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Passive solar energy: everything you need to know

Passive solar energy is still a great unknown for the population. We tell you everything you need to know about this type of energy and the differences that exist with active energy.

The average energy consumption of households has increased by 28% after the confinement suffered during the Covid-19 pandemic. We spend more time at home and energy consumption has skyrocketed in many homes where teleworking has been established to stay. Currently, we have the possibility of opting for renewable energies , which help us move towards a more ecological energy transition such as solar energy or other sources of non-polluting origin, helping us to achieve energy and economic savings on our electricity bill.

Passive solar energy: everything you need to know

When we refer to solar energy, we must consider the existence of two operating models: passive and active energy . Normally, we are not capable of differentiating these two terms and passive solar energy is still a great unknown for which the benefits it can bring to the home’s electricity consumption are not known.

The increase in caring for the environment and the fight against climate change in recent years has been quite remarkable. This impact has set off alarms in the Spanish Government and the European Union, where measures are being taken to promote renewable and clean sources, leaving behind fossil fuels, such as coal or oil.

The European Union in its plan for the recovery of Europe has already established actions to improve the energy efficiency of buildings, where newly built homes must be built in such a way that energy efficiency is high, producing practically all of the energy that will be consumed. These types of buildings are known by the nomenclature nZEB , that is, nearly zero energy buildings .

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Spain has also established measures in line with Europe. In the Basic Document on Energy Savings, a regulation belonging to the Technical Building Code, actions have been taken that will reduce the energy consumption of current buildings by 40% .

The new measures that have been taken by the institutions regarding the construction of houses are linked to passive solar energy and in the following article we will see why.

For this reason, we show you below what passive solar energy is, its components , benefits, how to take advantage of it and application examples for your home.

Passive solar energy definition

Passive solar energy directly harnesses direct energy from the sun without transforming it . Therefore, they do not require any electrical device to carry out the transformation from one current to another and, where appropriate, for the accumulation of energy, as is the case with active energy.

How does this type of energy work?

The elements that make up the construction of passive buildings, that is, the walls and windows, are created in such a way that they take advantage of direct sunlight. These types of buildings are designed to fulfill two functions. One of them consists of capturing, storing and distributing the energy from the sun as heat during the winter season. The other function is to reject the heat that comes from the sun in summer. In this way, it will be possible to optimize all the possible heat of the house.

If we want to make the most of the opportunities offered by passive solar energy, we must take into account factors such as the climate of the region because the temperature and solar radiation will be very influential when it comes to producing this type of energy . And not only can it be applied to new buildings, it can also be adapted to existing constructions, although the cost incurred will be higher.

Basic considerations of a passive solar design


Before carrying out any construction where a passive solar design is developed , it is necessary to know a series of basic considerations that will help us understand the operation in a more exhaustive way. Below, we list and explain those components involved:

  • Location of windows and type of glazing
  • Thermal isolation
  • thermal mass
  • Shades


Location of windows and type of glazing

The location of the windows in a house that uses passive solar energy is a very important aspect, as it happens in the same way in the orientation and inclination of solar panels where this factor plays an important role.

How do you generate your own energy through the windows? Sunlight enters through the windows thanks to the glass that allows to capture solar radiation, keeping the interior of the house warm. But, also, we must take into account the dimensions of the windows, installing the appropriate size and orienting them towards the south to equalize heat gains and losses without overheating, since they can obtain unwanted heat in summer and generate significant heat losses. in winter. It is important to consider that during the winter season less heat is generated, approximately 5 hours. This balance of profit and loss can be sustained as long as the orientation of the windows is appropriate and the perfect glazing has been chosen for its maintenance.

Normally, the windows should be oriented to the south with an inclination of approximately 30º. If we locate the large windows to the south, we will obtain more solar energy for the interior of the house. However, north-facing homes must have smaller windows since they are not capable of absorbing the same amount of solar energy as south-facing windows.

The type of glazing is an equally important factor as the location of windows. We must avoid excessive glazing because it could lead to a loss of energy, due to the small heating loads that originate in new homes.
Thanks to the technological development of windows, the insulation properties that allow heat to be maintained in those areas of the house where it is necessary have been improved, avoiding unnecessary energy losses.

Thermal isolation

Thermal insulation is an essential factor in passive solar design buildings . It intervenes as an obstacle to the flow of heat, that is, it keeps the house warm , reducing heat loss in winter and reducing heat in summer so that our home maintains a cool and comfortable climate, thus withstanding the high temperatures reached in this season. of the year. Said insulation must be carried out in all the components of the construction, both in windows and walls and even ceilings.

If we select poor thermal insulation , heat loss in the home could reach 25%-30% in winter , thus wasting the energy we have generated.

Therefore, the better the insulation, the warmer our home will be. In more extreme climates, superior insulation should be made and in good condition to prevent unnecessary heat leakage.

In order to avoid this heat loss, it is convenient for most of the insulation to be concentrated on the roof because it is the space where greater temperature control is required.

thermal mass

Thermal mass refers to the heat that is absorbed through walls, ceilings or floors built with elements that have the capacity to absorb solar energy in large proportions, such as tiles, in such a way that the energy is stored in order to be used for home use . On the contrary, to make the house cooler in summer, this heat gain is reduced through installed projections or by using the blinds.

A good external ventilation installed on the roofs of the house will also allow the heat to dissipate inside, without concentrating in a specific area since the surface of the roof, being the most exposed to the sun, receives more solar radiation than the rest. of construction elements.

To absorb a greater amount of energy, we can use materials such as brick, concrete or stone in constructions that will allow greater efficiency than other types of components. On the contrary, if we build buildings with less robust or light materials such as wood, the thermal mass will be reduced and the amount of energy generated will also be reduced. Have you ever felt the heat given off when leaning on stones in the middle of nature? Well, the operation is similar to that carried out in a passive solar house because they capture all the possible energy and progressively release the heat that has been previously stored. The heat that is stored throughout the day is gradually distributedthroughout the interior of the house to achieve a pleasant and comfortable temperature throughout the night.

We can say that the great advantage of thermal mass lies in its ability to maintain the right temperature , regardless of the season of the year in which we find ourselves. Its proper use will help us get the most out of the passive solar system, turning our home into a more comfortable space and significantly reducing energy costs. Instead, a misuse of thermal mass could cause problems in more extreme climates, reducing our comfort and energy efficiency.



The shadow factor is also a component that greatly influences passive solar energy. The shadows generated by the vegetation of the geographical area affect the solar radiation received, reducing the sunlight perceived in summer, being beneficial for the home. On the other hand, when we approach the winter seasons, the shadows will have a positive effect so that overheating does not occur.

The orientation of the house is a very important point to take into account so that the shadows that affect the building work correctly to perceive the correct passive solar energy and do not cause excesses that reduce efficiency. Window glazing should face south to avoid loads and overheating in winter.

Sun losses can become significant if the windows are continuously shaded without the possibility of recovering that energy again. How can we avoid this problem? We will only have to maintain a distance between the cornice and the upper part of the glazing of 50% or, if possible, 30% with respect to the height of the window.

Differences between active and passive solar energy


Solar energy has two ways of being used, through active energy, which is the best known since photovoltaic and thermal energy are included at this point, and through passive solar energy .

There are several differences between the two technologies, but the most important and characteristic is that active energy consists of a transformation of energy , converting the direct current generated by solar energy into alternating current available for use in all electrical appliances in our home. However, passive solar energy allows you to directly enjoy the energy produced by the sun without having entered into any process of energy transformation. And this, what is due? Thanks to the elements incorporated in the structure of the building, the energy of sunlight can be used more efficiently.

Once the main difference between both types of applications has been made clear, we are going to list and detail the rest of the differences between active and passive solar energy :

  • Active solar energy requires an electrical device that transforms direct current into alternating current and thus be able to take advantage of the solar energy generated by the solar panels. On the other hand, passive energy does not need additional equipment to perform this transformation.
  • To establish passive solar energy, a special design is necessary in the building, however, this is not necessary when we refer to active energy.
  • The perceived solar radiation is captured through the different elements that make up the structure of the house, such as the walls, ceilings or windows. Instead, active energy absorbs solar energy through the system’s solar panels.

Of course, both are classified as 100% renewable energies that help reduce pollution, taking care of the environment and avoiding sources of polluting origin that destroy the planet.

Use of passive solar energy in housing


A good passive solar design of a house allows to take advantage of the energy for different functions in the house . It is mainly used for lighting as well as for the production of hot water and heating. Thanks to the properties of the building, we will not need electrical devices to instantly enjoy the energy generated by the sun.

The materials belonging to the construction present distinctive characteristics that will achieve a uniform heat throughout the year, adapting to each season of the year. However, in areas where winter temperatures can be more extreme, passive energy will act in a complementary way to active energy to produce all the energy necessary to cover our consumption needs.

The use of passive solar energy allows:

  • Reduction of spending on bills
  • Get the best comfort adapted to our needs
  • Maintain the ideal temperature at all times, gradually distributing the heat throughout the house and taking advantage of the energy efficiency that this type of structure allows.
  • Reduce dependence on external electrical energy and take greater advantage of natural light

In order to enjoy or make the most of passive solar energy, it is necessary that the newly created houses contain the necessary elements to get the most out of it. This technology can also be used for existing homes, but it will be necessary to carry out a reform to incorporate the corresponding materials for its use, such as windows or walls. Also, the rest of the factors that we have explained above must be taken into account, such as the location of windows, the type of glazing or thermal insulation.

In conclusion, we have seen that passive energy can be used both for heating and cooling the interior of the house , as well as for lighting, which will lead to greater energy and economic savings.

Examples of use of passive solar energy


Passive solar energy has numerous applications for the home and, like active energy, they are inexhaustible and clean sources that we must take advantage of as much as possible and that bring us benefits in many aspects.

Below, we have prepared a list of examples of how to use passive solar energy in your home:

  • Heating by radiators or underfloor heating
  • Hot water production
  • Electrical energy for domestic consumption: any type of electronic device
  • Cooling devices such as air conditioning
  • Hot water for swimming pools
  • Lightning

Benefits of passive solar energy

A material designed to produce passive solar energy can achieve energy savings of 70%. In addition to this great advantage, we show you the main benefits that passive solar energy can bring us :

  • Reduced maintenance cost . Since there is no external equipment to harness the energy, the maintenance required will be practically zero.
  • It is a 100% renewable energy . It does not emit polluting gases and helps maintain the environment, in addition to being an inexhaustible source that is the sun and we can always have it.
  • Energy and economic savings .
  • Reduction in the cost of electricity and gas bills.
  • Compatible with solar panel installations . In fact, currently, it is considered as a complementary technology.

Currently, passive solar energy is constantly being developed to improve its technology and offer its maximum potential for consumption in our homes. It is a technology that coexists with active solar energy and is increasingly being implemented in buildings and offices.

It is true that it requires a significant initial investment due to the incorporation of certain components in the building, but the amortization period will be reduced compared to what it can provide us, achieving significant energy and economic savings. In addition, the maintenance cost is reduced since all the elements are in the structure of the house itself and it does not require external equipment for its operation.

The use of passive solar energy will improve energy efficiency and achieve greater economic savings, always respecting the environment. That said, there will be many homes whose adaptation to passive energy, due to location or characteristics, is complicated, for them the option of photovoltaic panels is a magnificent option to continue taking advantage of the potential of the sun to operate your home. At Otovo, we can help you study the best facilities for your home.

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