Cork and innovation
The isolation with cork is particularly effective because it reduces the input power requirements and increases the thermal comfort and humidity of the building.
It is not a coincidence that this system is used to solve problems related to poor thermal insulation of existing buildings and often also as complete solution for the construction of new homes. However, the problem of thermal insulation yet it is seen almost exclusively to protect from the cold and savings on winter heating costs.
We do not worry enough about, ensuring a good performance of the building during summer, when the cost of cooling of our houses are equal or perhaps more than the central heating. It is also neglected the acoustic protection, a correct humidity balance in all seasons and a long durability. To underestimate these aspects leads to the use of cheap materials, but with obvious poor performance resulting in little benefit.
In this regard, it should be remembered that in terms of cost of a high quality insulating material and cost of installation such as labour, scaffolding and finishes are the same. It is not the same the final outcome, in terms of hygrothermal welfare and durability. The comparison between a synthetic product like polystyrene, mineral fibre (rock or glass) and the blond natural cork boiled and ventilated by Coverd to carry out an insulate coat systems regarding thermal performance, the differences are minimal.
According to the data declared by the producers of the average thermal conductivity λ of the polystyrene panels is approximately 0035 W / m ° K, mineral fibre is about 0040 W / m ° K, while the panels by cork is 0042 W / m ° K. The result is, in equal thermal insulation of the wall, if required, to increase slightly the thickness of the thermal coat made with cork panels. This can be a small initial advantage for the polystyrene and mineral wool.
This is totally a different issue, going to examine a number of other aspects. The first is the U thermal transmittance.
When you look for a thermal insulation for a structure (wall) we inevitably evaluate this parameter, that represents only the heat flow in a steady state, a situation that at our latitude never happen, it is obvious the delta thermal between day and night. What's happening in real conditions is that the external temperature varies during the day, more pronounced in the summer than in winter. There is another action that may be more or less significant, but not entirely negligible, due to the thermal radiation. The above mentioned, introduces the concept of thermal inertia, which we will not explain now, and the two topics related to it:
"Damping" and "thermal lag".
- 1 The thermal damping of a structure is the reduction of temperature that we detected on the outer surface despite the temperature of the inner surface calculated on a daily average.
- 2 thermal lag delay of a structure is the time that takes the heat from outside to inside measured in ° C.
In both cases, the more the value is high and higher is the insulation and consequently gives comfort inside the house. It is obvious for example that if the maximum external peak heat (15 hours) will be felt inside when the temperature ambient will drop to more moderate values (23 hours), it will be more tolerate, simply open the windows. The same goes for the minimum winter night’s temperature.
The cork panels have both thermal damping and thermal lag delay, significantly higher than polystyrene panels and mineral fibre (see table), which makes them a superior insulation performance despite the value of thermal transmittance U.
It is important when designing or assessing the choice of an “insulation system “entrust these tasks to protect the building from heat and humidity by using insulating material, having high damping and thermal lag performances and not to be added to the wall brick or concrete of the building facade.
An aspect not to be neglect is the breathability of the insulating coat, on which depends the comfort of the homes. In this way, the synthetic products such as polystyrene, act as a vapour barrier (0.94 E-12 kg / sm Pa), which leads to an ineffective transpiration and risk of forming condensation between the panel and bricks.
For their physical features, the mineral fibre panels (150E-12 kg / Pa sm) requires a vapour barrier on the warm side of the thermal insulation; in the case of its absence, is often subject to the formation of interstitial condensation while on the cold side of the plastering which normally has a lower permeability to the insulation (from 6E to 18E-12 kg / Pa sm), holding up the disposal of water vapour. The insulation coat made with the cork panels gives higher breathability (17.5 E-12 kg / Pa sm) protecting from possible condensation and creating a healthy home temperature.
Regarding the durability over the years, it is known that synthetic products tend to deteriorate because of temperature changes, which cause the aging of the material and the reduction of mechanical and insulation panels as described in UNI 10351. cork panels are thermally stable and their chemical and physical characteristics remain intact in a range of temperatures from -50 ° C to + 250 ° C and therefore they have an unlimited duration.
As regard the mechanical strength, a simple tangible and visual examination, shows that the synthetic fibre panel and mineral they plastically deformed if they are compressed (the synthetic panel deforms in a stable manner), while the cork panel remain intact. Thanks to its high density. This difference is substantial in the case of accidental impacts which may cause from human activities, but also by bad weather conditions such as hail stone. The method of installation of the synthetic and mineral fibre panels provided by major manufacturers says that you must use cement in small quantity on the four corners and in the centre of the panel (embosses panel fix) completed with knobs. This creates a very little space between the panel and the surface creating the formation of condensation.
