The role of gas in insulating glass

The role of gas in insulating glass
Since the beginning of insulating glass occurs, we are researching to have better ways of how to get better U value. There are many factors in building insulating glass, and we are going to talk about the role of gas inside insulating glass.
The effect of the glass part to the windows performance
Effect on the thermal insulation
Glass thickness
Distance between glass panes
Number of glass panes
Inert gas
Type of low emissivity glass
U value=the value of heat transfer coefficient.
It describes how well a material conducts heat over a given area in standardized conditions. The U value is defined as U=1/R=Qa/dT(W/M2K)6. It is also known as the inverse of R value, the measure of thermal resistance. The lower the U value is, the better is the thermal performance of the glass.
1.    What is the gas used in Insulating glass
Noble gases such as argon and krypton, even xenon are used as inert gases in insulating glass unit, because they transfer and conduct heat much less than standard air.
2.    Why should we fill in gas?  Function of gas
In a standard window roughly a half of the heat loss is caused by the radiation between glass panes and the other half by thermal conductivity of inert gas and the flows in it.
Noble gas has an effect on the thermal insulation of the insulating glass unit. Argon is the most popular used inert gas due to its low price and easy availability. It is non toxic and non reactive gas which has roughly 30% lower thermal conductivity than air (0.0179 W/mk against 0.0262 W/mk) reducing the thermal conductivity of the unit.
As a non reactive gas, the argon also protects other items used in insulating glass unit.
When 90 percent argon gas fill is used in a low-e IGU instead of air, the window's u-value can be improved by up to 16 percent. Similarly, krypton improves the u-value in a low-e IGU by up to 27 percent. However, using a noble gas instead of air in an IGU costs both time and extra cost to the production.
3.    How to fill in gas?
Gas filling can be performed either with online gas filling line or with manual gas filling machine.
Our LBZ2500 vertical insulating glass production online gas filling line can automatically fill in gas while you choose gas filling function. The manual gas filling machine ZCJ02 works with oxygen sensor to determine the oxygen rate inside insulating glass. When there is no oxygen out from output pipe, the machine will stop Argon gas filling, which means the insulating glass is full of Argon.
4.    How to detect the gas?
Both the IGU machinery manufacturers and their customers should have the ability to check the goods they’ve purchased or produced to ensure they meet the expectations and requirements.
Currently a number of ways exist for determining the gas filled level within insulating glass units. However, we recommend two ways without any damaged to final insulating glass products.

Helantec Helantec GmbH Insert the pipe inside spacer.

Helantec tester

Sparklike Oy  Without damage to IGU. 

sparlike tester

5.    How much percent of the gas?  85% or 90%
Argon gas fill rate is also required by different standards. The China national insulating glass standards requires 85%, while European standards aim to gas fill level of 90% with permitted annual leakage less than 1% setting high requirements for the process.
6.    What kind of impact influence the gas retention?
Some potential problems occur when using gas filling in insulating glass production. Gas filling can be performed either with online gas filling or with manual gas filling methods of which both have their own risks and quality control issues. When operating an automated gas filler the user needs to verify the machinery and the filling process is working properly.  As the inert gases are invisible and odorless and the detecting is difficult without appropriate control tool.  Manual gas filling ls also vulnerable to human errors in the process for example when sealing the fill holes or during secondary sealing.  Additionally the filling result might be turbulent or the gas is not homogenized.  Even though the gas filling process would be successful, problems might still occur. The inert gas might leak out slowly because of production process, bad materials or workmanship. The process should verify the gas concentration multiple times during the process to ensure that all the production phases are working as they should.

Regarding the primary and secondary sealant, which has great influence on gas retention. Please check below tables. As silicone sealant is not water and gas tighten, so butyl sealant must be tight. 


The purpose of this article was to provide the new glass processor companies with basic understanding of gas inside insulating glass, and how to detect the gas concentration and keep it within insulating glass unit.