I’m curious who has set up purpose built grow spaces for their hobby. Something like dedicated rooms with air filtration individual separate temperature and ventilation control etc? If so do you separate grow spaces from work spaces? Agar from spawn etc etc. when I get the last phase of home remodel done I’m seriously considering using the space I have now that needs at a minimum walls torn out into an insulated space where I can do something like recirculated hepa filtration with a fresh air intake, simple temperature control and possibly filtered positive pressure as well, then house storage for colonization and a greenhouse. It all sounds more complicated than what I have in mind and I have the tools, most of the skills and access to the specialty materials necessary to do it all.
It just seems so much easier to repurpose surplus material and have a functioning clean space than constantly be dicking with what I have to work with now and the space, basically a large outdoor “closet” needs the drywall replaced already. Insulation and air handling in such a small space seems trivial and hackable at that point.
Ideally yes, you would separate work space from clean-room space. And clean room space from fruiting space. Commercial spawn producers and growers are generally completely separate operations (and companies). Mostly we can't do that kind of thing at the "hobby" level because we lack the room or budget to build an addition on to our house.
What kind of growing system will be used in the room? Fruiting in trays/bins or using the whole room as one big fruiting humidified chamber? Drywall would not be ideal for the latter, among other considerations. You can also do things to treat the studs, etc. before enclosing them that will help prevent mold problems. I use this stuff wherever I can: https://mycotopia.ne...evention-spray/
In most climates cooling the space will be much more challenging than heating it, mainly because air conditioners are also inevitable mold factories (even mini-splits, though they are far less problematic than typical central HVAC systems, and window units are the worst of all). I can envision a way to cleanly cool a grow space in a subtropical climate (if it works in that climate it'll work anywhere) but it would take a lot of work and be fairly expensive to build and operate.
I found it easier to just shut down all indoor projects through the Summer where I live (or whenever I'd need to start cooling the space). The last thing I try to do before shutting down is make a bunch of spawn for outdoor beds and then focus on those until Fall. I would design it so that the only air handling equipment involved is the flow hood and a positive-pressure HEPA filter for the room. It might be easier to clean and maintain if the walls were FRP rather than drywall, but that gets expensive fast (though like other prohibitively-expensive stuff that makes life easier it's REALLY nice to have). The best floor IMO is concrete sealed with epoxy paint (the 2-part stuff sold for garages works great). A linear floor drain would be pure decadence; imagine being able to quickly hose down or pressure-wash your grow room (use a small electric pressure washer for that!) vs. mopping...
For heat I use an oil-filled radiant heater plugged in to a much more precise temperature controlled relay (the thermostats on the heaters are worthless). This controller has never let me down, and I can keep a fairly well-insulated room to within ~5 degrees of my set temp (I wired two of them into heavy duty extension cords so that they're portable, and I added a GFI to one that I use outside with my steam pasteurizer [photo])
Purpose-built space is an awesome luxury to have, so long as you define it's purpose very specifically so it's built for the actual purpose (how you grow) it will be put to.
To design such a space I map out every single step of how I grow from spore to harvest, and see if the space allows me to design an efficient workflow that saves time and effort. I go through the motions in my mind and see if there are any ways to make things easier (and to ensure I'm not designing myself into any corners).
Something else to keep in mind is that it's worth doing whatever it takes to avoid the presence of any stairs in your process (even just one). I dealt with that for years, and even though it only involved two steps between where I set up my PCs and the hallway to my clean room, it was a huge PITA every time since I use the big AA941's which are about ~80lbs when full and I had to carry two of them (one at a time, lol) up those stairs while they were still hot and under some pressure, which was probably a pretty dumb thing to do considering what could've happened if I'd dropped one. It's really nice and exponentially safer to use a cart to move large scalding-hot pressure cookers around. Or even small ones, frankly.
This all might be crazy overkill but it wasn't apparent what scale you intend to grow at, and this reply was largely focused on medium to large grows ("large" being relative to a residential setting, so for example more than 4-5 bins but fewer than 40 or however many is too many to keep up with by yourself; growing more than that is better accomplished with a full-scale commercial-style climate-controlled grow room).