About Me

Preparing for My Dream Home

My husband and I have spent a lot of time consulting with an architect. After living in our cramped, starter home for the past 11 years, we were finally ready to make some needed changes to it. We have added an extra 600 square feet of space onto our house. Before the construction began, we finalized the plans for our new heating and air conditioning unit with our HVAC contractor. Because our home was going to be substantially bigger than it is now, we purchased a larger HVAC system. We also installed a new, digital thermostat inside my home. On this blog, I hope you will discover the best types of HVAC units to buy for mid-size homes. Enjoy!


Preparing for My Dream Home

Multistage Or Modulating Furnace—What's The Difference?

by Rita Richardson

Selecting a furnace can be confusing for anyone who's not an HVAC technician or expert. Many people go into the process believing they'll need to select an appropriate size for their furnace, but this decision is largely out of your hands and determined by your home's size and environment. Instead, you'll need to select between options that will affect your furnace's efficiency, comfort, and noise level.

If you've already started your selection process, you've probably come across terms like "multistage" or "variable speed." These features are often the primary difference between low- and high-end furnaces, but what do they mean? And do you need them for your home?

Understanding Single-Stage Furnaces

The most basic furnace type you can buy is a single-stage unit, and it's important to understand how these function to understand the benefits of more sophisticated models. You can think of a single-stage furnace as a binary furnace; it only has "on" and "off" states. The burners receive a preset amount of gas to create a uniform flame, and the blower always operates at full speed.

These furnaces keep your home heated by running at full power until the thermostat reports the correct temperature. A single-stage furnace will then sit idle for a while until the temperature drops due to heat loss, at which point it turns back on and runs at full blast again. A well-sized single-stage furnace can effectively heat your home, but they have some downsides.

Improving on the Basics

There are a few reasons why you may not want a single-stage unit in your home. Since these furnaces only run at full blast, you'll hear the blower running at maximum speed anytime the furnace is on. Likewise, you'll probably feel a noticeably warm breeze from your vents, even when the outside air isn't very chilly.

Multistage and modulating furnaces improve on these issues, but some subtle differences exist. First, it's important to recognize the difference between your burner and your blower motor. A modulating burner varies the amount of gas that the furnace receives. As a result, the furnace can control its heat output by modulating the gas valve. This design improves furnace efficiency.

On the other hand, a multistage or variable blower adjusts the amount of air that moves through your vents. These units can reduce airflow when less cooling is needed, helping to keep your home more comfortable and help ensure more even heating. These blowers also produce less noise since they typically don't operate at full power.

Choosing the Right Option

Always start with your budget. Single-stage furnaces are perfectly adequate if correctly sized, so they're a reasonable choice if your budget doesn't allow splurging on a higher-end model. At the other end of the scale, furnaces with modulating burners and variable-stage blower motors will provide the absolute peak of comfort, efficiency, and low noise levels.

Since most people will fall somewhere in between, you'll need to decide based on your priorities. For many households, a two-stage or variable-speed blower motor offers the best bang for the buck. This design can mean a quieter and more comfortable home without needing to blow your budget on a furnace that does it all. 

Contact a local HVAC service, such as Missouri Furnace & Air Conditioning, to learn more.