How loft insulation works?

How does loft insulation stop heat loss?

If your roof is not insulated, you will lose a quarter of your heat through it. 

As a result of loft insulation, the air below the loft remains warmer for a longer period of time. The material slows the upward movement of air and prevents it from escaping, but still contains enough fibres to prevent the trapped air from circulating and causing a convection current or condensation.

Loft Insulation dos and don'ts

It is best to consider all factors before carrying out insulation. We have carried out research and compiled a list of dos and don’ts for you to check.


  • Block any vents or ventilation spaces that are installed
  • Don’t squash or compact the insulation as this can reduce the thermal performance overall making it much less efficient.
  • Install loft boards straight onto joists.
  • Remove any insulation as this will again reduce the effectiveness and thermal performance of it.


  • Construct a raised boarded area above the insulation to allow more room for more to be added. Use products such as tri supports and uni supports for this.
  • Complete your research on guidelines and suppliers before beginning your project.
  • Check your current insulation as it might need to be removed.

Should loft insulation go to the edges?

Loft insulation should be brought right to the edges of the roof but it should not block the eaves. Ventilation is important to ensure that the necessary air movement, this will prevent condensation from water vapour forming.

Disadvantages of loft insulation

There aren’t any disadvantages to loft insulation as such. There have been complaints in relation to damp issues being a problem among forums etc, these types of complaints usually are related to the installation process and not the insulation itself.

How long does loft insulation last

Loft insulation has a long lifespan at an average of 40 years. It should more than pay for itself over this time through savings in your energy bills. 

The types of insulation used also have an impact on the lifespan as for example if an insulation that attracts pests is used this will result in them causing damage and deterioration to it the same as insulation that retains water will end up with a lower lifespan.

The climate and surrounding conditions will also impact the length of time insulation will uphold as cold temperatures and wet as well as warm temperatures will affect its durability over time as will general wear and tear.

Do read Can loft insulation cause condensation to know more about loft insulation before using it

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