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How to Guide for Roof Insulation

roof insulation

Roof insulation is a vital addition to UK housing to help to keep homes warm, especially during the colder months in Autumn and Winter.  Roof insulation for both commercial and residential buildings provide a long-term benefit to the occupants. Although insulation can be costly, its advantages far outweigh its initial investment.

This guide will go through the types of insulation materials, benefits of roof insulation and factors to consider when installing roof insulation.

Types of insulation materials

Rigid insulation boards

The boards are made from thick sheets of closed-cell forms. They include polystyrene,  polyurethane and Polyiso. You can utilise the boards virtually anywhere in your home, from the basement, roofs, living spaces and attic spaces.

There are three main types of rigid foam insulation boards. They are:

  • Extruded Polystyrene(XPS) – It’s usually pink or blue with a plastic surface. In addition, it’s water-resistant. However, with much exposure, it deteriorates with time and is highly flammable.
  • Expanded Polystyrene(ESP) – It’s a good option for homeowners under a tight budget.
  • Polyisocyanurate – it’s the most expensive option of the three as it comes with an extra coating of foil that acts as a radiant barrier.


  • DIY capability – Insulation boards are easy to attach to your wall or rafters.
  • Environmentally friendly – They are made from straws, cocks or wood.


  • Easily damaged – The UV rays can cause damage to the rigid foam after continuous exposure to sunlight.
  • It’s fire-retardant – Most foam insulation boards are made with a flame retardant chemical. The retardants can cause significant health issues like reproductive toxicity and cancer.

Spray form insulation

This type of insulation is the most common and effective type of insulation. Using polyurethane spray form effectively seals all cracks. Additionally, it’s heat and wind-resistant. When purchasing the spray form, it’s essential to differentiate between low-density open-cell spray form and high-density closed-cell spray form.

The cells are intentionally left open for low-density open-cell spray form, making them flexible and suitable for indoor applications like soundproofing. On the other hand, in high-density closed-cell spray form, the cells are close together, becoming rigid and stable, making them suitable for larger areas.


  • It’s eco-friendly – If used in a greenhouse roof, there are reduced carbon emissions into the air as it improves the room’s energy efficiency.
  • Seals off all gaps – The spray form acts as a barrier and is water-resistant. This helps in reducing moisture and air from outside.
  • It reduces the utility bill – There will be less reliance on the HVAC system when your home is using the spray form as the insulation keeps your home in moderate controlled temperatures.
  • It’s long-lasting – Spray form is made of isocyanate and polyurethane that hardens when applied and doesn’t lose shape. So, there will be no need to replace it after using it for an extended period.


  • It’s expensive – Despite cutting down your utility bills, the initial upfront installation fee can cost from £20 to £50 per square metre.
  • You’ll require the services of a professional – Although it’s an easy process, spray form insulation is made from chemicals that can cause eye, skin and respiratory issues. Also, the vapour is highly flammable.


Loose-fill insulation

This type of insulation is appropriate for areas that are hard to reach. It can either be cellulose or fibreglass.  During the application, a long flexible tube is used to access the hard-to-reach places.

Pros of fibreglass loose-fill insulation

  • It’s non-flammable – Although fibreglass may contain traces of glass and it can easily catch fire, blown-in fibreglass is entirely fire-resistant.

Cons of fibreglass loose-fill insulation

  • It’s unsuitable for cold places as fibreglass loses up to 50% of its efficiency when subjected to different interior and exterior temperatures.
  • It can cause health concerns – Wear protective gear when handling fibreglass spray form as contact with your skin may cause irritation and lung cancer when inhaled.

Pros of cellulose loose-fill insulation

  • It’s durable – Unlike fibreglass, it does not degrade when subjected to extreme temperatures making it a good option for cold areas.
  • It does not pose any health risk as it’s made out of paper, primarily recycled newspaper, thus being environmentally friendly.

Cons of cellulose loose-fill insulation

  • It’s made out of paper and highly flammable.

Things to consider when installing roof insulation.

When considering installing roof insulation, you should consider a few things. Below are some of the factors you should consider before installing a roof insulation system in your home.

  1. Ventilation

A home requires fresh air circulation to allow the house to stay dry and healthy. Therefore, when installing the roof insulation, provided that you do not seal or block any ventilation spaces like the grills, airbricks and vents.

The building regulations establish the standards to be observed when installing roof insulation. It usually entails adding up more vents if they are not enough. Before the installation, ensure to check with your local building control office to find out the exact requirements for your home.

2. Damp roof

Dampness is not uncommon in most homes in the UK due to the humid conditions experienced throughout the year. Insulation prevents heat from escaping your house, which in turn, traps moisture in the roof.

Therefore, if you previously had damp issues resulting from condensation, it could worsen the situation. So, it’s advisable to increase the ventilation in your roof before installing the insulation. In addition, you should first fix any damp issues.

3. Warm roof.

A warm roof is an alternative when it comes to roof insulation. However, you need to call in professional services to have this fitted because of the job’s complexity.


  • You can board the floor for storage without worrying about raising it to create extra depth.
  • There are lower chances of experiencing frozen pipes and tanks compared to when you have standard roof insulation.


  • Apart from insulating your roof, you will have to protect the surrounding areas like the chimney, party, and gable walls. If the spaces are left uninsulated, heat will seep through, making it ineffective.
  • Insulating your home at a raft level is considerably more expensive than the standard roof insulation

3. Room on the roof.

If you consider living in the attic, or it’s already a living space, you must ensure the ceiling and the walls between the unheated and heated rooms are well insulated. Additionally, ensure to protect any dormer windows either on the wall or ceiling.

3. Inaccessible spaces on the roof.

If the space on your roof is insufficient, call in a professional with special equipment to blow the appropriate insulation material like treated cellulose, polyurethane foam, or mineral wool fibre.

Benefits of insulating your roof

Insulation slows down the transfer of heat between the outside world and your living space. As a result, it allows the environment in your home to be warm during the winter and cool during summer. Other benefits attributed to roof insulation include:

  • It’s an additional layer of protection.

Your roof is the first part of contact with the natural elements from the outside. Due to exposure, your roof is vulnerable to leaking and cracking. However, if your roof is insulated, its longevity is guaranteed as it is protected from damage caused by ice dams and moisture.

  • It saves you extra costs.

30% of the heat loss around your home is from the roof. Therefore, when insulation protects your roof, it efficiently works to help your home retain heat. Consequently, you won’t require extra warmth from an external source thus, reducing energy costs.

  • It reduces your home’s carbon footprint.

Studies and research suggest that efficient roof insulation reduces the emission of carbon dioxide into the air, which helps fight against air pollution.

  • It prevents the growth of moulds

A sound roof insulation system regulates the moisture and temperature of your building. Therefore, you reduce the probability of the growth of moulds.

  • Fewer HVAC wear and tear

A majority of older houses have outdated and inefficient insulation systems. As a result, the heating and cooling system works overtime attempting to regulate the temperature and moisture in your home. However, if the roof is well insulated, there’s less reliance on the heating and cooling system as the house achieves a conducive temperature with less reliance on external sources. In addition, the insulation acts as a buffer against all the excess heat from outside.

When planning on choosing the best insulation material for your home, even for a DIY, it’s highly advisable to seek the services of a professional. This way, the most appropriate roof insulation will be fitted in your home, reducing your energy bills, keeping your home warm, reducing carbon emission and ensuring a controlled and moderate temperature during the warmer seasons.

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