Thermal comfort, how to air condition efficiently?

Finding the right formula to give us the best comfort at home is something that is not easy but certainly worth achieving. Our well-being, the performance we can enjoy at work, or even our good mood are aspects that will be conditioned by the climatic conditions of our homes. And it is notably influenced by thermal comfort, which is based on the needs of homes to reach a situation where we feel comfortable in terms of temperature, but also humidity, air quality, and other factors.

The thermal comfort -which in technical terms is usually referred to as hygrothermal comfort- is simply defined as the absence of thermal discomfort. This is how public organizations and administrations define it. But, of course, it goes much further and is considered a fundamental control parameter in the habitability of interior spaces. Whether personal or professional.

In past decades, the search for comfort at home in relation to temperature and air conditions was solely based on installing traditional air conditioning systems, such as air conditioning or heating. Without paying much attention to indoor air quality -which affects us in many ways- when the air we breathe is of poor quality, we are putting our health at risk.

This erroneous search for thermal comfort solely relying on traditional air conditioning could lead to significant energy costs as well, since it did not take into account the proper construction of the home to retain heat in winter and prevent its entry in summer. That is why many Spanish homes are affected by energy poverty, in the sense that the investment they need to climatize the home is too high due to poor construction of the building.

In this regard, what does it mean to enjoy good thermal comfort and what do we need to know?

Conditions to achieve optimal thermal comfort

The hygrothermal comfort allows us to rest much better, with a more restorative sleep. It also makes us feel more productive and more optimistic. It eliminates irritability and also helps our skin feel rejuvenated.

What factors influence achieving good thermal comfort? The first is the natural feeling of comfort. By this, we mean that we should not go against the current and try to be hot in winter and cold in summer. Ideally, wearing light and comfortable clothing should make us feel good, but always depending on the season of the year.

• Air temperature. This is the most notable factor, but not the only one to consider. It should be between 20°C and 25°C depending on the season we are in.
• In winter, it is ideal to be close to 20°C, as we tend to wear thicker clothes and more garments than in warmer months.
• In summer, the ideal is to hover around 25°C, without going lower.
• The vertical thermal gradient should not exceed 3° Kelvin. What does this mean? Basically, that we cannot have very cold feet and a hot head. In fact, it should be the other way around. And for that, it is necessary to rely on different air renewal solutions such as mechanical ventilation systems.
• The humidity in the environment is almost as important as temperature, as very high or too low values will change how we feel heat and cold. The relative humidity should be 30% to 40% at a minimum and 60% to 70% at a maximum.
• Air movement is important too. Normally, having air currents indoors from 0.1 to 0.2 m/s gives us a good sense of well-being. However, if those movements carry very cold air, they will be uncomfortable. For this, it is important to renew the air with a ventilation system and keep in mind that having a strong fan, while it may seem pleasant at first, does not favor our hygrothermal comfort.
• The mean radiant temperature is also important. It is the heat emitted in the form of radiation by elements in the environment, along with the average temperatures in the environment. It must guarantee a practically equal temperature near the heat source that far away.

All of this will help us achieve better comfort at home and enjoy good well-being. It is not enough to have an air conditioning system; it is necessary to ensure that, in both winter and summer, we enjoy the same thermal sensation of well-being.

Why seek naturalness in hygrothermal comfort?

Many of us have suffered the effects in offices and workplaces where in summer you had to wear a jacket and in winter short sleeves. That is a bad thermal sensation, it can cause illness and is negative for our body.

Moreover, something that we have discussed previously comes into play, the vertical thermal gradient. Cold air, if not in motion, tends to settle at the bottom of the rooms. And warm air at the top. Humans need to keep our heads cool and our feet warm, and for that, it is very important to have that air renewal.

• Air conditioning systems blow cold air but do not renew the air, so it is usually installed near our feet when what we need is to feel comfortable in the upper middle part of our body.
• Heating creates warm air that tends to install itself at the elevated part of the room when we need to keep our feet warm.

That is why, to achieve true thermal comfort, it is necessary to invest in mechanical ventilation systems and also in a different structure of homes.

For instance, in sustainable homes -like Nearly Zero Energy Buildings which will be mandatory starting in 2020- the estimated values of this type are:

• Temperature in the rooms: from a minimum of 18°C in winter to a maximum of 26°C in summer.
• Mean radiant temperature of the room: from a minimum of 18°C in winter to a maximum of 26°C in summer.
• Air speed inside the rooms: should not exceed 2 m/s.
• Relative humidity in the environment: between 40% and 65%.

These temperature values between 18°C and 26°C are the broadest measure, but in bedrooms and bathrooms it is important not to reach either extreme in case of illness.

How to achieve good thermal comfort at home?

The thermal comfort, as we have discussed, does not simply depend on using air conditioning systems. Just as it is counterproductive to dress in summer in winter and waste supplies in what would be an unnatural situation. Because hygrothermal comfort seeks the same naturalness as those days of respite where it is neither cold nor hot, and in which the humidity conditions are correct.

The first thing that would be necessary to achieve good thermal comfort is to have a construction in our homes and workplaces that seeks tightness to prevent the entry of cold and heat. The main enemy of our comfort is the extreme climate of the warmest and coldest months. And before needing the introduction of heat or cold, it is necessary to prevent unwanted climates from seeping in.

Older houses and constructions suffer the most, so in search of true thermal comfort, it is a good idea to consider a complete renovation. Windows, doors, walls, and ceilings need to be more airtight, something that was not done a few decades ago when building buildings.

A complete renovation of a building or a room would greatly improve thermal comfort. However, it is not the only measure we can take.

To guarantee the best hygrothermal comfort, it is necessary to have a double-flow mechanical ventilation system. With it:

• Air is renewed, thus solving the problem of stagnant air.
• Thanks to the same system, it is possible to enjoy the same degree of temperature and humidity throughout the room. It’s not hot or cold near the air conditioning unit.
• It is possible to introduce cold air in summer and warm air in winter by directly extracting it from the outside. This is possible thanks to a heat pump, which tempers the incoming air. It works in both cold and warm months.
• It prevents the entry of pollutants and harmful particles, thanks to air filters. This ensures that we have higher quality air, making our comfort at home greater.
• It automatically eliminates excess humidity when necessary. We do not have to worry about anything since the system is capable of doing all this.

The thermal comfort at home depends on many factors, but above all, it must be kept in mind that it is a set of factors. Among them, the ventilation system and how the building has been constructed will significantly influence. We can also use humidifiers for drier climates or opt for ventilated roofs and facades that make our lives easier.

Certainly, we must avoid cases where traditional air conditioning systems are overly used, as that gives us heat or cold but does not guarantee any thermal comfort. Because the main thing is to protect against climatic adversities and have air renewal that will also help us with our health.