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Complete Guide To Sleeping Cool

Image of different mattress layers and depth
Woman Side sleeping
There is possibly nothing more frustrating than not being able to sleep because your bed is too hot. At first, our bodies start cool but begin to warm up under the sheets, and we arrive at just the right temperature just in time to go to sleep. As the hour’s tick on, the bed continues to heat up. At some point, most of us start to get hot, making it difficult to sleep without tossing and turning in an attempt to get cool. Why is that?

As a general rule, most people overestimate their bed role in sleeping hot. Two factors determine the micro-climate in bed, which are thermal regulation and moisture regulation. Research by the Ergonomic Institute in Munich has shown that the duvet determines about 70% of the micro-climate. 

 

Can your Mattress make you sweat?

 

The material of our mattresses and sheets play an important role in why we “sleep hot”. Sleeping causes a slight decrease in core body temperature, enabling excess moisture and heat to be trapped within certain sheets and mattresses.

Memory foam mattresses and sheets with high thread counts (extremely dense) are especially susceptible to this issue. There are many reasons why people get so hot while sleeping, including bedding design, bedding materials, and sleeping environment.

In general, the fabrics and layers of your bedding are closer to your skin which means they will have a bigger effect on airflow, moisture transport, and temperature regulation than your Mattress. This is because the layers and components of your bed are further away from your skin. Most people will have a sheet and mattress cover between them and the core materials of the Mattress. This means that the type of mattress cover, sheets and duvet cover will have a more important role in causing you to sleep hot.

 

Soft Mattresses Are Hotter Than Firm Ones

That is not to say that your Mattress has no effect. Softer mattresses or foam toppers that conform to the body will tend to be more “insulating” and trap heat. For this reason, some people find that firmer mattresses are better for staying cool because less heat is trapped, and moisture can escape easier, which works in combination with your bedding to keep you cool with different versions of the same material.

Memory Foam is the Hottest Type of Mattress 

Memory foam mattresses are the one type of Mattress that is likely to make you hot. Memory foam works by requiring body heat to soften and contour to your body. It only makes sense that it would retain some of this warmth and insulate as well. Due to this, memory foam does tend to sleep more warmly than other materials. Furthermore, if we’re able to prevent your memory foam mattress from getting hot, this would reduce its effectiveness since it needs heat to work. A cool memory foam mattress is stiff and doesn’t provide pressure relief.

 

 

How Mattress Temperature Works


The Science of Sleeping Hot

There are two levels to sleeping hot. From the surface of it, it seems like a comfort issue. It’s just more challenging for a person to fall asleep when there is a discrepancy in their body temperature and surroundings, whether too cold or too hot. 

On a deeper level, temperature regulation and sleep is a pretty complicated relationship. In most cases, our body temperature and especially our core body temperature change throughout the day in predictable ways. Our core body temperature and the degree to which we feel sleepy at any given time are related.

Circadian rhythm 

Circadian rhythm refers to the regular changes in our core body temperature that happen daily. During the waking hours of the morning, our core body temperature is at its lowest. After that, it increases throughout the day and reaches a peak about two hours before we start to feel sleepy at night. The reason for that is that after our body’s core temperature peaks and then starts to drop, we tend to become sleepy from that cooling of the core. For this reason, if you take a hot bath or use a hot tub, afterwards it is common for people to feel tired afterwards. It’s very common for people to assume it is because they are very relaxed. That’s part of it. Yet the main factor seems to be that when you sit in hot water, your core temperature rises, then when you get out, your core temperature rapidly drops, and the rapid cooling of the core tends to make people sleepy.

Irregular fluctuations in temperature are probably indicative of a hot sleeper. The body is generally good at maintaining body temperature at the same level; however, if you sleep hot, your body or sleeping environment is probably the cause.

Your Bed’s Microclimate

Did you know that as we go to sleep, we unconsciously create a ‘microclimate’ that helps us temperature regulate?

One study looked at the “microclimate” of your bedding environment. Basically, the room temperature is one thing, but the temperature inside your bedding is another.

The human body has an average temperature of 98.6 F or 37 degrees C.

 

Thermoneutrality

Definition of thermoneutrality: a state of thermal balance between an organism and its environments such that bodily thermoregulatory mechanisms are inactive

So, in order to comfortably maintain our optimal body temperature, our sleep bedding microclimate must be in the range of 30°C, the Netherlands based study found. The optimal “thermoneutrality zone” is about 30 degrees celsius, says the study.

This is the temperature in your bedding where most people find a balance of not having to heat their body and remaining comfortable. Thermoneutrality was kept stable with ambient air temperature from 19-22 degrees C.

Different people have different needs in respect of achieving comfort in their sleep environment. You likely know this from sleeping with a partner who may sleep “hot” or “cold”. Colder ambient temperatures tend to have a more disruptive effect on people vs warmer air temperatures.

Moisture

Moisture and humidity can have an impact on sleep comfort. As little 3% to 5% added moisture could be enough to trigger sensations of discomfort and dampness. We recommend a wool mattress protector to help draw moisture away from your sleep surface and to regulate temperature.

In a UK Imperial College of London study of mice and thermoregulation, there is a cycle that occurs throughout the night. Core temperature drops from sleep onset. Other mammals such as cats, chimpanzees and humans all thermoregulate during sleep.

Humans do this unconsciously by increasing their exposed area as ambient temperature rises. This study found that we attempt to establish skin microclimates of between 31- 35

 

How Can I Cool Down My Mattress?

 

Often overlooked by traditional manufacturers, moisture control in mattresses and bedding is probably one of the most important components of undisturbed sleep. When we sleep, we perspire. If that moisture is trapped in the fabrics next to our bodies, we get clammy and hot and are usually woken up by it. To alleviate this issue, we will throw off the blankets, causing the moisture to evaporate so quickly that we get a chill. We then repeat this process over and over, destroying any hope of having a good night’s rest. 

 

Use Bedding With Natural Fibres

Introducing natural fibres into your bedding products are good ways to regulate body temperatures naturally throughout the night. Wool will continue to feel dry even when it has absorbed 30% – 50% of its weight in moisture – think of those sheep which live in many different climates around the world! Capillary action (wicking) moves the moisture along the fibres and away from your body, keeping you cool and dry. Alpaca fibre is hollow works much like wool but even better, with faster drying and better capillary action. Alpaca does not contain lanolin which we love for its antibacterial and anti-dust mite properties. It is often blended with wool for this reason. 

 

Avoid Synthetic Fibres

In closing, research will tell you there are many synthetic wicking fibres on the market today. They are used in sportswear and traditional mattresses, and bedding and show excellent capillary action. Unfortunately, tests show they do not offer the quick-drying ability of wool, resulting in bacteria being trapped in the fibre pores leaving behind an odour. Most of us have purchased these high tech garments and have been surprised by the seemingly impossible to remove smell after just a few workouts. Manufacturers then combat this problem by adding even more chemicals to mask the odour – something none of us need in our chemical-soaked environment. These are just a few properties outlining why Wool and Alpaca are naturally better – keep cool, keep warm, and of course, keep clean!

 

 

What Mattress Is Best For Sleeping Cool?

The best Mattress for night sweats is one that either has springs or foam with an open-cell structure. Open celled foams are breathable, which allows cool air to circulate through the Mattress at night. Additionally, perforations in mattress foam can help keep a mattress cool. Perforations work in a similar way to how open-cell foams work by allowing air to move inside the Mattress. 

As a general rule, natural latex mattresses are a great type of mattress if you want to sleep cool. Natural Latex mattresses provide amazing pressure relief and temperature regulation. They don’t sleep “cool” or “hot” instead they neutralise body heat.

 

 

What Causes Night Sweats?

Sometimes when you sleep, you may start feeling hot, but the fix is usually simple. But for people who experience night sweats, the solution might not be as straight forward. Sleepless nights accompanied by excessive sweating are commonly called night sweats. These are experienced with hot flashes only during sleep, totally unrelated to the room you sleep in being overheated.

Various factors can cause night sweat. Night sweat can occur due to some medical conditions, including cancers, infections, hormonal disorders, neurological problems, and even menopause. If you are experiencing night sweats, your health care provider can help you identify the underlying cause.

 

Why Does My Mattress Cover Make Me Sweat?

Breathability is the most important feature of a cover if you want to sleep cool. Breathability is the degree to which a fabric allows air and moisture to pass through it. If you find that your cover makes you sweat chances are you are using bedding made from polyester or have poor breathability. Instead, choose a breathable fibre that is also natural.

 

Do Foam Mattresses Sleep Hot?

Memory foam and natural latex are often confused for each other. This leads some people to believe that both memory foam and natural latex mattresses sleep hot. However, they are both very different materials, and they both have distinct thermoregulatory properties.

Memory Foam

Memory foam is notorious for sleeping hot and for a good reason. Memory foam is loved for its ability to contour to the body, which is good for pressure relief. However, this feature of memory foam requires heat to work as memory foam gets softer as your body heat warms the foam. Since the foam contours to your body, this traps heat. Furthermore, since it is a petroleum product, it has no natural or intrinsic temperature regulating properties. Suppose you sleep hot; memory foam mattresses are probably not for you. If you take steps to cool your Mattress, you won’t get to experience the pressure-relieving qualities of memory foam since it requires heat to work.

Natural Latex

The millions of interconnected microscopic air chambers in latex foam ensure good heat insulation, optimal evaporation of transpiration fluid and constant air circulation, creating good ventilation. Extra ventilation channels are typically inserted in the latex foam. The sleeper’s change in posture during the night creates a pump effect that generates proper air circulation. 

Researchers at the Ergonomic Institute in Munich examined different mattress technologies and came to the conclusion that mattresses with a fairly high natural latex content have “medium” thermo-regulating properties, meaning that they are neither too hot nor too cold to sleep on.

 

Are my bedsheets making me sweat?

More often than not, your bedsheets and cover are the most responsible for causing sleeping hot at night. Ideally, your sheets should wick away moisture from your skin. As little 3% to 5% added moisture could be enough to trigger sensations of discomfort and dampness. 

The problem with bed sheets is often not that they sweat but that the moisture accumulates and is trapped in the sheets. This is what gives you that feeling of dampness that is caused by your sheets not wicking away moisture or allowing that moisture to evaporate. 

If you find that your sheets are causing you to sweat, check and see if your bedding is made from synthetic materials such as polyester. In most cases, natural fibres are better are wicking away moisture and allowing evaporation. For example, sheep’s wool will continue to feel dry even when it has absorbed 30% – 50% of its weight in moisture. For those who would prefer not to use wool, Tencel is an innovative natural fabric that sleeps cooler than linen and is also softer than silk while also being one of the most eco-friendly materials in the world. 

 

How do I stop my memory foam from sweating?

It can be very challenging to stop a memory foam mattress from causing you to sweat. Memory foam requires body heat to make it soft. Without that heat, memory foam would feel firm and stiff. This is why it often takes a couple of minutes for a memory foam mattress to become comfortable and pressure relieving.

The problem begins when the foam conforms to your body which traps heat. While this has the effect of making some people sweat, it also further softens the foam. This is why many people complain of feeling ‘stuck’ in memory foam mattresses the longer you stay in one place.

When you try to prevent a memory foam mattress from heating up, you are reducing its pressure-relieving properties. For this reason, we recommend that people shouldn’t purchase a memory foam mattress unless they don’t mind sleeping hot.

 

Is my waterproof mattress protector making me sweat?

The problem with waterproof mattress protectors is that they are made from plastic. This means they are not breathable and trap heat. There is not much that can be done to prevent a mattress protect from causing you to sleep at night. Since it rests directly under your sheet, this means that it will be close to your skin which prevents moisture from evaporating and reflects heat. While the type of sheet you have can help overcome the problems of using a mattress protector, your bed will probably still sleep hot, and your Mattress will never be as cool as one without a protector.

That being said, the best temperature for sleep is not ice cold. If you get the right bedding, you can significantly improve how hot your bed sleeps, even with a mattress protector. Furthermore, colder room temperatures have been shown in studies to be more disruptive to sleep than warmer air temperatures. We generally find that sleeping a bit too hot is better than sleeping too cold.

9 Tips for staying cool at night.

 

How to Sleep Cool

While the merits of being cool are up for debate, there’s a proven benefit to sleeping cool.

From making it easier to fall asleep to waking up feeling more rested, maintaining lower temperatures at night can reap many rewards.

Seasonal fluctuations in temperature and humidity will have a direct effect on your sleep environment, which can affect the quality of your sleep. Fortunately, there are a wide variety of steps you can take, including a cooling mattress pad that will ensure your bed is a haven of restfulness.

So while we can’t recommend a cool leather jacket or a popular pair of skinny jeans, our top six “be cool” tips can at least ensure higher quality sleep:

We have listed our top tips for how to cool down when you sleep hot, regardless of whether you are a naturally hot sleeper or find sleeping hot uncomfortable.

  1. Avoid Memory Foam: Memory foam mattresses are not recommended for hot sleepers. Make sure to find a different mattress type or get a topper.
  2. Set your thermostat between 15-20 degrees Celcius: This is the ideal temperature for sleeping. However, if you sleep hot, you might want to set it even cooler.
  3. Wear comfortable clothing: Wear lightweight, loose clothing or sleep naked during sleep to keep your body cool.
  4. Take a hot bath or shower: When you get out of the bath or shower, you will find your body temperature starts to fall, telling your body it’s early for bed.
  5. Sleep on breathable bedding:  A linen or Tencel sheet will help you stay cool even during the summer months because of its moisture-wicking qualities.
  6. Kick out your furry friends: Our furry friends are our best companions, but it could be due to them when you feel too hot while sleeping. Consider letting them sleep in their bed.
  7. Maintain a relative humidity between 30 and 50%: As the saying goes, “it’s not the heat, it’s the humidity.” In other words, even a moderate temperature can feel too warm when mixed with excess moisture in the air. This is because humidity hampers your body’s natural ability to maintain body temperature through sweating. 
  8. Run fans in the bedroom. Fans help keep you cool because circulated air does a better job of evaporating sweat from your skin. This, in turn, helps your body regulate temperature. 
  9. Use breathable sheets. You don’t want the fabrics touching your skin to absorb moisture and trap it next to your body. Instead, they should wick moisture away, helping to keep you cool. A great way to accomplish this is by using sheets made from a breathable material. 

 

Conclusion: Finding the Right Mattress for hot sleepers

Throughout our research, we’ve observed a common problem among people is sleeping hot. Even if the perfect room temperature of 15-20 degrees never changes, there are significant variations in relative humidity and moisture in the bed covers and Mattress. Dense bedding products, which reduce airflow, are one of the major causes of this condition. We’ve put a lot of thought and design into the products we design at The Spinery.

We provide products that help our bodies sleep naturally by supporting them to maintain their body temperature during sleep. We spend almost one-third of our lives in bed, so cool mattresses and bedding are of particular importance if you sleep hot.

We designed our Mattress and pillow to promote balanced airflow by focusing on just the right fibres, thread count, and weave.

About Dr Lawrence Woods

My goal is to create the highest quality mattresses and pillows for unmatched comfort.

With 30 years of spinal healthcare experience in Ireland as a chiropractor, I learned the value of high quality sleep for living a happy and healthy life.

I have a Chiropractic Degree from Life Chiropractic College West and I am NBCE Physiotherapy certified.

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