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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment.

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    • CommentAuthorSprocket
    • CommentTimeMar 1st 2021 edited
     
    OK, I am starting on the new workshop/shed/office.
    5m x 4m footprint, timber frame inside, insulated cavity, stone block outer leaf.
    Hopefully fairly airtight. Heating requirements will be pretty low and occasional so I'm happy for this to be all electric. I was thinking nice and simple... just a few kW of electric heat mat in the floor.

    I've got a block and beam sub-floor, grouted over so we effectively have a sturdy concrete floor with air below.
    About 100mm foam insulation over this sub-floor.
    Original spec was for a 65mm floating cement screed over this. That would be structurally fine but the thermal mass of that screed would mean slow warm-up and cooling. This building will be for occasional use so to keep heating costs down I had in mind keeping it set-back and just warming it up when needed and preferably at half-hour notice rather than 4+ hours.

    So... rather than 65mm of floating cement fibre screed, What can I put on top of the 100mm foam-board insulation that will be sturdy enough to put machine tools along one edge in here and a workbench in the middle?

    I was thinking maybe 18 mm ply with sticky-mat heating cable over, then a liquid screed (maybe some sort of epoxy) surface. But I don't want to stick a couple of heavy machine tools (eg. 400kg) on one side only to find they sink slightly or bend the floor and lift the other side of the room.

    Should I be adding more support for the floor? Or a different floor build-up altogether?
    •  
      CommentAuthordjh
    • CommentTimeMar 1st 2021
     
    Wouldn't an alternative to electric UFH be a few radiant heaters up near the roof pointing down?
    • CommentAuthorowlman
    • CommentTimeMar 1st 2021
     
    What is the workshop for? You mention machine tools.
    • CommentAuthorSprocket
    • CommentTimeMar 1st 2021 edited
     
    Hi djh. I did think about radiant heaters and also oil-filled electric radiators. Those radiant heaters are fine in the pub beer garden but I don't find them very pleasant to work under. And the floor will still stay cold for a good while if it is still 65mm screed. I had underfloor (wet) in my last workshop and it was a nice gentle warmth to work in. That was in a passivhaus barn though so it was easy to keep that at 19 degrees all the time.

    I'm hoping that underfloor in the new workshop can give me a similar nice even ambient heat but it's a standalone building.

    Hi owlman. There will be a metalwork lathe and a milling machine, bandsaw, some steel workshop cabinets and tool storage. I've got peak winter heat-loss numbers looking like around 600W at 20 degrees inside and I'd like to keep it at 8-10 set-back most of the time. No intentional ventilation but I have a little automatic zeolite-based dehumidifier that will keep humidity safe as it cools. So heating costs are not going to be a problem but I'm at a loss how to do the insulated floor without a screed or cold bridging and still 'Keep It Simple'.

    Some smaller thermal mass might be useful on top... to spread the heat a bit. But a 20mm liquid screed would probably just crack with a few hundred kg on one side of the room.
    • CommentAuthorowlman
    • CommentTimeMar 1st 2021 edited
     
    I've got a woodwork workshop with a few heavy machines and I simply laid ply T@G on top of the uninsulated concrete so as not to be so cold to stand on, and prevent any serious damage to any dropped tools.
    You could do similar but with the added advantage of a solid insulated concrete sub-base. You could also look at industrial rubber anti fatigue tiles and/or mats near machines for oil spillages, and also a more comfortable standing work space.
    As for heating; IMO forget UFH. As djh suggests IR radiant ceiling or wall panels would be much more effective. They are almost instantaneous, relatively cheap to buy and install and have the advantage of heating the machine surfaces, and you, to make working more comfortable.
    • CommentAuthorbxman
    • CommentTimeMar 3rd 2021
     
    That would be structurally fine but the thermal mass of that screed would mean slow warm-up and cooling. This building will be for occasional use so to keep heating costs down I had in mind keeping it set-back and just warming it up when needed and preferably at half-hour notice rather than 4+ hours.


    IMO a block and beam sub-floor could at times be even colder than Slab on grade so if only "occasional use"

    Are you going to get any benefit from the insulation in the floor

    A heat mat to stand on and I/R heater or cooling fan directed at yourself might be more useful

    Take away the worry of where to locate your heavy machinery which will be to massive to warm up in the winter however much heat you supply.

    Good luck with it .

    Thank you for introducing me to foam glass
    cheers Patrick
    • CommentAuthorSimonD
    • CommentTimeMar 3rd 2021
     
    <blockquote><cite>Posted By: Sprocket</cite>Those radiant heaters are fine in the pub beer garden but I don't find them very pleasant to work under. </blockquote>

    Try the radiant panels. We have one from here https://www.suryaheating.co.uk/glass-ir-heating-panels/classic-panels.html. It heats our garden office and provides a lovely gentle warmth.

    Obviously it won't resolve the thermal mass issue with your floor.
    • CommentAuthorSprocket
    • CommentTimeMar 11th 2021
     
    Thanks. They're clearly not what I was imagining. I'll give them a go.
    I was as much concerned about sturdiness of the floor to put heavy machine tools on.
    In the end I gave up, scrapped the plan for PIR foam boards as insulation, and switched to Foamglas instead though it had to be quite bit thicker so I've had to raise a window and reduce the height of a doorway.
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