Monthly Archives: October 2010

Woolly Bear for Winter

Woolly Bear caterpillar in the fall

The Woolly Bear caterpillar is supposed to be able to forecast what kind of winter we will have. This is the common name for the caterpillar of the tiger moth, and it used to be pretty common. The old belief is that if it changes color to black or very dark brown, winter will be cold. If it stays its reddish brown color, then winter will be milder or shorter. As you can see, I spotted one today that is brown in the middle with just a bit of black at each end. So maybe we will have a predominantly mild winter – with colder bits at each end.
Or maybe the caterpillar is in the process of changing color before pupating and didn’t get all the way yet. After all it’s still amazingly mild. Or maybe it’s a fashion statement, I like the way it looks.


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Green Roofs – Residential

A green roof with a real lawn - and great views

A rooftop garden on a new house

The last post about Green Roofs was a bit “off topic” inasmuch as it showed examples of commercial buildings with vegetated roofs. Here is an example from a recent Green Home tour I attended in Philadelphia, in the Manayunk section. This roof is on a townhouse development called Sheldon’s Crossing, with magnificent views from this rooftop terrace and garden. The soil is a bit deeper here, about 6″. As you can see from the photos, it supports a fine lawn, as well as shrubs. The grass is fescue and needs mowing only once a year, we were told.

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Green Roofs

A green roof in West Philadelphia

Modular Green Roof

Green roofs are a neat idea and make environmental sense, at least in the city where they soften the environment and help retain stormwater.  I went on a tour of three roofs in Philadelphia last week (A tour arranged by our excellent Delaware Valley Green Building Council).  This picture is from one using modular trays, the easiest and cheapest solution for a extensive roof.   Extensive means that the planting medium, what would be the soil on the ground is shallow;  the favored type of plants are sedums, as in this example – they can survive a dry spell and are not damaged by the wind.  Intensive roofs are those that have more than 6″ of soil and can sustain more varied vegetation.
At least one of the roofs was making the old claim that vegetated roofs save energy.  They can cool down the air around the roof and thereby save airconditioning in adjacent buildings.  But they do nothing much to insulate the building – insulation can do that much much cheaper.  Their real Green (ie sustainable) benefits are in fact fairly limited but they are better than looking at expanses of bare roof, for sure.
Here is an old post I cam across where someone is confirming the point about thermal insulation:
“I can’t offer you peer reviewed ashrae stuff but everything I have heard/read seems to say that there is virtually no R value to a vegetated roof especially when they are doing their job and holding water- Perhaps when you get to the Chicago City Hall type roof with 4′ of dirt it is a different story but when you have a 4″ extensive type system I don’t think you get much at all.”
Dxxxx Bxxxx, AIA LEED AP
Senior Associate


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