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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
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    • CommentAuthorSprocket
    • CommentTimeJul 28th 2020
    Internal dimensions are about 5.2m by 4.0

    It is not built yet so amount of insulation is down to me. Currently looking at U value for walls of about 2.0 but I can adjust this at cost of thicker walls so just a bit less internal space. Space is a bit of a premium - I can't make it bigger than 6m x 4.6m externally.

    Big unknown at the moment is what is likely to be the best way to heat this space. Seems to me that if internal thermal mass is low I can maybe have the place sit at eg. 10 degrees in winter (to prevent condensation on engineering tools) and still be able to warm it up to 20 degrees fairly quickly when I want to go spend some time in there.

    Is it all too much bother for the size and I should just go electric? Fan or underfloor?
    Is there a simple appliance that will do what I want, preferably without unpleasant draughts and noise?
    Is there even a very small and quiet enough ASHP that would suit?

    Some of you must have heated garages or posh sheds so have already looked into this kind of thing?
    How do people heat those "Garden Room" offices that are all the rage in home improvement mags lately?
    IMO it largely depends upon usage. If you are spending a lot of time in there it would make sense to insulate to a good standard to minimise the heating costs. If it is infrequent visits or daily but short duration (hour or less) then an overcoat is probably the best option.
    I have heating in my workshop (ceramic stove) but I never use it because by the time the place is warm I have finished the job and its not worth heating for less than half a day. (It is a high thermal mass building) IF I have a bit of a longer job I will use a fan heater pointing at the work bench.
    • CommentAuthorEd Davies
    • CommentTimeJul 28th 2020 edited
    No particular thoughts for the moment but I'd think it'd all depend on how much you expect to use the workshop. A few days a week or one evening a month?

    Edit to add: PiH beat me to it by 17 seconds.
    Good idea to focus on warming yourself, rather than warming the mass of the building - consider radiant or fan heater you can move round according to what task you are doing (how physical). And copious mugs of tea...!

    Are you doing fine woodworking or painting jobs which need stable temperature/humidity?

    If you have a thin roof (especially metal) it can get sweaty on cold nights, worth lining/insulation there I think.

    Good to have big doors for moving stuff about or to open when doing something dusty, I found most of the dampness I had assumed was condensation was actually rain/snow creeping round the doors, fixed by weather stripping. Also big roof window helps for task lighting but also solar heat gains.

    I use some of my granddad's tools, still keep them wrapped in oily rags as he did to avoid condensation damage.

    I don't bring garden tools in eg mower broom hose, always seem to bring dampness.

    If it is a permanently heated space then maybe it ought to be insulated (save the planet folks) even if building regs/stds don't apply to it.

    If insulating internally then think how to mount shelves.

    Edit: I'd understood it was uninsulated U=2 but see it's insulated U=0.2 which sounds fine for a 10degC building.
    • CommentAuthorSprocket
    • CommentTimeJul 28th 2020
    Thanks. Contents are likely to be

    A small metalworking lathe (1.5m wide, about 200Kg)
    A small milling machine.
    Maybe a central carpenter's workbench.
    Several painted steel cupboards by Dura, worktops over.
    A small sink.

    I would envision spending 30 mins to several hours at a time in there. Just a once or twice a week.
    Needs to stay dry enough to have no risk of condensation on the lathe.

    Hmm, even at -1 outside and 19 inside, with U values around 0.2 for walls and roof (looks reasonable) it only looks to be about 600W. If I let that "frost protect" at 10 degrees, it's only just over 300W

    So heating cost is not looking like a major issue. It's next to a house that takes ~12kW in similar conditions. I suppose I may as well go all-electric. Maybe electric underfloor for sustained heat and a simple fan or IR heater for short duration stuff.

    Hmmm... big doors. Sounds like a good idea. Thanks.
    • CommentTimeJul 28th 2020
    Posted By: SprocketCurrently looking at U value for walls of about 2.0

    I presume that's a typo of some kind, or an unusual unit?

    How do people heat those "Garden Room" offices that are all the rage in home improvement mags lately?

    Electric storage heaters I think.

    Hmm, even at -1 outside and 19 inside, with U values around 0.2 for walls and roof (looks reasonable) it only looks to be about 600W. If I let that "frost protect" at 10 degrees, it's only just over 300W

    Ah, 0.2 sounds more plausible. You don't need 10°C for frost protection, 4°C or 5°C is plenty (i.e. the inside of a fridge). An infrared light bulb will do that - chicken heater or greenhouse heater. Plus a fan heater when you go in there to work for any length of time, or maybe a radiant heater. Be careful to ventilate any warm air out of the building when you leave, otherwise you'll get condensation as it cools, just like the inside of a car in winter.
    • CommentAuthorgyrogear
    • CommentTimeJul 28th 2020 edited
    Does it have a window ? What type of door ?
    What is the orientation like ?

    I am thinking "glazing" of course !
    For example if you can have a south-facing window, it could make a difference etc.

    Posted By: Sprocket
    I would envision spending 30 mins to several hours at a time in there. Just a once or twice a week.
    Needs to stay dry enough to have no risk of condensation on the lathe.

    To me this sounds like an overcoat with a fan heater for the longer jobs. And don't cover the lather with a plastic sheet.

    Posted By: Sprocket
    Maybe electric underfloor for sustained heat

    Underfloor heating sounds like cost over kill for the projected use.

    What is the construction to be? The type of construction will determine the possibility of condensation. My workshop is part concrete and part stone walls with a concrete ceiling and a standard tiled roof over. I have never seen condensation in there - but Hungary has a different climate. - well we have climate the UK has weather!
    • CommentAuthorrevor
    • CommentTimeJul 29th 2020
    In my previous house I had a workshop in the cellar. Condensation could be an issue particularly on a warm moist day the cold cellar would condense the air. Solution was a small dehumidifier on which I could set the humidistat on a low enough setting to avoid the condensation on my tools but still be economical to run. It is cheaper than keeping the area heated and for the times I was in there had a fan heater or gas heater.
    • CommentAuthorowlman
    • CommentTimeJul 29th 2020
    A quick look on eBay revealed 311 second hand oil filled radiators. A couple of those plus timers should do the trick.
    • CommentAuthorgoodevans
    • CommentTimeJul 31st 2020
    For intermittent use - a low mass internally insulated construction is indicated - i.e. insulate on the inside of the walls with as little covering on the insulation as possible - be sure to insulate the floor - cold feet makes for uncomfortable working. Insulate well and heat as needed/on demand with a fan heater or radiant heater.

    Assuming humidity is most closely related to the humidity outside - the main issue with condensation is that your large metal kit will take some time to warm up - it will lag the temperature of the air in the workshop. A humid day after a cold night is the danger point - mitigation is to reduce air infiltration and ensure all the surfaces are wood or plasterboard with a simple matt, non vinyl emulsion. This will buffer the humility - with luck the humidity inside will lag the humidity outside to match the temperature lag of your machinery. You may find little heating is required for condensation protection. If anti condensation heating is required - A Fan heater for this task may help heat the nooks and crannies better than a radiant heater.
    • CommentTimeAug 3rd 2020 edited
    Air to Air Heat Pump.
    There are some small, and cheap, units that can both heat and cool.

    Or similar
    • CommentAuthorowlman
    • CommentTimeAug 3rd 2020 edited
    Welcome back Steamy Tea I guess you've been lurking all along if a little quiet of late. I've missed your occasional pearls of wisdom. BTW I agree about your A2A suggestion. I'm sold on the technology after installing it in my own home, although in this instance a bit expensive compared to mine; of a couple of £15 second hand oil filled radiators.
    • CommentTimeAug 3rd 2020
    Posted By: owlmanlurking all along if a little quiet of late
    Always lurking.
    Should be possible, and cheap and easy for a garage/workshop to combine the unit with some ventilation. Should help control humidity as well.

    I am a great believer in basic electrical fan heaters, I have a 500W one that can heat my who house most of the time.
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