THERMOGRAPHY, THERMAL INSULATION AND MOLD
The survey thermographic is able to highlight problems due to cold zones of the inner wall surface, due to thermal bridges and / or insufficient insulation. Thermography is able to detect the surface temperature and then to verify the possibility of internal moisture condensation.
Thermography measures the surface temperature and so it is the ideal tool to analyze the problems of thermal insulation.
Please note that the D. Decree 311/06 provides that no one can form surface condensation on the element constructively at an internal temperature of 20 ° C with relative humidity of 65% (in the absence of a control system of the internal relative humidity.
E ‘can also perform the relief surface moisture.
The relief surface moisture is carried out by means of instrumentation dielectric professional, in confirmation of values of humidity of the masonry higher in these areas, with the extension of the problem – due to endothermic of the evaporation process.
You can also check on the outside of the poor thermal insulation and the lack of correction of thermal bridges, which cause mold problems in the home:
In the picture below you can see the detection of humidity on a wall in an area not affected by mold and in an area affected by the phenomenon:
Thermography is much more precise than an investigation carried out with a simple infrared thermometer, and is able to provide much more information.
The mold is formed at thermal bridges.
To assess whether the thermal bridge has been adequately correct, we make thermal analyzes of structural problems using the finite element software (emf) v Mold Simulator. 1.0.6. The tool allows you to calculate the condensation on the thermal bridges according to the UNI EN ISO 10211:2008 (thermal bridges in building construction – detailed calculation) as prescribed in the regulations UNI EN ISO 13788:2003 Note 3 of Section 5.3.
The UNI EN ISO 13788:2003 provides the design procedures of calculation for determining the surface temperature of the internal components and building elements to below which there is the likely growth of mold, as a function of the temperature and humidity inside the environment indoor air, determined in accordance with the use that has been planned for the building (offices, stores, homes, etc..). The external climatic conditions to be used for the calculation, defined by standard 10349, and employees are representative of the area where the building is located.
The surface condensation and mold growth, as well as the climatic conditions inside and outside, are governed by another fundamental parameter; the “thermal quality” of each element of the building envelope, represented by the factor of temperature on the inner surface fRSi. The higher this value is, the better the thermal insulation and thus the less, equal to the other aspects, the risk of condensation and mold.
This factor, in correspondence of thermal bridges, assumes lower values, and therefore the problem must be specifically evaluated in these points.
The standard defines:
• fRSi temperature factor in correspondence to the inner surface: the ratio of the difference between the temperature of the inner surface and the indoor air and the difference between the temperature of indoor air and outdoor air calculated with a surface resistance internal RSi;
• fRSi, min factor design temperature in correspondence to the inner surface: the temperature factor acceptable minimum in correspondence of the inner surface.
The value fRSi, min is the minimum acceptable value to avoid the formation of mold. In the two cases studied and simulated by the software turned out to be the worst month is January, corresponding to the request of the highest value of f RSi, min. Since the inner surfaces are found to have a surface temperature fRSi simulation lower than the value required by fRSi, min is justified the formation of mold in correspondence of thermal bridges.
Surface condensation can result in degradation of building materials sensitive to moisture.
To assess the risk of condensation surface, according to the UNI EN 13788 is necessary to calculate the relative humidity of the air, and then to calculate the acceptable moisture saturation density (or the pressure of the steam saturation on surface) on the basis of the relative humidity surface that is requested. From this value it determines the minimum temperature of the inner surface and then the “thermal quality” request from the casing construction (f RSi for a given internal temperature).
As prescribed in paragraph 5.3 of the UNI 13788, for verification of the goodness of thermal design in the absence of a system for monitoring the internal relative humidity, defined the type of environment and set at? = 0.8 is the value acceptable maximum relative humidity at the surface, for each month of the year performs the following tasks:
• define the outdoor air temperature according to UNI 10349;
• define the external moisture according to UNI 10349
• fix the internal temperature during the heating period at 20 ° C as by national legislation
• calculate the indoor relative humidity as specified in paragraph 4.2.4 of the rules
• the minimum acceptable surface temperature and the indoor and outdoor temperatures yields the factor f RSi, min
As mentioned above will be the worst month will correspond to the highest value of all f RSi, min have been calculated for each month, called the UNI EN 13788 with f RSi, max.
The building component must be designed so as to have a factor f RSi always greater than f RSi, max. The image below shows the simulation of a thermal bridge with finite element software: it is seen that there is formation of condensation and thus the thermal bridge is not correct.
The coupling of thermography with the design verification of condensation allows surveys to verify the proper insulation regardless of the directors’ report on L.10/91 on heat loss and the building’s energy, that alone does not ensures the absence of problems.