[Greenbuilding] Green Roof under deck

[John Salmen]

I would echo this. 

 

In urban settings I would say the priority for using a green roof is for
storm water retention (seattle has offered major incentives for this). It
has the goal of reducing the need for enlarging existing systems. Storm
water systems are designed for the first surge (5 minute flow). If that can
be held even briefly it can downsize a system. Gravel alone could accomplish
this and most designs are based on the substrate (can't rely on gardening).

 

For heat islands both gravel and light coloured membrane can also help this
without vegetation but they won't sequester co2. Even the most minimal green
roof (extensive type with sedum) can sequester the equivalent of about 2
vehicles c02 emissions per kilometer per square meter of sedum plantings
(msu). Not much mileage if your going to base your vehicle usage on your
green roof - but like everything it adds up.

 

Protecting roofing was a big design incentive for me as roofs are basically
bad design and environmental hogs because they have to endure the elements
directly. Soil (with or without plants) is an ideal protection. The end
result though is minimal cost and material wise as with a green roof due the
amount of material needed to reliably provide both long term water and root
protection and the potential work involved in restoration for leakage.

 

So I would venture that the primary motivation for a green roof is simply to
maintain as much surface area of the earth as possible as vegetative matter
(though many would argue that the urban population already supplies that in
excess).

 

From: Greenbuilding [mailto:greenbuilding-bounces at lists.bioenergylists.org]
On Behalf Of David Wentling
Sent: January-25-13 8:14 AM
To: Beatrice Dohrn; Green Building
Subject: Re: [Greenbuilding] Green Roof under deck

 

Green roof are for storm water control, reducing heat islands, aesthetics,
and protect roofing materials from UV exposure. Side benefit is reducing the
temperature gradient across the roof which effects indoor comfort. Lets be
clear, we do not construct green roofs for keeping buildings cooler. There
are more cost efficient ways to do that.

 

David Wentling
ConservFirst.com

  _____  

From: Beatrice Dohrn <beatricedohrn at yahoo.com>

Isn't the main point of a green roof to keep the house underneath cool?  So
if the deck were of an opaque material with that 2' airspace wouldn't the
deck the roof cool -- obviating the need for the vegetation?  

 

From: Gennaro Brooks-Church - Eco Brooklyn <info at ecobrooklyn.com>


I just salveged some tempered glass. I have a client who wants me to
build a 3" green roof on his brownstone plus a deck that sits 2' above
the roof.
I suggested a glass deck and green roof under it.
He is concerned the vegetation under the glass deck will not survive
since it will bake in the summer.
Are there any experienced landscapers on this list who can offer their
experience? 

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