by Allison Gunkel
People rarely give a second thought to the heating and cooling systems in their homes – they want it warm when it’s cold outside and they want it cool when it’s hot outside.
Typically until they have a complaint, their heating and cooling system gets prioritized well below other home appliances. HVAC is the acronym for “heating, ventilation, air-conditioning and cooling” and is often times referred to as “climate control” within a home. All areas of HVAC are closely interrelated, providing acceptable thermal comfort, indoor air quality, and preferably reasonable installation, operation, and maintenance. Clearly, heating and cooling systems are not only about the comfortable temperature of your home.
Central heating is used to heat most homes, especially in cold climates. It uses a boiler, furnace, or heat pump to heat water, steam or air in a central location (for example a boiler or furnace room). Piping or ductwork is necessary for distribution of heat combined with radiators to transfer heat to the air. Heating elements should be placed in the coolest part of the room and nearest to windows to reduce condensation.
Ventilation is the process of removing moisture, odors, smoke, heat, dust, and airborne bacteria by exchanging air to the outside and preventing stagnation of interior air. Ventilation is performed by one of two means:
- Mechanical or forced ventilation
Mechanical or forced ventilation is used to control indoor air quality. It controls excess odors, humidity, and contaminants by dilution or replacement with outside air. Kitchens and bathrooms typically have mechanical exhaust as a means of ventilation. Factoring in noise levels and flow rates are a must for effective home ventilation systems. Also, keep in mind that ceiling fans are not considered ventilation, as they do not replace air; they simply circulate it.
- Natural ventilation
Natural ventilation is ventilating a home with outside air without the use of fans or other mechanics. Warm air rises and flows outside through upper openings, which in turn forces cool air from outside in through lower openings. This is an energy efficient system, yet is not always practical, for example, in very humid or warm climates. Air conditioning units are often used as backups.
Air-conditioning is about the removal of heat by providing a medium that is colder. An air-conditioning unit can provide cooling, ventilation, and humidity control for all or part of a home via the refrigeration cycle using four essential elements:
- Compressor - provides compression for system
- Condenser - removes heat from system
- Evaporator - absorbs or adds heat to the system (also dehumidification)
- Metering device - acts as restriction ensuring heat absorption occurs at a proper rate
In addition to controlling thermal comfort, HVAC systems are essential to indoor air quality (IAQ). Paying closer attention to IAQ is important for a number of reasons. Besides having certain standards that installers are required to meet, efforts on behalf of IAQ aid marketability of homes and ensure flexibility and occupant health as future uses and buildings change. Numerous pollutants can compromise indoor air quality and should be kept in mind:
Bio-contaminants (microbial diseases, fungi, molds)
These are some of the most dangerous indoor air pollutants. They grow best in warm, dark, damp environments. Spaces that occupy ventilation air with contact to standing water can harbor such organisms.
Furnaces and boilers sometimes release carbon monoxide and nitrogen oxide, and natural gas and propane equipment release sulfur oxides and nitrogen oxides. All have been shown to affect health with chronic, low-level exposure, and can be fatal in high exposure due to faulty equipment or improper installation.
Outdoor air intakes and operable windows must carefully be placed away from building pollution sources such as vehicle exhausts, plumbing and combustion appliance vents. Without proper attention, the same air removed by home ventilation systems could be brought back into the home aggravating asthma and other respiratory health issues. Efficient filtering and generous amounts of unpolluted outdoor air can prevent poor IAQ.
Chlorofluorocarbon & Hydrochlorofluorocarbon refrigerant (CFCs and HCFCs)
CFC production is currently banned in nonessential uses internationally to protect further damage of the ozone layer. HCFC refrigerants are still permitted but are in a phasing out process. CFC-free chillers, air conditioners and heat pumps are currently in widespread, efficient use, preventing harm.
The last major consideration when looking into HVAC systems is energy efficiency. Today’s homes are aiming to be climate responsive, using as few non-renewable resources as possible. This is supported by minimum efficiency regulations such as the Seasonal Energy Efficiency Ratio (SEER) for air-conditioning units and the Coefficient of Performance (COP) used to regulate heat pump efficiency. These work similarly in that the higher the SEER or the COP then the higher the efficiency of the unit. There are a number of energy means that can be considered efficient depending on your home structure and location:
Electric and Gas
Direct electric heating and cooling is not particularly environmentally friendly as it uses fossil fuels exclusively, with two-thirds of energy lost at power stations and in transmission. Gas prices are continually rising causing the use of this natural resource for HVAC systems to become quite expensive. Despite these facts, there are steps being taken to utilize electric and gas heating and cooling capabilities by environmentally and cost efficient means.
Hybrid systems combine gas heating and electric cooling into all-in-one HVAC units that result in higher efficiency when operating and reduce energy loss when off. Using electric or gas heat pumps also reduces pollutant levels typically caused by combustion and can reduce the amount of electricity or natural gas utilized.
Geothermal energy is an exceptional means of heating and cooling homes. Beneath Earth’s surface the temperature is relatively constant year round, just waiting to be harvested to meet energy needs. The supply is practically unlimited, requires very little energy to remove, and produces no fossil fuel emissions.
The system employs a water-based solution that circulates through a loop extracting heat from the ground. This heat energy is transported to the geothermal unit where it is compressed and the extracted heat increases in temperature. It is then distributed through your home in a typical duct or radiant system.
The cooling cycle works oppositely. The earth is much cooler on a hot day than the air temperature; heat is removed from the home by the geothermal unit and deposited back into the cooler ground. The fluid is cooled by the ground temperature and returns to the unit to cool the home.
Advantages of Geothermal Heating and Cooling
- Very energy efficient and cost effective.
- Compact size – usually no larger than a small refrigerator.
- Low maintenance – no need for regular servicing, no hazardous emissions, and no combustion concerns.
- Multi-functional system can be used to heat water and system delivers heating and cooling.
Disadvantages of Geothermal Heating and Cooling
- It is not 100% eco-friendly as electric pump burns fossil fuels. However, “green electricity” providers are available or solar panels can be utilized to run.
- May use refrigerants depending on system and installer.
- It is cheaper than electric or oil, but gas is still less costly than geothermal cost despite gas prices being on the rise.
- You do need space to run the piping system, which can be expansive and costly if repairs are needed.
- Insulation is key to efficiency; home will need to be assessed.
- Installation can be quite expensive.
The means of using sunlight that is transformed into energy is varying and vast, making any homeowner’s head a little dizzy. In home design the uses are typically to maintain a preferred cozy temperature during the sun’s daily and annual cycles. This usually is performed via active or passive solar heating.
Active solar heating uses pumps that move air or liquid from a solar collector into the home. Passive solar heating does not use electrical or mechanical equipment, rather it relies on the design or structure of the house to collect, store and distribute heat within the building. Passive solar heating can use direct, indirect or isolated solar gain depending on your home’s location and climate.
Advantages of Solar Heating and Cooling
- Eliminates the need for new power lines in remote areas.
- Connects to existing power lines to boost energy output during periods of high demand.
- Can cost less in the long run than any other electricity means.
- Extremely flexible in mounting options- walls, windows, ceilings, shingles, etc.
- Extremely quiet.
- Meets growing energy demand while reducing greenhouse gases and pollutant emissions.
- Requires minimal maintenance.
Disadvantages of Solar Heating and Cooling
- Usually more expensive than fossil fuels outside of rural or remote areas.
- Can only be produced intermittently when the sun shines; varies with weather and time of day.
- Often requires creative planning and home design to accommodate.
When it comes down to choosing an HVAC unit for your new home design, talking to a professional will be the most proficient way to get a system that will best serve your house plan, your budget, and the environment. Steps are being taken within the market to constantly increase energy efficiency in all homes, based largely on climates and resources. Professionals in your area will have this information. With their knowledge and your prevalent desire to utilize a system that is best for your home, you should have little trouble finding a system that works best for you.
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