Heating and insulating for a wide interior temperature swing
ranson
| Posted in Energy Efficiency and Durability on
I’m planning out my garage, which will be mostly for cars and storage. I may install a small mini-split or PTAC to keep the garage above freezing, and to occasionally cool the building if I’m working in it in the summer.
I’ve got a couple questions:
Is there any green motivation for insulating the building beyond what fits in the stud-bays (2×6 likely), given that I’m letting the temperature swing widely?
Is there any issue with operating a mini-split with a 40F building temperature?
Are there any vapor management concerns for a building that has wide interior temperature swings?
John
Rochester, NY
Zone 5
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Replies
John,
Q. "Is there any green motivation for insulating the building beyond what fits in the stud-bays (2x6 likely), given that I'm letting the temperature swing widely?"
A. Most people wouldn't do a cost-effectiveness analysis here, but briefly, the answer depends on (a) your environmental values, your analysis of the level of crisis that our planet faces, the source of your electricity, and (b) whether or not you have access to cheap recycled rigid foam and free labor.
Q. "Is there any issue with operating a mini-split with a 40°F building temperature?"
A. Most ductless minisplits do not allow users to set the thermostat at 40°F; I think that many minisplit thermostats bottom out at 55°F or 60°F. Dana Dorsett and Charlie Sullivan were talking about one brand of minisplit with a low thermostat setting, but I forget which one it was. Otherwise, there are work-arounds -- like installing a tiny electric bulb under the thermostat to fool it.
Q. "Are there any vapor management concerns for a building that has wide interior temperature swings?"
A. If you condition the garage occasionally, you'll be doing your tools a favor compared to never conditioning the garage. Unconditioned buildings can lead to rusting tools; this occurs when cold weather is followed by a spell of warm, humid weather. In general, your garage will be fine.
-- Martin Holladay
Martin,
I think this is the discussion you were referencing: https://www.greenbuildingadvisor.com/community/forum/mechanicals/99699/mini-split-winter-heating
It looks like 50 degrees is the low end of the minimum heat mode.
Insulation below the slab can mitigate the tool rusting scenarios, if it's not too late for that.
Steve,
That's it -- thanks.
-- Martin Holladay