How Homes Help Us Beat the Heat

As many of us are enjoying the Spring season, there are those who are already dreading what is to come after it: Summer. It’s a season where, while the kids get to enjoy a few months away from school and get a chance to live it up with their friends, the rest of us must carry on and battle the heat as we go to work, get groceries or do outside housework like gardening and mowing the yard. Thankfully, many of us live in societies where we can take a break from the heat in our insulated, air-conditioned homes such as the one picture below. 

Picture of a comfortable, modern living room inside a home (Courtesy of Decorilla)

These homes are cozy environments where the air conditioning (A/C) blows cold in the scorching summer heat and where the walls keep the cool air in and the warm air out. How does this process work exactly? Let’s look at two very critical engineering principles used inside the home: Heat Transfer taking place between the many layers of the outermost walls of the home and Thermodynamics that, when using a little bit of energy, extracts the warm air out of the home and replaces it with cooler air.

Keeping Out the Wrong Kind of Energy

Even though it’s nice to have A/C in the summertime, it wouldn’t be nearly as effective if the enclosure it was serving didn’t have any insulation. This is where understanding Heat Transfer and how conduction, radiation and convection play a part in this process. Most of us are familiar with conduction, which is when energy is transferred along either a solid such as metal or a stationary liquid like water. 

Both kinds of materials have what is known as a material’s thermal conductivity, which is symbolized with the letter k. A material with a higher k value will transfer more heat than a material with a lower k value would. This constant is unique to each solid and liquid on Earth and is based on years of testing and research on these materials. 

With the walls that are used in homes, there are typically multiple layers to them: Hardie Plank or brick, wood, plywood, fiberglass, drywall, and then plaster. As you can imagine, the energy coming from the outside decreases as it travels through these materials via conduction. This is also why your face seems to burn when you’re next to a window: it has a relatively high k, meaning that the heat will more easily travel through the glass window than it would through the walls.

New home under construction (Courtesy of Texas A&M University Texas Real Estate Research Center)

Radiation also plays a role in this as well. As in conduction, each solid and liquid has a unique emissivity constant, which is denoted by the Greek letter epsilon ε. Similarly, those materials with a higher ε will emit more heat at the surface than those with a lower ε. Notice how I stated this phenomenon happens at the surface. Rather than emissivity occurring throughout the material, it only happens at the material’s surface. Nonetheless, this is still an important concept to understand when discussing heat transfer. For reference, according to Efficient Windows Collaborative, low-emissivity windows can reduce energy losses associated with windows by as much as 40%.

Diagram showing how low emissivity windows work (Courtesy of Stanek Windows by Great Day Improvements)

Last, but not least, in this heat transfer process is the process of convection. This is when heated particles in a fluid such as air and water move through the liquid and transfer heat. This is different from a completely stationary liquid acting as a conductor. For example, the water in a pot of boiling water will move on a circular path transferring heat from high to low. This is like how the hot air outside our homes’ functions. The warm air carries heat as it blows across the exterior surface of the house’s walls. This also influences how heat is transferred inside the home.

Altogether, the radiation, convection, and conduction occurring on the surface of and within the outer walls of our homes and living spaces all contribute to how much heat is being transferred through our walls. These factors alone determine how well our homes separate us, who like living in our internal oases, from the unforgiving heat and warm air that only summer can bring. This is why the walls in homes are made up of various kinds of materials. Through radiation, convection and conduction, our homes take a real beating during the summer and need to be built to withstand these conditions. Without having a solid understanding of Heat Transfer, homes could be downright insufferable during the summer season and could seriously impact the lives of hundreds of millions of people throughout the United States.

The Art of Staying Cool Under High Heat

Great, now we have the walls figured out and how heat transfer plays a critical role in this process. What about the A/C? How does that work?

Typical A/C Units that play a vital role in maintaining cool temperatures inside a home (Courtesy of Super Hear, Air, And Plumbing)

This is where Thermodynamics comes to play. I remember this section of the course as basically being heat transfer between two different fluids; mainly, air and the freon inside the A/C unit. As in Heat Transfer, heat moves from high to low and, therefore, the removal of hot air from our homes and the cool air that replaces it goes against the natural flow of heat. This is why, depending on the day in the summer you’re in, your electric bill can get sky high. This is also why understanding how the materials used in home construction affect your home’s overall efficiency.

By the way, if this sounds like a refrigerator to you, then you’d be mostly correct. Both a fridge and an A/C unit have the same moving parts, but just different refrigerants, or the fluid components inside the fridge and the A/C unit that assist in the heat exchange process, and slightly different overall objectives. One is trying to keep a space cold to prevent food from going bad, the other is used to help everyday folks live a more comfortable life. This article from Airedale Cooling Services does a good job explaining the differences between both units.

Both refrigerators and A/C units have similar parts, but have different overall objectives (Courtesy of LG Electronics)

 How Walls and A/C Units Help Everyone

Overall, without both the A/C Unit and without proper home construction, we’d literally be toast! During certain parts of the year, many people struggle more than they already do during the summer. Moreover, warm Southern States such as Texas and Florida are experiencing rapid growth, thereby placing more demands on homebuilders and A/C manufacturers to produce more high-quality and long-lasting homes and A/C units for years to come.

Understanding what materials home builders use for walls inside and outside the home is as every bit as important as how an A/C unit for a home is designed and what materials are used for it. Both walls and A/C units need to endure various weather conditions, including hot and cold weather, thereby placing greater strain on these systems. Most importantly, understanding how walls and A/C units both play a role in maintaining a comfortable internal environment can also help you plan accordingly to a hot summer or a cold winter.

What do you think? Is there any way we could make homes withstand the heat better so that A/C units wouldn’t have to work so hard during the summer? Could A/C units be more efficient by using a different refrigerant other than freon or use an upgraded design on their evaporator coils? Let us know what you think!

You can see more content from Everyday Engineering here!

Check out the rest of I Truss the Process here!

First time visiting I Truss the Process? Check out our Who We Are and Our Story pages to see our beginnings, our vision and the values we hold ourselves to everyday.