Insulating Heating and Hot Water Pipes and Fittings

Retrofitting insulation to uninsulated heating pipes, hot water lines and fittings in unheated areas (basements, shafts, plant rooms).

How does insulating heating and hot water pipes work?

Uninsulated pipes release their heat to the surroundings through convection and radiation. One metre of DN20 to DN25 heating pipe at a medium temperature of 60 °C loses around 40 to 50 W – over a heating season of 5,500 hours, that is 220 to 275 kWh per metre, and correspondingly more with year-round hot water circulation. In cellars, shafts and plant rooms, this heat is lost. An insulation shell of mineral wool or foam around the pipe reduces losses by more than 70 %. The rule of thumb: insulation thickness equal to pipe diameter at a thermal conductivity of 0.035 W/(m·K). For fittings, pumps, valves and mixers – which often cause the largest individual losses – flexible, re-closable insulation jackets are available.

Which buildings benefit from pipe insulation?

The measure pays off wherever pipes in unheated areas are accessible: cellar distribution in apartment buildings, plant rooms in office buildings, industrial halls with long distribution pipes. In older buildings in particular, heating risers in the cellar are frequently uninsulated or only partially insulated, and insulation on fittings is almost always missing. Pipes in the screed or in closed walls are not accessible and are ruled out. The potential is particularly high for hot water circulation pipes, because they are kept warm 8,760 hours a year. The work can be carried out without interfering with the system and also during the heating season.

What does pipe insulation actually deliver?

Final energy demand falls by 2 to 8 %, and more in buildings with long uninsulated distribution runs. An apartment building with 80 m of uninsulated DN25 cellar distribution saves around 17,000 kWh of natural gas and about 3.4 t of CO2 per year. Costs are 12 to 25 € per metre of pipe insulation and 50 to 150 € per fitting insulation jacket. Over a 20-year service life, the measure pays back in 1 to 3 years, often even under 2 years – making pipe insulation one of the most cost-effective measures on a heating system.

Energy carrier

Erdgas, Heizöl, Pellet, Fernwärme → Erdgas, Heizöl, Pellet, Fernwärme

Savings potential

2-8 % (oft mit höchster Wirtschaftlichkeit)

Worked example

In an apartment building, 80 m of DN25 heating distribution pipe runs uninsulated through the unheated cellar. The flow temperature is 60 °C, the heating season comprises 5,500 operating hours, and the heat is supplied by a gas boiler with an efficiency of 0.90. According to VDI 2055, an uninsulated pipe of this size loses around 45 W per metre at 60 °C. With 20 mm mineral wool insulation, the loss drops to about 10 W per metre. The saving is calculated from the loss difference, pipe length, operating time and boiler efficiency: (45 − 10) × 80 × 5,500 / 0.90 / 1,000 = 35 × 80 × 5,500 / 900 = 17,111 kWh of natural gas per year. With an emission factor of 0.201 kg CO2/kWh, this corresponds to around 3.4 t of CO2 annually. At 12 to 25 € per metre, the insulation costs 960 to 2,000 € and pays back in less than 2 years.

Investment & payback

12-25 €/m Rohrdämmung; 50-150 € pro Armaturendämmkappe · Service life: 20 a · Payback: 1-3 a

Applicability

Requirements

Exclusion criteria

Typical buildings

Frequently asked questions

How much does it cost to insulate heating pipes?

Retrofitting insulation to heating pipes costs 12 to 25 € per metre including material and installation, and insulation jackets for pumps, valves and mixers 50 to 150 € each. For 80 m of cellar distribution, that is around 960 to 2,000 €. With savings of several thousand kilowatt-hours per year, the measure pays back in 1 to 3 years, over a service life of 20 years.

How thick should pipe insulation be?

The insulation thickness should equal the internal pipe diameter, based on a thermal conductivity of 0.035 W/(m·K). For pipes up to 22 mm, that is at least 20 mm, for pipes up to 35 mm at least 30 mm of insulation. This so-called 100 % insulation is mandatory in Germany under GEG Annex 8 for pipes in unheated rooms. In confined installation situations, 50 % is permitted, as it is for wall and ceiling penetrations.

Is insulating heating pipes mandatory?

In Germany, insulating heating and hot water pipes in unheated rooms is mandatory under the Building Energy Act (GEG), including retrofitting for accessible pipes. In Austria, there is no general retrofit obligation for existing buildings; for new builds and refurbishments, the requirements of OIB Guideline 6 apply. Regardless of the legal situation, the measure is almost always economical thanks to its short payback of 1 to 3 years.

Is it worth insulating fittings and valves?

Yes, insulating fittings is particularly worthwhile. An uninsulated fitting loses as much heat as one to two metres of uninsulated pipe, because its surface area is large and it often sits at a central point in the distribution. Flexible insulation jackets with hook-and-loop fasteners can be removed for maintenance and refitted. At 50 to 150 € per jacket, they pay back within one to two heating seasons.

Can you insulate heating pipes yourself?

Straight pipe runs can be insulated yourself with pre-slit insulation shells from the DIY store; joints and longitudinal cuts are glued. Gap-free installation and the correct insulation thickness are important. Bends, T-pieces and fittings are more complex and should be done professionally so that no thermal bridges remain. In larger plant rooms with many branches, a specialist contractor is usually more economical than DIY.

Related measures

Standards & sources

Metering points in the EDM Toolbox

Wärmemengenzähler vor und nach der Maßnahme zeigen den Effekt klar; in Verbindung mit Außentemperatur-Korrektur über LineMetrics-Wetterdatenanbindung lässt sich der Effekt von normalen Witterungsschwankungen trennen.

All measures