1) S I CAN INCREASE ENERGY CLASS OF AN OLD HOUSE?
Even old buildings can achieve a significant improvement in energy performance, and if you consider that in buildings built up to 1990 thermal insulation is almost non-existent, you can guess why today most houses are in class G, or at most, F, with great margins for performance growth. The extent of the improvement of the energy class depends on the type of restructuring/requalification works that are carried out. On the Energy Performance Certificate, the certifier lists some of the possible (even if not immediately mandatory) interventions to improve energy efficiency: for example, insulation, an adaptation of systems and use of solar thermal energy.
2) C OME REACHING ENERGY CLASS “A”
To reach class A starting from a low class (eg G or F), it is not enough to improve the thermal insulation a little or to intervene slightly on the heating system, but it is necessary to intervene heavily on several fronts. In practice, at least two of the following interventions must be carried out: (a) external insulation, eliminating thermal bridges, replacing the panes with triple panes; (2) replace the heating system with one with a heat pump and with floor panels, or in any case at low temperature; (3) to produce energy from renewable sources. Of course, a professional will be able to indicate the most suitable interventions in your specific case and perform the calculations to verify that the proposed solution allows you to reach the desired energy class. At that point, taking into account the cost of materials and labour, it will be possible to know the extent of the expenditure and assess whether or not to carry out the restructuring/requalification interventions.
3) G THE IMPROVEMENT INTERVENTIONS ON THE BUILDING ENVELOPE
One of the best ways to increase the energy class of a building is to intervene in the building envelope, which separates the external from the internal part of the building itself. The older buildings mainly used materials with high thermal transmittance, i.e. poor thermal insulation. These materials can then be replaced – or better integrated – using insulating materials of suitable thickness, for example, blown into the cavity or applied as internal or external coats. The latter represents the best solution, when practicable, given the enveloping character of the insulation that is thus obtained. Moreover, the replacement of single glazing with double or triple glazing with very low thermal transmittance falls within this category of interventions, since windows usually represent one of the weak points of the thermal insulation of a building. The performance of the enclosure is defined by a class, which ranges from I (the best) to V (the worst).
4) G INTERVENTIONS ON HOUSE SYSTEMS
The systems connected to the energy efficiency of a house are those of heating, domestic hot water and cooling. An old boiler in bad condition could be replaced with a modern high-efficiency model (e.g. condensing gas or, better, biomass) or with a heat pump. A low-temperature heating system, e.g. with radiant panels, allows further energy savings, even if it is a major renovation. For domestic hot water, and instantaneous condensing boiler or the same heat pump or a biomass boiler with storage tank can be used. Remember that the energy classes can be different depending on the performance they attest winter, summer air conditioning, production of domestic hot water. If your consumption indicates a very unfavourable energy class, you should take action as soon as possible to save money.
5) L AND CLASS ENERGY PROVIDED: FROM “G” AD TIL “A +” The energy classes depart from the G (lower energy efficiency) until arriving at A and A + (better energy efficiency). The class is then associated with a value, expressed in kWh / m2 per year, which represents the energy required each year for the winter heating of the real estate unit in question. For example, a 100 sq m class C apartment with an energy performance index of 75 kWh / sq m requires a heat requirement of 100 x 75 = 7,500 kWh per year. A building is therefore classified according to the possible reference energy classes (A +, A, B, C, D, E, F,
primary energy for winter heating, expressed in kWh / year per square meter of useful area, or kWh / year per cubic meter of volume. The value of a class A or B certified building (practically only new houses) is on average higher than 20-25% (and higher for small-sized properties) than the average for properties in class E and F.