Why One Room In the House is Not Cooling? 3 Common Causes

Uneven cooling is a problem in many homes, but you don’t have to avoid one room because it isn’t as cool as the other. Instead, you should understand why it isn’t cooling enough and solve the issue.

When one room in your house isn’t cooling, it might be dirty air filters, air ducts, and faulty evaporator coils. The wrong size of your cooling system and poor insulation can also be blamed. You might also have a problem with your home’s design.

In this article, I’ll share some of the most common reasons one room in your house isn’t cooling enough compared to the others. More importantly, I’ll also list down the solutions that might work.

1. The A/C Has a Dirty Or Clogged Air Filter 

The air filter is one of the essential parts of your home’s air conditioning system, as it removes contaminants such as pollen, dust, and smoke, which makes it vital in improving air quality. 

When the filters are dirty or clogged, the cooling system may end up inefficient. 

You’ll need to replace the air filter regularly. Otherwise, you’ll not only be circulating dirty air, but it can also restrict airflow, which is why cool air may not reach other rooms in your house, making the temperature uncomfortable. 

The Solution 

The easiest fix is to replace the air filter when necessary. There’s no general rule on when you should do so, but in most cases, it must be at least once every three months. The environmental conditions in your home and the type of air filter impact the frequency you must change them. 

Read: Why AC Is Not Cooling? 3 Troubleshooting Steps

2. You Have the Wrong HVAC Size For Your House

Determining the right HVAC size guarantees optimal functionality. If it’s too small, the unit works harder to cool other rooms, but it might not be able to do so. But if it’s too large, parts of your house may become humid and stuffy. 

The Solution 

To identify the right size of the air conditioning system your house needs, determine the square footage of the area you like to cool. Then match it with the HVAC system’s BTU or British Thermal Unit. 

However, high ceilings can increase the cooling capacity you need. 

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Read: Geothermal Heating And Cooling – Pros And Cons

3. Your Home Has Poor Insulation 

Proper insulation is crucial for energy efficiency in your home, as it resists heat flow, making it essential for lowering cooling costs. It also makes your home more comfortable while saving money and doing something good for the environment. 

In areas of your home with the proper insulation, you’ll notice that the temperature is cooler. However, the rooms with poor insulation may end up hotter, even when the air conditioning is in full blast. 

The Solution 

Consider the different types of insulation for your home, including the following: 

  • Blanket insulation: Fiberglass, natural fiber, mineral wool, and plastic fiber are the most common types of this insulation. They are best for floors, ceilings, and unfinished walls. 
  • Reflective insulation: Often installed in the attic ceiling, it reflects sunlight and reduces radiant heat transfer. 
  • Foam board insulation: It’s available in different materials, such as polystyrene and polyurethane. It’s popular for being thin while having high insulating value. 
  • Insulating concrete forms: Made of foam blocks or boards, they are for unfinished walls at the start of construction. It has a high thermal resistance. 
  • Loose fill insulation: Also called blown-in insulation, it uses loose fibers for the attic. It uses special equipment to blow insulation in place. 

Read: What Is The Most Efficient Heating And Cooling System

4. Unsealed Doors and Windows Let Out the Cool Air

Cool air can leak from old doors and windows, especially unsealed ones. Cracks in these places can make your air conditioning inefficient and increase your cooling costs. Replacing them can be expensive, so sealing can be a better alternative. 

The Solution

Different solutions are available for sealing the gaps in your windows and doors such as: 

  • Add a draft cloth. 
  • Put up shrink-and-seal insulation using double-sided tape. 
  • Use weatherstripping and caulking around your windows and doors.

These are all good for preventing hot air from getting in or cool air from escaping. Do you need help with how to seal your windows and doors? Watch the video below and learn how to do it: 

5. Blocked Vents Keep Cool Air From Moving Through the House

Vents are where cool air passes through, passing from room to room to ensure even cooling across all areas. You might not have noticed it, but the vents can be blocked by large furniture or dirt and debris. 

The Solution

Blocked registers prevent cool air from circulating in the room, so the easiest solution is to remove any hindrance. It’s also good to clean the vents regularly to remove debris impeding air circulation. If the vents are old, you might need to replace them to optimize functionality. 

Read: Heat Pump Cooling Efficiency In Hot Weather

6. Dirty Air Ducts Prevent Air Circulation

Aside from vents, ducts are crucial components in your home cooling system to ensure optimal air circulation. It’s connected to your vents, so the problems are complementary. Use a flashlight to look inside the vents, so you’ll know if it’s already dirty or blocked. 

The Solution 

Air duct cleaning is necessary to prevent indoor air pollution and ensure efficient cooling. The latter is especially essential when you notice visible mold growth in your house and when people suffer from allergies or similar health conditions. It’s also required when there is vermin infestation.  

7. Dirty Evaporator Coils Don’t Absorb Your Home’s Heat

The evaporator coil absorbs heat in your house, as its primary responsibility is cooling the refrigerant for better temperature management, and it works in conjunction with the condenser coil. Dirt in the evaporator coils can cause uneven heating across several rooms.

The Solution 

Regular A/C maintenance can help fix the problem, ensuring a clean cooling system, including the evaporator coils. Remember, these coils are sensitive components, so you must handle them carefully. Your best bet is to leave the work to the pros with experience and expertise. 

8. Your Home’s Design Doesn’t Allow Efficient Cooling

The design of your home can also be the culprit when one room is not cooling. One common problem is the design of the windows, especially when they are too large. Your home might be designed so that too much sunlight comes in. 

The Solution 

If you’re building your home from scratch, ensure the design allows proper air circulation. Adding closing curtains and blinds can also help to improve window design, as well as painting your walls in a cooler color. It’s also a good idea to avoid clutter in all rooms to not obstruct cool air.  

9. Some Appliances Generate Too Much Heat 

This is one thing many people may not realize, but it has a significant impact on your home’s cooling system. You might notice that the kitchen is often hotter than in other rooms, especially when you cook, which can generate heat and restrict air circulation. 

The Solution 

A quick fix is to turn off or even unplug the appliances when you’re not using them. Use small appliances that produce little heat, or cook outside if the weather permits. You can also save large cooking jobs until the evening hours when it’s cooler outside. 

If you’re not using the appliances, turn them off to keep your kitchen as soon as possible.


It’s frustrating and uncomfortable when one room doesn’t get as cool as the others, but the problem can be fixed relatively easily, especially if it’s a matter of cleaning. The vent, air ducts, doors, and windows, can also be the culprits. You might also have problems with your home design and heat from the appliances.