Passive solar house design

A passive solar house is a type of eco-friendly home that functions by capturing heat from the sun passively.

In this sense, solar energy is the key factor in achieving a home that functions autonomously. With current knowledge and techniques, it is possible to build a well-oriented, well-insulated house with enough passive elements to operate almost entirely on solar energy; this is the challenge we set for ourselves with every new project at Slow Studio.

1 Orientation

Firstly, something that seems obvious but is not always easy to achieve, especially if we do not have a suitable location.

When looking for land for our home, it is very important to consider the possibility of opening south-facing windows.

This implies, first of all, that the plot is located in a sunny area; if we are in a mountainous region, it is crucial to look for a south-facing slope so the mountain itself does not cast a shadow. If we encounter sloping terrain, it is important to check that the gradient faces south, and if we find land with neighboring houses or dense vegetation, it will be essential to ensure that these do not block the sun’s rays, especially in winter.

2 Windows

Once we have the right plot, it is time to design based on the primary criterion of maintaining large south-facing windows.

However, we must not forget that in our climate, solar protection is just as important as solar gain.

Thus, our home should have a good window, but also opaque protection or, even better, adjustable louvers that allow us to control the solar input during each season of the year.

3 Insulation

We will never tire of emphasizing the importance of insulation in an eco-friendly home. There is no point in gaining solar heat if we cannot store it inside. In a passive solar house, insulation is just as important as the airtightness of the walls, which is simply the absence of leaks.

In this regard, we always like to use the example of the teapot and the thermos. A thermos manages to keep the coffee hot inside because it is very well insulated and has a lid that seals hermetically. A teapot can store hot tea or coffee, but only for a few minutes, as it releases heat through all its walls.

This is why teapots need handles and thermoses do not. Thermoses do not burn us when we hold them because they do not allow the internal heat to escape.

Thus, our house must be a “thermos house,” which, once it has gained solar heat, keeps it inside so that no additional heating is required.

4 Thermal inertia

Just as important as insulation is thermal inertia.

Thermal inertia is the ability of materials to store energy, which is due to their mass. It is always advisable to have an element with high thermal inertia in our home, whether it is a wall or a floor, as this element will be responsible for storing heat and, together with the insulation, turning our house into a passive solar home.

This is important if our house is made of wood; although it is the quintessential ecological material as well as a good insulator, wood lacks thermal inertia. Therefore, if we are going to build a passive wooden house, we will need to incorporate an element such as a concrete floor or an interior stone wall capable of storing heat for hours.

5 Proper room distribution

Finally, we would like to mention the correct distribution of rooms. Whether in a passive solar house or not, we must consider our family’s lifestyle in relation to the sun.

In general, we place daytime spaces such as living areas or the kitchen with a south and south-west orientation to take advantage of the sun’s heat during the day and afternoon.

In the case of bedrooms and nighttime areas, these can be located in the east zone, where they will receive the first rays of the morning sun.

Service areas such as the laundry room, pantry, storage room, or garage are intended to buffer the cold from the north facade.