Engineering New Uses

by Don Friedman on October 20, 2016

A roof-top farm in Chicago (credit to Linda from Chicago):

new_crops-chicago_urban_farm


The future arrives slowly, piecemeal. This article by Karrie Jacobs, The Farm Upstairs, discusses the growth of green roofs including, specifically, food gardens on roofs. There have always been plants in the building-occupied portions of cities (think flowerpots and window boxes), and there have always been farms and food gardens in unbuilt portions of cities (the last working farm in New York closed in 2004). The use of roof space makes possible the presence of real farms in built-up urban areas, which is something new.

My direct interaction with this topic, so far, has been fairly small: I’ve investigated the load capacity of several roofs as part of an overall assessment of whether it made sense to create a farm. In short, if a lot of money has to be spent on structural upgrades to make the farm feasible, it’s probably a bad idea economically. Some existing roofs can take the extra load and some can’t.

Besides the psychic rewards to the farmers and the creation of fresh produce locally, there are two big benefits to rooftop farms. First, the amount of rain runoff that needs to be addressed is greatly reduced. This reduces the strain on pubic and private infrastructure (the sewers and the building’s rain retention system, respectively). Second, the absorption of light and infrared from the sun by the plants helps reduce the urban heat inland effect.

So: a lot of benefits, and the only downside is the cost of upgrading structure. It sounds like engineers need to step up to find a way to make this less expensive.

 

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