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Furnace Not Heating House Evenly? Top 5 Causes (+ Fixes)

A home that isn’t heated evenly isn’t a fun home to be in. It’s important to get to the bottom of the issue so you can comfortably use every room in your home when it’s cold out.

To fix a furnace that isn’t heating your house evenly, start by looking for blocked vents, consider whether the furnace has an appropriate size for your home, clean the air filter in the furnace, and check if you can find any duct leaks. 

In this article, I’ll explain the top 5 causes for this problem, as well as walk you through how to fix each issue. Let’s get started!

1. Air Vents Are Closed or Blocked Off

The most common cause isn’t the furnace itself – it’s the air vents that distribute the heat throughout the home.

Air vents are an important part of your HVAC system. As the furnace heats the air, the blower distributes the air through the ductwork in your house. The air is then pushed out to all the air vents that are found in the building. 

If there is a blockage of an air vent, then air cannot escape into your home at this point. The same applies to an air vent that is closed. If air cannot enter a room through a vent, more of this heated air pushes through to other rooms. This means some rooms will be warmer than expected, while the remaining rooms feel cold. 

How To Fix

In most cases, determining if the air vents are the problem behind the furnace not heating the house evenly requires no access to the furnace’s interior parts. Instead, you will simply need to take a walk through your house. 

  1. You should know more or less where all the vents in your home are located. Take a look at each of the vents. 
  2. See if any of the vents are closed. If this is the case, then open up the vent. 
  3. Take note of furniture and other obstacles blocking a vent. This can also cause problems with air distribution. Try to move the furniture to ensure it does not cause a blockage in the front of the vent. 

2. Your Furnace Is Too Weak

There is a wide variety of furnaces on the market. Some are bigger than others. When installing a furnace in your home, taking your home’s size and structure into account is important. 

With this in mind, when only a few rooms feel warm when the furnace is on, there is a chance that your furnace is not strong enough for the building. 

This particular scenario might mean you need a new furnace installed to provide efficient heating throughout your house. 

How To Fix

  1. Take a closer look at the furnace installed in your house. You should consider the model number and the size of the furnace. 
  2. Now measure the interior of your house. You need a rough figure to work with, at least. 
  3. Look at the coverage that the installed furnace can provide. You can use an online calculator for this purpose or refer to the manual that came with the furnace. 
  4. Compare the coverage area of the furnace to the size of your home. If you find that the coverage is less than the building’s square foot measurement, then the furnace is not strong enough. 

Here is a useful video that explains how you can determine the right-sized furnace for your house:

3. A Lack of Maintenance

Many people don’t touch their furnace after it is installed. As long as the furnace continues to provide heat throughout your building, you almost forget it exists – and forget to provide it with necessary maintenance.

Failure to attend to the servicing and maintenance of the furnace can lead to problems in the future. Furnace maintenance ensures the device is thoroughly cleaned and inspected on frequent occasions. There are different routine steps to follow when implementing a furnace maintenance plan. 

How To Fix

Here are a few steps to follow to keep the maintenance of your furnace up to date.

  1. You need to keep the furnace’s air filter free of debris throughout the year.
  2. You should test the CO detectors frequently.
  3. Make sure dirt and dust aren’t collecting inside the furnace.
  4. Make sure the flame sensor is clean and not affected by corrosion.

For more details on furnace maintenance, take a look at this video:

4. The Air Filter Is Dirty

As time goes by, you may find that your furnace is pushing less and less air into your home. This can be a sign that the air filter is dirty and needs cleaning. 

With regular maintenance, you might already be cleaning the air filter regularly. If you do not do maintenance on the furnace frequently, then this is a great time to look at the filter. 

Dust and several other particles flow through the furnace. The filter is responsible for keeping these particles from entering your home. This means all the particles accumulate on the filter. The dirt and grime on the filter constricts the amount of air that can flow through it. 

How To Fix

Before cleaning the air filter ,you should switch off the furnace. Whenever you work inside the furnace, there should be no power going to the device. 

  1. You will start by opening up the furnace. Refer to your owner’s manual to determine where the filter is located.
  2. Look for the filter inside the furnace. If the filter is particularly dirty, you may have found the reason that your furnace is not heating the house evenly. 
  3. Remove the filter from its slot and clean it. To clean the filter, you can use some water. Never use any harsh chemicals, as you do not want to damage the filter. 
  4. Use a paper towel to dry the filter and place it back inside the furnace. 

The video below shows you how to remove and clean the furnace filter:

5. The Ducts Have Leaks

Ductwork runs through your home to supply different rooms with heated air from the furnace. The ducts need to be sealed in all areas to ensure air does not leak, affecting the supply of heated air to homes with multiple rooms. If there are leaks, then heat won’t be distributed evenly.

How To Fix

A visual inspection of your ductwork is the best option here. You should walk along the entire duct system and look for signs of damage, such as cracks, dings, or holes.

Turn the furnace on before you start walking along the duct. If there is a leak in the ducts, then you will likely feel some air escaping at the specific points. 

Wrapping Up

A dirty air filter, failure to implement a furnace maintenance plan, and leaks in your ductwork can cause problems with the air supply throughout your house. A furnace not heating the house evenly cause some rooms to be too hot, while other rooms are cold. 

To diagnose this issue and get the most appropriate fix, we highly recommend getting an expert’s help. An HVAC expert can also provide you with annual maintenance to avoid further problems in the future. 


  • Alanna Greene

    Alanna is an avid traveler who lives in Michigan. In addition to writing for Temperature Master, he also sells crafts on Etsy and takes long walks through the forests near her home.

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