Thermal Conductivity of Different Roof Insulations

[hocho]

For concrete roof. Thermal Conductivity is about 1.28 W/mK.

For PIR insulated panel. it's about 0.020 W/mK.

How about for typical roof insulated sheet that you put beneath the thin rigged or corrugated roofing material. What is it's thermal conductivity? I wonder if it would approach close to the PIR insulated panel.

What insulations do you use and what is your estimate of its thermal conductivity compared to concrete?

 

[IRstuff]

Why do you need estimates when there is already a table:

https://en.wikipedia.org/wiki/R-value_(insulation)#Typical_per-unit-thickness_R-values_for_material

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[hocho]

Why do you need estimates when there is already a table:

https://en.wikipedia.org/wiki/R-value_(insulation)...

I'm only familiar with the unit W/mK. Your units are in reverse mk/W and not all materials have values.

Please refer to:

http://www.engineeringtoolbox.com/thermal-conductivity-d_429.html

In insulation forms they put beneath roofing.. What is the specific name of the insulation so I can see it's W/mK value?

 

[IRstuff]

As the article and other related articles explain, the construction industry uses an R-value, which is derived from the thermal resistivity.

As you can see, commercial roof insulation materials are specified by their R-values:

http://www.homedepot.com/s/roof%20insulation?NCNI-5

http://www.homedepot.com/catalog/pdfImages/3e/3ed37fbb-73d8-4fee-bee3-2d20e75c4643.pdf

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[hocho]

IRstuff (Aerospace) 30 Sep 15 04:33

As the article and other related articles explain, the construction industry uses an R-value, which is derived from the thermal resistivity.

As you can see, commercial roof insulation materials are specified by their R-values:

http://www.homedepot.com/s/roof%20insulation?NCN...

http://www.homedepot.com/catalog/pdfImages/3e/3ed3...

20
The brand i'm interested in doesn't have any R-Value. It has only thermal conductivity of 0.020 W/mk.. to convert it to R.. it is said to divide it by length.. the length of the insulated panel is 1 meter by 7 meters.. so dividing it by 0.020 W/mk = 0.00287 to get U value.. the R value is 1/U or 350.. but the value is wrong.. so how do you convert thermal conductivity of 0.020 W/mk to R?

 

[moltenmetal]

The length is the THICKNESS of the material through which the heat is being transmitted, such that thicker insulation gives a higher R value.

 

[IRstuff]

0.02 W/m*K is 50 m*K/W, which, in the table, points you to two sorts of foam. That's about as good as it gets unless you want to use an aerogel panel.

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[hocho]

Are the insulations you use fireproof or can they burn? For instance.. the latest sandwich panels (or Polyisocyanurate being offered to me) can burn and flashover within 30 mins. See

https://www.youtube.com/watch?v=AimeoIgReEs

 

[IRstuff]

Yes, they probably can, but you depend on the roofing material itself to minimize the risk. Aluminum, for example, has something like 4 hr contact burn resistance, i.e., a chunk of burning wood will not cause the aluminum to fail for at least 4 hr.

Have you tried Googling this? There's tons of information on the web.

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[Ron]

The brand i'm interested in doesn't have any R-Value. It has only thermal conductivity of 0.020 W/mk.. to convert it to R.. it is said to divide it by length.. the length of the insulated panel is 1 meter by 7 meters.. so dividing it by 0.020 W/mk = 0.00287 to get U value.. the R value is 1/U or 350.. but the value is wrong.. so how do you convert thermal conductivity of 0.020 W/mk to R?

I gather from this statement that you do not understand the concepts discussed and are attaching numbers to an issue in an effort to solve something. Unfortunately that will not work. You need to have some basic understanding of roofing, thermal transmission, construction materials and application techniques. It would appear that you are not from the US considering the units you are using. There are numerous basic roofing/insulation courses available online, some of which are free. There is also a lot of good technical information available if you are willing to research it.

For many years, the most common element of a building to fail was the roof. Improvements in materials and training have resulted from need. Unfortunately building envelope failures now rival the frequency of roof failures, but for mostly the same reasons.

Spend some time researching your issue with various manufacturers and technical groups to gain more knowledge about the materials and concepts. Here is a list of common roofing insulations, but each has its proper application and use and one type of insulation is not necessarily appropriate for all types of roof coverings.

Glass fiber board
Polyisocyanurate board
Perlite and vermiculite board
wood fiber board
extruded and expanded polystyrene board
lightweight insulating concrete
cellular concrete
....and various combinations of these.

Good luck.

 

[DBronson]

hocho:

You should refer to the ASHRAE "Handbook of Fundamentals". It has extensive tables of R values for most construction materials. As Ron points out, you seem to have some confusion about this subject. The Handbook has excellent discussions of these topics plus detailed examples of calculating the R value of the entire roof assembly. Look for the SI version for metric values.

Regards,

DB