External insulation in masonry of historic buildings

External thermal insulation for historic buildings

In a previous article, related to the realization of coats thermal insulation for buildings, I highlighted the difference from the operational point of view of this intervention, in relation to the type of building, with particular reference toepoch of construction of the property subject to intervention.

This difference becomes relevant in the presence of buildings falling in particular areas and therefore subject to specifications protection rules, architectural and environmental, often controversial and not easy to apply.

To do some clarity the Ministry of Culture provided for the matter with circular letter 4/2021, in which the answers to all the questions posed by the various Italian regions, regarding the executive methods of such interventions.

In the circular in question, it is specified that for energy efficiency interventions, for which the installation of the thermal coat, landscape authorization must be requested.

Thermal insulation and contrasting regulations

At a regulatory level, this requested authorization refers to Presidential Decree 31/2017, in which the interventions subject to landscape authorization are those carried out in the interest landscape, identified by art. 142 of Legislative Decree 42/2004, paragraph 1.

This request has greatly worried the operators in the sector, considering the timing of the landscape authorization process, which is completed on average in no less than 4 months.

Replacement window frames in historic building
Doubts about the need for this authorization, in order to carry out interventions minor importance as the simple maintenance of the facades or the replacement of fixtures, prompted the various municipal administrations to ask for clarification on the matter.

The doubts also arise from the consideration that the provisions do not differentiate much from those already present before the approval of Presidential Decree 31/2017, for the works that provided for ordinary and extraordinary maintenance, static consolidation and conservative restoration, without alter the state of the places and the external appearance of the buildings.

Simplified thermal insulation and environmental protection

In light of this general situation, Mibac deemed it necessary to provide some clarifications on the application criteria of Presidential Decree 31/2017, by doing distinction among the interventions of minor excluded from landscape authorization and those subject to a simpler type of authorization e rapid precisely defined simplified procedure.

Buildings included in protected areas for which landscape authorization is required
Consequently, it was specified that the most important interventions, such as those described in Annex A of Presidential Decree 31/2017, concerning in particular buildings, included in points A1 and A6, it is necessary to request the landscape authorization.

In summary, these interventions mainly include those on historical buildings.
Precisely, the internal works that do not alter the external appearance of the buildings, interventions on the fa├žades or on the roofs of the buildings, as long as they are carried out in compliance with any color plans in force in the Municipality.

For these interventions the respect of the architectural, morpho-typological characteristics, of the existing materials and finishes, even in the case of interventions that have the purpose of static consolidation.

External insulation and problems of volume

Among the interventions of static nature works that are necessary for improvement or adaptation for the purposes are included anti-seismic.
This as long as do not involve changes the morpho-typological characteristics, the finishing or cladding materials or the volume and height of the building.

And speaking of the volume of the building, being able to create a thermal coat without modifying it it raises not a few doubts.

Thermal cladding with an increase in the existing volume
The answer to these doubts is given in Annex B of the same Presidential Decree, which lists the interventions that can be carried out with the simplified authorization, including those that involve increases volumetric not more than 10%, carried out in compliance with the architectural, morpho-typological characteristics, materials and existing finishes.

This last aspect concerns precisely the realization of thermal coats.

In these circumstances, the Ministry clarified how the obligation to obtain landscape authorization depends on the nature of the bond landscaped, from relevance landscape and historical-architectural and historical-testimonial interest present in the area where the building on which you want to intervene falls.

Thermal insulation and intervention complexity

It is clear to those who know the techniques of applying thermal coats, how much it is complex, if not impossible, to create in some cases a thermal coat that guarantees at the same time containment of energy consumption and compliance with the aforementioned regulations.

Another fundamental aspect that needed to be clarified lies in the identification of types of buildings on which it is possible to intervene to create a thermal coat insulation, without altering its architectural appearance, given that the national building heritage is quite vast and differentiated.

Thermal insulation: pay attention to the time of construction

A clarification to this effect is given in the conclusion of the aforementioned Ministerial circular, which indicates the areas enclosed in historical centers and in areas subject to restrictions, as long as they are considered to be of public interest by the Code of Cultural Heritage and Landscape (Legislative Decree 42/2004).

In these areas theauthorization landscaping is always required, for interventions of isolation a coat on the historic buildings built before 1945.

Differentiate interventions within landscaped areas, by virtue of the time of construction of the individual building
The introduction of landscape authorization simplified by the Ministry, though reducing 20 days, the approval process of the Superintendencies, compared to the 105 days provided for by the normal landscape authorization, still represents a aggravation of procedures foreseen by the interventions of energy improvement provided for by the Budget decree.

The only ones possible interventions of energy efficiency exempt from this authorization are those relating to contemporary building buildings after 1945, provided that they do not alter the external appearance of the building, including in terms of finishes.

As can be seen, even in the latter case, the required condition does not seem to want to help resolve the perplexities of those who have to intervene.

Thermal insulation by dividing the interventions

It therefore appears clear how to carry out a complete energy efficiency work, through the sole construction of a outer coat, it becomes a difficult undertaking.
For this reason, in many cases it will be necessary to implement one serie of interventions that as a whole reduce heat losses, even without completely covering the entire building.

Thermal insulation roof covering performed inside
To proceed in this sense, it is necessary to use new generation insulating materials, characterized by reduced thicknesses, together with interventions by internal insulation to be practiced on those surfaces, devoid of particular friezes and decorations.

The isolation of the coverage, for which fewer operational difficulties are encountered, this facilitation derives from the possibility of being able to intervene inside attics habitable and not, through different insulation techniques.

The insulation of these roofs is also possible from theexternal, but in this case it is necessary to pay close attention to the respect of the ministerial norms mentioned.

Thermal coats the importance of ancillary works

The replacement of the fixtures external represents for these buildings another useful intervention to reduce energy consumption, given their larger size than those of the new generation, provided that their pose is done correctly.

The mistakes Frequently encountered in the installation of fixtures include the use of controtelai metal, or in any case for arranging the compartments incorrectly

Remember that if the subframe must be replaced for technical reasons, it is good practice to use materials that are not conductive, such as iron and aluminum.

External fixtures of historic buildings equipped with large mirrored fixtures to be replaced
Where possible, it is useful to use a subframe insulating able to to interrupt the continuity of the window sill, in order to avoid dispersions by establishing a thermal bridge.

Finally, it is necessary to pose with scruple the insulating coating, in such a way that it folds up into the side shoulders, until it joins the insulating subframe previously laid.

External insulation: the importance of correct installation

Regarding the correct installation of the thermal insulation system, I recall what has already been illustrated in a previous article, relative to the need for do not use different materials from a thermal point of view, in finishing the side cladding of the fixtures, in order not to alter the thermal behavior insulation, with consequent thermal dispersions.

Insulating material to insulate internal surfaces
The realization of a partial insulation, is foreseen by the rules that regulate the recent tax concessions in terms of energy saving.

They provide that the realization of a partial isolation can take advantage of the facilities provided.

In fact, all interventions concerning sloping, vertical and horizontal opaque surfaces (delimiting the heated volume, towards the outside, the unheated rooms or the ground, including the roof) that affect the building envelope, fall within these facilities. with an incidence higher in fact, 25% of the gross dispersing surface of the building are among the subsidized ones.

Source: LAVORINCASA.it by www.lavorincasa.it.

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