Detached garage HVAC

A homeowner is renovating the second floor of a detached, two-story garage into a roughly 600-square-foot office and exercise space, split into two rooms. The project involves removing the existing truss structure and adding a structural ridge beam, replacing all windows, and improving insulation throughout: R-20 batts under the gambrel roof sides, R-13/R-5 on the side walls, and either closed-cell spray foam or rigid foam board for the roof deck. Three skylights and new siding are also part of the plan.

The current heating and cooling system, an 18,000 BTU ductless mini-split (a compact heat pump that sends warm or cool air through a wall-mounted unit rather than ducts), has not worked well, and the two rooms end up at noticeably different temperatures during hot or cold weather. The homeowner is weighing two replacement options: separate ductless mini-split heads for each room, sized around 6,000 and 9,000 BTU given the planned insulation upgrades, or a single ducted mini-split system with duct runs built into floor chases. They're also considering adding a wall-mounted energy recovery ventilator (a device that brings in fresh air while recovering heat from the air being exhausted) to the mix.

Separately, the homeowner is looking for a roof material for the garage that can handle regular impacts from a basketball hoop mounted on the building, without shedding granules onto the sport court below, while still being practical to install on the gambrel roof's angles.