ᐅ Installing Rolled Roofing Felt / Ceiling Felt in the Attic

Hello forum readers,

I am planning to insulate my unused attic with a roll roofing felt or blanket insulation to improve thermal performance during winter and summer. I did some research and came across this webpage:

[MEDIA=YouTube]yB2dFg8uFvs[/MEDIA]

The video clearly shows how the installation should be approached and carried out. Since the video appears to be directly from ISOVER, I am assuming that the instructions are accurate as presented.
My questions:

• Has anyone had good or bad experiences using these materials and would recommend or advise against them?

• Does this type of insulation deliver the expected improvements in heating cost savings and overall thermal performance?

• What thickness of insulation would you recommend? The area is about 80 sqm (860 sq ft); the building was constructed around 1965; otherwise, my situation looks quite similar to the one shown in the video.

• How can costs be minimized when purchasing materials? Does anyone know of a good, affordable building materials supplier that allows online ordering and reliable delivery?

• The installation doesn’t seem to require special expertise. I plan to do it together with a neighboring tradesperson from the construction industry. Do you have any other tips or recommendations?

I appreciate any advice or additional insights!

Best regards

Hi, according to official statistics, this is a very cost-effective measure. To reach the current insulation standard, you should choose at least 16 cm (6.3 inches) of insulation thickness.

Be cautious with installing a vapor retarder film underneath – depending on the type of ceiling you have below, it can either improve the result or cause mold issues. It’s better to have an independent energy consultant take a look. Check the list from BAFA.

You can also simply lay the insulation material without any foil underneath or on top, allowing any moisture vapor to escape.

If you want to keep it cooler in the summer as well, lightweight materials are not ideal. In that case, consider natural insulation materials such as wood fiber boards or recycled options like cellulose made from shredded newspaper.

One more tip: if you install 24 cm (9.4 inches) of insulation thickness, you will likely meet the subsidy requirements from KfW and can receive a 10% investment grant – you’ll need to calculate if this makes sense considering the additional costs. The application is also done through an energy consultant – this time only those listed as energy efficiency experts.

Good luck with your project
Susanne Junghans