General Insulation FAQs | Knauf Insulation

Can I install kraft faced product over existing kraft faced material?

No, it is not recommended to install insulation with a kraft facing over another. When installing layers of insulation, there should only be one vapor retarder installed in the appropriate location. It is not good practice to incorporate two vapor retarders in an insulation system. Moisture could become trapped between the two layers and not be able to dry.

Can the kraft facing be left exposed?

Kraft facing should not be left exposed. For insulation material to be left exposed, building codes require the surface of the material to have a flame spread index of 25 or less. Insulation with kraft facing does not have the required flame spread index and must be covered by an appropriated material like drywall.

Can you install fiberglass blowing insulation over cellulose or visa versa?

Fiberglass installs at a lighter weight than cellulose. Therefore, fiberglass can be blown on top of cellulose without the threat of compressing the existing insulation. Since cellulose must be installed at a much higher density or weight, it cannot be installed on top of fiberglass due to the potential to compress the existing insulation.

Do I get the same R-value if the product is compressed into a cavity?

When fiberglass batt insulation is compressed, the R-value per inch is increased, but the overall R-value is decreased because there is less inches or thickness of insulation.

Learn more about R-Value.

Does insulation really help with sound movement?

Yes, the installation of fiberglass insulation delivers excellent sound absorption. Sound insulation can significantly reduce noise between rooms and from external sources.

Learn more about how fiberglass insulation helps control sound.

Is fiberglass fire proof?

Fiberglass is not considered fire proof. However, unfaced fiberglass insulation batts are noncombustible per ASTM E136 and can be used where noncombustible insulation is allowed. It requires no additional fire-retardant chemical treatments. Be aware: the addition of facings may change this rating. Therefore, refer to the manufacturer’s technical data for each product for specific surface burning characteristics.

Many fiberglass insulation products manufactured by Knauf Insulation have surface burning characteristics of a flame spread index of 25 or less and a smoke developed index of 50 or less, which meets all national building and mechanical codes for insulation.

Discover Knauf Inner Safe Concealed Batt Insulation that is a fire code compliant alternative.

Learn more about insulation fire protection.

Is kraft faced material required on interior walls?

No, kraft faced insulation is not typically used when insulating internal walls. A kraft facing is a vapor retarder which helps with moisture migration from unconditioned air outside. Since interior walls are exposed to the same ambient conditions on either side of the wall, a kraft facing is not required.

Learn more about insulating walls here.

How do I save documents?

Easily save documents like data sheets, UL Validations, EPDs and even create submittals with My Documents. Find your documents anywhere on the website and click the 'add to folder' icon. This will save the file to your project folder (much like adding a product to an online shopping cart). Save the folder for later and even fill out an included coversheet for a project submittal. You can download every document in the folder as a single PDF for easy sharing. Edit, copy, delete, or download them again and again.

This is your project. Let's get building.

Find the document(s) you would like to save and click the 'add to folder icon.'
This will save it to a folder much like adding a product to an online shopping cart.
Click the icon again or go up to 'My Documents' at the top of the page to open your folder.
Create an account or login to save the documents in your folder.
Once saved, you can complete a cover sheet that can be used for a project submittal.
Download the entire folder as a single PDF for easy sharing that includes all of the documents and the cover sheet.
Or, download only the documents or each document individually. Whichever you desire.
Manage your document folders at anytime. Edit, copy, delete, or download them again.

Questions? Feel free to contact us anytime and a representative will be happy to help.

What is an ice dam?

An ice dam is ice that forms on the roof that stops melting snow from draining properly. A lack of sufficient insulation in a home can cause heat to disperse, melt the snow on a roof and create ice dams. Ice dams have been known to push water into cracks within homes, causing potentially devastating water damage.

What is k value?

The thermal conductivity, or k value, is a measure of the ability of a material to conduct or transfer heat. Lower k values represent insulators, while high k values represent conductors. The inverse of the k value is the material's resistivity, or R-Value per inch.

What is r value?

R value is the measurement of a material's resistance to heat flow. The higher the r value, the greater the insulating power.

Learn more about insulation r-value.

What is u value?

The overall heat transmission coefficient, or u value, is a measure of the heat transmission through a building assembly. Instead of a single material property such as R-Value, the U value includes the impact of different elements in an assembly and their orientation. Engineers use this property to calculate the heat gain or loss by multiplying the u value by the temperature difference of the assembly.

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