An Interesting Study on Sleep

I recently read a book by Matthew Walker, Ph.D., called "Why We Sleep." Walker is a professor and sleep researcher who studies the importance of sleep. He published decades of research in this book that serves as a wake-up call for anyone interested in their health and quality of life.

A significant focus in the book is the importance of recommended sleep times — seven to nine hours, to be exact. His team’s research found sleeping less than six hours per night causes the following medical issues:

• A weakened immune system
• Increases in certain forms of cancer
• Risk of developing Alzheimer's
• Disruption in blood sugar levels
• Increased likelihood of coronary arteries becoming blocked or brittle
• Contributing factor all major psychiatric conditions, including depression, anxiety, and suicidal tendencies
• An increased desire to eat

Walker concludes that shorter sleep times equal shorter life spans. So, what does this have to do with HVAC, and why should you care?

The Connection Between Comfort and Sleep

Comfort results from a properly operating HVAC system. One part of Walker's book that hit close to home was the connection between comfort and sleep quality. I knew comfort made a significant difference in how we sleep, but I did not know how much. In fact, it is the most underappreciated aspect that influences how well we sleep.

Walker says a major factor affecting sleep is your "thermal environment" because it affects the temperature around your body. We lose most of our body heat through our head, hands, and feet. So, if you ever wake up with your hands and feet outside the covers, the reason is that your body is trying to cool off.

According to Walker's data, our core temperatures should decrease 2-3°F to fall asleep easier and stay that way. A hot room makes it much harder to fall asleep and often causes us to wake up because of nighttime sweating.

Walker found that a room temperature of 65°F is reasonable for a sleeping environment. Very few people would have issues setting the temperature this low in the fall or winter. But what about the summer? Most people adjust their thermostats too high for optimal sleep conditions.

(Note: There is no mention in Walker's research about indoor relative humidity at the recommended indoor temperatures. Indoor relative humidity makes a substantial difference in comfortable conditions and the effective temperature people feel when they sleep.)

The U.S. Department of Energy (DOE) recommends 78°F as a summer thermostat setting. Many utility companies and equipment manufacturers also make this recommendation. However, though the 78°F set point is great from an energy usage standpoint, it is terrible for comfortable sleeping conditions.

While a 65°F room temperature may sound too cold for comfort, lowering the room temperature has sleep benefits. Walker and his team found lowering room temperatures 3-5°F drastically helps patients with insomnia. It is the first step he recommends in treating their condition.

In one of his study groups, they kept room temperatures warmer. As a result, those participants had a 58% chance of waking up in the last half of the night. They also struggled to get back to sleep once awake. However, once the participants cooled off, the sleepless results dropped to 4%.

Some of your customers don't have the luxury of lowering their room temperatures to comfortable sleeping conditions. Instead, their system can barely keep up with a 78°F set point.

Every Customer is Different

There is no one-size-fits-all rule for comfort — each customer is different. Individual metabolism dictates comfort conditions based on how rapidly a person loses body heat. For example, some customers are comfortable sleeping at 75°F, but others have extra insulation and may want it 65°F when they sleep.

I believe 65°F is a little aggressive for summer conditions, especially if you can control indoor humidity. But 70°F is more realistic and achievable in most homes. It is also a temperature that most people lose sensible heat from their bodies at a rate that provides comfort.

Interestingly, if you raise the room temperature to 80°F, the skin's heat loss decreases 75% of its value from 70°F. In other words, your core temperature rises. Consider how close that temperature is to the DOE recommendation of 78°F.

Do you assume what dictates your customer's comfort or base their comfort on industry standards? When was the last time you asked a customer what temperature they would like in their bedroom when they go to sleep?

Try a Little Experiment

Do you have sleep problems? Maybe you have a hard time going to sleep, or you wake up with night sweats. If this sounds like you, turn the temperature setting on your thermostat down to 70°F at night and see if you sleep better.

I tried this test since I had sleeping troubles and often woke up multiple times during the night with my feet sticking out of the covers. My thermostat's cooling setting was 74°F, and the humidity at this temperature was 52%. Those indoor conditions are close to the Air Conditioning Contractors of America (ACCA) recommended design cooling conditions.

For one week, I turned my thermostat temperature down to 70°F around 8:00 p.m. The results were obvious after the first night. I slept better and woke up feeling refreshed instead of needing a cup of coffee to get going. So, after questioning my family about their sleep, we decided the Richardson household will continue setting our sleeping temperature cooler.

What if you try this experiment and can't get your bedroom to a comfortable temperature? You need to ask yourself why. What is keeping your home from reaching acceptable sleeping conditions? In my next column, we will look at HVAC tests and solutions you can use to diagnose the problems preventing you and your customers from sleeping their best.