How to Keep You House Cool in Summer (Without AC)

I grew up in a house with no AC. Even when my family put an addition on, they chose not to install central air—in part for cost savings but also out of stubbornness. We had one or two old window units, but they could never keep up with the steadily rising temperatures on the hottest days of summer. So, I learned the tricks—creating a cross breeze, keeping the space dark, and when all else failed, hanging out in the basement.

I still have a streak of stubbornness that has me sweating rather than spending a few hundred dollars on a new window unit, but working in the building industry I’ve learned that there are more ways of keeping your house cool without AC. So, in this blog, I’ll give you some advice on how to keep your house cool in summer, by leveraging both new technology for passive cooling and the old-fashioned tricks.

What is Passive Cooling?

What if your house could work for you instead of you working (and paying) for it to stay cool? Passive cooling leverages design choices in the construction of the home that passively reduce heat gain and increase heat dissipation. The goal is to keep your home at a more stable temperature, even when you’re hitting record temps outside. This reduces the need for electricity to cool your home through portable or even permanent cooling systems, saving you money.

From home orientation to materials used in construction, there are diverse passive cooling techniques that can assist in keeping your house cool without AC. While most passive cooling design choices are made when constructing a new home, some can be incorporated during the renovation of an existing home.

Does Insulation Keep Heat Out?

When we think of insulation, we often think first of how it helps to keep us warm, like a good winter coat. But proper insulation can also work conversely to prevent high external temperatures from impacting your home’s comfort. First, you need to understand how your home gets hot: without any barriers, warm air naturally flows toward cooler areas until there is no difference in temperature. Insulation slows down this conductive transfer of heat, keeping your home’s interior cooler for longer.

Heat resistance is measured in terms of a material’s R-value—higher R-values mean higher resistance. Choosing the right insulation material and properly installing it in key areas will improve your home’s passive cooling ability. Consider choosing innovative insulation technologies like wood fiber insulation which is designed to reduce the heating and cooling loads of buildings in all seasons and climates. Tested to US standards, wood fiber insulation can curb energy loss thanks to its higher density providing excellent draft reduction and the naturally high thermal diffusivity of wood.

Ideally, your new home would be built using a combination of wood fiber boards, batts, and loose-fill insulation to ensure all exterior walls are protected from fluctuating external temperatures. However, even existing homes can utilize passive cooling techniques by adding high-performance wood fiber insulation in key areas. Insulating your attic, for example, can save homeowners up to 15% on heating and cooling costs. Wood fiber insulation can also be installed over or alongside existing insulation materials.

There’s another reason to consider wood fiber insulation, especially continuous insulation installed behind the siding or under roofing materials. Along with excellent R-value, wood fiber insulation provides summertime heat protection with a greater capacity to delay heat gains than other conventional products on the market, even those with higher R values! It gets a little complex, but we explore this further in our technical library and in our Guide for Builders.

Reflective Materials & Cool Roofs

There’s a good reason why light-colored clothes are popular in the summer—they reflect heat! And just like your choice of warm-weather fashion, your home’s exterior can also provide passive cooling. We recommend ensuring your attic is airtight to your living space below. If you don’t have insulation, (or even if you do) simply move the insulation and use tapes, sealants, or canned foam to seal around any cracks or openings to the living space.

Cool roofs reflect the sun to reduce heat gain in the home. They are light in color and are made of materials with high solar resistance, like painted metal tiles or terracotta shingles. Some roofing materials can even be retrofitted as cool roofs by adding a cool coating or paint. However, you should consider your local climate before choosing to install a cool roof as they can also reduce heat gain during the winter when a helping hand from the sun might be welcome.

Energy Efficient Windows & Doors

Your fenestration—aka openings in your home—can also play a significant role in how to keep your house cool. Highly energy-efficient windows and doors have multi-layer glazing and framing to reduce convection heat transfer and have a strong seal to prevent air leakage. Depending on your climate, you may also seek windows that have a low solar heat gain coefficient (SHGC) which better shades your home from sunlight. You can learn more about energy efficiency ratings and how to read window and door labels from the US Department of Energy. Don’t forget to airseal around them by removing the indoor trim and using a backer rod and sealants, tapes, or canned foam.

Landscaping as Passive Cooling

Ventilation! Ventilation! Ventilation!

So far, we’ve talked a lot about preventing hot air from moving into your house but equally as important is your home’s ability to let air out. Ventilation can be as simple as opening windows, but you can also integrate ventilation into your home design for even more efficient heat loss. For example, positioning larger windows on the leeward side of the house and smaller openings on the windward side creates a vacuum effect that pulls air through your home. Stack ventilation systems, like solar chimneys, draw warm air up from within your home to be released outside. And of course, incorporating ventilation in your attic, where the air is hottest, is key to releasing heat before it can be absorbed into your living spaces.

5 Tips for How to Keep Your House Cool That Never Go Out of Style

All of these passive cooling techniques can help take some of the thought and cost out of keeping your house cool in the summer. But the truth remains that some of the age-old tricks can do a lot to make your home comfortable if you are diligent.

• Night Flushing: Without the sun, nights are naturally cooler. Take advantage of the lower external air temperatures by opening windows at night.
• Keep it Dark: During the day, close blinds and curtains to block sun transmission and keep interiors cooler. Do your best to leave the lights off as well.
• Choose LEDs: Incandescent bulbs produce more heat than LEDs. Switch to energy-saving lightbulbs to not only reduce heat but also save on energy costs—win-win!
• Limit Appliance Use: Don’t do laundry or bake a batch of cookies during the hottest part of the day. And as tempting as it may be, don’t stand slack-jawed in front of your open refrigerator.
• Use Fans Strategically: Set up fans to create horizontal air flow through your house. At night, you can even point fans on upper floors out a window to help expel hot air. Set ceiling fans to rotate counterclockwise to push air directly down.