You may experience an odd sensation occasionally of walking from one room of your house to another to find it is an entirely different temperature. The feeling can be a bit unnerving not to mention uncomfortable but don’t worry, it’s not Casper the Friendly Ghost playing a trick on you, there’s actually an air conditioner related answer.

Why Is My House Unevenly Cooled?

Often, people think their air conditioner isn’t large enough to cool the entire house properly, or, that the ductwork isn’t large enough. It’s easy to get talked into investing in something larger if your HVAC technician isn’t looking out for air quality before their wallet. Read on to find out some causes and solutions.

A larger system could solve the problem of unevenly cooled rooms, yes, but it could also actually cause issues in your home. Aside from costing more than necessary, an oversized system will bring your home to the desired temperature too quickly. While this may seem like a good thing, your system actually needs to run for a little while to help remove humidity from the air. Your home may be cooled, but with an oversized system, there can be a moist environment not great for humans, but wonderful for mold growth.

The reason we don’t typically recommend an increase in capacity or ductwork size right away, is because all homes constructed within the last 30 years have had their air conditioner’s capacity (size) and their air ducts calculated through a mathematical process known as a “Manual J” and a “Manual D”, prior to building plans approval.

So it’s best to troubleshoot some other causes before investing in a larger HVAC system.

The most common cause of unevenly heated rooms is the uneven solar heating of the house. “But I don’t have solar panels…” you might be thinking. Solar heating is just the sun’s effect on your house. As the sunlight warms the exterior walls of your home, the rooms with the most exposure will warm up quicker. Without a system-wide circulation of air movement, a centrally located thermostat is unable to sense the uneven room temperatures.

Troubleshooting for unevenly cooled rooms…

The first question to ask yourself in trying to discern whether it’s a solar heating issue is this: is the room…

1. Warmer than the rest of the house year-round, or

2. Hot in the summer and cold in the winter

If you answered #1, then that indicates it’s a solar heating issue, as the sun is keeping that room warmer in the winter as well.

If you answered #2, this indicates an undersize in the air ducts because the cooled air in the summer and heated air in the winter isn’t reaching that room well enough. This can be typically be fixed by increasing the air duct size or adding a booster fan for those distant rooms. For these instances, it’s important to note, any increase in cooling will also result in an equal increase in heating. Therefore, a warm natured person who doesn’t mind the cooler than normal room in the winter may find themselves uncomfortably warm throughout the winter if the ductwork is oversized and or a booster fan is installed to compensate for a warm room in the summer. If this is you, you may want to add a small, affordable, mini-split system just for that room instead.

What’s wrong with my air conditioner?

It’s not that something is wrong with your HVAC exactly, but it may just need a little help and fine-tuning. We often refer to our HVAC systems as being “central” heating & cooling but they’re frequently not very central at all. In the hierarchy of home design, architects design attractively styled homes, and engineers make them structurally sound and then lastly, the heating & cooling is considered. Ideally, a house should have centrally located equipment (air handler or furnace). This would ensure that all rooms are of equal air duct length and would have equal air distributed to them. Modern design rarely accommodates for this and we often have more of a so-called “front left or right” or worse yet “1st floor, lower left or right” versus the desired “central” air conditioning system. Any time the air is required to travel a greater distance or forced to wind itself between floors through a labyrinthine pathway of structural floor joists, there’s going to be a reduction in the volume and temperature of the air.

Multi-level homes, if properly constructed, will have at least one HVAC system per floor nearly without exception. Unfortunately, the caveat to this is cost and often air conditioning contractors are forced by the builder to make cost-effective changes to the designed comfort within the house. The price point builder is the problem here and not the heating and cooling system or the air conditioning contractor who designed and installed the system.

So as you can see, hot spots are often a circulation problem and not a capacity or duct size problem, simply due to the difficulty of getting air into every nook and cranny of a home.

For rooms that feel hotter at night than the thermostat setting

Just as stones can be warmed in a campfire to keep you warm throughout the night, the exterior walls of your home are warmed daily in the sun. This radiant heating can account for some discomfort and kicking off of the covers – who hasn’t woken up thinking “Why is it so HOT in here?!”

But often in the evening, it’s not actually the sensible temperature that’s rising, but the relative humidity which is affecting the “feels like” temperature within the room. This accounts for why most people need to turn their air conditioner down a degree or two at night and while they sleep. You see, we think of air conditioners as these things that cool the air because we can quantify it as it registers on our thermostats. But, the real magic is in the latent, or “unseen” heat removal. This is the humidity side of the equation and it is the most relevant to comfort because you can feel the humidity on your skin. As the night progresses and the home naturally cools, the heat load or cooling demand for the air conditioner decreases. Since most thermostats only sense temperature and not humidity, the air conditioners simply don’t run as much as during the day, and therefore just don’t run enough to remove a substantial amount of humidity. This results in ever-increasing humidity levels and the uncomfortable “feels like” sensation that wakes you in the middle of the night.

If this is your issue, it definitely can’t be solved with a larger HVAC system, which as we discussed before can actually have its own problem properly reducing humidity.

Consideration of electronics

These days, our bedrooms can be filled with big-screen TVs and computer gaming systems. It’s important to note that these additional heat sources were in no way considered within the design process. This may be adding additional heat to certain rooms.

What Can Be Done?

While there is no one solution when addressing problems such as these. Our recommendation is to first try and identify the root cause, whether it be the afternoon sun, inadequate airflow or a circulation problem. Then starting at the top of our list, attempt to implement as many of the following solutions as practically possible. For your convenience, we’ve kept these in a logical order beginning with the simplest and most likely culprits to the more expensive but assertive solutions.

1. Crack your bedroom doors.

The first rule in creating an evenly conditioned environment is to leave your bedroom doors open as often as possible unless there is a return air grille (not just a register) located in that room. That way air can flow evenly to and from the rooms. As you sleep, leaving them cracked just a couple of inches is all you need.

2. Make use of your HVAC’s fan.

By turning the thermostat to the “Fan On” position, the air conditioning system’s blower (fan) will operate continuously. But don’t worry, the cooling produced by the air conditioner will cycle normally within this continuous operation of the fan! This creates a sort of “stirring of the pot” effect, causing the stagnant air warming in the extremities to be drawn back into circulation where it can be mixed with the cooler, centrally located air and re-sensed by the thermostat to cycle the cooling on/off appropriately.

3. Turn down your A/C a few degrees at night

This is also a good time to use your fan setting to help equalize the circulation.

4. Change your filter

Restrictively dirty filters impede airflow and reduce cooling efficiency in very much the same way as driving a car on flat tires would lessen its performance and economy. Now, we can all imagine the stifling effect a dirty filter can have on air flowing but did you know your decision to purchase a well-marketed allergy filter could be part of the problem too? Allergy filters are by design very restrictive, the media required to catch microscopic allergens has to be very dense and thus restrictive or they just wouldn’t be very effective at capturing those fine particulates. It’s important to understand, air conditioners make horrible air cleaners and its filtration system is by design there to protect the equipment and not you… If allergies are a concern within your household, consider investing in one of the many stand-alone room filtration systems available on the market these days.

5. Install a humidity sensing thermostat

Replace your current thermostat with one that senses and accounts for humidity as well as the temperature preferably one with wireless remote room sensors. These consider the average temperature within all of the rooms, versus just the living room where the thermostat is most likely located now.

6. Have an AC tune-up completed

When a system is slightly low on capacity either from a dirty coil or just simply low on coolant it’s often noticed first in the extremities of the home.

7. Crank up the volume

While your HVAC professional is there performing the AC tune-up, ask them to check the blower speed and ensure on your fan up to its highest setting.

8. Have your windows tinted

Especially on the side the sun hits your home the most, having your windows tinted as well as heat blocking blinds can help equalize rooms that are more exposed to the sun.

9. Plant a tree

Sometimes, there’s a very simple, practical solution – add more shade to the exposed side of the house, by planting a tree. This can even be a fun activity for your family to do together, and a practical application of sustainability for kids. If you live in a good climate for fruit trees, you could choose a tree that will bring your home shade and your family healthy treats. Choose a tree that loses its leaves in the winter so that the sun can help warm your house to save on heating costs then.

10. Check out your attic insulation

Your attic is the closest part of your house to the sun’s exposure, so having efficient insulation there can really help with unevenly heated areas, as well as save money on cooling costs.

11. Bring in backup

Consider adding an additional air conditioner just for the warmer room. Mini-split systems are small, affordable air conditioners that are suited ideally for a warm master bedroom.

12. When it’s time to replace, change it up

When replacing your HVAC, communicate your concerns with your air conditioning contractor and look into purchasing a system with a variable speed air handler. These air handlers produce greater dehumidification and better airflow through an increase in static pressure. This is the horsepower that forces the air through the ductwork. Also, 2-stage and variable speed compressors may be recommended for additional dehumidification.

Lastly, Don’t expect ceiling fans to perform miracles

Note that ceiling fans can improve tolerance of the heat, and slightly help to circulate air if there is a return air grille, but does nothing to cool or circulate air beyond the room itself.

We hope this has helped you to figure out what might be causing your unevenly cooled rooms. As always, feel free to give us a call or a text with your questions!

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