Guidance on Aluminum Window Frame Simulation (ISO 10077-2)

[Sara Daas]

Hello,

I hope you are doing well.

I am currently simulating my aluminum window frame in accordance with ISO 10077-2. My simulation conditions represent the climate in Saudi Arabia, with:

• Outdoor temperature at 45°C and hc​=23W/m2⋅K
• Indoor temperature at 23°C and hc​=8W/m2⋅K, and then reduced to hc​=5W/m2⋅K for increased resistance

These values define the boundary conditions in the attached THERM file:

• The indoor boundary is labeled “Frame”
• The outdoor boundary is labeled “Frame ex”

As specified by the standard, I replaced the double glass with a calibration panel. I noticed that assigning the calibration panel sides a “none” tag results in a U-value of approximately 12.9800, whereas assigning them “Frame” and “Frame ex” tags yields about 4.7408. or should they be assigned an Adibatic boundry condition? 

I am unsure which approach is correct according to the standard. Could you please review the attached THERM file and let me know if I am following ISO 10077-2 correctly?

Thank you in advance for your time and assistance.

[archi...@gmail.com]

Hi Sara.

I will take a look at your Therm file.

It is certainly an interesting theme, because in your case heat transfer goes from outdoor to indoor, situation which is not included in EN ISO 10077-2:2018 where it is written  (6.3.4) that "the reference temperature conditions shall be 20°C internal and 0°C external" .

Since flux direction is crucial to the equivalent thermal conductivity of unventilated air cavities this could result in different Uf values. It would be useful to have here the opinion of some other window frames calculators.

Finally, I wonder if EN ISO 10077-2 technical standard is applicable in your country.

Ciao

Fabrizio

[archi...@gmail.com]

Hi Sara.

I took a look at your therm file and made some corrections according to EN ISO 10077-2:2018 std.
- the insulation panel substituting the glass panel has now exactly 19cm width (bp)
- external temperature = 0°C  internale temperature 20°C
- CEN frame cavities (instead NFRC): unventilated (emissivity 0.3/0.3) and slightly ventilated (emissivity 0.9/0.3).
I'm not completely sure if I correctly considered where to apply Rsi=0.20 m2K/W since this particular geometry (inferior frame of a sliding door I presume) is not described in 10077-2. As I written it would be really useful to have here the opinion of some other window frames calculators.
However, I still wonder if the EN ISO 10077-2 technical standard is applicable in your country, since the thermal conditions are so different.
I attach the complete calculation using F.1 formula and the modified therm model.

Ciao
Fabrizio

[Alex Ent]

Hello together, 

it's a really very interesting discussion. As I used earlier ISO 10077-2 I can say that it's a standardized procedure to define Uf  - window / door frame thermal transmittance and linear linear transmittance at glass unit fixing (i.e. spacer) Psi. These values are to be used for a generalized Uw value of a window / door according ISO 10077-1. 

In this meaning for a standardized procedure you have to use the rules in it:

To define Uf
Te =0;
Ti = 20 degr.  
Rse = 0.04 (Hc = 25)
Rsi =  0.13 (Hc =7.69) normal panel surface
Substituting panel 0.035 W/m2K with thickness equal to glass d = dg

To define Psi
In regard to define linear thermal transmittance you need to replace the panel with a real glass unit with a spacer.

After you have these values you can define the Uw of the entire window according 10077-1. For all these determinations you are using simplified models and standardized procedures. The local conditions aren't to be used here.

After you define Uw (windows) and Uwall, you will need these for entire building energy balance, where you will use together with local conditions - temperatures, humidity, sun radiation etc.

It is another topic if you need to make an analysis of thermal behaviour of the door frame for local conditions in regard to defining condensation possibility, heat loss on thermal bridges etc.
Please correct me if I'm wrong .
Regards
Alexandar 

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Това е моя подпис 

А тук пробвам да вкарам снимка

[Fabrizio Prato]

Hi Alex,

Thanks, you brightly summarised the EN ISO 10077 series process. I think you are definitely right to distinguish the thermal and boundary conditions to be used for Uf calculation from those used to analyse the frame behaviour with local conditions. In this case, with the external temperature cited by Sara (45°C), the frame  internal  surfaces would be quite hot.

Ciao

Fabrizio 

[Hamid BADI]