The southern wall undergoes the greatest changes in houses using passive systems to obtain thermal energy. All elements of the building structure located on the south side, are shaped in such a way, so that, in addition to traditional functions, they can obtain heat from solar radiation in a maximum way. So, the form of the southern wall is a function of the passive systems used in the building. Depending on which solution is chosen, it is most often an image of a combination of at least two systems, that have been used in the building.
In Polish climates, passive systems only support traditional heating, therefore, limiting their size due to the possibility of overheating of rooms is inappropriate. So, in the southern wall, these devices should occupy as large areas as possible.

For the average single-family house, meeting Polish surface standards (Ok. 220 m2 of total area), the total area of the rooms located in the southern part of the building, such as: living room, Dining room, workshop, bathroom, ranges from 60 into 80 m2. The area of window openings in the direct system will therefore be from 20 into 28 m2 or ok. 50% façade, which also coincides with the previous digit. Very rarely there is only this system of obtaining thermal energy from solar radiation.

Examples of southern walls with a direct profit system: a) house W. N.Milford— 42'N (UNITED STATES) with 1975 r., Arch. N. Lasar, b) house in Fayetteville Arkansas (UNITED STATES) with 1980 r., Arch. J. Lamoeth

Due to the danger of a great nuisance for residents, the shading method should be carefully developed.

In intermediate systems, the surface of the Trombe wall, or collectors of light type, also difficult to determine, strictly depends on the surface, what we want to heat and from the material, from which collector elements are made. For similar usable areas, as calculated above, size of typical (concrete) Trombe's walls will oscillate within the limits of 50 m2, if it is to heat the rooms in a significant way. Such a large area, implemented in the form of a uniform plane, will create a very monotonous southern façade. Designers compose it from several smaller planes or juxtapose it with elements of other systems.

Examples of southern facades in houses using indirect systems: a) dom w Princetown — N. Jersey (UNITED STATES) with 1975 r., Arch. D. Kelbauhg, b) house in Briancon (half. France) with 1975 r., Arch. Ch. Next to, c) house in Bebbington (In. Britain) with 1979 r.