|vines on walls are a traditional element of a living building
By 2010 over 50
percent of the world's population, some 3.3 billion people, will live in urban
areas. While cities offer opportunities for living with a low ecological
footprint, they suffer environmental problems such as pollution, noise and
remoteness from nature. Integrating vegetation into the urban fabric
improves these quality of life issues, while offering
many innovative opportunities for ‘green’ architecture. Whether part
of a highly engineered wetland, or simply a low-tech way of providing
dappled shade, plants can be a central part of a sustainable design
solution. At the same time, they offer biophilic
inhabitants, increase the ecological productivity of the site, and
connect buildings with their unique local environment.
We have moved beyond considering the attributes of a high performance
building envelope just in terms of daylight, insulation and BIPVs, to
incorporate rainwater collection, vegetation and even hydroponic
food production. Now when designing a building, we
evaluate each building surface for its best use and the value it can bring
to a “productive building".
|Bronx Riverhouse with a double layer moss-vines wall.
Vegetation can bring multiple benefits to the building envelope
and mechanical and plumbing systems. Basic architectural
strategies can include using evergreen vegetation as a buffer against
prevailing cold winter winds. Evergreen vines on a wall trap an insulating
cushion of air and reduce wind chill. Deciduous vegetation can be
used for seasonal shading, and also, through evapotranspiration,
can cool the surrounding air. Depending on climate, well irrigated
vines (preferably with gray or rainwater) can result in temperatures
up to 10°F cooler than the surrounding air. A 10°F (5.5°C) reduction
in the temperature immediately outside of a building can reduce the
amount of energy needed for air-conditioning by 50 to 70 percent.
Storm and gray water strategies
|Landscape swale to
capture stormwater, Remsen Avenue
architects have the benefits of xeriscaping (landscape that does
not require supplemental irrigation) foremost in their minds. Although
it is important to eliminate the use of potable water for plant irrigation,
we consider all sources of wastewater that can be used. Irrigation
can greatly increase the rate of growth of plants, their rate of
evapotranspiration and their possible contribution to summertime
cooling strategies. Using storm and graywater can also contribute
to the stormwater management and waste water treatment systems. Vegetated
roofs, facades and designed landscapes can allow downsizing or elimination
of conventional plumbed stormwater systems. Especially important
in areas with combined storm and sanitary sewers, this helps reduce
overloading of the system with resultant overflows of raw sewage
into nearby waters. Extensive green roofs (with 4 inch substrate)
have been shown to retain 70 to 100 percent of summer rainfall and
40 to 50 percent of winter rainfall. Designed landscapes such as
bioswales, rain gardens and constructed wetlands purify stormwater
and allow it to infiltrate into the ground to recharge the aquifers
instead of entering a piped sewer system. Remsen
Avenue incorporates a landscaped swale for stormwater infiltration. Solar
2 incorporates a raingarden to infiltrate excess stormwater
and avoid any stormwater flowing to the combined sewer.
Biological Waste Treatment
More extensive purification of gray
and black water can be done by biological wastewater treatment systems
that use aquatic and wetland plants in conjunction with bacteria,
algae, and other organisms. (Gray water is wastewater from bathing,
hand-washing, dishwashing and laundry; black water contains sewage).
A constructed wetland is an exterior system, and serves as an intermediate
step between a septic tank and a drainfield, making pollution of
groundwater less likely. An interior system treats gray and blackwater
waste within planted tanks in a greenhouse space and may reuse the
water for nonpotable uses (such as an “eco-machine” or a “living
machine TM”). Solar 2, Green Energy, Arts and Education Center, will
incorporate such an onsite intensive biological waste treatment system.
Cooling and Air Purification
When cities increase the amount of
vegetation within them, reduction of particulates, pollution and
carbon dioxide, and lessening of the urban heat island effect can
be observed. A 2002 study in Toronto found that urban summertime
temperatures in the city could be reduced by up 2 to 4°F if just
6 percent of the cities rooftops were greened. Plants, especially
locally native ones, provide food and habitat for birds and
insects, enhance biodiversity. The site can be made ecologically
productive by sequestering carbon dioxide for the life of the plants
(and beyond as carbon within the soil).
Indoor plants purify, humidify and oxygenate air, improving indoor
air quality greatly. Research at the University of Guelph led to
a design for an indoor green ‘biowall’ which circulates air through
it, oxygenating the air and removing pollutants, especially volatile
organic compounds and carbon monoxide. Purifying air in this way
can lead to lower requirements for exterior air, and associated conditioning,
|grapevines on a trellis
the most cost effective and rewarding benefit of integrating vegetation
into buildings is the biophilic connection it gives to building occupants.
Biophilia has been defined as "the connections that human beings
subconsciously seek with the rest of life”. Studies have been done
similar to those showing the benefits of daylighting to student learning
in schools, retail sales or employee productivity. Views of plants
have been shown to increase worker productivity, decrease absenteeism
and reduce recovery times for patients in healthcare settings.
Plants are part of the high quality environment that sustainable
architecture should provide. As building technology improved throughout
the 20th century the possibility of providing a uniform environment
led to many buildings losing their vital connection with their environment.
People are now beginning to question the desirability of that uniformity.
Many opportunities for richness and meaning come from connecting
a building to its environment, animating architecture through the
play of daylight on a wall, the passing of a breeze, or the variety
of light, shade and color that plants can give.
Human food production within buildings or on rooftop greenhouses
is also a possibility. The ecological cost of transporting food
thousands of miles from farm to table is huge, and indoor urban
agriculture allows food production year round for local consumption.
roof, bushwick inlet park
Green roofs include thin ‘extensive’ green roofs (2 to 6 inches),
thicker ‘intensive’ green roofs (typically an accessible roof garden)
or removable modular green roofs.
Extensive green roof plants are typically sedums and other rocky
alpine plants as they can tolerate extreme conditions and are
virtually maintenance free. Intensive green roofs can support a much
larger variety of plant species. Although some green roof systems
incorporate a rainwater detention layer, many green roofs will need
supplemental irrigation, which can be provided by graywater or stored
rainwater. This can be dispersed by a drip irrigation system, or
by a layer of felt below the surface and irrigated from one edge.
A well irrigated green roof can keep the roof much cooler throughout
the summer than a dry green roof.
Bushwick Inlet Park is covered
by an accessible green roof, allowing 100% of the park area to be
used by the public. A grassy slope rises up and over the building
to an overlook two stories above Kent Avenue. A meandering path provides
access to a series of plazas on the roof/hillside. The green roof
is irrigated by rainwater collected from the terraces and summer
playground sprinkler, and stored in a below ground 20,000 gallon
rainwater tank. Other green roof projects by K+C include: Pitt
St Residence and Heliodomi. General
green roof information is available at: http://www.greenroofs.org/
Green facades or screens
|solar 2 green screen
Green facades or screens (vines climbing up screens
/walls) can be vine covered. Trellises can keep vines largely within
designed areas and can be placed in front of glazed areas, allowing
deciduous vines to provide seasonal shading of the interior spaces.
Climbers may be self-clinging or they many need supports. Certain
climbers require certain types of supports – some twine around trellises,
or vertical or horizontal supports while others have suckers or aerial
roots to attach to walls. Steel cable or strong plastic meshes can
be used as the support for vines.
Solar 2 is on a narrow North-South site, meaning long east and west
facades are unavoidable. The design suspends a vine screen to the
east, and a wall clinging deciduous vine to the west, to shade the
building’s vulnerable windows in the summer and yet welcome the sun’s
warming rays in the winter. Bronx River Greenway Riverhouse combines seasonal shading through
vines with a security screen for the project.
Green / Living walls
|bronx riverhouse site section
Green / Living walls (plants growing on walls)
can be planted with mosses, or plants in pockets of the walls
to form a green wall. Retaining walls can also be made up of modules
that have space for planting. Designed green wall systems may
have soil held in compartments, but the most successful ones are
hydroponic – where bare roots are kept moist and irrigated with
a nutrient solution. In the Bronx
River Greenway Riverhouse project a rainscreen on the AAC
block wall is covered in mosses, while an outer screen is covered
in vines. This will result in local cooling of up to 7°F and mimics
the ecological productivity of a temperate rainforest.
Successful integration of plants into buildings and their systems
requires a team approach. Maintenance requirements need to be considered
from the outset. The client, landscape architect, architect, structural
engineers, civil engineers, mechanical, electrical, and plumbing
engineers and an ecologist may all need to be involved. Most of these
team members are not used to designing with regard to time. When
integrating vegetation into buildings architects need to be aware
how their design will look in each season and before and after the
optimal growth period. It is very easy to think of vegetation as
another building material that can be used in any orientation, exposure
or size. Plant textures applied to renderings can seduce the architects
and clients into thinking that this is possible, and the real world
installation may well fall short of expectations. However, many built
examples show that where a team member has close knowledge of plants
and their requirements, and the whole team works together to make
the installation a reality, then incredibly lush, verdant installations
can be created.
An ecological approach calls for the use of native plants in exterior
locations (Indoor plants will normally be tropical or other warm
weather plants, since the indoor environment is always warm). Native
plants offer many advantages, link to the region, and greatly increase
the available habitat for animals. Adapted, or non-invasive plants
may also be considered, but it is worth considering the level of
ecological productivity and animal life supported by native plants
can be orders of magnitude higher.
A holistic sustainable approach to design offers many synergies.
Using plants to treat wastewater increases their growth and possibilities
of summer time cooling. At the same time it increases biodiversity
and habitat. Studies have looked at combining photovoltaic (PV) and
green roofs and found that there may be benefits to both – the PVs
are more efficient since they are kept cooler and the green roofs
benefit from some shade. However, there will be situations where
tradeoffs need to be made. With productive buildings the whole building
skin becomes a precious opportunity to harvest environmental benefits,
such as whether a surface should be clad in solar panels, vegetation
or glazed. The design team needs to think of the whole picture, and
measure advantages and priorities, while avoiding token gestures
integrated agriculture >