Verification of the construction

The structural trend to lightweight construction ways made the use of complex components and structural systems necessary. Numerous parts with external construction components are required, in order both the pyrometric and the demands from the building design aspect, which result from it, to fulfill. With the construction design however it is overlooked multiple that also an optimum air-tightness is necessary for the reaching of the demands from the building design aspect and for the minimisation of the losses of energy.

Wärmebild der Luftdichtheit

Measurement principle: With the building tightness surveys by means of a tarpaulin a fan is built into an outer door of the building. With this fan in the building an artificial over or vacuum is created. The promoted air volume related to the space reservoir results in the tightness value for a building. With the infrared camera the leakages can be made visible.

Typical leaks in one-family houses: Practically with all design changes (roof area - deviation from pulse flatness - outside wall - floor) groove leakages can occur. Above all, if basic components, as Trame, purlins or rafters are visibly executed, often solid tightness defects occur.

Wärmebild einer Dachbodentreppe

Attic stairways are usually very leaking. Both the stairways themselves, and the installation to these brings often substantial defects.

Measuring method/Blower - air-tightness - Door:

Messverfahren Blower

The technique for the determination of the air-tightness is defined in the DIN EN 13829 (differential pressure techniques).

By the Blower Door test leakages can be tightened, because a wind load is simulated as follows: All structural openings (windows, outer doors) are concluded, all internal doors are however opened. Then inside the house a vacuum is built up by 50 Pascal. This pressure corresponds to a wind velocity of approximately nine metres in the second or scarcely wind force 5.

The differential pressure constructs, a largedimensioned fan attached in an outer door, which withdraws permanently air from the building. The air volume, which flows in one hour by the fan from the inside outward, is calculated in dependency of the weather conditions. It results in the “n50-Wert”, with which the tightness of a building can be quantified. Air, which flows during the inspection procedure, arrives by leaking grooves or other leaks into the building cover. The “n50-Wert” may not exceed 1.5 h-1 (1,5-facher change of air per hour) according to DIN 4108-7 or EnEV with buildings with window ventilation 3 h-1 (triple change of air per hour) and with buildings with room air-technical annexes.

With artificial smoke or a wind velocity measuring device leakages can be localised and visualised. The Blower Door technique permits both under and over-pressure tests. The duration of a survey depends on the periphery and the structural state of the building. The minimum expenditure of time consists of two hours.

Possible is also the additional thermalgraphic data collection of these air flows. If the camera is inside the house settled under vacuum, then cold air flowing in from the outside seems on the Wärmebild as blue flag. If the camera is placed however before the house and built up in the building an over-pressure of 50 Pascal, then hot, “red” interior air blows by the leaking grooves outward. Thermalgraphic results supply only cause predicates to the tightness, since they are interpretation needy.


Test assembly check of the air parameters with SF6-Methode and photo-acoustic infrared.

Microwave measuring method

Who doesn't know the problem? Wetness spots at the walls and the question: „Why? “
By a supersaturation of air with water vapour, continuing at longer term, gradually also the water content of the space walls increases.
In order to fathom the causes for the emergence of a wet spot at the surface of a wall, already „a view is into the brick-work “required. Only the few measuring devices permit such a view in the inside to the wall.
The microwave measuring method offers such possibilities and bring along directly several benefits in relation to other conventional techniques as e.g. for the Darr weigh technique or conductivity measurements.

MOIST - Hygrometer

First of all it operates non destructive and absolutely clean. Thereby surveys become possible also in inhabited spaces. Only in extreme cases still small bores are required, in order to insert depth sensors into the material.

Secondly surveys of the surface and in the reservoir become possible. In particular the survey in the reservoir represents a very substantial relief in the building diagnostics, since over half of the humidity faults at the surface do not arise, but becomes there only visible. The distribution of the humidity inside a material in the compromise to the humidity distribution at the surface almost always informs against it about of where from those
Moisture into the wall occurs.
Thirdly the technique is independent of the degree of the salting of the material. It plays thus no more role whether an older or new building will align.
Fourth the measured values in real time are obtained and indicated immediately at the measuring device. Enormous saving of time for individual survey arise, or leave themselves within a short time a great many surveys would go straight through. Again statistical safety increases regarding the measured values.
The fifth and probably largest benefit result from the combination of several advantages of the technique: Large hold surveys become possible, whereby the humidity budget of a total building (e.g. a wall) can be represented generally speaking. Only with it can be obtained with high, often with absolute safety the origin of humidity faults.
The hygrometers (MOIST), with which our company operate, offer even the possibility for the diagram of the humidity distribution. However this fact facilitates the diagnosis and evaluation of humidity faults enormously.
The following figures indicate such hold surveys:

Surface survey screed base after damage caused by water by heater tube fracture (unity: Weight humidity in %)

Deep or volume measurement 0.5 m of a strong mixing brick-work

The dark ranges represent a increased humidity, bright of ranges a low. The first figure indicates a hold survey after a surface survey of a screed base, which came by a heater tube fracture to fault. The measuring device was calibrated on “usually applied construction materials”. The second figure represents a deep or a volume measurement of a mixing brick-work with a strength of 0,5 m.
Our company operates with the newest measuring devices and is always endeavours the best devices and techniques to assign. Only the use of progressive technology guaranties a very good gutachterliche valuation and specifications for the construction drying process.

Source of text: hf sensor GmbH (manufacturer of the measuring devices) ->


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