Berkeley Lab has been serving Industry, the public and Policymakers with informed research for over 50 years.All their software helps designers and architects to calculate the glass,windows optical and thermal performance.

Before the WINDOW 7 was updated in April ,2016,it’s difficult to calculate the vacuum glazing performance,because it’s difficult to define the vacuum space conductivity,the pillar systems conductivity that decide the final performance of vacuum glass,Window 7 update helps us more easier to confirm the glass combination and the right low-E used in  vacuum glazing,more details: Vacuum Glazings.

Berkeley lab offer solutions to windows &glass thermal insulation calculation

Berkeley lab offer solutions to windows &glass thermal insulation calculation

This post is a guide to calculate the vacuum glass performance with window software.

  1. Download Window series software.

Berkeley Lab software used to calculate glass performance(whether it’s monolithic,laminated,insulated and vacuum glazing) include WINDOW, OPTICS, IGDB.

WINDOW 7.8.28 :a publicly available computer program for calculating total window thermal performance indices (i.e. U-values, solar heat gain coefficients, shading coefficients, and visible transmittances).

Optics 6: a software that help users to create their own glass combination (insulated or laminated) that don’t exist in the IGDB.

IGCB 83.0:The IGDB is a collection of optical data for glazing products. Spectral transmittance and reflectance is measured in a spectrophotometer and contributed to the IGDB by the manufacturer of the glazing product subject to a careful review.

All these software are free and users can download and select the right coating and create their own glass configuration based on the unique project requirement.

If you’re new users of Window software,better to read the Window user manual to install and try first.

  1. Create vacuum gap in the gap library.

Window has several default gap options,including air,argon,Krypton and mix gas options,we need to set up new gap options for the vacuum spacing based on the actual vacuum glazing design.

Gap Options in window

Gap Options in window

After that we need to set every details of the vacuum glazing gaps.

As the vacuum glazing performance is decided by the vacuum degree,the pillars which will conduct the thermal,as well as the low-E coating to reflect the solar radiation and far infrared,so the details in the gap setting are all based on the vacuum degree and pillars.

Steps 1 to create vacuum glazing gap

Steps 1 to create vacuum glazing gap

Below is HaanGlas setting based on our actual product.

vacuum gap setting

vacuum gap setting

Haan vacuum glass is sealed in 10-4Pa high vacuum condition,which will eliminate the air convection inside the glass,which is the most important point deciding final U value .

Pillars consist of 3-5 micro pillars total diameter 0.5mm,and distance is 50*50mm in a diamond shape.Contacting area with the glass is much less than other vacuum glass there’s only circular shape options here,we set the radius 0.45mm and spacing 50mm.

Now total conductance of the vacuum gap is 0.000801W/M2.K.

Important note:Window only calculate the glass center U value,edge is excluded.Because every factory has different pillar materials,shapes and contact area,as well as different vacuum degree,and conductivity of edge sealing materials,it’s suggested to adjust the parameter settings here and get the conductance that is close to actual test data.

  1. Calculate glass performance.

Select the low-E coating from glass library and fill the code ,as well as the inner piece code,here let’s take TG PDE80A02(IGDB6518) as example.

Inert the new established gap code and thickness setting based on actual data,whether it’s 0.3mm or 0.15mm.

Calculate Vacuum glass with window

Calculate Vacuum glass with window

And now we get the result,actually almost all the performance (optical,SC ,SHGC is same as same combination insulated glass),the only difference is the U value.

Test result

Test result

The U value based onNFRC100-2010 standard is 0.47W/M2.K,which is vary close to our test reslt 0.47W/M2.K based on heat flow meter method(Steady state U value).

Users can also calculate the performance for vacuum laminated glass,vacuum insulated glass with Window software.


The method to calculate VIG performance with Window is not mature and not systematic,as every vacuum glass manufacturer has their unique production method,sealing edge technology,pillar shape and placement,even though after complex setting ,we can get a rough U value,but it’s still suggested to refer to the actual tested U value based on heat flow meter method.

Haan VIG with double silver low-E U value reach 0.47W/M2.K ,and 0.71 with single silver low-E.Kindly contact us for more info.