Design Approaches for Beijing Materials in Beijing Multi-family Dwellings

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 and repeatable

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.

1. 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. and aesthetics).
2. 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.
3. 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.
4. 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.
5. 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.

Proposed Considerations

1. 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 during construction.
2. 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.
3. 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.
4. Centralized HVAC systems or planned locations and proper sleeves for penetrations.
5. 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 mix.
6. Air barriers and flashing systems: These systems are proven in their effectiveness to minimize energy consumption and maximize building longevity.