Argon Gas Properties

[Anonymous]

Hi everybody!

i have a simpli question for you. I have noted that when i put a new layer of gas, for example "Argon" it happens a strange thing, becouse in "material list Details" the Argon has 0.016 W/m.K of condutivity while in "Layer Name" the Argon has 5.560 W/m.K of Conductivity.

How is it possible?! 

thanks a lot!

[Pennetier1]

Hello nursetangofiesta, 

That is a good question.  The reason is that air, argon or other gases, have  a different  thermal behavior than other solid material when enclosed in a gap such as between panes of glass or within a wall cavity.  Although they each have a particular conductivity, this will be affected by the thikness of the gap, and even the direction of the heat flow through that gap (ceiling and wall will be different) and the emittance of the surfaces facing the gap.

The Conductance of an 1" thick air gap (25 mm) is approximated at 5.56 W/mK, or a RSI value of ~0.17.

Now, I am not sure what is the value for 25 mm of Argon gas; Ecotect seems to use the similar value than an Air gap, even though we know that Argon has a lower conductivity.

This is another reason I do not use the layers to create glazing materials; instead I rely on the thermal properties given by the manufacturer.

I hope that helps a little bit.

Let me know if you have more questions on this topic, otherwise please accept as a solution so that others can benefit from this information.

Cheers,

[Anonymous]

Hi Oliver!

First of all thanks for your job and support my profession of building engineer.

Second one this problem it is the same when i flood the "mm" of the argon layer.

I mean that if i flood the argon layer probably the conductivity should to became to lower, isn't it?! Or generally it must be changed!

But it remains always the same! : (

How is it possible!?

Do you have a tutorial to fixe this problem!? or in general a tutorial that can show me how i can create a window with 3 glasses and 2 layer of Gas Argon?

Couse i'm doing an OFF-THE-GRID building here in France.

I told you that becouse when i have done the computation by my hands of that configuration and the conductivity of Argon for 25 mm results more lower than that value ( i mean 5.5 W/m K ). 

Really thanks for your support. I appreciate that.

Piercosimo 

[Pennetier1]

Hello nursetangofiesta, 

I suspect Ecotect is not handling the Argon layer correctly, and instead sees it as similar as the Air Gap layer.  I would suspect Ecotect should use about 2.5 instead of the 5.56 conductivity.

But this once again emphasiszes the fact that you should not use the Layer tab to create your own windows; Even if there was no issue with the Argon layer, things would still not be correct as the true U-value of a window should take into account the framing of the window, which you cannot account for in the layers options.  A metal frame window will have a much higher U-value than a Vinyl frame window with the same glazing and air gap.

Secondly, most windows now have special films - Low e - that change the U-value of the glazing, and again cannot be input in the Layer option.

Do not try to build your own window in Ecotect, as it will only give you erroneous results.

Instead use the glazing manufacturer's energy performance data for your particular window.  They typically give the U-value and the Solar Heat Gain Coefficient (SHGC).  Set that into the main property window and let the Visible Transmittance to 1.0 for thermal calculations.

If you insist of building your own window, I would recommend using the free software WINDOW from the Lawrence Berkeley Lab in California.

You can then create your own glazing system given a large library of glazing products, and it will calculate the U-value, SHGC and many more data for that glazing.

Let me know if you have more questions on this topic, otherwise please accept as a solution so that others can benefit from this information.

Cheers,

[Anonymous]

"Instead use the glazing manufacturer's energy performance data for your particular window.  They typically give the U-value and the Solar Heat Gain Coefficient (SHGC).  Set that into the main property window and let the Visible Transmittance to 1.0 for thermal calculations."

what is "the glazing manufacturer's energy performance data". I dont understand what i have to do.

My problem is i have a building in revit ( photo 1), i saved it in Gbxml and then i import all in Ecotect. 

In revit i set the windows with this properties ( photo 2 ). When i work in ecotect the same window have a different features. ( photo 3).

Now There are two different ways for me: 

1- there is a way that i can use to import correctly from revit to ecotect my windows properties?

2- You can teach me a way to configure my window in ecotect?

Sorry if i maybe repeat the same question but i would like to understand better, what i have to do.

really thanks.

Pier

[Pennetier1]

Hello Pier, 

Unfortunately, the material properties do not translate from Revit to Ecotect, so you do have to re-create these materials in Ecotect.

Revit does perform energy analyses if you are keen on using it, so that you would not have to export to Ecotect, but simply run the calculations through Revit.

If you are using Ecotect, simply create a new window object with the values you are using in Revit:

1. Select your window object in Ecotect and go to the material properties.

2. Give the object a new name for your new window material.

3. Under U-value, enter your value 1.454 W/m2k.

4. Under SHGC, enter your value of 0.26

5. If running thermal calculations, enter 1.0 under Visible Transmittance; if running Daylighting calculations, enter your value of 0.55 under Visible Transmittance, and enter 1.0 under SHGC. You can leave all the other values the same for now.

6. Click the "Add New Element" button to add your new object to your library.

7. Make sure that your windows in your model are assigned your new window material.

That should do it.  These glazing thermal properties you have in Revit are what is known as the window manufacturer's thermal properties, or energy performance data as some manufacturers call it.

I hope it makes sense.

Let me know if you have more questions on this topic, otherwise please accept as a solution so that others can benefit from this information.

Cheers,