Insulation classes and calculation according to DS 452

Determine whether it is an HVAC system (heating, ventilation or cooling) or an industrial plant with high medium temperatures. Industrial plants where the medium temperature makes it impossible to meet a heat loss requirement are instead insulated to a permitted surface temperature of 49–50 °C.

Any installation with an ambient temperature below 5 °C is regarded as 'outside' (outside the building envelope), and anything above 5 °C as 'inside'. If the pipe is in an uninsulated loft, it is counted as outside the building envelope, even though the average temperature there is typically estimated at approx. 8 °C.

Find the correct insulation class (1–6) in DS 452 based on the installation's type and location. Class 1 is used for installations that only operate for a few weeks or months a year, while class 6 is used for continuous operation outside the building envelope. Distribution pipes inside the building envelope require, for example, class 3, and outside class 6.

Measure the diameter of the pipe or duct. Round pipes and ducts up to 400 mm are calculated as circular elements; anything over 400 mm is calculated as a flat surface. For rectangular ducts, the circumference (2 × height + 2 × width) is calculated and divided by 3.14 to find the equivalent circular diameter. If this exceeds 400 mm, it is calculated as a flat surface.

Record the medium temperature in the pipe/duct as well as the ambient temperature. The greater the temperature difference, the higher the insulation class may be. For installations in an uninsulated loft, the local average temperature of approx. 8 °C is used as the ambient temperature in the calculation itself.

Investigate whether the installation is exposed to wind. Outdoor installations require knowledge of the local wind speed. Installations in an uninsulated loft (with no direct wind exposure) are set to a wind speed of 0.1 m/s, as the calculation programme Isodin cannot use zero as an input value.

Determine whether the finished insulation surface is bright (e.g. aluminium foil) or matt. The emissivity differs for the two surfaces and affects the calculated heat loss. Since insulation with an aluminium foil jacket becomes matt over time, it is recommended to calculate with a matt surface so the standard is met throughout the life of the insulation.

Assume a matt surface — aluminium foil becomes matt over time.

Determine whether the pipe supports are insulated or not. Uninsulated supports resting directly on the pipe increase heat loss by up to 15 % and, in the worst case, can mean the entire pipe run has to be insulated with up to 40 % more insulation. If insulated supports are used, the insulation thickness can in some cases be reduced by one thickness class.

Decide which type of insulation to use: pipe sections, lamella mat, elastomeric foam or insulation boards (e.g. IP2). The type has a direct influence on the calculated insulation thickness and must be entered correctly in the calculation program.

Ventilation ducts are classified separately in DS 452. Supply air ducts located in the room they serve require no insulation. Supply air ducts with mechanical cooling (15–23 °C air temperature) require class 1 indoors. Supply air ducts with a design air temperature below 15 °C or above 23 °C require class 3 and class 2–4 respectively, depending on location.

District heating pipes inside the building require class 4, and distribution pipes between buildings likewise class 4. Solar collector pipes require class 4 whether they are inside or outside. The buffer tank for solar collectors requires class 6 outside the building envelope and class 5 inside. Connecting pipes in the same room as a heat emitter (radiator) are not insulated.

Enter all recorded parameters (diameter/format, medium and ambient temperature, insulation type, surface finish, wind speed value and support type) into the Isodin calculation program. The program then calculates the required insulation thickness as well as the expected heat loss in watts per metre and the required centre distance between the pipes.

Record the calculated insulation thickness, the remaining heat loss (W/m) and the centre distance between the pipes. Check that the insulation thickness is sufficient to meet the heat loss limit of the chosen insulation class, and that the surface temperature does not exceed 50 °C (except for connecting pipes and heat emitters). The result is documented in the work description.