Boiler, buffer tank: adding extra insulation to reduce energy consumption

This page is a translated version of the page Boiler, réservoir tampon :surisoler pour diminuer la consommation and the translation is 100% complete.

Tutorial de avatarBaudouin Labrique | Categories : Housing, Water, Energy

Hot water boilers and buffer tanks never come with enough insulation. The result is a needless increase in the consumption of electricity, fuel, gas. Here is a really simple solution which will save you tons of money. In fact, it pays for itself in less than a year.

Very easy
2 hour(s)
100 EUR (€)
Other languages:
English • ‎español • ‎français
License : Attribution (CC BY)


Most accommodations have an electric boiler which produce hot, clean water. Some even come with a heat exchanger (water to water), like a buffer tank, to improve the efficiency of the heating system: solar thermal panels, heat pumps, cogeneration... Unfortunately, the cover which is designed to reduce heat loss is far too thin. Result: a loss of several degrees in temperature in a short span of time and an overall rise in energy consumption.

I followed the advice of Test-Achats (A Belgian NGO) ( who recommend surrounding the boiler from all possible angles with either glass wool or mineral wool, paying particular attention to the joins, for minimal air exposure. Then all you have to do is cover it with adhesive aluminium tape. When I did this, the heat loss from my hot water boiler and my buffer tank dropped by one degree (from 4 degrees a day to 3). According to Test-Achats' calculations, a single boiler wastes 600kWh every year. To put it positively, that would mean an annual saving of up to 150€. If you choose to invest in the recommended insulation material (glass or mineral wool wrapped in a thick layer of aluminium), you will make your money back in just 6 months - and it only takes one hour to set up! You would also be doing something positive for the planet, because every boiler treated in this way emits 100kg less CO2 every year (the same amount as a 1000km car journey). My personal recommendation is the safer mineral wool option, which has the same temperature coefficient as glass wool, but you don't need to go through the hassle of wearing gloves and safety goggles.


- Rolls of glass wool (mineral wool is better, as already stated) at least 6cm thick and with aluminium foil and a border (to help with setup and avoid wasted energy). N.B: The one in the picture doesn't have a border.

- Adhesive aluminium tape (wide)


  • Stanley knife (or box cutter)
  • Gloves and safety goggles, if using glass wool

Step 1 - Setting it up

  • Work out how many rolls you need (for most boilers it will be two)
  • Begin by wrapping the insulation material round the boiler and stick it down with the aluminium tape
  • Put some underneath the boiler (if you can raise it); if needed, you can slide a slab of polyurethane or some other insulating material underneath the boiler (this is because a lot of the heat is actually lost from the bottom)
  • Lastly, put some on top (again, you can add a layer of hard insulating material before covering it with your glass/mineral wool)
  • N.B: The tubing will need extra insulation surrounding the sheath which is already present.

This English translation has been possible thanks to the PerMondo project: Free translation of website and documents for non-profit organisations. A project managed by Mondo Agit. Translator: Andrew Christou