to about 0.6 so at the same conditions your heat loss would be about 310 watts

The heat loss though the slab whilst its a bit high its not that bad IMO and you might be better concentrating on the walls and roof?

Jimmy

 

[Jelly]

Thanks for that.

The wall/roof insulation once complete should achieve 0.18-0.21w/m²K, so the losses through the floor would be about 1¼-1¾ times those through the walls and roof based on relative areas...

An overall loss of about 600w during cold spells should be acceptable from an economic point of view.

 

[jimmy_s]

You're welcome

You will have a heat loss to infiltration which at an air change per hour would be about 20w/sqm which will push it up a bit but depending on your construction etc it might only be about half an air change per hour or 10w/sqm. If you have lights etc on then they will probably result in a heat gain of about 6 watts per sqm and a person emits about 100w to put the overall heat loss into perspective.

 

[Inspector]

This is an interesting idea, producing a much gentler thermal gradient between the inside and outside, and effectively making the slab plus a good chunk of earth into (relatively poor) insulation, but so thick as to still have a meaningful impact, l like the lateral thinking.

I'm not sure if I was clear enough but what I suggest is the insulation being around the outside of the building. There are virtually no dwellings made here without insulation on the outside of the foundation, the frost line being up to 10'/3metre deep. The insulation can be vertical against the cement or sloping out and away from the structure, still underground. If you have access to peel the soil back is easier than trying to cut a channel inside the wall to lay in insulation.

It looks like Jimmy has shown that the heat loss will be minimal given your mild climate so you can live with it as is.

Pete

 

[Jelly]

I'm not sure if I was clear enough but what I suggest is the insulation being around the outside of the building.

I got that, it made total sense to me when I built a little picture of the heat transfer regime involved in my head which I now realize would be easy to draw, but really difficult to explain in words.

 

[TFrench]

If your machines are mounted on levelling feet you'll be able to get rubber floor tiles (decent ones, not the foam rubber type) under them, and just cut around the levelling pads. If it's a good smooth floor and you dont have anything in there it might be worth looking at altro flooring - heavy industrial lino. Again you could cut out around the pads if you're worried about compression.

 

[TFrench]

Also, I can't wait to see pics of this! An FP3 and a Mascot sized lathe? I'm in!