how to insulate?
Most decisions about building insulation are taken without first getting a thermographic diagnosis of the types and distribution of defects. Typically, an investor instructs a contractor to insulate based on a single selection criterion: price, which usually means the thinnest layer of insulation.
Nobody (neither contractor nor investor) takes the trouble to consider the types of materials used, or the purpose of the rooms to be insulated, to get the best results.
The effectiveness of the insulation after installation is not verified, and the only criterion for acceptance is the appearance of the installation. In this case, the generally accepted stereotype is that if it looks good, then it was done well.
This carries two kinds of risks, which fundamentally influence the effectiveness of an investment:
the risk of faulty insulation solutions
the risk of low quality installation
It is not uncommon for these two risks to come together in a single investment with a terrible effect on its effectiveness.
Infrared photography is an invaluable tool for diagnosing the state of the building structure before insulation, and the quality of the installation of insulation. Detecting defects in the structure is the first step towards removing them, and it can be compared to a medical diagnosis. The diagnosis means little to the patient - the patient wants to be healed.
The same situation occurs in the case of infrared imaging depicting areas with increased heat loss, and removing the insulation material is not always the only cure.
Defects are not always the result of bad insulation, but can arise through a number of other factors, which ultimately result in large local energy losses.
Thermal imaging examinations show the exact locations which need particular attention.
In order to apply the appropriate solution, a number of factors should be taken into account:
the density of the cavities,
the materials used in building the structure,
the state of dampness within the cavities,
the purpose of the rooms,
the location of the building,
the location of the rooms in the building,
how the rooms will be used.
With this knowledge of the premises, the results of thermal imaging can be used with modern numerical analysis for any type of building to find the optimal solution and to indicate the type of insulation, its thickness and its density.
For a closer look at these issues, the analyses below are conducted with regard to the optimisation of insulation, depending on the use of the room.
In the example analyses there are two example barriers of the same construction, but differing in how they are used on the inside.
example A - barrier not shielded on the inside
example B - barrier shielded on the inside, e.g. covered by a wardrobe or other fittings
The analyses were carried out at the temperatures indicated in the figures and taking into account actual construction materials. The vertical barrier is made of fired bricks (whole and hollow), plaster cement outside and inside - limestone, concrete slab with polystyrene insulation, damp-proof course, concrete screed and wooden floor.
Fig. 1 - example A, presenting the temperature profile for an exterior barrier, not covered (no fittings) on the inside.
Fig. 2 - example B, presenting the temperature profile for the same barrier, but with fittings on the inside.
For both examples, the thermal camera will register a drop in temperature in the corner, but in example B the temperature difference will be much higher, which will be confirmed by calculations.
Figures 3 and 4 show energy loss in the barriers, whose temperature profiles were shown in figures 1 and 2. The measurement of loss in heat flux is written in W/m2. In the literature, it is marked with the letter q. Heat flux depends on the heat characteristics of the materials the barrier is made of, and the temperature difference (internal and external).
Comparing the heat flux values in Figures 3 and 4, you can see that the losses are greater in the upper part of the vertical barrier in example A, which seems counter-intuitive, if we jump to conclusions only on this basis.
As already mentioned, heat loss depends on the temperature difference, and in example B (Fig. 4), the inner surface of the wall is blocked, and has no contact with the air from which it could absorb heat, so the temperature is lower, leading to less loss because of the lower heat difference.
The reduced temperature in barrier B causes the water vapour in the room diffusing within the barrier (diffusion from within the room to the outside) to condense within it, significantly reducing the effectivity of the insulation in the barriers.
This leads to the condensation of water vapour closer to the inner surface and to the development of mould and mildew.
Because of this, there can often be a black infestation visible on the walls when higher fittings are removed.
In the case of relative humidity (water vapour in the air) inside the room of around 60% and relative humidity on the outside of about 85% (which is typical in winter), the temperature of condensation is about +12°C. Thus, water vapour condensates in every part of the partition where the temperature drops below this value, creating conditions for the development of mould and mildew.
Fig. 5 shows the temperature profile for an exterior barrier insulated from the outside with 10cm of polystyrene, not covered on the inside - example A.
Fig. 6 shows the temperature profile for the same barrier, also insulated from the outside with 10cm of polystyrene, but with fittings on the inside - example B.
Insulation of a layer of polystyrene caused a significant rise in temperature in the room for example A (Fig. 5). For example B (Fig. 6) a rise in temperature is also visible at a value of around +4°C to +8°C. This is still a temperature below the condensation point of steam, and the wall was insulated.
Figures 7 and 8 present energy losses of partitions where the temperature distributions were shown in Figures 5 and 6. In relation to the situation shown in Figure 3 and 4, the improvement in the entire cross section of both cases can be noticed, but this is not an optimal solution for example A and quite unacceptable for example B, due to a failure to remove defect of condensation in the partition for temperature conditions, which can be found in our climate zone. Of course, these conditions are present for few or several days during a year, while it is warmer during the other days, but for a few, several days as a result of condensation of water vapour the partition loses its insulating properties (due to the rise in humidity) and its properties in higher outdoor temperatures will be inadequate.
Below is the correct solution of thermal insulation applied for the B case, which eliminates the risk of condensation in the partition and limits the losses on the structural node.
Figure 9 shows the temperature distribution for the B case after application of different thicknesses of insulation. Polystyrene with a thickness of 25 cm was used in the upper part of the partition whereas polystyrene with a thickness of 10 cm was used in the remaining part. The floor was insulated from the bottom with polystyrene with a thickness of 10 cm.
Temperatures achieved in a cross-section of the partition prevented surface condensation of vapour. Maximum energy losses have been reduced by approximately 30% compared to the solution assuming the use of the insulation by means of the polystyrene layer with a thickness of 10 cm (Fig. 8) and ca. 50% in relation to the partition without insulation (Figure 4).
In the area shown in Figure 10 a thermal bridge can be seen that cause local heavy losses due to improper design of the floor connection, which was not properly isolated from the external partition. The solution to this problem lies with the internal construction and may also be subject to computation.
Quality of thermal insulation
The effectiveness of thermal insulation determines the quality of the works performed. Even the best configured insulation could be undermined by inadequate performance. The figures below show distribution of temperature for the B case (Fig. 11) with the proper performance of thermal insulation, and for the same case, where a gap of 2 mm was left between the polystyrene boards which was then covered with plaster from and which becomes invisible from the outside in visible light (Fig. 12).
The figure 12 shows the effect of the gap in thermal insulation to the temperature distribution from the side of the inner wall – temperatures are significantly lower compared to the distribution presented in the figure 11. Its distribution is similar to that presented in the figure 6, which related to the distribution of temperature for insulation with the polystyrene layer with the thickness of 10 cm over the entire surface of the partition. It should be noted that this gap can have a length equal to the length of the plate of insulating material or multiplication of this length. Spread of disorder that is introduced by the discontinuity may be important as it comes to the effectiveness of thermal insulation. It may also cause condensation in the area of the impact of a gap to reduction of the partition temperature. Such defect is visible only in the infrared images.
It follows that in order to guarantee return on this investment and its effectiveness the following procedure must be applied:
1. thermovision measurement of the facility,
2. numerical analysis of the structural elements with particular focus to the areas suggested with the results of thermovision measurements,
3. proposal of applying thermal insulation of particular structural nodes,
4. quality control of the performance of insulation by means of thermal imaging techniques.