Welcome to the Chatroom.

There is no benefit to leaving an air space above the insulation in the ceiling, so you can put as much up there as you like, although the electrical cables are going to make that something of a challenge.

Do you know if the walls had vapour barrier applied to the inside of the insulation, just behind the OSB? You might be able to see it if you take the cover plate off the light switch, or at the edges of the door/window.

Does the room have an insulated door?

Do you plan to surface mount whatever electrical receptacles that you need, or will the one(s) under the electrical panel suffice?

If you’re not planning to finish the ceiling, nor do anything with the walls beyond painting, then I suggest that your plan for the floor is overkill. You’re not going to lose much heat through the floor. There is going to be a temperature gradient in this room, with it being cold at the floor and warm at the ceiling, but insulating for floor isn’t going to affect that very much. You’ll end up using a small auxiliary space heater under your desk, or resorting to wearing warm footwear in your office. You could just paint the floor to make it look a bit nicer or use some other type of modular flooring intended to lay directly on concrete without fastening.

 

Thanks for the thoughts. Yes, there is vapour barrier- can see it at the seams of the OSB in places and at the top of the wall.

All electrical will be enclosed surface mounted.

My thought with the floor was to try to make a small gain on temperature, as well as just have a more comfortable substrate than direct concrete (or LVP over concrete) for standing. YEs, IU'm a standing desk guy.

Perhaps I should be looking at a ceiling fan to push heat back down?

 

No advantage to insulation on the floor, it is in the mid 50s now and it will be much the same when the insulation is there for a day.
Solid block between the joists flush with the the outer edge of the wall and fill the joist bays with insulation.
No air gap needed there.

 

I would consider heating the floor instead of that baseboard, a little more expense and work but well worth the effort.
240V, 70 sqft Coverage Floor Heating Mat Kit w/ Thermostat (heattechproducts.com)
Cover it with self leveling and then put down LV plank.

 

Thanks for the idea. I considered this, but this may be a fairly temporary setup so don't want to get too into redoing the floor...if this room goes back to its old purpose, would rather just rip up some 2x4s than have a few hundred bucks in radiant heat and self leveling on it.

 

Maybe carpet? Your feet directly on slab will feel colder. No difference if you insulated. Floor will be warm only if you keep it heated all the time. If some day hours or occasional, I would think robust space heater with big enough fan would be better. Volnado room heater. If wanting it warm whenever you want, then I think carpet and insulated walls and ceiling and maintain the heat, maybe turn it on in the morning and off at night. Maybe thicker or insulated door. But I think you should hold off and try the space in summer. 8x8 space is too little for me, even if just office/study. 8x8 is also too small for smallest window ac, I think. I've read portable ac is undercapacity, so it may work.

 

Thanks- it will be intermittently used- I'll be in for a few days, and then may be out for a week at a time where I'm just keeping the heat above freezing until I'm back in.

Wish I could wait until the summer, but unfortunately I don't think the baby who is on its way to occupy my current main-house office space will postpone 😅

Sizing is fine for me, I've worked in small spaces before and it doesn't bother me.

 

Also curious on the lack of a need for air gap- everything I've read suggests I need one for moisture control. Is the thought that in an unconditioned barn, things aren't going to be tight enough to worry about moisture accumulation anyways?

 

If you post a link to what you’ve been reading we can rebut it. Consider the walls, which have polyethylene as the moisture barrier with the entirety of the stud bays filled with insulation (hopefully). The polyethylene that you plan to put over the insulation in the ceiling should, if applied properly, prevent any moisture from your breathing or steaming cups of coffee from escaping the room until you open the door. Even if you don’t do the sealing properly and warm moist air escapes up into the insulated ceiling cavity, leaving an air gap there wouldn’t be of value. There would be nothing to cause the air to move along the joist bay, carrying the moisture with it. If your office was on the upper floor and you were insulating the sloped rafter bays of the roof, then you would leave a gap to allow air to flow over the insulation from the soffits to the vents in the top of the roof. In that case the slope of the roof will cause the more buoyant warmer air to migrate upwards to the vents.

 

Carpeting in a horse barn is going to look like h*!! in very short order.