Instructions for installing Thermano thermal insulation under the rafters of a sloping roof

Instructions for installing Thermano thermal insulation under the rafters of a sloping roof

Thermal insulation installed under the rafters, or inside the attic, is perfect when we need to improve the thermal performance of a building without interfering with the roofing structure. 
The very low lambda of Thermano sandwich panels (λ = 0.023 W/mK — the lower the value, the better the thermal insulating performance) greatly improves the thermal insulating performance of the building with the minimum insulation layer thickness.

Most heat escapes a building through a roof when its thermal insulation barrier is poor. A good roof thermal insulation system provides a suitable level of indoor thermal comfort and great savings on heating costs. The PIR-core sandwich panels are the best choice when we need superior A++ class insulating materials.

 

How much does an under-the-rafter thermal improvement of a pitched roof cost?

Thermal improvement by installing the insulation under the rafters does not require removal of the roofing. This is the best way for fast, inexpensive and effective reduction of heat losses from a building. 

 

Step-by-step under the rafter thermal improvement of a pitched roof

You will need the following to install the Thermano panels:

  • Thermano panels       
  • aluminium tape
  • vapour breathing membrane to isolate the air vent over the mineral wool filling the rafter spans
  • wood screws
  • low-pressure insulating foamlow-pressure insulating foam
  • tack gun to fasten the vapour breathing barrier
  • nails and cord to secure the mineral wool panels in place
  • saw or other tool to cut and trim the Thermano panels.

1. This example demonstrates how to install thermal insulation in an atticcomprising a rafter infill of mineral wool and Thermano panels under the rafters.

2. Prior to the installation work, make sure that the top wall sections at the edges of the roof slope are insulated with thin EPS boards or another thermal insulator,as shown here in the video.

3. Start by installing the mineral wool panels. Remember to leave clearance for air venting. Here the recommended air vent clearance is 3 cm minimum. This clearance can be maintained by using slats of an appropriate thickness. The air venting protects the whole structure against moisture and effectively removes any in the form of a condensed steam from the mineral wool layer. The air gap will also extend the life span of the rafters and help keep them dry if the timber humidity rises over 18%.

4. The vapour breathing membrane serves a similar purpose. It shields the mineral wool infill across the entire roof slope. 1: The membrane will secure the wool fibres against loss. 2: The membrane will prevent cold air draughts. Both phenomena are critical to the thermal insulation performance of the mineral wool layers. Tack down the vapour breathing membrane with the tack gun to the air vent clearance slats.

5. Next, the space between the rafters is filled with the mineral wool panels. Secure each panel in place with the cord to prevent movement. A network is created by attaching the cords to the nails driven into the underside of the rafters. This cord net will keep the mineral wool panels in place.

6. Now lay the Thermano panels. Fasten the Thermano panels directly to the timber. This is much easier with metal profiles attached earlier to the rafters.

Start the installation from the bottom and proceed upward, laying each panel horizontally, side by side. Temporarily fix the Thermano panels with single wood screws driven into the rafters. The final fixing takes place later, along with the installation of the drywall panels. 

Lay each successive row of the Thermano panels in a staggered pattern, secured by the locks. 

The edge panels at the walls and window openings need to be trimmed to size with a hand saw.

7. Seal the gaps at the edges using LP insulating foam.

8. Now use the aluminium tape to seal all the panel joints.

9. The last stage of the project is to install the drywall panels. It is critical to fasten the frame to the structural members, the rafters in this case, either perpendicularly, or to the walls. Choose a suitable screw length to fix deep into the rafters.

 

If we install a Thermano thermal insulation system...

  • We save the attic surface area by installing relatively thin sandwich panels having great thermal insulating performance.

  • We also contribute to improving environmental protection. Less energy input means fewer pollutants in the air.

  • We significantly reduce our energy bills for heating and cooling.

 

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If you have any questions, please contact:

+48 801 000 807