Are there any cost-cutting shortcuts for planting a green roof on my urban townhouse? My urban townhouse has a flat roof, and I'd like to green it up. Are there viable green-roof shortcuts that would have some insulating and stormwater-attenuating benefits? I was thinking of placing flats of plants around the roof rather than constructing a full planting bed. I'm hoping to avoid the expense of a full engineering study to determine the roof's weight-bearing capacity.

Sent by Rachel

Answered by: Mark Schrieber, Envi

Many green roofing manufacturers offer modular products that can be laid down in the manner you describe. These products are similar to plant flats, allowing for easy installation; they're lightweight, come pre-planted, and are more flexible than installing a permanent green roof system. A green roof constructed of modular units will still have all the benefits of a permanent, built-in green roof, including stormwater management, insulation, and reduced heat island effect.

Although a modular green roof will weigh less than an intensive green roof system, I still recommend you have an engineer complete a review of the roof structure to ensure it can accommodate the extra load. The cost for an engineer's site visit shouldn't be too much (I would expect $500–$1,000) and will be worth it for the peace of mind. If an engineering consultation or necessary retrofits to your roof structure prove too expensive for a green roof to be viable, try a white roof to achieve similar insulating benefits...

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