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If you’re looking to purchase an HVAC system you’ve likely come across the terms variable speed, two-stage, and single-stage – but, what do they mean?

These terms are really referring to the capacity at which your system is able to operate as it conditions your home, and that’s all determined by the number of stages on the system. Single-stage systems have a compressor or furnace that can only operate at one setting. Meanwhile, two-stage systems have compressors or furnaces with two settings, and variable speed systems have compressors with many settings.

What is a single-stage system?

Single-stage, or single-speed, systems are the most basic systems. They have two settings: on or off, meaning they operate at full capacity or not at all. These systems work at full speed to heat or cool your home and the system shuts off completely once the indoor temperature has satisfied. Because of the frequent switch from on to off, and because they can only operate at 100% max speed, single-stage systems are usually the most expensive to operate over time.

What is a two-stage system?

Two-stage, or two-speed, systems take single-stage systems up a notch and control the temperature in your home a bit more accurately. While single-stage systems must be at either 0 percent or 100 percent capacity, two-stage systems add more variety by offering a high and low setting. In most cases, the low stage operates around 65 percent capacity, while the high stage operates at 100 percent capacity. Compared to single-stage systems, the two-stage system offers a middle ground for temperature control. This means that on milder days, you will be using less energy to condition your home. While these systems may seem to run for longer periods, they are using less energy to do so and lead to a more comfortable home.

What is a variable speed system?

Variable speed, or variable stage, systems are the most efficient and advanced systems on the market. When you set a temperature on your thermostat, a variable speed system takes into account the indoor and outdoor temperatures, the indoor and outdoor humidity levels, and the run time needed to reach your desired temperature, in order to determine the appropriate output. Variable speed systems can operate anywhere from 25 percent capacity to 100 percent capacity to meet your temperature needs. Variable speed systems reach and maintain your home's desired temperature within half a degree, and because they can operate at lower speeds, they consume less power, which makes them the least expensive to operate over time.

What to consider when choosing a system

Now that you know a bit more about each type of system, the next step is choosing which one is right for your home. Consider these factors so you can make the best purchase possible for your home.


Cost typically plays a significant role in most purchases, and your HVAC system isn’t any different. While single-stage systems are the lowest in cost upfront, they’ll cost more to operate in the long run. On the flip side, variable speed systems are the most expensive option upfront, but cost less to operate since they run on a lower operating speed and draw less power most of their operating runtime. Two-stage systems are the middle ground for both upfront cost and cost overtime.

Energy efficiency

Energy efficiency is an important measure to consider, as the more energy efficient your system, the less it’ll cost you in utility bills. Single-stage systems are the least energy efficient because they must operate at 100 percent capacity when they’re on. Since two-stage systems operate at a high and low setting, they use less energy than single-stage systems, but more energy than variable speed systems. Variable speed systems are the most energy efficient.

Humidity control

As we discussed in our IAQ post, too much or too little humidity in your home can have negative consequences, so it’s crucial your HVAC system can keep your indoor humidity at an optimal level. Two-stage systems are more efficient in removing moisture in the air than single-stage systems, which reduces humidity in the home. But, like most factors on this list, variable speed systems are the best at regulating humidity and are ideal for people living in high humidity environments.

Choosing the right HVAC system for you

Now that you have more information about the differences among single-stage, two-stage, and variable speed systems, you can choose the right HVAC system for your home. As you have learned, climate, energy efficiency, and budget can all play a role in helping you determine which system best fits your unique needs. Let us know if you need help choosing which system best suits your needs!

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With the spring season right around the corner, that means allergies are on their way too!

Allergies are one of the many things that proper Indoor Air Quality (IAQ) enhancements can remedy. Continue reading for a list of some of the system enhancements Green Comfort Systems offers and how they can benefit your health and comfort.

Why is Indoor Air Quality so important?

According to the United States EPA (Environmental Protection Agency), Americans on average spend approximately 90 percent of their time indoors, where the concentrations of some pollutants are often 2 to 5 times higher than typical outdoor concentrations. People who are often most susceptible to the adverse effects of pollution (e.g., the very young, older adults, people with cardiovascular or respiratory disease) tend to spend even more time indoors.

Indoor concentrations of some pollutants have increased in recent decades due to such factors as energy-efficient building construction (when it lacks sufficient mechanical ventilation to ensure adequate air exchange) and increased use of synthetic building materials, furnishings, personal care products, pesticides, and household cleaners.

What can we do about it?

UV Lights

The evaporator coil of your air conditioning system can be the perfect breeding ground for bacteria and other microbial growth to flourish. While most people understand that air conditioners cool their homes, they might not understand that an even more crucial step of that process is dehumidification. This process happens when the hot humid air touches the surface of the cold coil, causing the moisture in the air to condense and go down the drain.

This leaves a dark damp place for microbes to grow. The system fan then comes on to cool your home and spreads these spores all over. This is why we recommend installing a UV light near the coil to kill any old growth and prevent new growth from sprouting. This also increases system air flow and efficiency as it prevents any organic material from growing on the coil and blocking the air passages.

Media Filters

These are a little easier to explain as the technology is fairly basic. These are similar to standard air filters, however they are larger and more dense, collecting more of the dirt, dust, pollutants, and other small particles that you'd rather not have floating around your home. While standard furnace filters help keep forced air furnaces and ductwork clean, they don’t improve the air quality in a business or home.

Media filters on the other hand are designed to improve air quality in residential and commercial facilities. Not only do media filters help improve air quality, they also are much more effective than standard furnace filters at keeping HVAC systems, including forced air furnaces, clean.


The dehumidifiers we offer are larger versions of ones you may have seen or purchased at a big box store. These central dehumidifiers can be tied into your ductwork system to remove moisture from your whole house, not just from the room you have it in.

Dehumidifiers are less about keeping the air clean and more about keeping you comfortable. That said, they do still contribute to healthy air quality. Many people are aware that damp humid conditions can lead to mold and mildew growth, however there are also a lot of bacteria and other pollutants that thrive at the other end of the spectrum- having too low humidity. It is recommended to maintain between 30-50% relative humidity for the most healthy air.

This will also save you on your utilities, as a lower humidity level would allow you to keep the temperature at a higher set point, preventing your AC from running as often.

Air Scrubbers

The Air Scrubber attaches directly to the HVAC system ductwork to remove air pollution, VOCs, surface contaminants, pet dander, odors and dust, resulting in a cleaner, healthier and more efficient home. The perfect solution for homeowners and businesses who want to reduce and eliminate harmful contaminants. Technology used by NASA substantially reduces odors, visible smoke in the air, and microbial populations on surfaces using ActivePure technology consisting of a special UV light and photocatalyst target, creating an oxidation process containing many friendly oxidizers. Protect, Purify, and attack contaminants in your air!

The Air Scrubber pulls free oxygen and water molecules in the air through ActivePure's patented honeycomb matrix. The technology creates powerful oxidizers, known as ActivePure Molecules, that are then released back into the room, where they seek and destroy DNA and RNA viruses including SARS-CoV-2 (novel coronavirus), Swine Flu (H1N1), Avian Bird Flu (H5N8), Hepatitis A (HAV) and MS2 bacteriophage, regardless of their size, on surfaces and in the air.

As of October 2020 ActivePure technology was tested and approved for use by the FDA and in tests following FDA protocols it demonstrated a 99.98% surface kill rate of SARS-CoV-2 novel Coronavirus within 7 hours. For more information click here: The First Air Purifier Scientifically Proven to Reduce COVID-19 on Surfaces.

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While Certified Home Inspectors have a broad understanding of most parts of your home, they are not licensed HVAC technicians and do not have the advanced experience and knowledge that may help spot potential issues before you buy a new home. Your HVAC equipment is one of the largest investments you make, so it just makes sense to have it thoroughly inspected by a licensed HVAC technician.

1. Check the furnace

Your technician should be able to tell you the condition of the furnace, and let you know about any potential repairs or costs you could face in the near future.

With your realtor’s help, you may even be able to subtract all or part of the cost of the furnace from the seller’s asking price. If the existing furnace does pass inspection, have it rechecked annually. Be sure to keep your family safe by installing carbon monoxide detectors in your home.

2. Check the air conditioners

If your older home does not have an air conditioning system, you may be wondering how much it will cost to install a new central air conditioner. We can provide you with a free quote including the cost of installation, labor and equipment for central or Minisplit systems.

Even if the home does have an existing central air conditioning system, you may still consider replacing it. Older air conditioners are usually less efficient than newer models, and replacing old systems could result in significant energy savings over the life of the system.

3. Check the ductwork

Ductwork is one of the most common issues with HVAC systems. Most of the time the ductwork is undersized, reducing the efficiency of the equipment, and reducing it's lifespan.

This can also cause spotty comfort where one area may be cooler or hotter than the rest of the house.

If the home does not have ductwork, you may also opt for a ductless system. As the name suggests, these systems do not require ducts, but rather run small refrigerant and drainage lines from an outdoor unit to one or more indoor units. You can have up to 5 separate indoor units on one outdoor, each with their own temperature control so you can say goodbye to those hot or cold spots, while saving money only tempering the rooms in use!

If you are looking for assistance with your home buying process, give us a call to see how we can help! 667-231-9462

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