06/18/2026
Cooling Basics:
Washington State is starting to experience some very warm weather, and I wanted to share a few tips about today's heating and cooling systems.
As I've said before, newer HVAC systems operate a little differently than the older equipment many of us grew up with. In most cases, the best approach is to "set it and forget it." Keeping your system at a consistent temperature is usually more efficient than shutting it off during the day and expecting it to cool the entire home quickly when you get home.
When a house sits all day in 90° to 100° weather, the heat doesn't just build up in the air. The walls, floors, furniture, countertops, and attic all absorb heat. That stored heat is called thermal mass. Once everything inside the home becomes warm, your HVAC system has to remove all that heat before the house starts feeling comfortable again.
Most HVAC systems are designed according to state codes, climate zone requirements, industry standards, and federal energy efficiency regulations. Here in Washington's Marine 4 climate zone, equipment is selected based on long-term weather data and design temperatures used by engineers and code officials. The Marine 4 design charts use temperatures around 24° in winter and 89° in summer based on historical weather averages. During extreme heat events that exceed those design conditions, homeowners may notice their systems running longer than normal. In many cases, that means the system is doing exactly what it was designed to do.
One of the biggest mistakes homeowners make is turning the thermostat way down. Setting your thermostat from 72° to 60° does not make the air conditioner blow colder air. The system only produces air at a certain cooling temperature. Lowering the thermostat simply tells the equipment to run longer.
Another thing to remember is that comfort is not just about temperature. Humidity plays a big role in how your home feels. A properly operating air conditioner removes both heat and moisture from the air, which is one reason maintaining a steady indoor temperature often provides better comfort than constantly turning the system on and off.
Airflow is equally important. A larger system does not automatically mean better cooling. Proper airflow, clean filters, open registers, and correctly sized ductwork all work together to help your system perform efficiently.
To help your system perform its best during hot weather:
• Keep your thermostat at a steady temperature.
• Close blinds and curtains on sunny windows to reduce solar heat gain.
• Replace or clean air filters regularly.
• Make sure all supply and return registers remain open.
• Keep furniture away from registers and returns.
• Keep the outdoor condenser coil clean and free of debris.
• Have the indoor evaporator coil inspected and cleaned when needed.
• Schedule regular maintenance to keep the system operating efficiently.
• Keep trees and landscaping trimmed around outdoor equipment to maintain proper airflow.
Modern systems have computers and sensors that constantly monitor operation. If airflow becomes restricted from a dirty filter, blocked registers, or a dirty coil, the equipment will try to compensate. Reduced airflow can eventually lead to ice forming on the indoor coil, which can cause poor cooling, reduced airflow, and sometimes a complete loss of cooling until the ice melts.
If you notice ice forming on the refrigerant lines or outdoor unit, turn the cooling system OFF and switch the thermostat fan setting to ON. This will help thaw the coil and may prevent further damage while waiting for service.
Ductless mini-split systems are no different. They also require regular filter cleaning, coil cleaning, and maintenance to maintain efficiency and performance.
A few extra tips for 99° days:
• Avoid using ovens during the hottest part of the day.
• Run bathroom fans and kitchen exhaust fans only when needed because they remove conditioned air from the home.
• Change ceiling fans to summer mode (counterclockwise) to help circulate cool air.
• Limit opening exterior doors.
• Check attic ventilation if your home consistently struggles to stay cool. Make sure soffit vents are clear and ridge vents are unobstructed. Proper attic ventilation can help reduce heat buildup.
• If you have a two-story home, remember that heat naturally rises, making upper floors harder to cool.
• Stay hydrated and check on elderly family members, neighbors, and pets during extreme heat.
If your system seems to be running all day during extreme heat, don't panic. A properly operating system may run continuously during the hottest part of the afternoon. The goal is maintaining comfort, not necessarily cycling on and off every few minutes.
Remember, air conditioning systems don't create cold—they remove heat. The easier we make that job, the better the system will perform and the lower your operating costs can be.
Stay cool, stay hydrated, and if your system isn't keeping up, give HeatGuy LLC a call. We're happy to help make sure your equipment is ready for the summer heat.
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