Performance
Technical Information
Technical Information / Performance
Installed vs. Pre-Installed R-value
When it comes to insulating metal buildings, it is crucial to be aware of the differences between the “Pre-Installed R-value” vs. the “Installed R-value”. The 'traditional' method metal building insulation is installed is unlike any other means of insulating roofs and walls. Traditional methods promote the compression of the insulation and defective vapor retarder placement above purlins and behind girts. This method negatively effects the performance of the insulation. We would never design and insulate our homes this way, so why even consider doing this in your metal building?
Pre-Installed R-value – Package label R-value is stated on the packaging label as well as printed on the fiberglass. The metal building insulation industry takes great pride in the fact the laminated insulation delivered to the job site is that of the package label. In fact, there are industry certifications in place that assure the package label R-value is achieved after the insulation is laminated onto a vapor retarder facing.
Installed R-value – Typically referred to the performance of the insulation assembly as a whole, which should be representative of typical installation construction. The installed R-value is commonly equates to the U-factor of the assembly.
U-factor (thermal transmittance): heat transmission in unit time through unit area of a material or construction and the boundary air films, induced by unit temperature difference between the environments on each side. Units of U are Btu/h·ft2·ºF.
~ definition from ASHRAE Standard 90.1
A simple conversion of a U-factor will provide an installed R-value.
Get What You Pay For
Don't be mislead by the “Package Label R-value” of the insulation because majority of the time, it essentially has very little to do with the U-factor (installed R-value). Here is a closer look at a few examples of typical metal building insulation package label R-value and installed R-value.
Performance is based on the January 2010 ASHRAE News Release and ASHRAE 90.1-2013
Getting What You Specified? Most Don't!
What if 95 percent of the metal buildings you have worked on the past dozen years performed 20 to 40 percent below actual insulation code intent? What if those building owners came back looking for an explanation and remedy? Learn what the term "Value Engineering" typically equates to for insulation and red flags you should be on the look out for. Read full article published in Metal Architecture
