Solar greenhouse: what does the legislation say?

What does the legislation say about the design and installation of a solar greenhouse? In the previous article we explained how these structures can improve the energy efficiency of a property. Let's take a look at the main types of bioclimatic greenhouses and the permits required for their installation in our domestic spaces.

Main types of solar greenhouses

There are mainly three types of solar greenhouses that can be designed and built:

• Direct gain bioclimatic greenhouses: there are no partition walls between the greenhouse and the interior spaces, so the heat is released directly into the building;
• Bioclimatic greenhouses with collective exchange: there is a partition between the greenhouse and the interior spaces. In this case, the heat is transmitted into the building by means of air ducts installed at the top and bottom of the wall;
• Bioclimatic greenhouses with radiant heat exchange: Here, too, there is a partition wall between the greenhouse and the interior spaces, but this acts as a heat accumulator. The wall itself releases heat into the interior.

Difference between solar greenhouse and pergola

From an aesthetic point of view, the solar greenhouse is very similar to the bioclimatic pergola or veranda. The pergola is also built close to a building. However, the solar greenhouse has a distinctive feature: the structure is built to produce and store solar energy, which can then be used to heat the interior. It is therefore an environmentally sustainable solution, which is why it is classified as a green building project, since it is designed to have an impact on energy saving.

Do I need a permit to build a solar greenhouse?

From a technical point of view, the solar greenhouse is considered a "technical volume": even if it does not change the volume of the building, it is not a habitable structure, but an installation that simply contributes to the energy efficiency of a building. If you build a solar greenhouse in the right way, you can access the Ecobonus - Bonus ristrutturazioni - with incentives equal to 50% for building renovation works.

As far as permits are concerned, we can generally say that since it is considered a technical volume, the solar greenhouse is not subject to the request for special permits. Unfortunately, it must be pointed out that national legislation is very diverse, as regions and municipalities deal with and regulate the matter in different ways. For this reason, irrespective of your region or municipality of residence, it is always better to rely on specialised technicians who will have the necessary expertise to deal with the bureaucratic process.

In any case, there are common national requirements for the construction of a solar greenhouse:

• As a technical volume, the solar greenhouse cannot be a permanent living space - it cannot therefore become a room in the building;
• The exposure of a solar greenhouse must always be between south-east and south-west;
• The glass surface of the structure must represent the prevailing percentage (required percentage numbers differ from region to region);
• The total volume of the greenhouse must not exceed 15% of the building on which it is built;
• The total volume of the greenhouse must not exceed 15% of the building to which it is attached; The screens must be mobile, to avoid overheating during the summer season and to ensure proper ventilation throughout the year;
• The structure must guarantee an energy gain of at least 20%;
• The structure must guarantee a reduction in energy consumption of at least 10%;
• The solar greenhouse must not benefit from the air conditioning system of the building to which it is attached.