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Pipework Insulation

Pipe insulation or pipe lagging is a foam or mineral fiber like material that is placed around hot and cold pipework to reduce the possibility of freezing, condensation, acoustic absorption or prevention of heat loss from the pipe. A post on Rockwool’s site suggests that applying insulation to hot pipes can lead to energy savings of 20% creating a return on investment within three years. 

 

By reducing heat loss from unheated areas in the home and retaining the heat energy within the pipework heating systems maintain the optimum flow temperature set by the boiler allowing the heat to be transported further around the system to the emitters than uninsulated pipework, effectively reducing energy consumption which leads to less wear on system and boiler components and increased comfort levels for the home. 

 

It’s said that lagging can deliver the temperature 2 to 4 degrees (depending on lagging thickness) hotter than uninsulated pipework can, allowing you to lower the output temperature of the boiler. When combined with 'weather compensation' or 'load compensation' controls the benefits are noticed dramatically. Lower heating curves can be achieved and flow and return temperatures are reduced. 

 

The Pipes That Require Lagging:

  • All pipework connected to hot water storage vessel, including the vent pipe, should be insulated for at least 1m from their point of connection to the cylinder.
  • Primary flow and return pipes from the boiler.
  • The hot water pipes, under sinks, basins and behind the bath panels.
  • Central heating pipework – all heating pipes should be insulated under the floors to the radiators.
  • Primary circulation pipes for domestic hot water circuits should be insulated throughout their length, subject only to practical constraints imposed by the need to penetrate joists and other structural elements.
  • If secondary circulation is used, all pipes kept hot by that circulation should be insulated.

 

The installation of insulation materials should be of the closed-cell type with mitered joints and adhesives used on all seamed joints. Thickness of insulation fitted should be sized to provide protection for up to 12 hours and the thermal conductivity does not exceed 0.045 W/m K.

 

Thickness of insulation for cold water pipework to prevent freezing.

Pipe diameter (mm)

Within the insulated envelope of building - normal conditions

Outside the insulated  envelope of building -  extreme conditions

15 25 32
22 19 25
28 19 19

 

Heating system pipework minimum thickness of insulation in (mm) required with a thermal conductivity at 40°C (W/m K)

Pipe diameter (mm) 0.025 0.030 0.035 0.040 0.045  Max permissible   heat loss (W/m) 
15 9 12 15 20 26 7.89
22 11 14 18 23 29 9.12
28 12 16 20 25 31 10.07

 

A low thermal conductivity allows specified thermal performance standards to be achieved with thinner insulation. When comparing brands, cross referencing the products technical details with give an indication of what thickness to use.

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