Chem321:Passive Solar Houses and Sustainable Design
Contents
Introduction
The planning and building of homes can have negative impacts on the environment. There are phases in the life cycle of the construction of a home that contributes to these negative effects. A home needs to be thought of as a product that needs to be designed with the interest of the people who will be living in it as well as the effects it can have on the environment it is in.
Some factors to consider in designing sustainable, “green” homes should include energy efficiency, use of primary energy, CO2 emissions, costs, and the level of living comfort for the family that will be living in the home. Working with nature is the most efficient way to building a sustainable home. The key is to start implementing a wide scale, sustainable design approach to how we construct our buildings and homes. Current environmental strategies in “green” or “ecological” housing tend to focus on the individual building rather than the development as a whole (Marsh et al., 2001).
Globally, the life cycle of buildings and homes contribute vastly to the total amount of consumed energy. The life cycle requires large amounts of non-renewable fossil fuels- such as coal, oil, and gas, that give off harmful emissions into our Earth’s atmosphere leading to polluted air and global warming. One solution to this problem is to change how we look at the design and development of our buildings and homes. Our approach should follow the philosophy of sustainable, “green,” design, which uses innovative thinking to find ways to design and build homes that will comply with the principles of social, economic, and ecological sustainability. The intention of sustainable design is to "eliminate negative environmental impact completely through skillful, sensitive design". (McLennan, 2004) The underlying principle of sustainable design is to design for a purpose. As Albert Einstein once said, “We cannot solve our problems with the same thinking we used when we created them.” Architects and designers will be planning more creatively and quantitatively by following the “green” design approach.
Sustainable design aims to:
• Respect people by creating healthy and nourishing homes while working alongside nature. “It is about honoring diversity and giving control back to people for their environments and personal comfort.” (McLennan, 2004)
• Respect our ecosystems and land. Housing should maintain a symbiosis with the local environment that it is built in.
• Learn from nature. Janine Benyus (2002) describes in her book “Biomimicry: Innovation Inspired by Nature” how we should emulate nature’s time-tested pattern and strategies when innovating new sustainable solutions. As Aristotle stated, “Nature does nothing uselessly.”
• Respect energy and natural resources. Nature provides many ways for us to harness and store energy. There are many different physical, chemical, and biological processes that nature uses to achieve this.
• Respect the future. This is one of the most important aims of sustainable design because everything that we do now will have a consequence in the future. Our decisions have a great impact on the future of our planet’s resources. We should be looking to find ways to heal the planet by using renewable energy sources.
• Think systematically. The systems thinking approach must be used to achieve success in the sustainable design. Impacts on the environment, businesses, people, and economy all need to be considered in the design process. (McLennan, 2004)
While there are many different factors to consider in designing a sustainable, “green” home, one factor that needs to be thought about in the process is how the home will be heated and cooled. It is beneficial to the homeowner and the environment that we plan to design and use methods of heating and cooling that will use a primary, renewable energy source. One of the major primary energy sources provided to us is the sun. Solar energy is one of the most promising forms of alternative energy that we are working with today. Using the sun’s energy gives us high levels of energy saving due to its availability and renewability. There are two ways that solar radiation can be converted into heat: passive (using only passive solar components and materials) and active (using technical components that harness the sun’s energy). This paper will talk specifically about the passive solar design approach to building homes.
Characteristics of Passive Solar Design
Passive solar home design uses natural processes, such as radiation, conduction, and convection, to distribute thermal heat provided by the sun throughout the home. The aim is to integrate features in the home with its natural surroundings that absorb the sun’s low rays in winter and deflect the sun’s high rays in summer to naturally warm and cool the interior. (EPA, 2014) Architects and builders use their knowledge of solar geometry, window technology, and local climate to design a home that meets the specifications that will utilize the sun’s energy appropriately. Optimizing the use of solar energy requires the proper orientation of the building, roof and wall colors, as well as proper shading (Kruzner et al., 2013).
The key elements, outlined by the US Department of Energy (2013), that need to be in place for the passive solar design approach to be successful include:
1) Proper site planning- Solar Apertures
• Solar apertures (windows) are protected from unwanted shade from other elements around the house during the season when the house needs heating.
• Windows should face within 30 degrees of true south, and during winter months they should not be shaded from 9a.m. to 3 p.m.
• Windows should be placed on specific sides of the home based on the climate they are built in. (Example: in warmer climates, use north facing windows along with shaded south-facing windows)
2) Absorber-
• The exposed hard, darkened surface of the storage element that is situated in the direct path of the sunlight. The sunlight hits this surface and is then absorbed as heat.
3) Thermal Mass-
• A material that is below the absorber that retains the heat produced by sunlight during the heating season and absorbs heat from warm air in the house during the cooling season
• Materials that are used as thermal masses include concrete, brick, stone, and tile
4) Proper heat distribution & mechanisms-
• The natural processes of conduction, convection, and radiation transfer the heat that is collected and stored to different areas of the house
• Mechanisms may be needed to help distribute this heat. They can include: small fans and blowers.
5) Control strategies-
• Roof overhangs provide shade to south facing windows during the summer months.
• Electronic sensing devices- thermostats that can signal fans to turn on.
• Vents and dampers that restrict or allow heat to flow
• Low-emissivity blinds
• Insulating shutters
• Awnings
There are also three categories of passive solar heating techniques: direct gain, indirect gain, and isolated gain.
• Direct gain is the simplest technique where the space of the home is directly heated by the sunlight. The materials within the space will absorb the heat and the airflow in the room will distribute it.
• Indirect gain uses a technique where its thermal storage is present between the south-facing windows and the living spaces. They term this thermal storage wall a Trombe wall and it sits about 1 inch or less from a mounted layer of mounted glass. The idea here is that solar heat is absorbed because of the outside, dark surface and then stored in the wall’s mass, where it will then radiate into the living area. This process occurs over several hours.
• Isolated gain is also referred to as a sunspace. A sunspace can experience a high amount of both heat gain and heat loss so it needs to be moderated by thermal mass and low-emissivity windows. Sunspaces look and act much like a greenhouse functions with the main difference being that a greenhouse is designed to grow plants while a sunspace is utilized for helping to heat the home. All three passive solar heating techniques utilize a thermal mass and need good insulation and air sealing to maintain the heating and cooling in the house. (US Department of Energy, 2013 & Kachadorian, 1997)
The “Dirty” Process of Using Fossil Fuels to Heat Our Homes
The reliance on “dirty” fossil fuels to heat our homes is expensive and environmentally unsafe as compared to renewable resources. Fossil fuels, formed from the organic remains of prehistoric plants and animals, have been the primary resource for much of the world’s electric power and total energy demands. There are advantages and disadvantages to using fossil fuels. Some advantages to using fossil fuels to heat a home includes: generating large amounts of electricity, they are easily attainable, and the technology we use to harness the energy from fossil fuels is well developed. But, there are many disadvantages of fossil fuels that need to be thought about in planning for our planet’s future. The biggest disadvantage to using fossil fuels is that when they are burned during the combustion process they give off carbon dioxide (CO2), which is the number one greenhouse gas that is contributing to global warming. “Greenhouse gas emissions from businesses and homes arise primarily from fossil fuels burned for heat and make up 12% of 2013 greenhouse gas emissions” (EPA, 2013) By the year 2020, world energy consumption is projected to increase by 50 percent, or an additional 207 quadrillion BTUs. If the global consumption of renewable energy sources remains constant, the world’s available fossil fuel reserves will be consumed in 104 years or early in the 22nd century. (US Department of Energy, 2013) Fossil fuels also cause air pollution, which effects human health, plant growth, and natural ecosystems. The cons seem to outweigh the pros when it comes to burning fossil fuels. We need to transition to renewable resources that we can depend on for reliable, cheap, environmentally friendly energy.
Obstacles of Passive Solar Design
The early design stage of house construction is the best time to implement passive solar principles, but there are some obstacles to overcome described by Yannas (1994) namely; the lack of design information; credibility and applicability of passive solar principles; marketability of passive solar; lack of incentive from the government to adopt these technologies; perceived increase in the costs when these technologies are adopted and design (aesthetic) quality. Housing developers need to be the driving force to make sure that construction plans and decisions that are made for the design of the home are cost effective and environmentally sound. Bordass (2000) states that it is often difficult even for professionals well trained in environmental or “green” design to differentiate between an environmentally friendly dwelling and one that merely claims to be. Negative perceptions of passive solar design need to be overcome so that sustainable design can be applied to building homes.
Benefits and Viability of Passive Solar Design
Investigation into housing developments provides verification that passive solar projects provide more benefits to the homebuyer and environment than current construction and layouts (Yannas, 1994) In general, passive solar design improves the comfort of the house by keeping the room temperature more even, primarily, due to the use of natural ventilation (Eicker, 2003). Other benefits to passive solar architecture include: 1) Reduced need to cool the building in the summer, as there is no overheat. 2) Decrease in total energy consumption. 3) Decrease in environmental pollution. 4) Cost-effective as long as the house is planned out properly following the principles of passive solar design. Passive solar solutions not only reduce the need for additional equipment and technology in the house, but above all, reduces the use of fossil fuels and prevents the further development of climate change (Kruzner et al., 2013). Passive solar design may have to overcome some obstacles to become utilized in more housing design plans, but it is definitely a viable approach to using the sun’s radiation, a renewable resource, as an alternative energy source.
Conclusion
The principles of sustainable design are important in understanding why passive solar design of homes is a viable option for the future. Utilizing the processes that nature already has provided for us is a more efficient way to design and plan out the design of our homes. As humans, we are like any other species trying to find a way to survive in the environment around us. Historically, we have made some good and bad decisions when it comes to our environment. Due to increases in population, we no longer have the luxury of relying on non-renewable resources that the planet can longer provide for us. We need to work with nature to heal our planet and create a more sustainable world for us to live in!
RESOURCES
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