Air conditioning a shop

[Jim S.]

I have 1360 square feet of pole barn-type shop, with an open gable roof inside that rises to 17 feet. It is well insulated with Reflectix as an outer skin and R-14 inside. Slow to heat up inside when it is closed up.

I am planning to put a/c in it. I do a lot of bodywork and sweating on bare metal doesn't work well for me. LOL. Plus it is so humid here, and it is better to paint in low humidity.

I was thinking of running a mobile home type package a/c, putting the ducts through the wall, running the outlet duct up the gable post, then run across the top with a "sock" (Its a plastic tube with holes in it that inflates when the a/c is on and hangs loose when it is not).

Heat is hydronic, so that's taken care of. But before I do the a/c, I thought I'd post here for other suggestions. Never hurts, often helps.

One thing before you say window a/c, I am pretty sure that would be inadequate for a 40-foot-long space.

I had also considered split units, but cost is a factor.

What say you, then, shop dudes?

[Stephen in SOKY]

I had a regular central heat/Air unit put in mine. Does a good job, but, the flexible duct I attached to one of the register feeds puts cold air EXACTLY WHERE I WANT IT! Yes, I have to replace the flexible duct occasionally, but it's cheap & easy to replace. Might stir up dust if you paint in there, but realy nice to have.

[Bearfootfarm]

If you ran the ducts along the walls instead of at the peak, you wouldnt be cooling all the hot air at the top as much. It only needs to be cool about 6 ft above the floor.

[Ed Norman]

How about you run cold water thru the hydronics system and cool the slab?

[bill not in oh]

I'm a fan of using hydrinic systems for heating and cooling. However in your application I'd be in favor of running the cold water through pipes in the wall (if the interior is not finished). Spending any significant time walking on a 60 degree surface takes its toll on feet/legs and I'd be concerned about condensation on the floor. If the interior walls are finished, or used for cabinets/workbenches, a series of 'radiators' could be installed in the free wall space available to provide the same effect as horizontal pipes running the length of the building Since cold air has a fluid property, it should cover the 34' width easily. Plus, it would lower humidity through condensation on the pipe which could be collected for possible alternate use. I'd be careful how I used this water as it would probably contain byproducts of the activities in the shop. There certainly might be some logistic issues with this, but in the long term should pay off substantially through savings in electricity.

[agmantoo]

Jim, take time an acquaint yourself with a heatpump version of a PTAC. Instead of installing one get two and place them in the building to where one is the primary and the other is the secondary. Run both units to get near the temperature you desire then set one to cut off and let the other hum along to maintain the temp and to dehumidify. This is a very efficient method to condition an area. These units can be bought refurbished but even new ones are cheaper than a mobile home packaged type AC. As heatpumps they will also provide heat in moderate climates very economically.
http://ptac4less.com/used_units.shtml

[Ross]

Check out high velocity mini ducting, and diffusers....... you could run spot cooling to where you want extra cooling and get the whole shop cooled effectively without disturbing too much of your structure.

[Jim S.]

Thanks for all the replies. I am just getting the time to look at them now.

Ed Norman and others, I am in a HIGH humidity area. My shop floor would be wet always and moldy within a week, which is why I can't cool with hydronics. Or else I would.

agman, the only trouble with the PTACs is that every a/c man I talk to -- to a person -- has said they are high maintenance and repair compared to a slab unit.

Still mulling this, thanks again all.

[agmantoo]

Jim, I do not think the AC people like PTACs as it takes work away (interpret that as $$$$) from them. Think it through, the heatpump version contains nothing but the same components as in a slab unit but with the benefit of a factory filled and tested system. I can buy a complete new replacement system for slightly more than the service and labor on a slab unit. I can fix the common problems myself. This puts me way ahead. AC people do not like geothermal units either, eventhough they are far more economical because they do not want to learn or do anything new. It is a matter of to whom the itch belongs and from whom the scratch will be extracted.