Home HVAC System Guide

So you've bought a new home and your home inspector turns to you and blithely says, "Oh, great new HVAC system."

"A what?" you say in response.

"You know," he says "a thermodynamic system that takes care of all of your heating, ventilation and airconditioning."

So that's what the acronym HVAC stands for you think to yourself.

Welcome to the world of climate control.  Even though most people know a little something about air conditioning and heating, few of us stop to think much about it.  We tend to take our comfort for granted until the furnace runs out of oil or the air conditioner's compressor dies.  Then, suddenly, we wish we were experts on the subject.

What an HVAC Does
The primary purpose of an HVAC system is to regulate room temperature, humidity, and air flow within acceptable and safe limits to ensure that we are comfortable and healthy.

Room temperature - Room temperature regulation is accomplished by both heating and cooling the air in a room.  Simply put, on cold days the system adds heat to the air and on warm days the air is cooled.  Obviously the human body is not meant to be subjected to cold temperatures for long periods or hypothermia and perhaps death can occur. Conversely, consistently high temperatures can cause heat stroke or death.  Children and elderly folks are particularly susceptible to extreme temperatures because they are more likely to have immature or poorly functioning temperature regulation mechanisms.

Humidity - Too much humidity in the air is not only uncomfortable, but it encourages the growth of molds, some of which are harmful to our health. High humidity can also cause fatigue by decreasing physical strength.  Likewise, too little humidity creates moisture-deprived air that dries the membranes in our noses, throats and lungs making us more susceptible to disease.  The proper regulation of humidity in our indoor air, therefore, has both comfort and health implications.

Air flow - Simply adding or subtracting warm or cold air is not enough to accomplish effective temperature control.  It is also necessary to move the air around or distribute it evenly and efficiently.  The movement of air within a building or system and the exchanging of inside and outside air is a process called ventilation. Ventilation changes or replaces room air, subtracts humidity and filters out impurities such as allergens, odors, airborne bacteria and toxic gases. When ventilation is efficient, the airflow from room to room is equalized in such a way that a specified room temperature is achieved throughout the home, air quality is maintained at safe levels and stagnation of the interior air is prevented.

Components of an HVAC System
The basic components of a modern HVAC system are designed to work together as an integrated unit. The usual components are:
Furnace
Air conditioner
Heat pump
Humidifier
Air handler
Heat coil
Air filtration system
Programmable thermostats
Sensors
Duct system

Selecting an HVAC System
Most HVAC systems are initially installed by a HVAC contractor who contracts out equipment and installation services to a builder.  But if you are thinking about replacing your current heating/air conditioning system, you will want to gather as much information as you can on the pros and cons before purchasing a product.

If you are considering replacing only part of your current system such as an air handler or condenser, you should know that the industry recommendation is to replace the entire system to ensure reliability and efficiency; otherwise the efficiency rating, which is based on the entire working system, may be erroneous.

Efficiency Rating
What is an efficiency rating you ask?  It is a measure of the percentage of energy used efficiently.  The U.S. government, in an effort to provide consumers with the means to make informed decisions, requires an efficiency rating for all HVAC equipment.  Efficiency ratings vary by name depending on the type of equipment.  For example, air conditioning equipment is rated by the Seasonal Energy Efficiency Rating (SEER). Heat pump equipment is rated by the Heating Seasonal Performance Factor (HSPF) and gas furnaces are rated according to their Annual Fuel Utilization Efficiency (AFUE).  A high rating in any category means a high level of efficiency.

What Can a HVAC Contractor/Technician Do For Me?
There are many HVAC systems on the market affording you the liberty to choose the one that is right for your home.  However, selecting and installing a new HVAC unit is not a simple process.  If you are an average home owner, under no circumstances should you purchase a system yourself without the advice of a trusted licensed and insured HVAC contractor.

HVAC technicians can give you advice too, but their primary job is to service and repair existing systems, not install them.  Some companies have both contractors and technicians on board and others have repair technicians only. You will need to ask what services are offered by each company.  Always ask the contractor about his years of experience and for references.

Equipment Sizing
When planning to buy a new piece of heating or cooling equipment, you will want to know how many BTUs (British Thermal Units) per hour of heat the equipment must produce or remove to keep your home comfortable.  This is called the heat load.  The heat load calculation determines the size of your system.  Correct sizing is directly related to your comfort and the cost of operating the equipment.  For example, if the equipment is undersized, your home will not be adequately cooled or heated.  Too large and the system cycles on and off more frequently than it should which increases your operating cost.

Load Calculation
HVAC contractors can determine the size of the system that meets your home's particular specifications by doing a load calculation.  A load calculation includes some of the following elements:
Square feet of home
Climate
Condition, number and type of windows (heat/cold retention)
Warm or cool air that may be lost through ceilings, walls and attics (insulation)
Inefficient ducts (location, distance from energy source, insulation, etc.)
Heat emitted by appliances, lights, and the residents themselves
Shrubbery, trees, and roof overhangs
Overall home design

Do I Need a New HVAC System?
The answer to this question is unfortunately not easily generalized because all equipment isn't alike.  However, there are several rules of thumb you can take into consideration when deciding to go "new" or stick with the old.  Some experts will say that if your system is broken and the repair will cost more than $500.00 that the smart investment in the long run is to replace rather than repair.  The avearge life-expectancy of a furnace is a long 16-20 years, but if yours is better than 10 years old, you may want to begin considering replacement options.  The other factor to take into account in making your decision is the efficiency of your furnace.  An old furnace, even if it appears to be working well, may be cheating you out of dollars by extracting only 60% of the available heat from your heating fuel.  Newer models extract as much as 90% of the heat.  You have to balance the cost of your fuel against the output you are receiving.

The same holds true with heat pumps and air conditioners.  Older ones operate at a 60% efficiency whereas newer ones achieve 90% or more efficiency.  To illustrate in dollars and cents,  if your monthy fuel or power bill is $100.00 and you install a new system, you could see your energy cost drop to as little as $65.00/month, a savings of $35.00/month.  Multiply that by twelve months and you have a yearly savings of $420.00.

An easily added, inexpensive programmable thermostat will help save dollars too, especially if no one is home during the day.

Other factors that may point to the need to consult an HVAC specialist are:
Some rooms are too hot and others are too cold
You have humidity problems (too humid in the summer and too dry in the winter)
Your home seems to be excessively dusty
Your cooling system is noisey

Selecting the Right Contractor
As mentioned earlier, your HVAC contractor should be licensed, bonded and experienced in the type of equipment you want installed.  Ask for references and ask how long the contractor has been installing HVACs.  Select someone with whom you feel at ease, who listens and who is an effective communicator.  Ask for a detailed written proposal that includes all the costs.  The proposal should decribe each step in the process including what will be done, the materials that will be used and a time-line for the completion of each step.  Periodic maintenance will be important in keeping the system running smoothly once it is installed so ask your contractor if he offers an annual service contract and what service is included.  Does he offer price reductions on repairs or deliver priority service to customers installing a new system?

Regulating the HVAC Industry
In the past, the HVAC industry was regulated by the manufacturers of HVAC equipment, but now there are a number of organizations that provide regulation and standards such as The American Society of Heating, Refrigerating and Air Conditioning Engineers (ASRAE) www.ashrae.org, Sheet Metal and Air Conditioning Contractors' National Association (SMACNA) www.smacna.org, and the Air Conditioning Contractors of America (ACCA) www.acca.org.  The Uniform Mechanical Code, a source of codes for HVAC professionals, sets forth requirements for the installation and maintenance of heating, ventilating, cooling, and refrigeration systems.

Tax Credits
If you need an incentive to begin investigating a replacement system, the American Recovery and Reinvestment Act of 2009 may stimulate you to purchase sooner than later.  Tax credits are available at 30% of the cost, up to $1,500, in 2009 & 2010 (for existing homes only) for some HVAC components.  To be certain your planned improvement qualifies, check with your tax professional, HVAC specialist or watch for the new federal energy-savings guidelines to be released soon.

Aside from saving money, receiving tax credits and conserving energy, the most important reward for buying a new HVAC system or overhauling your current one is the peace of mind you will experience knowing that the health and safety of your family is protected.