Target Insulation

The UK’s goal to achieve net zero greenhouse gas emissions by 2050 likely entails incentives for home insulation. Here’s an overview of insulation approaches and considerations to help mitigate damp issues:

External Wall Insulation (EWI): EWI usually employs non-porous material on an external wall, shielded by render. Key drawbacks include:

  1. “Shallow fit” installations: This cost-saving approach inadequately applies insulation, especially around windows, doors, and behind gutters or downpipes. Remedying shallow fit involves internally insulating these areas and ensuring proper ventilation and/or dehumidification.
  2. EWI can hinder a wall’s rainwater evaporation ability. Defects like cracks may lead to water ingress, resulting in wet walls, which poorly insulate, and could cause wall damage, internal dampness, and mould.

Internal Insulation: Consider Vapour Permeability: If internal wall surfaces are permeable, like typical plaster and external brick, vapour-permeable insulation is advisable, especially with underlying timber joists. However, impermeable insulation like Celotex or Kingspan PIR alters the wall’s heat profile, making it colder internally and risking interstitial condensation within the wall. This moisture might drip down, risking rot in structural timber.

In your situation, risk is low as the externally rendered wall is in good condition, and sub-floor timber is removed. Reduce moisture risk in the wall by maintaining the external render and keeping internal humidity around 65%RH via ventilation or dehumidification. Alternatively, wood fibre or SpaceTherm, though more expensive, are effective vapour-permeable insulation choices.

Focus on Low-Cost, High Heat Loss Areas First:

  1. Insulate around heat sources, e.g., behind radiators (radiator insulation) and surrounding the boiler.
  2. Target high heat loss areas, possibly using a thermal imaging lens in colder weather. Common heat loss areas include lofts, windows, eaves, reveals, base of walls, and pipes for water, gas, ventilation, and waste.
  3. Explore inexpensive solutions like thermal lined curtains, shutters, and draught-proofing, balanced with targeted ventilation.

A selective approach on the initial £2,000 expenditure can yield about 5% – 10% p.a. energy savings. This suggestion serves as a discussion starter, and should be evaluated against your financial and practical considerations.

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