heating little bits of a large barn ...

[gjbuilder]

3000 square foot barn, concrete floor is scheduled to be poured first week of January.

2000 square feet of the barn - a "cross" of open area - will be unfinished space. You can close the barn doors, but other than that, it's essentially outdoor space (other than the roof on top).

But each of the four corners of the barn is a 250 square foot finished indoor space. Each of these rooms has a subfloor on top of the concrete built of 2x4 joists and plywood with a floor surface on top. We'd keep these rooms "warm" - about 62 degrees - continuously as they will be in regular use.

SO ....

- radiant in-floor heat seems not workable at all - even if you only had coils under the four rooms, wouldn't the 2000 sf of unheated slab absorb all of that heat ? And also, there are the subfloors on top of the concrete, so the heat won't get through that anyway ...

- the vented heater option is probably very nice, and I like the way heating outdoor air makes the heated indoor room very dry (like a home forced air system, right ?) ... but ... I would have to buy four of them - one for each room - since the rooms are unconnected. That's very expensive ...


Which direction should I be going with this ?

Thanks.

 

[finn]

Install a thermal break for each of the corner rooms if you go with in-floor heat.

I think mine is a piece of 1" or 1 1/2" foamboard standing on edge.

Works ok. You don't really notice the joint.

 

[theoldwizard1]

Where are you in the world so we can get an idea of what the weather is like ?

What is the size of the barn ?

Mini-split heat pump would work. You can run 2 rooms (one side) off of one compressor. Not cheap to install, but you will have AC in the summer !

 

[Stuart in MN]

For such a small space (250 square feet) a small electric unit heater or wall heater may make sense. Yes, electric heat is expensive but for small rooms it can be pretty effective.

 

[gjbuilder]

Where are you in the world so we can get an idea of what the weather is like ?

What is the size of the barn ?

Mini-split heat pump would work. You can run 2 rooms (one side) off of one compressor. Not cheap to install, but you will have AC in the summer !

Northern california ... we only get down to 18-20 degrees F in the winter, but we drop to 45-50 F every night all year, regardless of season.

Barn is 3000 sf, but each of the four corner rooms is only 250 sf.

I like the idea of the vented heaters since we're actually drying the room by heating outside air ... as opposed to simply warming it with an electric heater ... but buying four of those at $1500 each is too expensive ...

Even with thermal breaks, I still don't think radiant floor works because we are putting the joists over it and a subfloor on top of it ... I don't think radiant floor heat can make it through the wood floor on top, right ?

It sounds like it comes down to either a wall mounted vented heater, whose upside is dryer, well-vented (mold, etc) spaces ... but the downside is cost.

OR:

a wall mounted electric space heater which would be cheaper, and would work fine, but I'm not keeping things as dry ...


Is that a good summary ?

 

[Voi]

Even with thermal breaks, I still don't think radiant floor works because we are putting the joists over it and a subfloor on top of it ... I don't think radiant floor heat can make it through the wood floor on top, right ?

You can run a subfloor designed for pex tubing on top of your joists and run a zone up to each room. But it sounds like the floor in the area other than these four rooms won't be heated so I don't think it's worth the money.

If you like the floor heat option they make electric radiant heaters that go under tile, etc.

As far as electric radiant keeping things dry, my shop used to have a separate room that was heated with wall mounted radiant cove heaters. I felt like that room was really dry for what it is worth.

I feel like there was a thread recently that talked about using a mini split to heat/cool two rooms at opposite ends of a shop. Might dig around and see if you can find that thread.

 

[gjbuilder]

I feel like there was a thread recently that talked about using a mini split to heat/cool two rooms at opposite ends of a shop. Might dig around and see if you can find that thread.

Well, the good news is, in our climate, there is no need for AC ... summer days are 78-82 generally and it cools down quickly as the day goes on.

So there's no need to add the complication or infrastructure of AC. We just need heat

I think I will get wall mount electric heaters - like this one:

http://glamox.com/products/glamox-3001-tpa

... and if I need it somewhere (storage) I'll set up a dehumidifier. That sounds like the easiest thing to do ...

 

[tomroblee]

When you talk about a vented heater "drying" the air, I'm not sure that you fully understand what is happening.

Hot air can hold more moisture than cold air. If you take cold air and heat it, the air won't contain any less moisture--- it just that the hot air will have the ability to absorb even more moisture. (humidity doesn't change, but the relative humidity does.)

A high efficiency vented heater (or furnace) will use outdoor air for combustion. No outdoor air will be introduced into the heated environment. As far as humidity is concerned, a sealed combustion gas heater (or furnace) will function exactly the same as electric heat.

A lower efficiency vented heater (or furnace) will use indoor air for combustion. Outdoor air must be provided (through leaks or intentional openings) to replace the air that goes out the vent. The outdoor air may have more or less humidity than the indoor air it is replacing.

It appears that the electric heaters you are considering are resistance heaters. A heat pump type heater could be more efficient---but would be bulkier and make more noise.

A well insulated 250 sq. ft. room in a moderate climate like yours isn't going to require much heat. I would imagine that the smallest available vented gas heater would only run a few minutes per hour---and that wouldn't have much effect on humidity.