How to Choose Best Heat Insulation for roof

A common solution for anyone who wants to feel at home, insulation must be given special care. But what is the Best heat insulation for roof?. Starting by  properly insulating your roof and attic is ideal, because they are responsible for a third of heat loss.

What is the Best Heat insulation for roof? 

The heat insulation for roof allows substantial savings in energy and heating, provided you choose the right insulation. Whether it is a converted attic or a lost attic, the choice of insulating material will depend on: 

  • its coefficient of thermal resistance (R)
  •  its thickness
  • its ecological impact
  • its strength and durability

The R coefficient for thermal insulation

The coefficient of thermal resistance determines the effectiveness of the insulation. It is thus calculated R= thickness / lambda coefficient (its thermal conductivity, which reflects its heat transmission capacity) and is expressed in m².K / W. 

More concretely, the higher R will be, the more the material will be said to be insulating. 

A greener and efficient insulating material? 

Depending on the material chosen, your insulation will have a more or less marked ecological footprint . Make sure it performs well and releases few VOCs (volatile organic compounds) into your indoor air. Also consider its flammability, its resistance to humidity, but also its durability

The 5 best insulators 

Currently, five insulating materials are recommended for attics: 

  • mineral wool: glass wool (R= 2.5 to 3 for 10 cm) or rock wool (R= 2.3 to 2.9 for 10 cm)
  • vegetable wool; hemp wool (R= 2.4 for 10 cm)
  • animal wool: sheep wool (R= 2.5 for 10 cm)
  • extruded polystyrene (R= 2.8 for 10 cm)
  • polyurethane foam (R= 4.2 for 10 cm)

What type of insulation should I choose?

Heat insulation of attics

The ideal will be to move towards a roof insulation , because the volume will be heated. For this, cross layers of insulation (mineral wool or other) in rolls will be laid. Above all, care must be taken to avoid thermal bridges, which occur when the insulation is no longer continuous at the junction points. 

Do not forget the vapor barrier membrane, ideal to avoid condensation factors. 

You will thus obtain an attic that is protected from heat loss.

Heat insulation of floors

This solution is essential for lost attics. The insulation will then be unrolled on the ground, either directly on the floor, or along the joists in the absence of a floor. Another solution consists in depositing flakes of insulation posed by blowing or by spreading. In all cases, a vapor barrier membrane must be provided on the hot side to counter thermal bridges. 

How much will your roofing work cost?

Rates may vary depending on your project and your city.

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Comparison of heat insulation materials (natural, mineral, synthetic)

mineral wool

We will retain in this category two very popular insulating materials: 

  • glass wool : wooly in appearance, is made from sand (silica)
  • Rock wool: it comes from a low density volcanic rock, basalt

Mineral wool comes in rolls, semi-rigid panels or flakes. Very economical, it has the advantage of resisting fire, but not humidity, which reduces its thermal performance. 

The dust released by these insulators requires the wearing of a mask during your insulation work. 

Read more: Make Tawashi Sponge DIY

Biobased or natural materials

A distinction will be made between wool from animals (sheep wool) and plants (hemp wool). They compensate for their lower thermal performance with excellent acoustic insulation. They are available in rolls for roof insulation or loose for the floor. 

Their green value is often highlighted, because they are made from renewable raw materials. 

Synthetic materials

Composed of extruded or expanded polystyrene or polyurethane , these insulators are available in bulk or in semi-rigid panels for attic insulation. Their good thermal performance should not, however, overshadow their flammability and the obligation to call on a professional for installation by blowing.  

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How much insulation should I need for the attic?

Current standards are based on the coefficient of thermal resistance R to measure the effectiveness of insulation against heat loss. 

In renovation, to claim a tax credit and energy savings, the insulation work must result in R=6 m².k/W for the attic ceilings. In new construction, the roof insulation must reach a coefficient of 8. 

Thus, to calculate the ideal thickness to reach R=8, a simple multiplication by the lambda coefficient (thermal conductivity) will suffice. For rock wool with a lambda coefficient of 0.04, plan for a thickness of 8 x 0.04 = 0.32 m or 32 cm of insulation. 

Standards and certificates to know

First and foremost, opt for CE marking for all your insulation materials, which must be confirmed by ACERMI certification . Then focus on the indoor air emissions rating, and of course the thermal performance. 

Choosing Best Heat Insulation for Roof

When choosing the best heat insulation for a roof, consider the following factors:

1. Climate: The climate of the location plays a critical role in determining the insulation needed. For colder climates, higher R-values are crucial to reduce heat loss, while in warmer climates, materials with a high solar reflectance can help maintain indoor temperatures.

2. Roof type: The type of roof (gable, hip, flat, etc.) and its construction (pitched, attic, etc.) will impact the insulation choice. Some materials work better in specific roof designs and may require specific installation techniques.

3. R-value: Choose insulation materials with a high R-value. R-value measures the thermal resistance of a material, and higher values indicate better insulation. Local building codes might suggest minimum R-value requirements.

4. Moisture resistance: Consider materials that are water-resistant and have a high moisture vapor transmission rate to prevent condensation, mold, and rot. PIR or closed-cell polyurethane spray foam are examples of materials with good moisture resistance.

5. Fire resistance: Some insulation materials are naturally fire-resistant, such as mineral wool or fiberglass. Look for materials with a good fire rating to meet local building codes and enhance safety.

6. Environmental impact: Opt for insulation materials with low environmental impact, such as those made from recycled content or with low off-gassing of volatile organic compounds (VOCs).

7. Installation: Proper installation is essential for maximizing insulation performance. Make sure to hire experienced professionals or follow guidelines for DIY installation.

8. Cost: Evaluate the cost-effectiveness of materials based on their initial cost, maintenance needs, and energy savings.

Sometimes, investing in higher-quality insulation can lead to significant long-term energy savings. By considering these factors, you can make an informed decision and choose the most suitable heat insulation for your roof.

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