Solar Chimney

There are some ways to take the advantages of sustainable ventilation during design and construction phases of a dwelling rather than the operation and maintenance phase that are called passive ventilation. Although these passive designs were traditionally popular for ages, they have become the center of attention in modern constructions due to their affordability, simplicity, efficiency and being environmental friendly.  

Solar chimney provides natural ventilation by utilizing the solar energy to create different air pressure and consequently air convection. Just like in fireplace that the air and smoke from a fire will raise through a chimney, the low dense warm air tends to go out through the tunnel and generates air movement and brings cooling effect. This movement can be intensified by increasing the gap between the low and high existing temperatures of the building envelope. Therefore, it is reasonable to make the sunlight collector a good energy absorber by using dark colored thermal mass materials. 

To further maximize the cooling effect, we can integrate the solar chimney with a Trombe wall and force the air to go through underground ducts before it is allowed to enter the building. This system may be reversed during the cold season, providing solar heating instead.

Some advantages of implementing this system are:

• The system even works with diffused solar radiation.
• It can be implemented in windless areas and is not necessarily reliant on wind.
• The system is reliable and not liable to break down.
• The system does not need a large space and minimal exposure to exterior is sufficient.
• Cooling water is not necessarily needed in this system which is important in countries with major problems with drinking water.
• The needed building materials are sufficiently available everywhere.
• In very hot days the system still has a suitable ventilation effect.

This simple system can be designed and built in much larger scale (solar tower) in order to generate electricity out of the solar-thermal energy. 

Trombe Wall

Trombe wall is defined as south facing mass wall (concrete, brick or masonry) that has the ability to absorb a lot of heat and is covered by a glazed surface (glass) that has a few inches gap between the pane of glass and the wall. Thermal mass gets the heat from sunlight and during night slowly releases it into the internal space through the upper vent in the wall. The function of glass is transferring short wave length radiation that heats the wall while stopping longer wave length radiation back out from the wall.

                                          

The function of Trombe wall can be better understood in these figures in which we can see two openings (vent) in the wall, one on top and the other in the bottom. In wintertime, the higher dense cold air near the floor enters the bottom opening and through the process of Trombe wall, it gets warmer and goes back to the inner space from the upper opening. The simple trick is that after the sun goes down, the hot wall will still keep heating air and exchanging that heat into the room. Once the wall gets cold, we need to stop the interaction of outside cold air with the inside air, therefore a one way flap is used on the bottom vent to prevent the reverse cooling cycle.

In summer we need to stop the Trombe wall heating inside. One way is using a proper roof overhang and shading trees. Another way is closing both vents; however we can take the advantages of another trick by making the Trombe wall act like a solar chimney. (how?)

A Need for Paradigm Shift in Evaluating Sustainable Building....... "Living Building Challenge"

In not a distant past, our recognition of the nature’s value and magnitude of our negative impacts on the built environment have arisen some major sustainable movements. Over the last twenty years, green building has attracted a major attention in building industry and has become one of the most important and progressive trends. This ever growing importance in reaching sustainable construction can be attributed to the fact that we will no longer have: a stable and predictable climate, adequate affordable and available energy, water and other critical resources; or that the natural life-supporting systems on the planet.

In today’s world, energy is one of the most valuable assets. Though, energy efficiency methods are the main principals of different operations within US, specifically for building construction with consuming 48% of the total energy and 76% of the nation’s electricity. Considering the high level of water and material usage by buildings as well as huge amounts of waste, the necessity of the shift to improve building’s energy efficiency is become more obvious. This will lead to longer life of the building and reducing energy cost, while the comfort of occupants is also insured. Efforts to improve a building’s energy efficiency will extend the life of the building, increase occupant comfort within the building, and reduce energy costs. These efforts will further enable sustainable development to bring environmental, social and financial benefits.

The growing market demand for certified green buildings and the associated need for ever-evolving benchmarks have brought the main impetus behind a paradigm shift that is currently underway in how buildings and developments are designed and built. This real appetite in marketplace has convinced those interested in going beyond LEED and net zero-architects, engineers and builders. Furthermore, the achievement of LEED certification for over 10,000 applied projects and around 30,000 registered projects at the present time while some of them are LEED-Platinum with small first-cost premiums, signaling the need for defining the next level of high performance buildings. In response, Living Building Challenge, “a philosophy, advocacy tool and certification program” that promotes the most advanced measurement of sustainability in achieving higher levels of sustainability in the built environment, is derived.

 The Living Building Challenge is a certification program for buildings that have been occupied for a minimum of one year and was originally endorsed by Jason F. McLennan with subsequent further development that initially launched in 2006 by the Cascadia Region Green Building Council a Chapter/Affiliate of USGBC to inspire the creation of true sustainability in the built environment. This strict technical requirement that covers all buildings at all scales, provides some substantially higher benchmarks for project teams seeking to move beyond the levels of the LEED Rating Systems with a performance-based, post-occupancy evaluation of a project’s efforts comprising maximum efficiency and sustainability. A more comprehensive set of criteria is being evaluated compared to other rating systems. Projects striving to meet these criteria need to employ innovative strategies and systems.

Living Building Challenge is a combination of seven performance areas (Petals): site, water, energy, health, materials, equity and beauty, which are further divided into 20 imperatives (shown in figure 5), each focusing on a specific sphere of influence named  “Typologies” including renovation, landscape or infrastructure, building, and neighborhood.  Projects should be aligned to one of these typologies to identify the needed imperatives. 

 Two rules govern the standard:

• All elements of the Living Building Challenge are required for a building to be certified. Some of the requirements have temporary exceptions to acknowledge current market limitations. Exceptions will be modified or removed as the market changes.

• Living Building designation is based on measured, rather than modeled or anticipated, performance. Therefore, buildings must be operational for at least twelve consecutive months prior to evaluation.

The above rules can be manifested in five stipulations:

1. The building must generate all of its own, renewable energy on-site

2. The building must capture and treat all of its own water

3. The building must use only non-toxic and sustainable-sourced construction materials

4. The building must be placed on already-developed sites in order to reduce urban sprawl, and

5. The building must be beautiful and inspiring to its occupants and others.

The overall goal of the trend is achieving a better sustainable construction and high-performance operations in order to decrease resource use, reduce operating costs and increase general effectiveness. Numerous systems and methods that were considered “alternative” a few years ago are being incorporated into codes and standards. Meanwhile, Studies have demonstrated that, on average, sustainable designed and operated buildings use less energy and water, have lower maintenance costs, and have higher levels of occupant satisfaction than comparable buildings. However, green building certification in framework of a third party system does not guarantee that a building will achieve continued optimum performance. Every building is unique and there is high variability in performance of a building.

Ref:

Anonymous. (2006). Cascadia Region Green Building Council Issues "Living Building Challenge, 9, 13

Eisenberg, D., Persram, S., Spataro, K. (2009), Code, Regulatory and Systemic Barriers Affecting Living Building Projects. The Summit Foundation King County Green Tools.

International Living Future Institute, LIVING BUILDING CHALLENGESM 2.1, (2012), www.livingbuildingchallenge.org

International Living Building Institute “FAQ.” (2011). URL: https://ilbi.org/about/faq

Krippendorf, J. (2010) New Living Building Challenge launched, Journal of Commerce, 20, 3

Spataro, K., Bjork, M., Masteller, M. (2011). Comparative Analysis of Prescriptive, Performance-Based, and Outcome-Based Energy Code Systems. Alaska Housing Finance Corporation.

Wang, N., Flower, KM., Sullivan, RS. (2012), Green Building Certification System Review, Pacific Northwest National Laboratory