«CSAAR (7: 2010: Amman) Sustainable Architecture and Urban Development \ Edited by Steffen Lehmann, Husam Al Waer, Jamal AI-Qawasmi. Amman: The Center ...»
9.1 Compactness (building form and building proportions) The compactness of a building indicates the surface per volume unit that is related with heat exchange between the building and the ambient environment and therefore according to the thermo physical characteristics of its materials defines the ability to store and release heat. The ratio of volume and surface is an indication of the rate at which a building heats up during the day and cools down during the night. In any project the urban design is detined by the parameters distance between buildings (density), orientation, access, parking and open spaces, which all have an influence for the later energy use. The building form and its compactness are relevant for the amount of heat transmission losses, which are proportional to the insulating quality and to the heat transmitting surface. The most compact shape for a freestanding house is a cube. Any design of an individual house should be considered with regard on compactness, natural lighting and solar heat gain. The compactness of a building is measured by a ratio ofsurface area (S) to volume (V) (compactness SN) CZEH [Clemson Zero Energy House]: Following the output of our research of the existing housing market, we decided to design a single-family house with (', Sustainable Architecture and Urban Development 219 3 bedrooms and 2.5 bathrooms.
Relating to the program of an average household on the American market today, the house is 25% smaller than and approximately 25 -50,000 USD cheaper than an average household.
Our building was designed around a compact two-story service core induding access, all wet spaces (such as kitchen, bath rooms and laundry) and the mechanical space. The adjacent living and bedrooms were situated in the north and to the South, offering optimal solar orientation and also possible expansion.
Figure 2: Roof top plan (Ieft) and section (right) showing the two-story service core, acting as a solar chimney and the overhangs in the South.
9.2 Orientation The orientation of a building must be considered in interaetion with the sun and prevailing winds. Unfortunately in most situations they do not coincide and therefore eompromises must be made. The solar orientation determines the
intensity of solar radiation; therefore the following rules need to be eonsidered:
The greatest intensity of solar radiation oecurs in horizontal surfaces. The greatest intensity of solar radiation on vertieal surfaees is on the eastern (morning) and western (afternoon) fac;ade. The southeastern surface gets less radiation during the hot season (high temperature) and more during cold seasons (Iow temperatures). The radiation inereases in northerly latitudes 9. While defining an equilibrium between the welcome solar gain in winter and defense against the undesired solar gain in summer, any kind of shading deviees, operable and permanently installed need to be implemented into the design process. lbe wind orientation should be eonsidered for maximizing the natural ventilation. The greatest pressure on the windward side of a building is gained Ulrike Heine when it is perpendicular to the direction of the wind, but even openings at a 45 degree angle to the prevailing wind direction increases the air velocity and improves the natural ventilation within the building (Holger Koch-Nielsen, 2007). Each building has to be studied holistically, taking into account all aspects of bioclimatic design.
Figure 3: North Facade (left) and South Facade (right) showing the two-story service core and the extensive openings in the South, shaded in summer by the overhangs CZEH: The orientation of our building follows the idea that the most used spaces during the day (like living, dining and children's bedrooms) take advantage of the southem sun, equipped with a precisely calculated roof overhang to block off the summer sun and provide the desired solar radiation input during the winter. The east and west fayade openings are minimized and the north fayade provides openings to optimize cross ventilation in all bedrooms.
9.3 Passive Ventilation
Ventilation should provide fresh air from the building's exterior and speed airflow to facilitate for example evaporative cooling ofthe air, the occupants and the structures. Normally the openings for the air movement correspond very poody with the ones for natural lighting; therefore they should be treated separately. We differentiate two kinds of natural ventilation Through wind-generated pressure differences (i.e. different sizes of openings) Through temperature-generated pressure differences (natural lifting forces) If the specific climate of the project provides a sufficient difference of temperature between day and night, night cooling should be considered as an efficient way of passive cooling. In this case the building mass should be closed during the day to avoid an overheating of the spaces and be opened during night.
CZEH: Our building is designed to provide cross ventilation in all living and bedroom spaces, the specific climate ofTers a great opportunity for night cooling Sustainable Architecture and Urban Development 221 during spring and fall. Therefore all windows were modified to two opening elements to provide a safe cooling during the nights.
Figure 4: Model showing the divided windows in the south fayade for safe night cooling
9.4 Passive Solar Design The passive solar design refers to the use ofthe sun's energy for the heating and cooling of inhabited spaces. In this approach, the building itself or some element of it takes advantage of natural energy characteristics in materials and air created by exposure to the sun. Passive systems are simple, have few moving parts and require minimal maintenance and require no mechanical systems.
Operable windows, thermal mass and thermal chimneys are common elements found in passive design. Operable windows are simply windows that can be opened. They should be oriented properly and their sizing should be optimized. Thermal mass refers to materials such as masonry and water that can store heat energy for extended time. Thermal mass will prevent rapid temperature fluctuations. Thermal chimneys create or reinforce the effect hot air rising to induce air movement for cooling purposes.
CZEH: The centered mechanical space of our building and its two-story design provides the option of implementing a solar chimney. Simulations for validation are underway.
9.5 Passive Cooling The topic cooling is linked to the concepts of ventilation. If the temperature inside is higher than outside, the heat can be removed by natural or mechanical ventilation. Cross ventilation forced by openings on two sides of the space optimizes natural heat extraction. Convective ventilation, mostly realized in high ceiling situations, takes advantage of the natural lifting forces and replaces the warm rising air with fresh air. The higher the spaces, the higher the air change rate. Heavy, massive elements can provide thermal capacity for the absorption of internal heating loads and the temperature fluctuation in aspace. The so-called approach of' Building Component Activation' takes advantage of this and warms or cools solid building components as walls or ceilings through active (water) or passive (ventilation) measures.
CZEH: The central service core provides the optimal position within the building to be realized in a different building material and also for the activation of the masses. The upcoming semester will focus on the specific materials of the building and their validation.
9.6 Natural Lighting
The concept of planning the lighting is to achieve the maximum daylight autonomy by optimization of the building. The openings need to be designed to provide an optimal amount of light in the house without and also be adjustable (shading devices). Sometimes natural light is impossible or even undesirable, in these cases an adequate source of artificial light needs to be provided, that fits to the usage and uses as little energy as possible. There are numerous computer programs to simulate the light situation in a building. Topics Iike color distortion, freedom of glare and good contrast should be considered (Hegger, Fuchs, Sark, Zeumer, 2008).
CZEH: All living and bedroom spaces, including all bathrooms and the kitchen are provided with natural light. The design was influenced by the idea, that there should be no need to switch on any light during the day. The mechanical space and the laundry as low occupancy spaces are excluded from this idea.
10 Active Strategies
In addition to the passive strategies, which influence the energy performance through smart design, the actual energy gain needs to be driven by active strategies. We are in the early stages of analysis, evaluating the combination of different strategies and their impact on each other and size them correctly by simulation. Initial costs and the return of investment are a very important parameter in the evaluation process.
Sustainable Arehiteeture and Urban Development 223
10.1 Solar Power and Photovoltaic
Solar Plants use solar eolleetors to harness solar energy for use in heating water and interior spaees. This system stores the resouree in thermal buffers over a long period of time. The installation would need at least 9sqft of a eolleetor area and about 25 gallons of gross storage area.
Photovoltaie systems generate power by eonverting solar radiation into eleetrieity. Houses ean be tied to an existing grid or operated as a stand-alone system. In the first ease you would take advantage of the publie grid for storage, in the seeond ease you would need a teehnieal unit with a battery.
The geothermal system takes advantage of the temperature of the earth, whieh varies from the erust to its eore by 2.5-3 degree Celsius for every 30 ft closer to the eore. The first 3 ft of earth varies in temperature as the air temperature ehanges. This first layer also insulates the ground below it and therefore retains a eonstant temperature below it throughout the year.
Ground heat systems take advantage of this different and constant temperature and passes water or air through a transfer system in eontact with the ground. In summer it eools the media, in winter it pre-eonditions the media. (The simplest system would be a 30-120 ft ductwork. buried in the ground at a depth of 3- J2 ft to preeondition air for a building.) CZEH: So far after the first eaIculations, the estimated building eosts of an 'aetive ready' low energy house, not including any active strategies. is at 142,500 USD. We are now at a point where the building needs to be situated at a specifie site to take the maximum advantage of any aetive strategies.
The awareness of our generation about the mistakes that were made in the past and in the present, espeeially in terms of our energy eonsumption, should lead us to a new and different way of design. Good arehiteeture is no longer just spatially beautiful and aesthetie it is also energy effieient and smart.
Energy is a physical entity and can thus be preeisely measured. This means that energy effieient buildings have also beeome quantifiable, a dreadful notion for many arehiteets. It is not intelligent for arehitects to go on the defensive when eonfronted with sustainable building. lnstead, they should eontinue working towards good architecture while including ideas of sustainability in their working methods.
224 Ulrike Heine Sustainable building does not have to become a new architecturallanguage as far as style is concerned. lt can be applied to any style. lt is energy efficient, has intelligent facades, uses materials optimally and has balanced, adequate building services. Constructive elements generate sustainable design processes; new materials generate new aesthetics. The secret to achieving a weIl-balanced, well designed and energy-efficient building is hidden in the equilibrium between saving and gaining, always in terms of local conditions.