Pipe insulation in the Isodine calculation program

Go to Isodine's online calculation programme via the internet. The programme is publicly available and requires no login or special permission. When the programme opens, you will see a number of blue dots, each representing a field you need to fill in.

Based on a prior classification of the pipe — for example using DS 452 — determine the required insulation thickness. In the example, it is a ventilation duct above a suspended ceiling with an ambient temperature of 20 °C and a medium temperature of 15–23 °C with mechanical cooling, which gives class 1. The corresponding insulation thickness is entered as 30 mm in the programme.

Specify that it is a circular duct, as ventilation ducts up to a diameter of 400 mm are classified as circular. In the example the diameter is 160 mm. If it were a rectangular duct or a flat surface, the relevant duct type would have to be selected instead.

Select whether the duct is positioned horizontally or vertically. As most ventilation ducts run horizontally, tick 'horizontal'. Then enter whether the duct is inside or outside the building envelope. In the example, the duct is located indoors above a suspended ceiling.

Make sure you tick the field for specified insulation thickness, so the programme uses the manually set thickness of 30 mm rather than a calculated default value.

Select 'aluminium, oxidised' as the surface finish, even though the aluminium foil looks shiny when installed. Over time the surface will dull, and as the insulation must last for up to 40 years, the emissivity must reflect the condition of the surface at the end of the period.

Enter the duct's diameter (160 mm) and the total pipe run length. The example uses 244.2 linear metres of pipe with a diameter of 160 mm.

Enter the ambient temperature — typically 20 °C indoors, unless otherwise specified. Then enter the medium temperature. Even though it ranges from 15 to 23 °C, 15 °C is used, as mechanical cooling gives the largest temperature difference (20 °C minus 15 °C = 5 °C), and it is more expensive to produce cooling than heat.

Isodine uses 3 m/s as the default flow velocity inside the duct. This suits most duct types and can generally be left unchanged.

Select the desired insulation type. In the example, an aluminium lamella mat is used, which is the most cost-effective solution. The insulation thickness is set to 30 mm in accordance with the class 1 requirements.

Tick 'Energy consumption'. This field is not enabled by default in Isodine, but enabling it unlocks a range of useful data: total energy consumption in kilowatts, annual costs in kroner and CO₂ footprint — both with and without insulation.

Enter the operating time. For year-round operation this is 8,760 hours a year, and it can be left unchanged. Then enter the current energy price per kilowatt. In the example the price is set to 2.25 kr./kWh for electricity. The energy price can be looked up in current energy price lists.

Enter the number of uninsulated supports. For ventilation ducts, the supports are in the vast majority of cases not insulated. This causes an extra heat loss of 5 % compared with insulated supports and must be included in the calculation to get a correct result.

Review the calculated results: heat loss per metre per hour (insulated and uninsulated), total heat loss for the entire pipe run, energy consumption in kilowatts, annual operating costs in kroner and CO₂ footprint. Subtract the relevant figures from each other to calculate the actual saving from insulation.

The program automatically calculates the required number of square metres of insulation material. The formula is: (diameter + 2 × insulation thickness) × π ÷ 1000 × pipe run length. In the example this gives (160 + 60) × 3.14 ÷ 1000 × 244.2 = 168.69 m². If you know the number of square metres per roll or bag, you can now calculate how many packs you need to bring.

(Ø + 2 × thickness) × π ÷ 1000 × length = m² of material.