Hi,
I’m currently using Hevacomp Design Database for generating (Part L) BRUKL document for one of my projects.
Couple of rooms in my building are exceeding solar gain limits. I understand this is due to the orientation of the building and the G-value of the glazing.
I tried applying the internal blind to the glazing but some default data in the glazing database does not seems to agree with the computed glazing properties.
For example default glazing type 8 has the same glazing construction as type 20. The only different is type 20 having internal blinds. Please see pictures below for type 8 & type 20.
In default type 8, glazing properties are U-value 1.5, light transmission 0.63, shading coefficient 0.57 and SHGC (G-value) 0.5 which is very similar to computed glazing properties based on the construction U-value 1.469 & G-value 0.6454.
However, in type 20, glazing properties G-value is completely different from computed glazing properties based on the construction. Computed glazing G-value is showing 0.2241 while the glazing properties SHGC (G-value) is at 0.5.
Is it safe to overwrite the type 20 SHGC (G-value) in glazing properties to the same value as the G-value shown in the computed glazing properties based on the type of blind assigned ?
From what I read on the forum, for Part L, we just need to input the U-value, Lighting Transmission, Shading Coefficient & the SHGC (G-value) figures from the manufacturer.
To incorporate the internal blind shading to Part L calculation for solar gain limits, is it safe to overwrite the Shading Coefficient & the G-value of the glazing properties with the G-value from computed glazing data with the type of blind used?
Best Regards,
Sean - Apologies. I've examined the input files for PARTL and the SHGC value *IS* being used. The G value is calculated directly from the build up of the glazing unit construction/layer data, whereas the SHGC is a fixed figure provided by glazing manufacturers. You can substitute the SHGC value with the G value if you wish.
Regards,
Hi Duncan,
Thanks for the reply.
I am trying to incorporate the internal blind shading performance into the glazing G-value get a pass on the solar gain limits in BRUKL document.
As the computed glazing data based on the construction is showing a significant improvement in G-value of the glazing with the incorporation of internal blinds based on the type of internal shading device, Would it be a fair assumption to overwrite with the computed glazing data G-value 0.2241 into glazing property SHGC 0.5 ?
Please see attached screenshot for reference.
Best Regards,
Sean
Sean - The PartL calculation is only interested in the U-Value of the glazing - other calculations consider Light Transmission, Shading Coefficients, etc.
If you wish to specify internal blinds, you need to select it on the Glazing data page
and then specified from within PartL on the Misc tab, Additional surface data. The type of blind is selected from the Glazing data, but you must specify the rest of the information yourself.
You should note, however, that internal blinds are not fully modelled, as the re-radiation effect of solar gains are not modelled after they have enter the space. See here for more information.
Regards,
Hi Duncan,
Apologies if I am repeating the same question that has already been answered.
On my initial compliance report with default glazing type 8 without blinds, the room solar gain limit exceeds massively. Please see attached below. In this case the G values are the same in computed and default input.
Default type 20 glazing which is the same construction as type 8 but with internal blind.
If I change the SGHC value to 0.23 which is a rounded up value from computed G-value with internal blinds, the solar gain limit won't exceed anymore. Please see attached.
Based on this two results, I am wondering if the computed glazing data G-value including internal blind can be used as overall G-value of the glazing ?
The PartL program doesn't use the SHGC figure - the SBEM calculation engine only requires a U-Value.
Regards,
Sean - Apologies. I've examined the input files for PARTL and the SHGC value *IS* being used. The G value is calculated directly from the build up of the glazing unit construction/layer data, whereas the SHGC is a fixed figure provided by glazing manufacturers. You can substitute the SHGC value with the G value if you wish.
Regards,
Duncan,
Thanks for your help.
Best Regards