Inspection and inspection of the house with a thermal imager when buying or controlling construction

Recommendation points

• Inspection with a thermal imager: how it works and what is it for
• When is thermal imaging required?
• External examination rules
• Filming from inside premises
• Features and pitfalls

The degree of thermal protection at home has long ceased to be a ghostly characteristic. Modern technical means allow you to check the quality of thermal insulation of any building with high accuracy and identify problem areas. We are talking about thermal imaging, which will be discussed in today’s review..

Inspection with a thermal imager: how it works and what is it for

In modern homes, most of the heat leaks through radiation. Heating from the inner surface of the walls is transmitted through temperature bridges to the outer one, from where it is dissipated into the external environment. This heat is invisible to the human eye and does not lend itself well to contact measurement methods, but with the help of special digital technology, you can clearly see how it spreads over the enclosing structures.

There are two types of devices for non-contact temperature measurement:

1. Pyrometers allow you to measure the temperature at a specific point from a certain distance. The relative cheapness of these devices makes their use available to anyone who wants to, however, pyrometric measurements cannot be called a method of objectively assessing the effectiveness of thermal protection. Measurements with their help are carried out in the most predictable places, without giving an overall visual picture..

2. Thermal imaging cameras. Their display shows a thermal histogram superimposed on the real image. This method of thermal imaging allows you to identify problem areas on the fly, and thanks to the built-in pyrometer, it can measure the temperature of a particular area with high accuracy..

On the basis of thermal traces, it is easy to understand in which areas of the building envelope the heat transfer proceeds most intensively and where additional insulation is needed. At the same time, thermal imaging can easily identify both thermal bridges and fistulas through which heat is transferred by air convection, and homogeneous areas where the insulation has lost its properties for various reasons.

Warning!Built-in thermal imaging cameras of mobile devices and special attachments for them are unsuitable for thermal imaging. At best, they can give a distorted picture and estimate the intensity of the heat flow in general terms. A real search for thermal protection vulnerabilities can only be performed with a thermal imaging camera with a built-in pyrometer.

When is thermal imaging required?

There are few owners of professional equipment in Russia, and those who know how to use it correctly and draw up an expert opinion are even fewer. Because of this, the cost of a complex thermal imaging survey of a house is quite high: 3-5 thousand rubles per 100 m². Few can afford such expenses just out of a whim, most often there is a specific reason for such an examination:

• Buying a country house. Thermal imaging allows you to assess the overall quality of thermal protection and predict future heating costs. This is especially important when buying a second home or a house from a developer with a dubious reputation: in 90% of cases, the energy efficiency indicated in the construction project is greatly overestimated.
• Acceptance and delivery examination of buildings. It is practiced not only on commercial and municipal real estate objects, but also for private houses, in the construction contract of which specific final characteristics are indicated. This is a rather rare excuse for thermal imaging only for the reason that developers do not indicate what qualities their creation will have after the object is put into operation..
• If the cost of heating is much higher than typical for this type of house. In such cases, a general survey is performed without drawing up a report in order to find the most vulnerable spots of body protection..
• If you plan to insulate a house, a thermal imaging survey allows you to establish real indicators of thermal conductivity of load-bearing walls and roofs in order to minimize the cost of thermal insulation.
• Periodic (once every 7-10 years) inspection of the house with a thermal imager allows you to establish whether the thermal protection needs repair or revision. A similar examination is practiced for frame houses in which mineral wool is subject to shrinkage, or for log cabins that need periodic caulking..

Among other things, thermal imaging does not have to be complete. Depending on the goals, an expert organization can provide a survey of individual zones: roof, floor, walls, openings and junctions. The conclusion can be provided in the form of a short report indicating problem areas, or a complete map of thermal conductivity with an indication of a detailed thermogram and the area on which certain temperature ranges are recorded.

External examination rules

A thermal imager is a differential type device, it determines all the temperature gradations in the observed area and compares them with each other. The accuracy and objectivity of the readings depend on how complete the range of all possible temperatures at a particular moment of shooting is. Therefore, the main rule for thermal imaging is that it should cover the entire surface of the wall under study, in the extreme case, it can be divided into two or three zones with crossed boundaries..

This requirement forces you to shoot from a sufficiently long distance or use special cameras with a wide viewing angle, which are many times more expensive than conventional cameras. In addition, the registration error at a large distance and at significant angles is very high. Therefore, an experienced expert first conducts a general survey, registering a global thermogram, and then checks individual areas, positioning the device so that its data is consistent with the readings taken at the previous stage..

It is useless to carry out thermal imaging when the temperature difference between the outside and inside the room is less than 25 ° C. This means that you need to plan an examination for the period when the outside air temperature is at around -10 … 15 ° С, but the snow has not yet fallen, or artificially raise the temperature inside the room, for example, using a heat gun for 2-3 hours. It is also necessary to exclude the factor of cooling the outer walls by the wind and their heating by the sun’s rays..

Filming from inside premises

Examining the inside of the walls gives the same big picture as shooting the outside of the building. Problematic areas and large bridges of cold are also clearly visible, but with a comprehensive thermal imaging survey, both types of photography must be performed.

Firstly, this method allows one to estimate the intensity of heat transfer not only through the normal to the surface, but also the distribution of heat in the thickness of the wall. This will give a more complete picture of the correct operation of the thermal insulation and the correct choice of the plane of its displacement..

Secondly, only an internal survey will reveal defective cold bridges, for example, fastening points, the heat from which dissipates in the outer zone, while cold spots are clearly visible from the inside. In the same way, the thermal imager will show errors in the insulation of slopes..

A useful opportunity is to identify vulnerable areas of the power grid, where heating of the cable and connections is observed, as well as violation of the thermal insulation of pipes hidden under the finishing.

But the internal heat survey also has its own problems. First, the dimensions of the premises often do not allow covering the entire wall as a whole, which is why the expert is forced to focus on the picture obtained during the external examination. Secondly, because of the furniture standing against the walls, it is impossible to obtain an objective assessment of some areas, this also affects the results of outdoor photography. Therefore, before the examination, furniture and stationary equipment must be moved away from the walls at least 1 m for a time sufficient to balance the thermal regime. As a rule, this takes at least a day..

Features and pitfalls

Thermal inspection is only a part and tool of the global expertise called thermal building audit. A classic example is checking thermal infiltration with an air door. The thermal imager acts as an auxiliary tool that allows you to identify local areas with damaged vapor barrier, which is especially critical for frame houses.

The quality of thermal imaging depends on many factors that can introduce a very serious error in the results. For example, a thermal survey of a roof can only be carried out using a flying drone: from the ground, it is impossible to provide an acceptable angle of the focal axis relative to the surface under study.

Another common mistake is an attempt to assess buildings surrounded by illegal armed groups with a thermal imager. The outer cladding is impervious to heat rays, and even if there are gaps in the thermal insulation, heating spots will be visible only in the area of ​​the roof eaves, where warm air comes out. This place is already quite an obvious thermal bridge..

It is best to carry out thermal imaging during the construction phase, when the box is assembled and the arrangement of the thermal protection belt with all protective barriers is completed. In this case, the openings can be temporarily sealed with polyethylene and intensively heated the building from the inside if the weather conditions do not meet the requirements for the temperature difference.

If we are talking about checking the buildings in use, you will have to partially disassemble the facade cladding or perform a check with excessive internal pressure when the infiltration flow is strong enough to warm the material of the curtain wall trim. Thermal imaging endoscopes can be another solution to the problem, but they can only identify local problems, without giving an overall assessment of the energy efficiency of the building..