Green Building
Green building refers to erecting or putting up structures using environmentally efficient ways starting from the initial design, construction, and maintenance to conserve the environment. Several technologies to support green building have emerged about reducing pollution and waste from homes while ensuring occupants’ health is not at risk. It also encompasses using energy and water efficiently within housing facilities. The green building aims to provide a sustainable environment for future generations and reduce effects leading to environmental degradation drastically (Yudelson 2009).
Green building is geared towards finding a balance between infrastructural development and a sustainable environment. Green building encompasses several components, which include: energy efficiency, water efficiency, indoor air quality, material efficiency, waste reduction, and sustainable development.
Indoor Air quality
Indoor air quality places much emphasis on aspects regarding moisture management, air circulation/ventilation, and filtration of air. It is important to design infrastructure based on required or recommended ventilation levels while keeping in mind acceptable humidity levels. Room temperatures should equally be observed and maintained at optimal levels. The goal of indoor environmental quality is to ‘help buildings breathe more efficiently.
Mechanical Ventilation Control System (MVCS)
All houses and apartments are required to provide occupants with fresh air. Traditionally, homebuilders have relied on natural ventilation, which depends on wind speed and temperature differences between indoors and outdoors. People can only control circulation by operating windows and doors. It is still very useful to a low-density house and apartment in this day and age. However, most of Hong Kong’s apartments are very tight. Due to the high density, outdoor air is very limited to each unit. Some units in the central of the building may not have windows. As a result, occupants have to turn on air-conditioning every day.
Moreover, the indoor air pollution arising from moisture, pets, furnishings, cigarette smoke, and aerosol sprays, may not be emitted easily. All houses and apartments need an efficient way to exhaust stale, moist indoor air and introduce clean outdoor air. A very practical and efficient technology, Mechanical Ventilation Control System (MVCS) can introduce fresh air indoors and protect the building structure from moisture damage at a low cost(Don, 1996).
Four Types of MVCS
There are many types of mechanical ventilation systems. The four common ones are listed below in table 1.
Comparison of Whole-House Ventilation Systems includes Supply Ventilation Systems, Exhaust Ventilation Systems, Balanced Ventilation Systems, and Energy Recovery Ventilation Systems.
Table 1. Comparison of Whole-House Ventilation Systems.
Although Hong Kong’s winter is not very cold, summer is extremely hot and humid, and lasts for long periods of time. Based on Hong Kong’s local climate, either Balanced Ventilation Systems or Energy Recover Ventilation System may be considered as suitable choices.
Balanced Ventilation System
According to Energy. Gov., a balanced ventilation system usually has two fans and two duct systems.Occupants can install fresh air supply and exhaust vents in every room. More so, occupants can install them separately, for example install exhaust vents in kitchen, bathrooms and living room air from rooms where moisture and pollutants are most often generated and supply vents in bedroom and living room. If occupants want to spend less money, they can only install balanced ventilation in certain rooms such as bedrooms and living rooms where they spend most of their time. Figure 1 in below illustrates the principle of Balanced Ventilation System.
The balanced ventilation system is appropriate for all climates, hence it can apply to Hong Kong. However, it usually costs more to install and operate because the system is larger than Exhaust and Supply Ventilation system, which does not require two ducts and two fans system. In addition, the Balanced Ventilation systems do not remove or temper moisture from the outside air before it enters the room. Consequently, it may increase heating and cooling costs (Energy. Gov. 2012).On the opposite, an energy recovery ventilation system keeps the energy bill low.
Energy-Recovery Ventilation Systems
According to the research of Energy. Gov., energy recovery ventilation system is a controllable ventilation system, which is also advanced in maximizing energy saving. They reduce the costs of cooling ventilated air in summer because the inside air can cool the outside warm air. In winter, the system can transfer heat from inside warm exhaust air to cold supply air.
There are two types of energy-recovery systems: heat-recovery ventilators (HRV) and energy-recovery (or enthalpy-recovery) ventilators (ERV).
The two systems have a heat exchanger and are fitted fans for purposes of driving the air out. Many models are equipped with whole-house ventilation systems meaning they have individual duct connections.
The heat recovery ventilator differs from the energy recovery ventilator in how the heat exchanger works. An energy recovery ventilator is fitted within the heat exchanger to transfer water vapor as well as heat energy. heat recovery ventilator only transfers heat.
In the house, humidity remains constant because the energy recovery ventilator transfers moisture from the air to the less humid air in the winter. As a result, the exchanger remains warm and freezing is eliminated.
The cost of energy recovery ventilation systems is much higher than other ventilation systems. To keep installation costs low, it is vital to share ductwork when installing these systems. More complex systems cost a lot to install and are re-known for being serviced regularly. These types of ventilation systems are rare.
All ducts in unheated spaces should be insulated. Devices to manage and avoid freezing and formation of frost in cold climates must be integrated into these systems. The cold air supply is responsible for the formation of frost within the heat exchanger and this may damage the system. Heavy buildup of frost may hamper appropriate ventilation. effectiveness of ventilation. Energy recovery ventilation systems have more maintenance issues compared to others. This is because they need to be cleaned thereby avoiding growths of mold and accumulating bacteria.
Material Efficiency
Material efficiency implies minimizing the negative impacts on climatic conditions and the environment through the use of sustainable materials. It necessitates leaving a lighter footprint on the environment through the utilization of resources efficiently and effectively. Therefore, construction must be undertaken using energy-efficient, recyclable, low maintenance, and cost-effective materials. Material efficiency leads to the creation of a healthy living environment that is productive.
Energy efficiency, as well as resource efficiency, is key. It should satisfy certain criteria. The possibility of renewable energy generation may be taken into perspective to attain material efficiency. Material efficiency also considers maintenance issues in the context of upgrading and permits easier refurbishment. Understanding the environmental impact of building materials is a major step towards attaining material efficiency (Minson 2013).
Achieving material efficiency through material selection
Material efficiency aims to minimize levels of waste produced and ensure or provide for maximum re-use and re-cycling. For this reason, building or construction companies must source raw materials from manufacturers situated offsite rather than produce these materials on-site where construction is taking place. Recycling ensures that high-quality environmentally friendly materials are manufactured. Furthermore, soliciting materials from off-site ensures that pollution levels arising from noise and particulate matter are greatly reduced in the main site. To achieve material efficiency, several aspects have to be considered in the selection of materials. Recycling timber for doors, floors, and windows should be preferred over buying new timber and lumbering.
Materials selected should have low energy contents with insulation being maintained at optimal levels. It is also important to consider locally sourced materials. Materials for finishing, like paints and furnishes, should be non-toxic and emphasis should be laid on water-based products. Improving energy efficiency levels of materials selected is likely to reduce the levels of carbon emission (Spiegel & Meadows 2010).
‘Going green’ in materials acquisition may necessitate the need to use timber， which is treated with reduced toxic chemicals considering the levels of negative environmental impact. It is also important to take into consideration the use of renewable plants, like bamboo, and recycle metals and stone.
Bamboo
It is an eco-friendly building material that can be utilized for a wide range of building purposes. In, China, for example, people build their whole houses with bamboo. Bamboo is a fast-growing plant, it can be replanted and it grows back quickly. It can also be grown almost anywhere in the world.
Reclaimed Timber
Use of reclaimed timber is preferred over lumbered timber. Reclaimed wood is obtained from demolished structures and the reuse of timber products through recycling. This facilitates sustainability.
Recycled Metal
Iron, copper, and aluminum are the three most recycled metals around the globe hence making them readily available. Mining however is responsible for a variety of negative environmental impacts like contamination of soil, disturbances from explosive activity, and creation of sinkholes.
Dimension stone
This is a natural building material that is readily available and usually preferred over metals, plastics, and glass, which are responsible for environmental pollution. Dimension stones cab be reclaimed for purposes of building and construction.
Sheep’s wool
Sheep’s wool is used for insulation and it is environmentally friendly. Wool is natural and does not have negative effects on the environment hence making it sustainable. One of the features is that it is usually thicker and uses less energy to manufacture.
References
Minson, A (2013), Resource and Material Efficiency. Web.
Spiegel, R & Meadows, D (2010), Green Building Materials: A Guide to Product Selection and Specification. John Wiley and Sons, USA.
Yudelson, J (2009), Green Building Revolution. Island Press, USA.