What is
Sustainable
Design?
Part Four:
Sustainable
Materials
The George and Kathy Dembroski Centre for Horticulture, Toronto
Presentation Summary
In this presentation, we will discuss:
• Green/less harmful materials
• Sourcing materials
• Materials that retain heat (thermal mass)
• Materials that reject heat (insulation)
• The colour of materials
• Exterior materials
• Heat Island Effect
• Embodied Energy
Presentation Credits
• This presentation was prepared by Terri Meyer Boake, BES, BArch, MArch,
LEED AP
• Associate Director School of Architecture University of Waterloo
• Past President of the Society of Building Science Educators
Materials First!
Materials
need to be
part of the
very initial
thoughts as a
building is
conceived.
A building’s
design is
intrinsically
linked to its
materiality.
Aldo Leopold Legacy Centre, Wisconsin
The Bird’s Nest, Beijing
Material Choices
• When designing buildings we
usually have a choice as to what
material to specify
• Materials can be compared as
being more or less harmful to
the environment
• We should obviously choose less
harmful materials
• We should use materials that use
less energy
• We should use materials that
make our buildings more
efficient
• Materials should be both
beautiful and enduring
The George and Kathy Dembroski Centre for Horticulture, Toronto
Define “harmful”!
•
•
•
•
•
•
•
Toxic to the environment
Harvest endangers wildlife/removes habitat
Harvest endangers/compromises local people
Processing or manufacturing harms the environment
Some materials are limited as a resource
Some materials are not easy to reuse or recycle
Some materials are energy intensive
Renewable vs Non-Renewable
• Materials can be
classed as either
renewable or nonrenewable
• Non renewable
materials includes
metals, and stones
and items that “do
not grow”
• Renewable materials
include wood, straw,
bamboo and other
“growing” substances
Virgin vs. Recycled or Reused
It is preferable to use renewable
materials, but when it is not
possible one can source:
– Recycled materials or materials
with a significant recycled
content: such as steel where a
good percentage of the product
is put back into the
manufacture of goods at the
“end of life”
– Reused materials: preferred as
it is not necessary to put
additional energy into
remanufacturing the product
TOHU, Permanent Bigtop, Montreal
Durability
• Preference is almost always
given to the use of more
durable/long lasting materials
• It is expensive to have to
replace windows, roofing
materials and cladding
• Expense can be measured both
in terms of dollars as well as
energy (and associated
greenhouse gas emissions)
Caisse du Depots et Placements, Montreal
Embodied Energy
Definition:
Embodied energy is the energy associated with the
harvesting/mining, manufacture, transportation and
construction of a material
Transportation energy is significant for ALL materials, even if
they are of the renewable variety
Materials with “high embodied energy” are less desirable from a
sustainable perspective
However, some high energy materials are irreplaceable for
certain uses: concrete for its thermal mass; aluminum for its
durability, steel for its strength
Retain vs Reject Heat
• Materials can be classed as those that RETAIN HEAT and those that REJECT
HEAT
• HEAT RETENTION is useful if we wish to store the free energy from the sun
in the material
• HEAT REJECTION is also called INSULATION.
• INSULATING materials are used to retard the heat flow through the
building envelope
• INSULATION at VERY HIGH LEVELS is essential in all elements of a cold
climate building envelope
• THERMAL BRIDGES are points in the building envelope where there
insulation is completely lacking
• THERMAL BRIDGES ARE TO BE AVOIDED as they result in heat loss and
normally degradation of the building envelope at the point of breach
(evidenced by condensation, mould, mildew or rust)
Insulation
Different types
perform
different ways,
as a function of
their materiality
and thickness.
More is more…
Soybean based spray
Styrofoam
R values of batt insulation
Some are less
environmentally
harmful than
others.
Fiberglass batt
Spray cellulose insulation
Rigid fiberglass
Heat Storage Capacity of Materials
The specific heat of materials is different than their ability to store this heat. This is
referred to as their “thermal mass” or “heat storage capacity”. Thermal mass is the
ability of a material to hold heat and slowly release it back into the environment
giving a flywheel effect.
We often make a choice,
depending on the climate, if we
need to store heat to have it
released later in the day, when the
sun is down and things have
“cooled off”.
Materials with a high thermal
mass are helpful in the heating of
building interiors in cold climates.
We need to select materials with a
high heat storage capacity but that
are not conductors (like metal).
Thermal Mass
Exposed concrete floors are
becoming increasingly common in
sustainable buildings.
The concrete is both structural and
acts as an excellent storage
material for free solar energy that
comes in through the windows.
It can be made less harmful by
replacing some of its cement
content with “flyash” which is a
waste product of the steel
industry.
The concrete can be stained with
different colours if desired.
IslandWood, Seattle
Materiality and Site
Microclimate and Site Materials
Microclimate is the “mini climate zone” around your building as
modified by local conditions.
Things that naturally change your microclimate are:
• amount of sun received over the day
• wind and natural breezes
• The natural materials of the site
Things that YOU select also change the microclimate:
• material choices: paving, roofing, wall materials and planting
• colour of materials
In a cold climate select materials to INCREASE HEAT in the
WINTER and DECREASE HEAT ABSORPTION in the SUMMER
Solar Access and Microclimate
Bain Avenue Coop, Toronto
The micro climates in the backyards on either side of the walkway are different as a
result of solar access, even though materially they are identical.
There are different
microclimates on the
front vs. the back of the
house due to materials,
amount of shade and
orientation (sun).
East elevation
The front of the house
has more paving and less
tree cover, which make it
hotter. The black asphalt
roof also raises the
general heat level of the
site.
West elevation
The Effect of “Found” Site Natural Materials
Natural materials and the natural site landscape and configuration will affect
the heating or cooling potential of the site.
Replacing natural “soft” materials with “hard or impervious” materials will
increase the heat retention potential of the site.
Pervious materials are preferred as they allow rainwater to be naturally cleaned
and cycled without being directed into the storm and sanitary systems.
Heat retention makes for a warm microclimate and can increase the cooling
requirements of buildings in the summer months.
The Effect of Roofing Choices
The choice of roofing material critically impacts heat retention.
- Dark materials absorb heat, which is redirected to the urban atmosphere,
where greenhouse gasses trap it in place.
- Light materials reflect the heat (aka “cool roofs”).
- Green roofs stay cool, produce oxygen and absorb rain water, reducing
pressure on the sewer system.
Cool Roofs Theory
Cool roof materials have two important surface properties: a high solar reflectance
or albedo and a high thermal emittance. Solar reflectance is the percentage of
solar energy that is reflected by a surface. Thermal emittance is defined as the
percentage of energy a material can radiate away after it is absorbed.
Vernacular
architecture in hot
climates normally
finish roofs in light
colours to reflect heat
as well as to provide a
clean surface for water
collection.
Green Roofs
Green roof technology started in
Germany over 30 years ago.
Proprietary systems are being looked
at with some seriousness in Canada at
this point.
Green roofs reduce urban heat island
effect and decrease carbon dioxide
levels in the city.
Vancouver Public Library
They also can provide a higher level of
insulation (but not necessarily).
Green roof treatments can cover the
entire roof, or just a smaller part,
depending on the requirements and
limitations of the project.
Children’s Museum, Boston
Imagine the environmental benefit and resultant cooling if all of those roofs
were either green roofs or cool roofs…. It would help to mitigate Urban Heat
Island Effect.
The Effect of Paving Choices
“Paving” or the displacement of pervious, green surfaces, with hard surfaces, is a
primary cause of negative changes to the local microclimate.
Paving can not only cause heat retention, and overheat the urban environment, but it
can also impact water runoff and absorption into the site.
Paving selections need to simultaneously:
- Allow for water to be absorbed into the earth (pervious)
- Be durable for winter traffic conditions and snow removal
- Create a cool microclimate to prevent heat island effect
Phoenix, Arizona: shopping centre with (white) roof and pavement...
Permeable Paving
Different materials are available that allow
for a level of durability for traffic, yet also
let water drain through.
Issues of snow removal must be
accounted for when choosing
materials. Permeable concrete is also
an option.
The Effect of Other Material Choices
Other materials on site, whether they are chosen for walls or accessory structures, will
affect the overall tendency of the site to retain heat and create a hot environment.
Shading your walls will help to prevent heat gain.
However, in very cold climates, where the sun angle is very low, material choice can be
used TO hold heat in the building and warm up outside spaces.
Presentation Summary
In this presentation, we discussed:
• Green materials
• Sourcing materials
• Materials that retain heat (thermal mass)
• Materials that reject heat (insulation)
• The colour of materials
• Exterior materials
• Heat Island Effect
• Embodied Energy