Hi Folks,
I’m trying to build a “pretty good” little apartment – and I’m interested in recommendations on how to best insulate the ceiling – as noted , rafters are 15 ft long 2 x 10’s on 2′-6 ctrs., with existing tin roof and the usual rolled out insulation package under the tin. (supposedly R 4 but is smashed to R-0 betw tin roof and rafters) I’m planning to run perpendicular battens with thermal breaks to span the 2’6″ gaps of the sheetrock installation.

Obvious options:

1) just stuff and fluff (2) 16″ wide R38 batts and retain w crossways battens

2) add another 2 x 10 between existing – this would be relatively easy.and gets me to readily available batts but adds another thermal bridge to insulate

3) blown spider glass: i’d think ideal but cannot find local installer.

Other details: 600 sf total floor area. This is actually a pole barn w raised floor on one end we’re building an apartment in. Walls are 2 x 6″ 16″ oc, and will be: installing thermal breaks under sheetrock, sealing all joints and doing blower door check. Floors 2 x 12’s w full depth insulation.

Cooling load handled w (2) small window units because of interior walls. Could not find mini split w less than 1.5 tons which would be way overcooled if i do my insulation and sealing right and is several multiples of window unit cost.

Heating solar thermal and outside air feed woodstove (if i can find one small enough)

Thanks for any help,

CCSC

P.S. I forgot to write: the location is Climate Zone 3 in South Carolina.