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Insulation of pipes

For decades, a minimum standard of pipe insulation has already been regulated by law in Germany in accordance with the Building Energy Act GEG (previously the EnEV, and even earlier the WschVO and HzAnlVO). Unfortunately, practical implementation on a broad scale has lagged behind the targets for the following reasons:

  • The requirements were often perceived as “inconvenient” and were implemented only half-heartedly (and often not even planned).
  • Although many existing “insulated” pipes are executed in an apparently good way on the outside, e.g. with neatly placed end caps - bare pipe sections are visible at every bend, attached fittings and at the connection to the storage tank. These constitute huge thermal bridges which decisively diminish the effectiveness of the insulation.1)
  • Implementation of these measures was left to very poorly paid insulation installers/laggers who “got the job done” as quickly as possible by sliding the pipe insulation sheaths/shells/pipe lagging onto the pipes and then turning the still open slit towards the back (so that it was not visible).

Subsequent insulation of weak points of heat-carrying pipes and heat storage tanks

In the case of heat-carrying pipes (containing heating water or domestic hot water), storage tanks, fittings and so on, with very few exceptions, improving the insulation is always expedient and does not present any risk as long as approved insulation materials are used. In particular, installing insulation subsequently at all those places where the pipes or fittings feel warm (or even hot) to the touch is quick and easy. Even inexperienced persons can easily carry out these measures, further details can be found here2) . Exceptions:

  • Electronic installations (e.g. heat meters) sometimes cannot tolerate the temperature level of the heating water and are therefore deliberately designed with “heat losses”. Caution is necessary here; this is usually noted in technical documents, if these can be found. There are also examples of exemplary fixtures/taps which are supplied already encased in insulation, which can be integrated into the insulation of the system.
  • Care should be taken in the case of pipes carrying cold mediums (e.g. cold drinking water). These can be identified by touching them. Their insulation usually does not have to be improved, neither should they be insulated “by mistake” or for the sake of convenience 3).
Heat-carrying pipes in the boiler room of an EnerPHit retrofit: on the left: not insulated yet, on the right: with mostly well executed insulation, but still quite recognisable heat losses.
Storage tank: poorly insulated on the left in the thermographic image, subsequently insulated successfully on the right

Hot water tanks in particular are often completely inadequately insulated (see thermographic image). Air (from below) often enters under the insulation and heats up at the surface of the tank and escapes as hot air in the upper area due to gaps, especially if the insulation jacket is not closed or does not lie against the tank (tight fit). Such losses can often be reduced easily and effectively with additional insulation (see picture on the right). It is especially crucial to prevent the passage of air along the (surface of the) tank - the insulation is pressed against the storage tank due to the “bandaging”. In particular, gaps where pipes enter the tank may then have to be packed with insulation as well. These measures cost little and require only a little time investment; lots of soft insulation materials are suitable for this purpose. In this example, this measure reduced the losses by approximately half (!) and thus saved around 4 kWh/(m²a) 4).

The fact that the potentials of pipe insulation are not yet fully utilised even with insulation of single pipes is demonstrated in the picture of the insulation of heat-carrying pipes (forward and return flow for heating, the hot water and circulation return pipes) during the construction of the first Passive House building in Darmstadt Kranichstein: the four individually “minimum insulated” pipes (25 mm) were enclosed in a single jacket of 100 mm thick insulation matting.

Thermal insulation of the heat-carrying pipes in the ceiling conduit (Passive House building in Darmstadt Kranichstein) with an insulation thickness of (25 + 100) mm; (construction site photograph by W. Feist 1991)

This further reduces the heat losses of the distribution system by more than 50% compared to the applicable requirements. It can easily be calculated that this is also worthwhile. Unfortunately, in most cases it is not so easy to install this as a retrofitting measure.

We have experienced again and again how completely surprised users are when they see that the greatest proportion of their costs for the hot water supply is due solely to compensating for the losses. Although it is not possible to bring these down to zero, it is possible to reduce the losses considerably.

Implementing insulation of pipes

Detailed instructions can be downloaded here: DIY instructions for insulation of pipes.

In the boiler room take a look to find out which pipes, fixtures, storage tanks etc. need to be insulated additionally. That's everything that feels hot to the touch; but also pipe sections that feel only “warm” can still lose a lot of heat. In this example we have documented this using the thermographic camera (far right, “thermographic image BEFORE”). The normal photograph shows a very hot uninsulated pipe (vertical). The lengths and diameters of the required pipe insulation sheaths/shells/ lagging can now be determined. Basic principle: Don't save on the insulation thickness (the procedure is the same, so do it right the first time). Insulate all connection areas at the same time, don't leave any gaps.

The pipe insulation sheaths/shells/ lagging are available from building supply stores and also online. The insulation should be as thick as possible. We recommend at least a thickness that is the same as the pipe diameter, more is better! All alternative materials available on the market are suitable - insulation shells consisting of flexible PE foam are easy to process. Solar lines can become especially hot, so special materials suitable for this purpose should be used here.

Pipe lagging/insulation shells can easily be cut to the desired length using a knife. A notch can be cut into the tube for corners so that the shell can be bent more easily. If there is less space in some places then some of the insulation can be cut out; when cutting, care should be taken that all pipes and components are continuously covered with insulation without any gaps.

Basic principles:

Insulation should always be as thick as reasonably possible: “If it's worth doing at all, then it's worth doing it well!”

In places where there is very little space, as much insulation as possible should still be used. Some insulation is always better than none at all.

Don't leave any gaps! “Difficult” places also can be insulated at least a little using self-adhesive insulating tape.

Bends or corners in the pipes, intersections and the like can also be insulated perfectly everywhere in this way. The joints must be sealed later on using the appropriate adhesive or suitable adhesive tapes; otherwise warm air will still be able to pass through easily.

The result: the vertical piece of pipe is now insulated, the thermographic image of the situation after insulation (far right) clearly shows the difference compared to the “BEFORE” picture. The bend in the pipe is not yet insulated in the picture on the far left, bottom - and the radiating heat can be seen clearly here.

The commissioner for energy saving in Germany actually made a video on this. It's really easy, anyone can do it. In addition, the materials for this are not expensive. The costs can be recovered again after one year, or at the latest two years. Incidentally, the energy needed to manufacture this kind of material (whether polyolefin foam or mineral wool) can even be saved again in a period of time less than the first heating period. The commissioner is right: get started right now if there are any uninsulated places somewhere in the pipe network.

By the way, it is our advice and also makes sense to use the maximum possible insulation thickness while you're at it. Even 200% insulation is not excessive; the material costs are minimal, maybe it will take a little longer, but it will still be worth it.

Back to overview "Building services measures"

The fact that even small uninsulated pipe sections in pipe networks lead to high additional losses has often been ignored. Water-carrying pipes have a high thermal conductivity and bring heat from the insulated pipe section into the non-insulated section of the pipe, this heat then dissipates easily.
Ensure that the pipe is completely enclosed, don't save on the thickness while you're at it, check the result with thermographic imaging.
Cold water pipe insulation: more about this later. Minimal insulation for protection against condensation is appropriate here; however, this insulation must be executed everywhere without any gaps and should be vapour impermeable, because “dripping” will still occur otherwise. The energy savings here are of secondary importance here. Of course, this can also be done at the same time if there are wet pipes somewhere (often visible in the summer).
Reference area: living area of the house. That’s a substantial share of the total losses!
efficiency_now/building_service/insulation_of_pipes.txt · Last modified: 2022/12/09 13:40 by