I walk in a commercial district unfamiliar to me and see a door with “Green Attics” written on it. When I look it up online, it is a business that installs insulation and does air conditioning repair. I have never installed insulation but know that it can make a huge difference in your air conditioning and heating bill. Air conditioning repair has always been a mystery to me, and I am very grateful that there are people who know how to do it. Am not sure there is even a school where you can learn this skill. It may just be on the job. There is a famous story about famous scientists gathered in a ballroom for a conference, and the ceiling starts leaking, but nobody knows how to fix it. There is a certain skill set for that kind of repair, and very few people have it. Thank goodness there are some people who do! To find out more about insulation and air conditioning repair, read on.
Thermal insulation
According to Wikipedia, thermal insulation is the reduction of heat transfer i.e., the transfer of thermal energy between objects of differing temperature between objects in thermal contact or in range of radiative influence. Thermal insulation can be achieved with specially engineered methods or processes, as well as with suitable object shapes and materials.
Heat flow is an inevitable consequence of contact between objects of different temperature. Thermal insulation provides a region of insulation in which thermal conduction is reduced or thermal radiation is reflected rather than absorbed by the lower-temperature body.
The insulating capability of a material is measured as the inverse of thermal conductivity. Low thermal conductivity is equivalent to high insulating capability or resistance value. In thermal engineering, other important properties of insulating materials are product density and specific heat capacity.
Building insulation
Building insulation is any object in a building used as insulation for any purpose. While the majority of insulation in buildings is for thermal purposes, the term also applies to acoustic insulation, fire insulation and impact insulation e.g., for vibrations caused by industrial applications. Often an insulation material will be chosen for its ability to perform several of these functions at once.
Insulated glazing
Insulating glass consists of two or more glass window panes separated by a vacuum or gas-filled space to reduce heat transfer across a part of the building envelope. A window with insulating glass is commonly known as double glazing or a double-paned window, triple glazing or a triple-paned window or quadruple glazing or a quadruple-paned window, depending upon how many panes of glass are used in its construction.
Insulating glass units are typically manufactured with glass in thicknesses from 1/8" to 3/8". Thicker glass is used in special applications. Laminated or tempered glass may also be used as part of the construction. Most units are produced with the same thickness of glass on both panes but special applications such as acoustic attenuation or security may require different thicknesses of glass to be incorporated in a unit.
Insulated pipe
Insulated pipes — called also preinsulated pipes or bonded pipe — are widely used for district heating and hot water supply in Europe. They consist of a steel pipe, an insulating layer and an outer casing. The main purpose of such pipes is to maintain the temperature of the fluid in the pipes. A common application is the hot water from district heating plants.
Most commonly used are single insulated pipes, but more recently in Europe it is becoming popular to use two pipes insulated within the same casing. By using insulated pipe supports, direct heat transfer between pipes and their supports are prevented.
The insulating material usually used is polyurethane foam or similar, with a coefficient of thermal conductivity k=0.033-0.024 W/mK (thermal conductivity). Outer casing is usually high-density. Production of preinsulated pipes for district heating in the European Union is regulated by the standard EN253. According to EN253:2003, pipes must be produced to work at constant temperature of 266 °F for 30 years, keeping thermal conductivity less than or equal to 0.033 W/mK. There are three insulation thickness levels.
Insulated pipelines are usually assembled from pipes of 20 feet, 39 feet or 52 feet in length, laid underground in depth 1 foot 4 inches–3 feet 3 inches. Efficient working life of district heating pipelines networks is estimated at 25–30 years, after which they need to be replaced with new pipes.
Electrical insulation may be used for metal pipes for corrosion prevention.
Insulated shipping containers
Insulated shipping containers are a type of packaging used to ship temperature sensitive products such as foods, pharmaceuticals, organs, blood, biologic materials, vaccines and chemicals. They are used as part of a cold chain to help maintain product freshness and efficacy. The term can also refer to insulated intermodal containers or insulated swap bodies.
Electrical insulator
An electrical insulator is a material in which the electron does not flow freely or the atom of the insulator have tightly bound electrons whose internal electric charges do not flow freely; very little electric current will flow through it under the influence of an electric field. This contrasts with other materials, semiconductors and conductors, which conduct an electric current more easily. The property that distinguishes an insulator is its resistivity; insulators have higher resistivity than semiconductors or conductors. The most common examples are non-metals.
A perfect insulator does not exist because even insulators contain small numbers of mobile charges (charge carriers) which can carry current. In addition, all insulators become electrically conductive when a sufficiently large voltage is applied that the electric field tears electrons away from the atoms. This is known as the breakdown voltage of an insulator. Some materials such as glass, paper and Teflon, which have high resistivity, are very good electrical insulators. A much larger class of materials, even though they may have lower bulk resistivity, are still good enough to prevent significant current from flowing at normally used voltages, and thus are employed as insulation for electrical wiring and cables. Examples include rubber-like polymers and most plastics which can be thermoset or thermoplastic in nature.
Insulators are used in electrical equipment to support and separate electrical conductors without allowing current through themselves. An insulating material used in bulk to wrap electrical cables or other equipment is called insulation. The term insulator is also used more specifically to refer to insulating supports used to attach electric power distribution or transmission lines to utility poles and transmission towers. They support the weight of the suspended wires without allowing the current to flow through the tower to ground.
Soundproofing is any means of reducing the sound pressure with respect to a specified sound source and receptor. There are several basic approaches to reducing sound: increasing the distance between source and receiver, using noise barriers to reflect or absorb the energy of the sound waves, using damping structures such as sound baffles, or using active anti-noise sound generators.
There are 5 elements in sound reduction — absorption, damping, decoupling, distance and adding mass. The "absorption" aspect in soundproofing should not be confused with sound-absorbing panels used in acoustic treatments. "Absorption" in this sense only refers to reducing a resonating frequency in a cavity by installing insulation between walls, ceilings or floors. Acoustic panels can play a role in a treatment only after walls or ceilings have been soundproofed, reducing the amplified reflection in the source room.
Two distinct soundproofing problems may need to be considered when designing acoustic treatments —t o improve the sound within a room and reduce sound leakage to/from adjacent rooms or outdoors. Acoustic quieting and noise control can be used to limit unwanted noise. Soundproofing can suppress unwanted indirect sound waves such as reflections that cause echoes and resonances that cause reverberation. Soundproofing can reduce the transmission of unwanted direct sound waves from the source to an involuntary listener through the use of distance and intervening objects in the sound path.
Air conditioning — often referred to as AC, A/C, or air con — is the process of removing heat and moisture from the interior of an occupied space to improve the comfort of occupants. Air conditioning can be used in both domestic and commercial environments. This process is most commonly used to achieve a more comfortable interior environment, typically for humans and other animals; however, air conditioning is also used to cool and dehumidify rooms filled with heat-producing electronic devices, such as computer servers, power amplifiers and to display and store some delicate products, such as artwork.
Air conditioners often use a fan to distribute the conditioned air to an enclosed space such as a building or a car to improve thermal comfort and indoor air quality. Electric refrigerant-based AC units range from small units that can cool a small bedroom, which can be carried by a single adult, to massive units installed on the roof of office towers that can cool an entire building. The cooling is typically achieved through a refrigeration cycle, but sometimes evaporation or free cooling is used. Air conditioning systems can also be made based on desiccants, chemicals that remove moisture from the air. Some AC systems reject or store heat in subterranean pipes.
In construction, a complete system of heating, ventilation and air conditioning is referred to as HVAC. As of 2018, 1.5 billion air conditioning units were installed, with the International Energy Agency expecting 5.6 billion units in use by 2050. Globally, current air conditioning accounts for 1/5 of energy usage in buildings globally, and the expected growth of the usage of air conditioning, will drive significant energy demand growth. In response to, in 2018 the United Nations called for the technology to be made more sustainable to mitigate climate change.
History
Evaporative cooling
Since prehistoric times, snow and ice were used for cooling. The business of harvesting ice during winter and storing for use in summer became popular towards the late 17th century. This practice was replaced by mechanical ice-making machines.
The basic concept behind air conditioning is said to have been applied in ancient Egypt, where reeds were hung in windows and were moistened with trickling water. The evaporation of water cooled the air blowing through the window. This process also made the air more humid, which can be beneficial in a dry desert climate. Other techniques in medieval Persia involved the use of cisterns and wind towers to cool buildings during the hot season.
The 2nd-century Chinese inventor Ding Huan of the Han Dynasty invented a rotary fan for air conditioning, with seven wheels10 feet in diameter and manually powered by prisoners. In 747, Empreor Xuanzong (r. 712–762) of the Tang Dynasty (618–907) had the Cool Hall built in the imperial palace, which the Tang Yulin describes as having water-powered fan wheels for air conditioning as well as rising jet streams of water from fountains. During the subsequent Song Dynasty (960–1279), written sources mentioned the air conditioning rotary fan as even more widely used.
In the 17th century, the Dutch inventor Cornelis Drebbl demonstrated "Turning Summer into Winter" as an early form of modern air conditioning for James I of England by adding salt to water.
Development of mechanical cooling
In 1758, Benjamin Franklin and John Hadley, a chemistry professor at Cambridge University, conducted an experiment to explore the principle of evaporation as a means to rapidly cool an object. Franklin and Hadley confirmed that the evaporation of highly volatile liquids — such as alcohol and ether — could be used to drive down the temperature of an object past the freezing point of water. They conducted their experiment with the bulb of a mercury thermometer as their object and with a bellows used to speed up the evaporation. They lowered the temperature of the thermometer bulb down to 7 °F while the ambient temperature was 64 °F. Franklin noted that soon after they passed the freezing point of water 32 °F, a thin film of ice formed on the surface of the thermometer's bulb and that the ice mass was about 1⁄4 inch-thick when they stopped the experiment upon reaching 7 °F. Franklin concluded: "From this experiment one may see the possibility of freezing a man to death on a warm summer's day."
In 1820, English scientist and inventor Michael Faraday discovered that compressing and liquefying ammonia could chill air when the liquefied ammonia was allowed to evaporate. In 1842, Florida physician John Gorrie used compressor technology to create ice, which he used to cool air for his patients in his hospital in Apalachiocola, Florida. He hoped to eventually use his ice-making machine to regulate the temperature of buildings. He even envisioned centralized air conditioning that could cool entire cities. Though his prototype leaked and performed irregularly, Gorrie was granted a patent in 1851 for his ice-making machine. Though his process improved the artificial production of ice, his hopes for its success vanished soon afterward when his chief financial backer died and Gorrie did not get the money he needed to develop the machine. According to his biographer, Vivian M. Sherlock, he blamed the "Ice King", Frederic Tudor, for his failure, suspecting that Tudor had launched a smear campaign against his invention. Dr. Gorrie died impoverished in 1855, and the dream of commonplace air conditioning went away for 50 years.
James Harrison's first mechanical ice-making machine began operation in 1851 on the banks of the Barwon River at Rocky Point in Geelong, Australia. His first commercial ice-making machine followed in 1853, and his patent for an ether vapor compression refrigeration system was granted in 1855. This novel system used a compressor to force the refrigeration gas to pass through a condenser, where it cooled down and liquefied. The liquefied gas then circulated through the refrigeration coils and vaporized again, cooling down the surrounding system. The machine produced three tons of ice per day.
Though Harrison had commercial success establishing a second ice company back in Sydney in 1860, he later entered the debate over how to compete against the American advantage of ice-refrigerated beef sales to the United Kingdom. He wrote: "Fresh meat frozen and packed as if for a voyage, so that the refrigerating process may be continued for any required period," and in 1873 prepared the sailing ship Norfolk for an experimental beef shipment to the United Kingdom. His choice of a cold room system instead of installing a refrigeration system upon the ship itself proved disastrous when the ice was consumed faster than expected.
Electrical air conditioning
The creation of the modern electrical air conditioning unit and industry is credited to the American inventor Willis H. Carrier. After graduating from Cornell University, Carrier found a job at the Buffalo Forge Co. There, he began experimenting with air conditioning as a way to solve an application problem for the Sackett-Wilhelms Lithographing and Publishing Co. in Brooklyn, New York. The first air conditioner — designed and built in Buffalo, New York by Carrier — began working on July 17, 1902.
Designed to improve manufacturing process control in a printing plant, Carrier's invention controlled not only temperature but also humidity. Carrier used his knowledge of the heating of objects with steam and reversed the process. Instead of sending air through hot coils, he sent it through cold coils filled with cold water. The air was cooled, and thereby the amount of moisture in the air could be controlled, which in turn made the humidity in the room controllable. The controlled temperature and humidity helped maintain consistent paper dimensions and ink alignment. Later, Carrier's technology was applied to increase productivity in the workplace, and The Carrier Air Conditioning Co. of America was formed to meet rising demand. Over time, air conditioning came to be used to improve comfort in homes and automobiles as well.
In 1906, Stuart W. Cramer of Charlotte was exploring ways to add moisture to the air in his textile mill. Cramer coined the term "air conditioning," using it in a patent claim he filed that year as analogous to "water conditioning," then a well-known process for making textiles easier to process. He combined moisture with ventilation to "condition" and change the air in the factories, controlling the humidity so necessary in textile plants. Willis Carrier adopted the term and incorporated it into the name of his company.
Shortly thereafter, the first private home to have air conditioning was built in Minneapolis in 1914, owned by Charles Gates. Realizing that air conditioning would one day be a standard feature of private homes, particularly in regions with warmer climate, David St. Pierre DuBose (1898-1994) designed a network of ductwork and vents for his home Meadowmont, all disguised behind intricate and attractive Georgian-style open moldings. This building is believed to be one of the first private homes in the United States equipped for central air conditioning.
In 1945, Robert Sherman of Lynn, Massachusetts invented a portable, in-window air conditioner that cooled, heated, humidified, dehumidified and filtered the air.
By the late 1960s, most newly built residential homes in the United States had central air conditioning. Box air conditioning units during this time also became more inexpensive which resulted in greater population growth in the states of Florida and Arizona. As of 2015, nearly 100 million homes or about 87% of US households had air conditioning systems.
Refrigerant development
The first air conditioners and refrigerators employed toxic or flammable gases, such as ammonia, methyl chloride or propane, that could result in fatal accidents when they leaked. Dr. Thomas Midgley Jr. created the first non-flammable, non-toxic chlorofluorocarbon gas, freon or R-12 in 1928. The name is a trademark name owned by DuPont for any chlorofluorocarbon or CFC, hydrochlorofluorocarbon or HCFC or hydrofluorocarbon or HFC refrigerant. The refrigerant names include a number indicating the molecular composition e.g., R-11, R-12, R-22, R-134A. The blend most used in direct-expansion home and building comfort cooling is an HCFC known as chlorodifluoromethane or R-22.
Dichlorodifluoromethane or R-12 was the most common blend used in automobiles in the U.S. until 1994, when most designs changed to R-134A due to the ozone-depleting potential of R-12. R-11 and R-12 are no longer manufactured in the U.S. for this type of application but are still imported and can be purchased and used by certified HVAC technicians.
Modern refrigerants have been developed to be more environmentally safe than many of the early chlorofluorocarbon-based refrigerants used in the early- and mid-twentieth century. These include HCFCs — R-22, as used in most U.S. homes before 2011 — and HFCs (R-134a, historically used in most cars, refrigerators and chillers) have replaced most CFC use. HCFCs, in turn, are supposed to have been in the process of being phased out under the Montreal Protocol and replaced by HFCs such asR-410A, which lack chlorine. HFCs, however, contribute to climate change problems. Moreover, policy and political influence by corporate executives resisted change. Corporations insisted that no alternatives to HFCs existed. The environmental organization Greenpeace provided funding to a former East German refrigerator company to research an alternative ozone- and climate-safe refrigerant in 1992. The company developed a hydrocarbon mix of isopentane andisobutane, but as a condition of the contract with Greenpeace could not patent the technology, which led to its widespread adoption by other firms. Their activist marketing first in Germany led to companies like Whirlpool, Bosch and later LG and others to incorporate the technology throughout Europe, then Asia, although the corporate executives resisted in Latin America, so that it arrived in Argentina produced by a domestic firm in 2003, and then finally with giant Bosch's production in Brazil by 2004.
In 1995, Germany made CFC refrigerators illegal. DuPont and other companies blocked the refrigerant in the U.S. with the U.S. EPA, disparaging the approach as "that German technology." Nevertheless, in 2004, Greenpeace worked with multinational corporations like Coca-Cola and Unilever, and later PepsiCo and others, to create a corporate coalition called Refrigerants Naturally!. Then, four years later, Ben & Jerry's of Unilever and General Electric began to take steps to support production and use in the U.S. In 2011 the EPA decided in favor of the ozone- and climate-safe refrigerant for U.S. manufacture. HFCs like R-404a, R-134a and R-410a are, as of 2020, being replaced with HFO and hydrocarbon refrigerants like R-1234ze in chillers for commercial refrigeration and air conditioning, R-1234yf in cars, R-32 in residential air conditioning and CO2 (R-744) in commercial refrigeration. R-600 (isobutane) is already widely used in residential refrigeration.
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