low-energy glazing - constructions database tips?

[MahBumble]

I'm modelling a low-energy dwelling built on passivhaus principals. We expect the planned triple glazing (http://bit.ly/bdgXt3 or similar) to achieve a U-value of around 0.8W/m2K (with a lower Ug-value). Any tips on how to best reflect this in the IES contructions?

I seem to have hit a limit of Ug = 1.73 W/m2K using two 6mm clear floats and a 6mm pilkington, with 12mm argon-filled cavities.

Thanks

[ZapBran]

I've not had time to check it out yet but I believe LBL labs (the guys that gave us Radiance) have a glazing tool that shows virtually any glass in a format that can be directly used to create ies windows... might be worth having a play.

[MahBumble]

I solved this a while back, but for anyone else stuck trying to get lower u-values:

The trick is in the emissivity of the inside and outside surface of each pane. Where the default for glass is something like 0.9, highly reflective coatings in the infra-red range bring it down to as low as ~0.03, and still leaves the emissivity in the visible light range high (~0.7). These values can be altered for each pane of glass in the window in the constructions menu.

Tom

[huntervu28]

Change cavity resistance to meet your demand, this tip is in <VE> official document, not my trick .

[MahBumble]

Change cavity resistance to meet your demand, this tip is in <VE> official document, not my trick .

- really? it's odd that they recommend modelling broken physics, when it can actually handle low-e glazing just fine without bending the rules!

[Yahya]

Hi there,
Would anybody be able to help here by suggesting some glzing properties that can be considered as 'low-e' and also another set of properties for 'reflective' glazing? I'm just trying to model some options that are possibly suitable for hot-arid climates.
I have come across some suggestions here i.e. changing the air gap resistance but not sure which values are reasonable.
Any advice is highly appreciated.
Yahya