Design of Structures in respect to heat efficiency

Introduction Heat efficiency in any architectural design is always a topic that must be addressed. Without this key element, structures would be totally inefficient to heat, not to mention extremely expensive. In order to design a heat efficient building you must first understand where heat is lost or where cold air enters the structure in question. My research will first be to determine what materials are best for insulation and which materials are not. Second, I will try to find where heat is most likely to escape in a structure by researching efficient designs. This, in turn, will provide information to where it is necessary to add more insulation to a particular structure. Background It has been proven time and time again that solar energy plays a crucial part in the heating of any structure regardless of its design. The intensity of solar energy is almost an exact constant only varying in energy about 0.2 % every 30 years. This intensity on average is about 1.37 ( 106 ergs per second per cm2, or about 2 calories per minute per cm2. This intensity can vary of course when the solar photons interact with different conditions in the atmosphere. This energy from the sun can be converted so that it is able to heat a structure in many different ways. During my experiment though, I will only be testing the effects of a structure's heat related to passive solar energy as illustrated in figure 1. Passive Solar energy is where the sun's heat is able to heat a structure without the use of specialized equipment such as a photovoltaic cell or other direct solar energy device. Many organizations in such countries as Australia and England are conducting nationwide heat energy efficiency ratings that can be used as references for engineers and architects. These ratings could inform a designer as to what designs work better and which do not. The program in Australia is titled the "Nationwide House Energy Rating Scheme" (NatHERS) and became available to all designers who wished to use it early in 1995. A parallel program to the NatHERS is New Zealand's "Window Energy Rating Scheme" (WERS) which allows homeowners to make better decisions about the selection and design of window systems from an energy perspective. The WERS rating system will not be available however until late 1996. Great Britain and many other nations have just recently begun conducting their own Energy Efficiency Rating systems that will not become available to the pubic until the early 21st century. So far though each of the research organizations has been making their own discoveries that have already begun to effect architectural designs of structures. Often a structure's ability to collect heat is directly associated with the materials it was built with. Depending on the material itself, it can either hinder or help the structure's ability to collect heat. A lustrous material such as a mirror for example, would reflect light but retain the heated photons. This effect would heat the structure extremely well because of the lustrous surface's ability to attract light towards it and collecting its heat. A dull material like natural wood, has proven not to attract much light nor to collect a substantial amount of heat. Plain wood would not be a wise decision to use if the material used in the structure was going to be how the structure was heated. Most often structures are built with internal systems that produce heat. The color of the material used to build a structure is also a key element. For the most part the darker the color the more heat it attracts and the more heat it can store. A structure that is entirely black in color will be far more easy to heat than one of any other color. Exactly opposite to dark colors are light colors that do not attract much heat at all and are not efficient at storing heat. The best combination is most often a dark, lustrous material if heat is the desired effect. A completely wrong choice would be materials that are dull and light in color unless cooling was the purpose. The design of a structure can contain an infinite number of different elements each either helping to make the structure efficient or hindering its ability. In my experimentation I am only going to focus on two design elements. These two elements pertain to if the structure has windows or if it is enclosed. The false-color image in figure 2 shows heat eminating from a house in the form of infrared radiation. The black regions radiate away the least amount of heat, while the white regions, which coincide with the house's windows, radiate away the most heat (NASA,1991). Because of the fact that solar energy can not be collected in any structure during the night, all of my experimentation will be conducted around noon in order to create a constant. Figure 2 shows heat escaping mainly through the windows but does not show that during the day windows are the most significant passive heat intakes for a structure. Windows are however, a disadvantage if the structure is being placed in a highly shaded area such as a forest. In this case heat would have to be contracted in some other way. A greenhouse is probably one of the best examples of passive heating. Without the aid of any other device, greenhouses are able to maintain a high temperature. As stated above, windows are also responsible for most heat loss in a directly heated home. In fact windows account for 41% of heat loss in a typical US home. Double-pane windows are one way to decrease heat loss from a structure but do not solve the problem entirely. If the structure is to be built in an area were lack of sunlight is not a problem then a structure with many windows should not be a problem for heat loss. An enclosed structure with no windows in theory should cut down on at least 41% of heat loss. This would also cut down on a large amount of heat gained during the day by passive energy through windows. That would then cause heating efficiency to decrease. Even though the efficiency would decrease it would probably still be less than 41% making it the better choice. Many designers do not choose to do this however because of the lack of view not having any windows would cause. Also windows serve as decoration in many designs. Research has shown that the best compromise is to have double-pane windows evenly placed throughout the structure in order to prevent one particular area from becoming too cold or too hot. Insulation in the walls, roof and floor is also a compromise. Too little insulation allows an excessive amount of heat escape from a structure while too much insulation allows almost no heat to enter. Most structures are directly heated from the inside allowing more insulation to be applicable. A combination of the right materials and correct design according to where the structure is to be placed is crucial. If a structure built in a cold, cloudy, climate was to be made purely of windows and white wood, the temperature inside the structure would be close to the temperature outside. Structural design must include many various factors. Only the three factors of luster, color and windows will be used in my experiment. Hypothesis & Experiment If different materials are used to build a scaled structure, then the structure with high luster will have a higher temperature than the structure with low luster. If different materials are used to build a scaled structure, then the structure with a darker color will have a higher temperature then the structure with a light color. If different materials are used to build a scaled structure, then the structure with an enclosed design (no transparent areas) will have a higher temperature than the structure with a transparent design. MATERIALS: 1 sheet of standard sheet metal 1 sheet of brown box cardboard 2 sheets of black plexi-glass 1 sheet of white plexi-glass 1 sheet of clear plexi-glass 2 thermometers 1 stopwatch or alarm clock 1 jigsaw 1 roll of duct tape PROCEDURE: Using the jigsaw, cut the sheet metal into 5 5"(5" squares. Then do the same with the cardboard. Using the duct tape, secure the 5 squares or sheet metal together forming a cube with 1 side missing. Then do the same for the cardboard. Place the 2 semi-cubes out side at about 11:00 a.m. with the missing side facing down. Place the thermometers inside the semi-cubes and use the stopwatch or alarm clock to time 2 hours. At about 1:00 p.m. check the thermometers and record the two temperatures in a data table. Using the 1st black sheet and the white sheet of plexi-glass, follow steps 1-4 the next day. Using the 2nd black sheet and the clear sheet of plexi-glass, follow steps 1-4 the 3rd day. SUMMARY The experiment in this paper will probably support my hypothesis based on the research collected. The NatHERS rating organization expressed that lustrous materials are much more likely to collect and store heat better than dull materials. They also express that darker colored materials will more often than not collect heat at a higher rate that that of a color such as white. In addition to these theories SOLARCH (National Solar Architecture Research Unit) has studied window advantages alongside WERS to support my own theory that enclosed structures store more heat than transparent structures. Further studies on my part could branch into the other areas of structural design and placement providing a more in detailed plan for experimentation.