KenWinco Company Nigeria

07/09/2017

What is propylene Glycol?
From the sound of its name, it’s probably no surprise that propylene glycol is a synthetic chemical. (It’s actually the main ingredient in antifreeze!) And although its safety is questionable, it’s an incredibly common food additive that the FDA considers “Generally Recognized As Safe” (along with artificial food dyes).
Have you ever seen propylene glycol on a nutrition label and wondered, is it safe? Me too, and here’s what I found out!
What Is Propylene Glycol?
Propylene glycol is derived from petroleum and is a viscous colorless, odorless substance with a sweet taste. Food makers value it for its ability to keep a substance moist, maintain texture, and mix with almost anything (oil, alcohol, and water). Because of these properties and because it is generally recognized as safe, it has become a common food additive in processed or ready-made food items.
Processed food items containing propylene glycol are typically foods that require thickening, emulsifying, or stabilizing properties. These include:
-Salad dressing
-Liquid artificial flavoring
-Ice cream
-Artificial sweetener
-Icing
-Soft drinks
-Soups
-Puddings and desserts
-Sauces and dips
Propylene glycol is also often added to body care products, cosmetics, and medications.
Is Propylene Glycol Safe?
The safety of propylene glycol depends on the dose and individual susceptibility. So it is possible that if you are 100% healthy, exposure to small amounts once in a blue moon might be okay.
Unfortunately, when people consume the processed foods listed above, they usually consume a sizable amount on a regular basis, which is definitely not healthy.
Physiological Side Effects of Propylene Glycol
Consumption of propylene glycol has many known effects … here are the biggies.
Acidifies the Blood
Propylene glycol absorbs very quickly in the small intestine with peak levels detected in the blood about an hour after ingestion. It is also quickly eliminated (almost 50% of what is consumed is left after 4 hours).
About 55% of this is metabolized into lactic and pyruvic acids, while the remaining is eliminated by the kidneys ( source).
These lactic and pyruvic acids make the blood more acidic. At low doses, the kidneys can immediately re-balance the blood alkalinity. But higher doses of propylene glycol can acidify the blood, injure the kidneys, and cause toxicity. This is why consistent consumption in large amounts is a bad idea.
In a large enough amount it can acidify the blood to the point that it requires emergency medical care. There are a few case reports, including in the New England Journal of Medicine , when patients injected with psychiatric drugs containing propylene glycol were shown to quickly develop acidosis that can cause a coma and kidney failure. Propylene glycol toxicity can also result in similar symptoms to sepsis or severe inflammatory response syndrome ( source).
While it is possible to achieve this dosage level by ingesting it, this reaction is typically only reported when it is administered at a very high dose of over ~2 grams ( source).
Contributes to Leaky Cells and Leaky Gut
Like soap, propylene glycol is a surfactant, which means it can break the barrier between fat and water. Our cell membranes are made with thin layers of fat molecules, which can be easily disrupted by surfactants like propylene glycol.
Pharmaceutical companies capitalize on this property by mixing or chemically binding drug molecules to propylene glycol to increase the drug absorption rate ( source). This is the case for both drugs that are taken orally and topically.
Cells exposed to propylene glycol become more permeable to other molecules ( source). (This is why the safety of e-cigarettes containing propylene glycol together with ni****ne and cancer-causing substances is very questionable).
Currently, there is no study that directly tests whether propylene glycol causes leaky gut and the inflammatory health problems caused by the leaky gut. However, in a test tube study, propylene glycol even at low concentration destroyed some gut cells ( source).
Those who struggle with leaky gut, autoimmune diseases, or digestive issues, may want to consider avoiding propylene glycol for these reasons.
Increases Risks of Childhood Allergies & Asthma
And if that’s not enough, it may affect our kids as well.
As a volatile organic compound (VOC) emitted from building materials, furniture, paint, carpet and the like, propylene glycol can aggravate the immune system. In a study evaluating the effects of propylene glycol and glycol ether v***rs in the air on preschool children’s health, the authors found that the presence of such chemicals in a child’s bedroom air is associated with:
1.5-fold increased risks of asthma
2.8-fold increased risks of allergic rhinitis (hay fever)
1.6-fold increased risks of eczema ( source)
A good air purifier can help remove airborne chemicals and is a great idea in any sleeping space.
Irritates the Skin
Propylene glycol has been reported as a skin irritant that can cause dermatitis, an eczema-like rash ( source). When added to skin, body care, and cosmetic products, it can really aggravate skin problems. (Ironically, it is often an ingredient in topical medications to treat these skin conditions! How does that make sense?!)
When to Avoid Propylene Glycol
Some people are more sensitive to the side effects of propylene glycol than others. Those who are generally cautioned to avoid it are:
People with liver or kidney problems, because the liver and kidneys are responsible for eliminating propylene glycol and its byproducts
Pregnant women, babies, and infants as they have reduced ability to handle these types of ingredients ( source)
People with inflammatory health problems because it can irritate cells and cause leaky gut
People with digestive problems because it will further irritate the gut cells
Fortunately, it is possible to avoid and/or reduce your exposure to as much as possible.
How to Avoid Propylene Glycol
Unfortunately, this additive is in a lot of common products, so it takes some diligence to
avoid it!
A few tips:
Avoid Processed Foods
The best way to avoid foods dangerous ingredients such as propylene glycol is to eat home-cooked meals the majority of the time. Fake ingredients are not necessary to make food delicious. It is possible to replace the effects of these types of additives with other, natural ingredients, such as gluten-free starch or gelatin as a thickener or stabilizer .
Read Labels and Buy from Trustworthy Brands
Always check the labels of your food ingredients and other household products for propylene glycol and its synonym, propane-1,2-diol.
I like to use brands that never put such dangerous ingredients in their products, like
Primal Kitchen for mayonnaise for sauces and dressings.
Check Your Skincare, Body Care, and Home Care Products
Propylene glycol is everywhere in conventional products that people put on their skin every single day. Not only that, these skin products often contain other toxic chemicals that will be more readily absorbed through your skin because it makes your skin more permeable.
Instead, rely on organic products or make your own beauty products instead.
Use Air and Water Purifiers
Despite best efforts to avoid propylene glycol in foods and other products, exposure is still possible in the air or water in your home. Good ventilation (including opening windows to air the house out), a good air purifier in sleeping rooms, and a water filter for drinking and shower water are important.

22/12/2016

22/12/2016

Heating energy[edit]
In the past, water heating was more efficient for heating buildings and was the standard in the United States. Today, forced air systems can double for air conditioning and are more popular.

Some benefits of forced air systems, which are now widely used in churches, schools and high-end residences, are

Better air conditioning effects
Energy savings of up to 15-20%
Even conditioning[citation needed]
A drawback is the installation cost, which can be slightly higher than traditional HVAC systems.

Energy efficiency can be improved even more in central heating systems by introducing zoned heating. This allows a more granular application of heat, similar to non-central heating systems. Zones are controlled by multiple thermostats. In water heating systems the thermostats control zone valves, and in forced air systems they control zone dampers inside the vents which selectively block the flow of air. In this case, the control system is very critical to maintaining a proper temperature.

Forecasting is another method of controlling building heating by calculating demand for heating energy that should be supplied to the building in each time unit.

Ground source heat pump[edit]
Main article: Geothermal heat pump
Ground source, or geothermal, heat pumps are similar to ordinary heat pumps, but instead of transferring heat to or from outside air, they rely on the stable, even temperature of the earth to provide heating and air conditioning. Many parts of the country experience seasonal temperature extremes, which would require large-capacity heating and cooling equipment to heat or cool buildings. For example, a conventional heat pump system used to heat a building in Montana's −70 °F (−57 °C) low temperature or cool a building in the highest temperature ever recorded in the US—134 °F (57 °C) in Death Valley, California, in 1913 would require a large amount of energy due to the extreme difference between inside and outside air temperatures. A few feet below the earth's surface, however, the ground remains at a relatively constant temperature. Utilizing this large source of relatively moderate temperature earth, a heating or cooling system's capacity can often be significantly reduced. Although ground temperatures vary according to latitude, at 6 feet (1.8 m) underground, temperatures generally only range from 45 to 75 °F (7 to 24 °C).

An example of a geothermal heat pump that uses a body of water as the heat sink, is the system used by the Trump International Hotel and Tower in Chicago, Illinois. This building is situated on the Chicago River, and uses cold river water by pumping it into a recirculating cooling system, where heat exchangers transfer heat from the building into the water, and then the now-warmed water is pumped back into the Chicago River.[21]

While they may be more costly to install than regular heat pumps, geothermal heat pumps can produce markedly lower energy bills – 30 to 40 percent lower, according to estimates from the US Environmental Protection Agency.[citation needed]

Ventilation energy recovery[edit]
Energy recovery systems sometimes utilize heat recovery ventilation or energy recovery ventilation systems that employ heat exchangers or enthalpy wheels to recover sensible or latent heat from exhausted air. This is done by transfer of energy to the incoming outside fresh air.

Air conditioning energy[edit]
The performance of v***r compression refrigeration cycles is limited by thermodynamics. These air conditioning and heat pump devices move heat rather than convert it from one form to another, so thermal efficiencies do not appropriately describe the performance of these devices. The Coefficient-of-Performance (COP) measures performance, but this dimensionless measure has not been adopted. Instead, the Energy Efficiency Ratio (EER) has traditionally been used to characterize the performance of many HVAC systems. EER is the Energy Efficiency Ratio based on a 35 °C (95 °F) outdoor temperature. To more accurately describe the performance of air conditioning equipment over a typical cooling season a modified version of the EER, the Seasonal Energy Efficiency Ratio (SEER), or in Europe the ESEER, is used. SEER ratings are based on seasonal temperature averages instead of a constant 35 °C (95 °F) outdoor temperature. The current industry minimum SEER rating is 14 SEER.[22]

Engineers have pointed out some areas where efficiency of the existing hardware could be improved. For example, the fan blades used to move the air are usually stamped from sheet metal, an economical method of manufacture, but as a result they are not aerodynamically efficient. A well-designed blade could reduce electrical power required to move the air by a third.[23]

Air filtration and cleaning[edit]
Main article: Air filter

Air handling unit, used for heating, cooling, and filtering the air
Air cleaning and filtration removes particles, contaminants, v***rs and gases from the air. The filtered and cleaned air then is used in heating, ventilation and air conditioning.[24]

There are several air filter types including fiberglass, polyester, HEPA (to filter 99.97 percent of all particles 0.3 microns or larger), and washable air filters.[25]

Clean air delivery rate and filter performance[edit]
Clean air delivery rate is the amount of clean air an air cleaner provides to a room or space. When determining CADR, the amount of airflow in a space is taken into account. For example, an air cleaner with a flow rate of 100 cfm (cubic feet per minute) and an efficiency of 50% has a CADR of 50 cfm. Along with CADR, filtration performance is very important when it comes to the air in our indoor environment. Filter performance depends on the size of the particle or fiber, the filter packing density and depth and also the air flow rate.[24]

HVAC industry and standards[edit]
The HVAC industry is a worldwide enterprise, with roles including operation and maintenance, system design and construction, equipment manufacturing and sales, and in education and research. The HVAC industry was historically regulated by the manufacturers of HVAC equipment, but regulating and standards organizations such as HARDI, ASHRAE, SMACNA, ACCA, Uniform Mechanical Code, International Mechanical Code, and AMCA have been established to support the industry and encourage high standards and achievement.

The starting point in carrying out an estimate both for cooling and heating depends on the exterior climate and interior specified conditions. However, before taking up the heat load calculation, it is necessary to find fresh air requirements for each area in detail, as pressurization is an important consideration.

International[edit]
ISO 16813:2006 is one of the ISO building environment standards.[26] It establishes the general principles of building environment design. It takes into account the need to provide a healthy indoor environment for the occupants as well as the need to protect the environment for future generations and promote collaboration among the various parties involved in building environmental design for sustainability. ISO16813 is applicable to new construction and the retrofit of existing buildings.[27]

The building environmental design standard aims to:[27]

provide the constraints concerning sustainability issues from the initial stage of the design process, with building and plant life cycle to be considered together with owning and operating costs from the beginning of the design process;
assess the proposed design with rational criteria for indoor air quality, thermal comfort, acoustical comfort, visual comfort, energy efficiency and HVAC system controls at every stage of the design process;
iterate decisions and evaluations of the design throughout the design process.
North America[edit]
United States[edit]
Main article: American Society of Heating, Refrigerating and Air-Conditioning Engineers
In the United States, HVAC engineers generally are members of the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE), EPA Universal CFC certified, or locally engineer certified such as a Special to Chief Boilers License issued by the state or, in some jurisdictions, the city. ASHRAE is an international technical society for all individuals and organizations interested in HVAC. The Society, organized into regions, chapters, and student branches, allows exchange of HVAC knowledge and experiences for the benefit of the field's practitioners and the public. ASHRAE provides many opportunities to participate in the development of new knowledge via, for example, research and its many technical committees. These committees typically meet twice per year at the ASHRAE Annual and Winter Meetings. A popular product show, the AHR Expo, is held in conjunction with each winter meeting. The Society has approximately 50,000 members and has headquarters in Atlanta, Georgia.

The most recognized standards for HVAC design are based on ASHRAE data. The most general of four volumes of the ASHRAE Handbook is Fundamentals; it includes heating and cooling calculations. Each volume of the ASHRAE Handbook is updated every four years. The design professional must consult ASHRAE data for the standards of design and care as the typical building codes provide little to no information on HVAC design practices; codes such as the UMC and IMC do include much detail on installation requirements, however. Other useful reference materials include items from SMACNA, ACGIH, and technical trade journals.

American design standards are legislated in the Uniform Mechanical Code or International Mechanical Code. In certain states, counties, or cities, either of these codes may be adopted and amended via various legislative processes. These codes are updated and published by the International Association of Plumbing and Mechanical Officials (IAPMO) or the International Code Council (ICC) respectively, on a 3-year code development cycle. Typically, local building permit departments are charged with enforcement of these standards on private and certain public properties.

HVAC professionals in the US can receive training through formal training institutions, where most earn associate degrees. Training for HVAC technicians includes classroom lectures and hands-on tasks, and can be followed by an apprenticeship wherein the recent graduate works alongside a professional HVAC technician for a temporary period.[28] HVAC techs who have been trained can also be certified in areas such as air conditioning, heat pumps, gas heating, and commercial refrigeration.[29]

Europe[edit]
United Kingdom[edit]
The Chartered Institution of Building Services Engineers is a body that covers the essential Service (systems architecture) that allow buildings to operate. It includes the electrotechnical, heating, ventilating, air conditioning, refrigeration and plumbing industries. To train as a building services engineer, the academic requirements are GCSEs (A-C) / Standard Grades (1-3) in Maths and Science, which are important in measurements, planning and theory. Employers will often want a degree in a branch of engineering, such as building environment engineering, electrical engineering or mechanical engineering. To become a full member of CIBSE, and so also to be registered by the Engineering Council UK as a chartered engineer, engineers must also attain an Honours Degree and a master's degree in a relevant engineering subject.

CIBSE publishes several guides to HVAC design relevant to the UK market, and also the Republic of Ireland, Australia, New Zealand and Hong Kong. These guides include various recommended design criteria and standards, some of which are cited within the UK building regulations, and therefore form a legislative requirement for major building services works. The main guides are:

Guide A: Environmental Design
Guide B: Heating, Ventilating, Air Conditioning and Refrigeration
Guide C: Reference Data
Guide D: Transportation systems in Buildings
Guide E: Fire Safety Engineering
Guide F: Energy Efficiency in Buildings
Guide G: Public Health Engineering
Guide H: Building Control Systems
Guide J: Weather, Solar and Illuminance Data
Guide K: Electricity in Buildings
Guide L: Sustainability
Guide M: Maintenance Engineering and Management
Within the construction sector, it is the job of the building services engineer to design and oversee the installation and maintenance of the essential services such as gas, electricity, water, heating and lighting, as well as many others. These all help to make buildings comfortable and healthy places to live and work in. Building Services is part of a sector that has over 51,000 businesses and employs represents 2%-3% of the GDP.

Australia[edit]
The Air Conditioning and Mechanical Contractors Association of Australia (AMCA), Australian Institute of Refrigeration, Air Conditioning and Heating (AIRAH), and CIBSE are responsible.

Asia[edit]
Asian architectural temperature-control have different priorities than European methods. For example, Asian heating traditionally focuses on maintaining temperatures of objects such as the floor or furnishings such as Kotatsu tables and directly warming people, as opposed to the Western focus, in modern periods, on designing air systems.

Philippines[edit]
The Philippine Society of Ventilating, Air Conditioning and Refrigerating Engineers (PSVARE) along with Philippine Society of Mechanical Engineers (PSME) govern on the codes and standards for HVAC / MVAC in the Philippines.

India[edit]
The Indian Society of Heating, Refrigerating and Air Conditioning Engineers (ISHRAE) was established to promote the HVAC industry in India. ISHRAE is an associate of ASHRAE. ISHRAE was started at Delhi in 1981 and a chapter was started in Bangalore in 1989. Between 1989 & 1993, ISHRAE chapters were formed in all major cities in India and also in the Middle East.

22/12/2016

Air conditioning[edit]
Main article: Air conditioning
An air conditioning system, or a standalone air conditioner, provides cooling and humidity control for all or part of a building. Air conditioned buildings often have sealed windows, because open windows would work against the system intended to maintain constant indoor air conditions. Outside, fresh air is generally drawn into the system by a vent into the indoor heat exchanger section, creating positive air pressure. The percentage of return air made up of fresh air can usually be manipulated by adjusting the opening of this vent. Typical fresh air intake is about 10%.

Air conditioning and refrigeration are provided through the removal of heat. Heat can be removed through radiation, convection, or conduction. Refrigeration conduction media such as water, air, ice, and chemicals are referred to as refrigerants. A refrigerant is employed either in a heat pump system in which a compressor is used to drive thermodynamic refrigeration cycle, or in a free cooling system which uses pumps to circulate a cool refrigerant (typically water or a glycol mix).

Refrigeration cycle[edit]
Main article: Refrigeration cycle

A simple stylized diagram of the refrigeration cycle: 1) condensing coil, 2) expansion valve, 3) ev***rator coil, 4) compressor
The refrigeration cycle uses four essential elements to cool.

The system refrigerant starts its cycle in a gaseous state. The compressor pumps the refrigerant gas up to a high pressure and temperature.
From there it enters a heat exchanger (sometimes called a condensing coil or condenser) where it loses energy (heat) to the outside, cools, and condenses into its liquid phase.
An expansion valve (also called metering device) regulates the refrigerant liquid to flow at the proper rate.
The liquid refrigerant is returned to another heat exchanger where it is allowed to ev***rate, hence the heat exchanger is often called an ev***rating coil or ev***rator. As the liquid refrigerant ev***rates it absorbs energy (heat) from the inside air, returns to the compressor, and repeats the cycle. In the process, heat is absorbed from indoors and transferred outdoors, resulting in cooling of the building.
In variable climates, the system may include a reversing valve that switches from heating in winter to cooling in summer. By reversing the flow of refrigerant, the heat pump refrigeration cycle is changed from cooling to heating or vice versa. This allows a facility to be heated and cooled by a single piece of equipment by the same means, and with the same hardware.

Free cooling[edit]
Main article: Free cooling
Free cooling systems can have very high efficiencies, and are sometimes combined with seasonal thermal energy storage so the cold of winter can be used for summer air conditioning. Common storage mediums are deep aquifers or a natural underground rock mass accessed via a cluster of small-diameter, heat-exchanger-equipped boreholes. Some systems with small storages are hybrids, using free cooling early in the cooling season, and later employing a heat pump to chill the circulation coming from the storage. The heat pump is added-in because the storage acts as a heat sink when the system is in cooling (as opposed to charging) mode, causing the temperature to gradually increase during the cooling season.

Some systems include an "economizer mode", which is sometimes called a "free-cooling mode". When economizing, the control system will open (fully or partially) the outside air damper and close (fully or partially) the return air damper. This will cause fresh, outside air to be supplied to the system. When the outside air is cooler than the demanded cool air, this will allow the demand to be met without using the mechanical supply of cooling (typically chilled water or a direct expansion "DX" unit), thus saving energy. The control system can compare the temperature of the outside air vs. return air, or it can compare the enthalpy of the air, as is frequently done in climates where humidity is more of an issue. In both cases, the outside air must be less energetic than the return air for the system to enter the economizer mode.

Central vs. split system[edit]
Central, "all-air" air-conditioning systems (or package systems) with a combined outdoor condenser/ev***rator unit are often installed in modern residences, offices, and public buildings, but are difficult to retrofit (install in a building that was not designed to receive it) because of the bulky air ducts required. (Minisplit ductless systems are used in these situations.)

An alternative to central systems is the use of separate indoor and outdoor coils in split systems. These systems, although most often seen in residential applications, are gaining popularity in small commercial buildings. The ev***rator coil is connected to a remote condenser unit using refrigerant piping between an indoor and outdoor unit instead of ducting air directly from the outdoor unit. Indoor units with directional vents mount onto walls, suspended from ceilings, or fit into the ceiling. Other indoor units mount inside the ceiling cavity, so that short lengths of duct handle air from the indoor unit to vents or diffusers around the rooms.

Dehumidification[edit]
Dehumidification (air drying) in an air conditioning system is provided by the ev***rator. Since the ev***rator operates at a temperature below the dew point, moisture in the air condenses on the ev***rator coil tubes. This moisture is collected at the bottom of the ev***rator in a pan and removed by piping to a central drain or onto the ground outside.

A dehumidifier is an air-conditioner-like device that controls the humidity of a room or building. It is often employed in basements which have a higher relative humidity because of their lower temperature (and propensity for damp floors and walls). In food retailing establishments, large open chiller cabinets are highly effective at dehumidifying the internal air. Conversely, a humidifier increases the humidity of a building.

Maintenance[edit]
All modern air conditioning systems, even small window package units, are equipped with internal air filters. These are generally of a lightweight gauzy material, and must be replaced or washed as conditions warrant. For example, a building in a high dust environment, or a home with furry pets, will need to have the filters changed more often than buildings without these dirt loads. Failure to replace these filters as needed will contribute to a lower heat exchange rate, resulting in wasted energy, shortened equipment life, and higher energy bills; low air flow can result in iced-over ev***rator coils, which can completely stop air flow. Additionally, very dirty or plugged filters can cause overheating during a heating cycle, and can result in damage to the system or even fire.

Because an air conditioner moves heat between the indoor coil and the outdoor coil, both must be kept clean. This means that, in addition to replacing the air filter at the ev***rator coil, it is also necessary to regularly clean the condenser coil. Failure to keep the condenser clean will eventually result in harm to the compressor, because the condenser coil is responsible for discharging both the indoor heat (as picked up by the ev***rator) and the heat generated by the electric motor driving the compressor.

Energy efficiency[edit]
Since the 1980s, manufacturers of HVAC equipment have been making an effort to make the systems they manufacture more efficient. This was originally driven by rising energy costs, and has more recently been driven by increased awareness of environmental issues. Additionally, improvements to the HVAC system efficiency can also help increase occupant health and productivity.[20] In the US, the EPA has imposed tighter restrictions over the years. There are several methods for making HVAC systems more efficient.

Heating energy[edit]
In the past, water heating was more efficient for heating buildings and was the standard in the United States. Today, forced air systems can double for air conditioning and are more popular.

Some benefits of forced air systems, which are now widely used in churches, schools and high-end residences, are

Better air conditioning effects
Energy savings of up to 15-20%
Even conditioning[citation needed]
A drawback is the installation cost, which can be slightly higher than traditional HVAC systems.

Energy efficiency can be improved even more in central heating systems by introducing zoned heating. This allows a more granular application of heat, similar to non-central heating systems. Zones are controlled by multiple thermostats. In water heating systems the thermostats control zone valves, and in forced air systems they control zone dampers inside the vents which selectively block the flow of air. In this case, the control system is very critical to maintaining a proper temperature.

Forecasting is another method of controlling building heating by calculating demand for heating energy that should be supplied to the building in each time unit.

Ground source heat pump[edit]
Main article: Geothermal heat pump
Ground source, or geothermal, heat pumps are similar to ordinary heat pumps, but instead of transferring heat to or from outside air, they rely on the stable, even temperature of the earth to provide heating and air conditioning. Many parts of the country experience seasonal temperature extremes, which would require large-capacity heating and cooling equipment to heat or cool buildings. For example, a conventional heat pump system used to heat a building in Montana's −70 °F (−57 °C) low temperature or cool a building in the highest temperature ever recorded in the US—134 °F (57 °C) in Death Valley, California, in 1913 would require a large amount of energy due to the extreme difference between inside and outside air temperatures. A few feet below the earth's surface, however, the ground remains at a relatively constant temperature. Utilizing this large source of relatively moderate temperature earth, a heating or cooling system's capacity can often be significantly reduced. Although ground temperatures vary according to latitude, at 6 feet (1.8 m) underground, temperatures generally only range from 45 to 75 °F (7 to 24 °C).

An example of a geothermal heat pump that uses a body of water as the heat sink, is the system used by the Trump International Hotel and Tower in Chicago, Illinois. This building is situated on the Chicago River, and uses cold river water by pumping it into a recirculating cooling system, where heat exchangers transfer heat from the building into the water, and then the now-warmed water is pumped back into the Chicago River.[21]

While they may be more costly to install than regular heat pumps, geothermal heat pumps can produce markedly lower energy bills – 30 to 40 percent lower, according to estimates from the US Environmental Protection Agency.[citation needed]

Ventilation energy recovery[edit]
Energy recovery systems sometimes utilize heat recovery ventilation or energy recovery ventilation systems that employ heat exchangers or enthalpy wheels to recover sensible or latent heat from exhausted air. This is done by transfer of energy to the incoming outside fresh air.