Construction company Hammer & Hand works with living roof producer Green Feathers on green roof.
Construction company Hammer & Hand recently completed an Emmons Architects-designed luxury addition remodel to a Portland West Hills house, adding a gracious new living room with mahogany casework and oak flooring. Above and stepped back a little, the team added a marble bathroom to the master bedroom, including a huge soaking tub with views of Portland and a two-person shower.
The view from the bedroom (and from the tub) would have been the plain, white roofing membrane of the addition below, spoiling the 200-degree view of trees and mountains. Working with Pioneer Roofers and Green Feathers, the owners chose a certified Live Roof, a type of green roof, to layer atop the addition.
Photos courtesy of client
The result is a carpet of perennial sedum that you can reach out and touch from the low bedroom and bathroom windows. It creates a green continuum to the view of the woods below, breaking up the line of the addition’s roof and hiding the white membrane and flashing.
Hammer & Hand’s Christopher “Coop” Cooper made sure the roof’s layout was optimal. The standard way is to roll out a mat on which the soil and plants live. He chose another format.
“With all the luxurious finishes and electronics below, we wanted to make sure that in the unlikely event of a roof leak, anyone could find and fix it quickly,” says Coop. This roof was laid down in a series of rectangular, two-inch high trays. Green Feathers custom grew all the plants for the trays over three months in its greenhouse.
“This lets you triangulate which tray the leak is under, and then you can cut out that one tray and fix the leak before it does any damage to the living room below.”
Hammer & Hand has done green roofs before although this was the first time with the modular (tray) system.
This belt and suspenders approach extended to the roofing materials too.
“The client wanted the green roof from the start, which was good,” says Skylar Swinford, Hammer & Hand’s building energy analyst. “So the engineers could beef up the roof specs from the start, so that it could take a load of around 30 pounds per square foot – the weight of the trays, soil, plants and water.” Adapting the flat roof later would have been expensive and disruptive.
The roof assembly’s insulative capacity is rated R-60, which is high. It consists of:
– a layer of foam insulation
– a layer of rigid foam board tapered for drainage
– a cover board
– finally an extra thick, 80 millimeter single-ply, fully-adhered roof membrane.
Swinford says the live roof itself does not contribute to energy efficiency. “Dirt and plants don’t really do much for insulation, though green roofs have other benefits. To ensure long term energy performance and durability the team focused on creating an air-tight roof deck with continuous tapered insulation over the deck coupled with a high performance cavity insulation. Every penetration and flashing detail was carefully planned and executed with heat, air, and moisture management in mind”
Green features are in vogue across the USA, particularly here in Portland: they are the water features of the 21st Century. This is not a patio for hanging out on, it is a visual accent.
The roof has a spigot for when it needs twice-monthly watering in the summer. Hammer & Hand added a bolt in the center of the roof to which a maintenance worker can tether himself while watering, cutting or inspecting the plants. This is needed because the parapet is only about eight inches high. Code states it must be at least 36 inches high if anyone is to walk on it.
The result is cool and natural, and very sensibly built.
“This live roof really was the cherry on top of a fantastic house,” adds Coop.
-Joseph
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