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How to insulate a cockloft / tiny (<30" tall) attic (without tearing up roof or ceiling)

dborowsk | Posted in GBA Pro Help on

Hey all, I’m an architect and renovating a townhouse in NYC and wondering (as the subject line suggests 🙂 how to insulate a cockloft (tiny attic) in a renovation, without tearing up the roof above or the ceiling below.    

We have a flat roof/low pitch that results in approx 30″ of attic space in the front of the house to around 6″ (maybe less) in the rear of the house.  There is an approx 24×24 access hatch near the front so I can see clearly everything inside. The roof joists span 20′ across from brick party wall to brick party wall and the plaster/lathe ceiling is hung from those roof joists with fairly light wood 2x downstands and 2×3(maybe smaller) ceiling framing holding the lathe and plaster spaced rather far apart (24″ maybe). Even if you weren’t intimidated by small spaces and wanted to climb inside, I’m not sure it would support an installer climbing around in there (I may be wrong about that as this as this was built in 1915 and is all old-growth lumber).  

My initial thought is blow-in insulation- perhaps a hole saw every (x feet TBD) then patch the holes?  I don’t know much about blow-in and am not sure how you would control for even distribution or if this is even the best way? 

Any advice on the best way to insulate this tight space? Has anyone else solved this problem either with blow in or roll-out batt or another way?

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