Glass Selection

Devil_Star · Posts: 4

Hi, there.
What can I do if I can’t find the glass I want for the project windows from the built-in library? I’m Australia based and the reference glass I use is Viridian Glass (formerly known as Pilkington & DMS prior to acquisition by CSR). Now it has a wide range of energy performance glass in their catalogue but I can’t find many types of them in DesignBuilder’s Built-in library.

In Australia the energy efficiency related properties of glazing required by the Building Code are just the U value and the Solar Heat Gain Coefficient value. Would you consider adding some glass customization features (i.e. create-your-own-glass features) into the future versions of DesignBuilder?

P.S. I know you held a DesignBuilder / EnergyPlus workshop in Sydney in April 2008. Unfortunately I missed that one. Do you have any plans giving another seminar in Sydney in the near future? I believe the market for building energy modeling is currently expanding rapidly here with the fast development of Compliance regulation - Section J Energy Efficiency in BCA (Building Code Australia), and Best-Practice Schemes - NABERS Energy (formerly known as ABGR) and GreenStar.

All the Best,

Lance Chen

bhandari · Posts: 89

Lance,

If you know the properties of the glass, you can create your own glass. Go to panes library and either copy an existing glass or create new glass.

As you know several combinations of glass/gap types can provide a particular U factor and SHGC. Code and standards generally refer to the whole product induces. DesignBuilder will include the capability of reverse calculation, i.e. if user provides U/SHGC for the whole product, DesignBuilder will provide a list of glazing combinations, in future version.

Mahabir

bhandari · Posts: 89

Lance,

Forgot to answer your P.S. question. There will be a DesignBuilder/EnergyPlus training in Sydney in October/November, Please contact: DesignBuildr Software Australia: (www.designbuilder.com.au) for more details.
Mahabir

AJ Lester · Posts: 86 Location: Auckland

Hi Lance,

Here in NZ we often make use of the Viridian product as Viridian is the same company across both countries.

What you will find is that although the products differ slightly, if you don't want to create your own glass to match the SuperGreen specs, the Pilkington North America EverGreen 6mm product is similar to Viridian SuperGreen 6mm. Since Viridian came from a merger including Pilkington NZ/Australia, it is likely the same basic glass as the North American product.

This glass type (EverGreen) is also a sensible starting point for modelling the Viridian SuperGreen product itself. Make a copy of the EverGreen product, modify the parameters that data are available for and if any values are unavailable, at least the values you will be using are a reasonably close match for the likely properties of SuperGreen.

Bear in mind that the calculations of U-Value and SHGC required for compliance with BCA are according to NFRC guidelines and should be calculated using Window5.2. As such the values for U-Value and SHGC that you get from inside DesignBuilder will not necessarily match the values you should be quoting to clients / trying to meet to comply with BCA requirements as DesignBuilder makes use of ASHRAE guidelines not NFRC. The differences are not always significant but in some cases it makes quite a difference to the rating acheived.

Apologies if all this is well known to you and I'm not helping. Just thought a full explanation might help as I went through the same process to try and sort out Viridian for my use here in NZ.

All the best with your work.

Andrew Lester

Devil_Star · Posts: 4

Thanks for your reply, Mahabir.
A reverse calculation feature would be a nice one as that's what our building code requires. It will be much easier for us to work out the compliant range of U & SHGC sets, and then recommend windows to clients, as clients may not go for the same brand of windows which we set reference against.

Devil_Star · Posts: 4

Hi, Andrew.
Thanks for the detailed explanation.
I have noticed the U & SHGC values achieved by different testing standards are really a pain on the neck, which creates a lot of troubles for glass selection.

Maybe the way i searched is wrong, but i found many Viridian energy performance glass unavailable in both Window5 and DesignBuilder, such as ITO clear 74 Enviroshield - non-reflective but high thermal performance glass specialised for large glazing frontage e.g. for the application of a showroom. Do you have any suggestions of what to do in such situations?

AJ Lester · Posts: 86 Location: Auckland

Hello again Lance,

Viridian products are not included in the IGDB. I suppose this is because the market sector of NZ/AUS is relatively small and the Viridian products have not been considered significant enough for inclusion. This is just my supposition.

At any rate the method I would typically use in order to model a glazing from Viridian is to locate a similar glazing type (as described in my last post Pilkington North American EverGreen for Viridian SuperGreen) and duplicate this record then modify the relevant details to match the properties of the Viridian product.

From the Viridian website you can get a datasheet detailling the performance of all their glazing types (as I'm sure you already know). This is the basis for your selection of a reference glazing to duplicate. Typical factors I look for are Solar Transmission & Reflection, Visible Transmission & Reflection, but also colour and whether or not the glazing is a laminate or a single layer float glass.

Once you have selected a glazing type to duplicate, do so and then modify the parameters to match. Window 5.2 is good for this as the performances quoted by Viridian are NFRC performances and Window 5.2 defaults to this standard as well. To check ASHRAE performance you would need to create the ASHRAE design conditions in the Window 5.2 database for environmental conditions and recalculate performance.

Then, once you have the performance of your simulation glazing mirroring the behaviour of the real thing, you need to get it into DesignBuilder. Matching the performances according to ASHRAE measurements is one way to do this, but you should have all the info you need to create the glazing in DB from the Window5 glazing you have created.

Hope this helps you to see one way of getting performances for glazing products from our corner of the world into the DesignBuilder environment. There may be other, better ways of doing this, but this is typically the approach I take.

All the best with your modelling efforts!

Regards,

Andrew Lester

P.S. Sorry for another (over)long post!

Devil_Star · Posts: 4

Thanks very much for your help, Andrew.
Based on my limited experience in energy modelling, i still can see that different standards/systems do complicate things and slow down processes. Hope more powerful features can be incorporated into DB to work things out in a more straightforward way.

All the best,

Lance

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