Ventilate to Reduce Excess Moisture in Your External Walls and Save Money

How Ventilation Can Save You Money

The thermal insulation of damp walls is far less when compared to the value of dry walls. The use of intelligent dehumidification systems, as in the ones supplied by RHLdirect, has the potential to increase the insulation value of your damp walls by up to 33%. This would enable economic saving and provide a warmer dryer healthier home.


The calculation is simple:

A wall which is exceeding its normal moisture content by 10% has an actual insulation value of only 23% of that of a dry wall! By way of example a 40 centimetres deep wall has actually only the thermal resistance of 10 centimetres due to being damp.
If the excess dampness of a wall is reduced by half its thermal insulation would increase up to one third!
In a typical home affected by damp walls the dehumidified equivalent would save around £250 in energy costs per year!

Add on insulation can cause the opposite effect, with the increased probability to breed mould and other bacteria, due to the reduction on the natural ‘breathability’ of a house.

The theoretical ‘worst’ scenario can be a house with:

  • Rendering on all sides
  • Cavity Insulation
  • Anti-Mould, Acrylic Based paint
  • Double glazed windows without passive ventilation
  • No Ventilation units-whether passive or mechanical
  • Sub-terrain – Tanked cellar/flat
  • Insulated attic – not vented


The issues facing the property above are numerous, however the most notable would be internally would be the walls being damp due to any water vapour created within the property, condensing on the wall, and running to the skirting boards and floor, with then ideal conditions that grow mould that rapidly spreads through the moist air around the home. The fabric can also suffer within these situation’s particularly by interstitial condensation water being trapped between the insulation) and rendering on the exterior; the water within this layer of substrate will sit in place, and, especially in the winter, when freezing and thawing become a regular thing, can cause bricks to crack and crumble.


The costing for supposed building solutions on average are (semi-detached 3 bed house):

  • Rendering- £4175 – £4400 – 7 days’ work
  • Cavity Insulation- £350 – 500 – 1 days’ work
  • Mould resistant paint- £10-20 per tin, 7-9 rooms plus stairs and landing/halls = 10-12 tins plus 3 days labour for a paint- £300 – £550
  • Double Glazing Costs based on average semi detached with 10 windows- £3300 – £5900 – 3 days work
  • Total: £8125 – £11350


Compare the figures above with a standard RHLdirect System (prices based on average cost and geographical location of 50 miles from RHLdirect headquarters, and standard brick construction property):



With running costs at for a year being:



In terms of economics the balance of insulation options vs. RHLdirect ventilation then the above figures demonstrates that RHLdirect ventilation is a best practice way forward


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