Roof insulation in a condominium: how it is done

Roof insulation is one of the most effective efficiency measures in a condominium, because the roof is the surface through which the building loses most of its heat upwards. Insulating the roof or the attic floor slab reduces heating consumption in winter, limits overheating of the top floors in summer and improves overall comfort. It is a measure that concerns a common part, the roof, listed among the common parts by Article 1117 of the Italian Civil Code, and as such it follows the condominium rules on resolution and allocation.

The most common insulation techniques

The choice of technique depends on the type of roof and on whether there is a walkable attic. The most used solutions are:

• Insulation at roof level, with panels laid above the roof structure during a re-roofing, the so-called ventilated roof or warm roof.
• Insulation of the non-habitable attic floor slab, cheaper, which insulates the walking surface of the top slab when the attic is a simple technical volume.
• Blown-in insulation into existing cavities, when the structure allows it.
• Insulation on the underside, applied below the pitch, when work from outside is not possible.

When re-roofing is needed anyway due to wear, taking the chance to insulate is the most rational choice, because the cost of scaffolding and laying is already partly borne.

How the works are resolved

Two situations must be distinguished. If insulation is part of a re-roofing made necessary by leaks or decay, it is extraordinary maintenance: the resolution follows the ordinary majorities for conservation works. If instead the insulation is conceived as an energy improvement of the envelope, it falls among the innovations aimed at containing energy consumption provided for by Article 1120, second paragraph, of the Italian Civil Code, with the reduced quorum of a majority of those attending representing at least half the value of the building.

The allocation of costs

The roof performs the function of covering for the benefit of the whole building: maintenance and re-roofing costs are split among all owners according to the thousandths (millesimi) of ownership, under the principle of Article 1123 of the Italian Civil Code. The criterion for exclusive-use flat roofs does not apply, because a pitched roof is by nature a common cover. An exception is where a portion of the roof serves only part of the building: in that case the cost falls on the owners who benefit from it, under the partial-service rule.

The benefit for the top floors and for everyone

Top-floor apartments are those most affected by heat loss through the roof and by summer heat. It is understandable that they are the most interested in the works, but the benefit is not theirs alone: an insulated roof reduces the energy demand of the entire building, protects the structure from thermal shocks and enhances all the units. Presenting the works as a collective advantage, and not as a favour to the top floors, helps build consensus at the meeting.

Coordinating the works with the audit and incentives

Roof insulation gives its best when it is part of a coherent efficiency plan, perhaps downstream of an energy audit that quantifies its savings. Combined with other envelope measures it can contribute to the jump in energy class required by some incentives. Before resolving, it is best to collect several comparative quotes and check the documentation needed for the building bonuses in force.

Managing quotes, resolutions, splits and deadlines of a roofing project is easier with management software such as AmministraPro, which keeps technical documents, dedicated accounting and owner communications together. The features are described on the /funzioni page and the plans with their costs on the /prezzi page.