When designing green spaces and outdoor spaces for a home, bioclimatic greenhouses are increasingly becoming popular. What are these architectural structures? What are their advantages?
Before delving into the benefits, prices, regulations, and tax deductions associated with this architectural element, it’s important to define a bioclimatic greenhouse.
The bioclimatic greenhouse: definition and difference from the veranda
A bioclimatic greenhouse is an enclosed outdoor space within a home, separated from the outside by glass walls that help increase the amount of solar radiation converted into thermal energy and stored within the greenhouse for the benefit of the building itself. The bioclimatic greenhouse roof itself can be made entirely of glass or opaque, depending on the orientation, latitude, and specific thermal needs.
A bioclimatic greenhouse differs from a common greenhouse, also called a veranda, not only in the regulations governing its construction, but primarily in the type of materials and glass used. Common greenhouses use standard sliding or folding glass, while bioclimatic greenhouses use low-emissivity glass to capture solar heat and gradually warm the space.
The bioclimatic greenhouse: types and design
There are different types of bioclimatic greenhouses: built-in, semi-built-in, and attached. The difference in how they are attached to the main building also determines the way heat is transmitted.
The built-in, or direct-gain, greenhouse does not provide a clear separation between the building and the greenhouse itself. The only acceptable separation is the insertion of movable and adjustable transparent walls. A key element for this type of greenhouse is the floor, which becomes the only heat storage element.
The semi-built-in, or convective exchange, greenhouse provides an opaque separation between the building and the greenhouse. In this case, the separating wall is not completely opaque, but there are slits at the top and bottom, adjustable by special windows that allow heat exchange by convection between the interior of the building and the interior of the greenhouse.
The attached, or radial exchange, greenhouse provides a clear separation between the two parts, the building and the greenhouse. The separating wall is completely opaque, allowing heat exchange by radiation. In this type of greenhouse, the fundamental element is the wall, which accumulates heat and releases it to the internal environment when it begins to cool down.
Designing the bioclimatic greenhouse
The first element to consider when designing a bioclimatic greenhouse is its orientation: it must face south, with a maximum tolerance of 30/40 degrees. West- and east-facing orientations should be strictly avoided, as they cause overheating that is difficult to manage and eliminate. Positioning a greenhouse facing north does not pose any overheating problems, but in the winter months, it could significantly reduce solar radiation.
Once the greenhouse’s orientation has been established, it is crucial to choose the materials, not only low-emissivity glass, but also a suitable flooring. This should not be underestimated, as it becomes an integral part of the structure and plays a key role in energy performance. Therefore, it is best to choose flooring whose surface can absorb heat and release it gradually throughout the day.
Regarding the glass walls, they should constitute approximately 70% of the greenhouse’s total surface area and must be highly insulating and high-performance. Aluminum is preferable to PVC for window and door frames, as it offers greater durability and resistance to weather, air, and sunlight.
Another factor to consider when designing a bioclimatic greenhouse is the external shading systems, which can be oriented and adjusted as needed.
Bioclimatic greenhouses: what regulations should be considered?
The construction of a bioclimatic greenhouse follows different regulatory procedures depending on the municipality in which it is built. At the national level, the reference standard is UNI EC 15316:2018, which establishes the calculations required to assess the energy performance of buildings in order to receive incentives.
The regulation is quite detailed, but, nevertheless, begins with some basic characteristics common to all municipalities. To be considered as such, a bioclimatic greenhouse must have:
An exposure between the southeast and southwest corners;
Have a glazed surface area of at least 70% of the total;
Ensure a reduction in energy consumption of at least 10%.
Assuming that a bioclimatic greenhouse is considered a technical space, a sort of air chamber, designed to improve the heating and climate comfort of a home, its construction requires authorization from the municipality.
Depending on the municipality and the size of the greenhouse, certified permits, such as CILA or SCIA, may be required, or in other cases, a Building Permit may be required.
The appointed designer must first verify the feasibility of the project and any existing constraints on the building. He or she must then certify the actual energy savings through an appropriate energy report.
Bioclimatic greenhouses: tax incentives and renovation bonuses
The construction and installation of a bioclimatic greenhouse is tax-advantaged thanks to the Renovation Bonus or Home Bonus. This bonus provides a 50% tax credit for the purchase and construction of the bioclimatic greenhouse, with a maximum expenditure limit of €96,000, in the form of an IRPEF tax deduction to be spread over 10 years.
This tax relief was approved by the 2020 Budget Law, which establishes that the installation of a bioclimatic greenhouse must fall within one of the categories of deductible interventions (building renovation, extraordinary maintenance, ordinary maintenance, and conservative restoration).
To apply for this Renovation Bonus, a list of expenses incurred must be submitted to ENEA within 90 days of completion of the work. Once the expenses have been recorded on the portal, you will need to include the property’s cadastral data in your tax return, along with the following documents:
Permits and permits required for the work
ICI-IMU payment receipts
Cadastral registration application.
Contrary to popular belief, installing a bioclimatic greenhouse does not qualify for tax breaks for energy efficiency upgrades of buildings, as the Ecobonus applies only to the structural elements of the building envelope.
Bioclimatic greenhouses: why are they worth building, and what are their advantages?
It’s clear, therefore, that this architectural structure offers many advantages:
It’s a passive solar system, whether used as a living space or as an energy collector; it’s an excellent heat recovery system.
Energy savings: a bioclimatic greenhouse system can reduce heating and cooling costs.
It improves living comfort throughout the year.
It increases the property’s market value.
It isn’t subject to taxation, unlike verandas. In fact, it’s considered green building, which increases the building’s volume but doesn’t require a building permit.
For more information about building a bioclimatic greenhouse, it’s always best to consult with industry professionals. Inside Project offers its expertise to help you build the bioclimatic greenhouse best suited to your needs.