for Beijing Materials in Beijing Multi-family Dwellings
Problems to address:
Context and Approach:
The selection and use of building materials,
in particular for large scale housing projects will have significant
energy, cost, and comfort implications. The impact of the current
and imminent growth in China's construction sector represents a
potential new prominence in world resource consumption.
Careful and creative selection of materials
and design and detailing of installation can significantly mitigate
this impact. The use of renewable materials should be given preference
to the use of non-renewables. Reusable and recyclable materials
should be give preference to non-recyclable, non-reusable materials.
Consideration should be given to the project's role in carbon dioxide
chains; outputs and inputs should be balanced. Designs must be reasonably
constructable; the need to import either labor or materials should
be minimized and limited to those resources that have significant
The building envelope, its walls and roof, should
be instrumental in minimizing the consumption of non-renewable resources
during the life of the building. This will minimize negative impacts
of fuel usage including operational costs.
The team recognizes potential risks and
benefits of the current transition to occupant ownership. The environmental
risks include: The effect of larger units, and the resultant per
capita material and energy consumption; Comfort zone evolution to
a more limited region that may will require more responsive buildings
and HVAC systems; The decentralization of knowledge base to the
market eliminates the potential for a unified approach The associated
benefits include the owner's increased stake in their dwellings
may lead to improved maintenance due to onsite care taking and responsibility.
Also, the potential of decentralized knowledge base may provide
means to implement new solutions.
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- AC units: Individual units are not efficient,
and typically are not carefully installed. Energy inefficiency
is compounded by air infiltration through unsealed condensate
and electric lines. Water leakage may present a long-term durability
and maintenance issue near these interruptions in the façade.
- Lack of insulation. There is conflicting
information regarding the use of insulation in existing and
recent construction. Insulating value is typically attributable
to clay or masonry materials that have very high thermal conductivity.
Their advantage in thermal lag are advantageous only when mean
diurnal temperatures are in the comfort zone. Therefore insulation
will be beneficial in most regions. The industry is currently
unaccustomed to designing insulated walls.
- Window construction: Typical systems are
single glazed and leaky (loose-fitting). According to the Ministry
of Construction, windows and doors account for 50% of energy
loss in Chinese buildings.
- Effective use of concrete: As the transition
continues from clay-brick to concrete construction, the overuse
/over design of concrete structures poses a significant environmental
hazard due to its large embodied energy and the significant
volumes of carbon dioxide emitted during its manufacture.
- Loss of agricultural land due to clay mining.
Apparently, 10,000 hectares of farmland is destroyed annually
to make clay brick. The apparent alternative is concrete blocks.
This technology is, like clay brick, also high in embodied energy.
- Integrated design approach: Holistic thinking
should be the first consideration in improving the quality of
housing. Integrating the consideration of materials with the
planning of mechanical systems can eliminate aesthetic problems
while avoiding damaging moisture penetration and energy consuming
air infiltration. A similar approach may be taken in the planning
and detailing of window openings. Vast improvements may be made
on each of these fronts by complete planning and rigorous follow-through
- Windows: A lot of money can be spent improving
the quality of windows. High-tech solutions are available globally
that would provide a radical improvement on the energy losses
and associated discomfort related to leaky windows. However,
importing technology shouldn't be considered as the only solution,
or even necessarily the best solution. Importation suggests
exporting jobs and money, and requires the expenditure of time,
money and energy for the transport of products. If windows are
to be imported, consideration should be given to purchasing
only frame stock. This will reduce the transportation associated
with heavy glass units, while concentrating on accessing the
higher-tech and highly engineered frames. The higher quality
frames will mitigate a majority of the energy and comfort issues
if installed correctly.
- Insulation: The most expensive way to insulate
a building is to leave the insulation out of the building. The
resultant energy consumption of buildings without insulation
is more expensive than simply putting insulation in the wall
to begin with. The most effective location for building insulation
is on the outside of the structure where it can be run past
the floor slabs, creating a continuous protective layer for
the building thereby minimizing thermal bridges.
- Centralized HVAC systems or planned locations
and proper sleeves for penetrations.
- Apply vernacular / regional technologies:
The environmental impact of concrete construction can be minimized
by careful engineering of the structures to avoid wasting material.
Local coal-burning power plants should be considered as mines
for fly ash, a material that can be used to replace portland
cement and thereby reduce carbon dioxide emissions of the concrete
- Air barriers and flashing systems: These
systems are proven in their effectiveness to minimize energy
consumption and maximize building longevity.
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