Stop Heat Loss: Is 20mm Insulation Enough for Heating Pipes?

You hear your heating system start up in the basement. Hot water flows through the pipes to warm your living spaces. But a large part of this expensively generated energy never reaches the radiator. It dissipates along the way, especially in cool basements and unused attics. Exposed heating pipes are like open windows for your heating costs. They heat rooms that do not need to be warm.

The good news: You can stop this heat loss easily and affordably. High-quality pipe insulation is one of the most effective ways to reduce your energy costs immediately. The key question is choosing the right insulation thickness. Is 20 mm enough, or do you need thicker insulation?

For many applications, a tried-and-tested solution is a good choice. The

CLIMAFLEX® 2m insulation tube Ø 28 mm x 20 mm insulation 50% Cu GEG

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Why is pipe insulation thickness so important?

The thickness of insulation determines its thermal resistance. The thicker the material, the less readily it conducts heat and the better it insulates. Think of it like your winter clothing: a thin shirt offers little protection from the cold, while a thick woollen jumper keeps you warm. The same principle applies to your heating pipes.

An uninsulated pipe releases its heat unhindered into the surrounding air. In an unheated basement at 10°C, a heating pipe with a flow temperature of 70°C constantly loses energy. The heating system has to compensate for these losses and cycles more frequently. That costs gas or oil. Thick pipe insulation acts like a protective layer around the pipe and keeps the heat where it belongs: in the heating water on its way to the radiator.

An investment in pipe insulation often pays for itself in the very first winter. It is one of the most effective measures any homeowner can carry out themselves to reduce energy consumption immediately.

Effectiveness increases with insulation thickness, but not linearly. The biggest reduction in energy loss is achieved with basic insulation. Doubling the insulation thickness does not double the savings, but it improves efficiency further, which is particularly worthwhile in very cold environments.

The GEG rule: What does the German Building Energy Act require?

Germany has legal requirements for insulating heat-carrying pipes. The German Building Energy Act (GEG) specifies minimum insulation thicknesses to ensure the energy efficiency of buildings. Two rules are particularly important for heating pipes: the 50% rule and the 100% rule.

The 50% rule

This rule states that the insulation thickness must be at least 50% of the outside pipe diameter. It applies to pipes installed in heated areas or in building components between heated rooms used by different occupants. A copper pipe with an outside diameter of 22 mm therefore requires at least 11 mm of insulation.

The 100% rule

Here, the insulation thickness must match the full outside pipe diameter. This stricter requirement applies to all heating and hot water pipes installed in unheated spaces (e.g. basements, attics) or underground. A 22-mm pipe in a cold basement therefore requires insulation at least 22 mm thick. You can find products that meet these requirements in our pipe insulation category.

20mm pipe insulation: The all-rounder for many applications?

An insulation thickness of 20 mm is a very good compromise and covers many household applications. For the most common pipe diameters from 22 mm to 28 mm, 20-mm insulation already meets the requirements of the 100% rule for unheated areas or comes very close. In heated zones, it significantly exceeds the 50% requirement and delivers excellent energy savings.

For DIY enthusiasts in particular, 20-mm material is still very easy to handle. It is flexible enough to follow gentle bends, but rigid enough to sit securely on the pipe. The previously mentioned CLIMAFLEX® insulation tube is a prime example of a user-friendly and highly effective solution.

In complex installations, you often encounter valves and branches or need to create flexible connections. This is where special components such as the

Stainless steel braided hose, flexible hose DN8, 3/8"ÜM 1500mm, suitable for drinking water

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How do I choose the right insulation thickness for my heating pipes?

Choosing the right insulation is no rocket science. Follow these four steps to find the ideal solution for your home.

1. Determine where the pipes are located: Walk through your house. Where do the heating pipes run? Make a note of which pipes pass through the cold basement, the unheated attic or heated living and hallway areas. This determines whether the 50% or 100% rule under the GEG applies.
2. Measure the pipe diameter: Use a vernier caliper or a flexible tape measure to determine the outside diameter of your heating pipes. The most common sizes for copper pipes are 15 mm, 18 mm, 22 mm and 28 mm. Steel pipe sizes are often given in inches. The insulation sleeve's inside diameter must match this outside diameter exactly.
3. Apply the GEG rule and calculate the insulation thickness: For pipes in a cold basement (100% rule), the insulation should be at least as thick as the pipe diameter. For a 28-mm pipe, this means at least 28 mm of insulation. For pipes running between heated rooms (50% rule), 14 mm is sufficient for a 28-mm pipe. 20-mm insulation is a good or even excellent choice in both cases.
4. Choose the material: For DIY projects, insulation sleeves made from PE foam (polyethylene) have become the standard. They are affordable, durable and easy to work with. Rubber is used for higher temperatures or special requirements, such as solar thermal systems. You can find the full range in our Insulation category.

Step-by-step guide: How to insulate heating pipes properly

With the right materials, installation is a simple weekend project that makes a big difference. Here is your guide to perfect insulation.

Step 1: Preparation

Make sure the heating system has cooled down. The pipes should be cool, dry and free of dust. Wipe them with a damp cloth if necessary. Have all the materials ready: insulation sleeves, a sharp utility knife, a tape measure and special PVC tape for sealing the joints.

Step 2: Cutting to size

Measure the straight sections of pipe and cut the insulation sleeves to the correct length. A long, smooth cut with a sharp knife works best. Do not compress the foam; instead, draw the blade through the material using gentle pressure.

Every uninsulated metre of heating pipe in the basement is like a small, permanently running radiator that you cannot turn down. The money literally disappears into the cold basement air.

Step 3: Installation

Most insulation sleeves are pre-slit. Open the sleeve along the slit and place it over the pipe. For self-adhesive versions such as CLIMAFLEX®, remove the protective film and press the adhesive surfaces firmly together. Make sure the sleeve fits snugly around the pipe.

Step 4: Seal joints and branches

No gaps should remain. Carefully seal all joints between two insulation sleeves with PVC tape. This prevents thermal bridges. For T-junctions and valves, cut suitable pieces from an insulation sleeve and fit them precisely. Tape will also ensure a tight seal here.

Remember safety when working in the boiler room. A clearly visible

Surface-mounted wet-room heating emergency switch IP55

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Insulating your heating pipes is a small investment with a major impact. Not only will you reduce your heating costs and save money, but you will also lower your CO2 emissions and help protect the environment. Whether 20 mm of insulation is sufficient depends on the location and diameter of your pipes. In most cases, however, it is an excellent choice that complies with regulations and drastically reduces heat loss from your heating system. Start your project and turn your boiler room into an energy-saving space instead of a source of waste.

Frequently Asked Questions

Do I need to insulate all the heating pipes in my home?

Insulate pipes that run through unheated areas such as basements, lofts or garages in particular. This is where heat loss is greatest. Insulation is less critical in heated living spaces, but is still worthwhile to ensure the heat reaches the radiators efficiently.

What is the best pipe insulation for heating pipes?

For DIYers, flexible insulation sleeves made from polyethylene (PE) or rubber are ideal. They are easy to work with, affordable and provide good insulation. PE sleeves such as CLIMAFLEX® are robust and an excellent choice for most applications around the home.

What does the label "50% Cu GEG" on pipe insulation mean?

This label means that the insulation meets the requirements of the German Building Energy Act (GEG) for an insulation thickness of 50% of the pipe's outside diameter. This is the minimum requirement for many installations in heated zones. "Cu" stands for copper pipe.

Can I insulate heating pipes myself?

Yes, this is an ideal DIY project. Most insulation sleeves are pre-slit and often self-adhesive. You only need a sharp knife for cutting and possibly some tape to seal the joints neatly. No specialist tools are required.

How much money can I save by insulating pipes?

The savings potential is considerable. Depending on the system temperature and ambient temperature, you can save up to 20 euros per year for every metre of uninsulated pipe. The investment in insulation material often pays for itself after the first heating season.