Ice House Lofts
1024 Dean Street Brooklyn,
Two different roof tops comprise the 2300 square
feet of green roof space at the Nassau Ice House. The top terrace
roof, which is accessible from one of the apartments, has unobstructed
southern lighting. It is 900 square feet with a 4 inch deep substrate.
The first layer is the waterproof membrane, which protects the roof
from erosion and possible leakage problems. The drainage layer is
made from a Barrett's Ram Roofscape 1241 Drainage/ Retention Mat;
16 millimeter high density polyethylene film and a 60 psi Dow Styrofoam
Plazamate. The next layer, the substrate is comprised of a mix of
70% expanded shale, which is lightweight and porous, 15% sand and
15% compost. The plant selection is mostly sedums, succulents and
small herbs. The selection includes chives, lavendar, blue spruce,
bailey's gold, white spurium, fameflower, dragon's blood and russian
stonecrop. The costs on this roof from consulting and design to
materials and installation totals $13.96 per square foot. The costs
of roofing istelf, comprises most of that cost at $8.33, making
the addition of green roof features only about $5.63.
The second green roof is a 1400 square foot wood
truss roof. It is 20 feet off the ground enabling the passengers
on the elevated subway train to view the roof. A Sarnafil PVC membrane
was used not only for waterproofing but to act as a root barrier
as well. Although this eliminated the need for a separate root barrier,
it is more costly. The drainage layer is a Mirafi N-Series Non-woven
Polypropylene geotextile, which is all that is needed for adequate
drainage because of the slope. The substrate layer is only 2 inches
deep and is comprised of 70% expanded gray shale, 15% compost and
15% sand. The roof has a 17 degree slope and a wood grid of L18"xW24"xH1.5"
boxes was constructed to allow the plants adequate maturation time
and to prevent substrate loss. The original wooden truss needed
steel reinforcement to increase the roof's load-bearing capacity
as a result of the extra 14 pounds the green roof added fully saturated.
Sedums and succulents were planted on this roof due to their ability
to survive in only 2 inches of substrate. The succulents were primarily
places at the top, where conditions are the most arid. The total
costs of this roof were $16.30 per square foot. Standard roofing
costs amounted to $12.65, making the cost of the additional green
roofing $3.65 per square foot. The developers recommend using pre-mixed
substrate, pre-washed stones and a cheaper membrane to act as a
root barrier, to cut costs even futher.