Problem with solar gains results

agosiiner · Posts: 2

Hello,

the problem is getting very big solar heat balance differences in simulation results between DB and PHPP2007 (Passive house planning package, using EN 13790 monthly method).
Tried several things but couldn´t find a mistake or a reason for the differences, also haven´t experienced smth like this before using DB.

Total solar heat gains DB: approx. 17000 kWh (solar gains exterior windows - glazing)
Total solar heat gains PHPP: approx. - 8000 kWh. (solar gains - transmission losses)

In both cases the frame values are included.

The difference comes from much bigger transmission losses according to PHPP2007, although the results should be comparable.

Since the building has big air spaces through several floors I also tried different solar shading calcs but that didn´t give that much difference.

If you could find a solution or suggest something it would be great.

Best Regs,
Ago Siiner

Ps. I added the file as attachment

Laurent_Support · Posts: 292 Location: Vincennes

Hello Ago,

I run your model and get these results:

agosiiner · Posts: 2

Hello,
thank You for the reply.

I used the yearly values from PHPP (monthly method. otherwise, yes, it sums up only the gains and losses during the heating period). So the problem is elsewhere.

I also think I found the problem. If I check the input file of E+ i cannot find the U -values for the window frames anywhere, I only found the glazing U-value and dimensions. When I calculated the average U-value of the windows and made the calculation in DB without window frames using the average U-value of the glazing the results are starting to look similar.

Maybe You can check why is it so?

Best Regs,
Ago

Laurent_Support · Posts: 292 Location: Vincennes

Hello Ago,

U-values are not existing in EnergyPlus idf file for it compute them at each calculation time step.

E+ use :
- materials you define (glazing, frame layouts)
- deltaT temperature at time step (U-value are calculated at precise normative condition)
- convection algorithms taking into account air velocity, surface roughness and radiation ...

And may be I forget other parameters! So U value is changing during simulation.
Of course, U-value will turn around the mean U-value you've got in the literature but this explains why U-value does not exists in the idf.

Regards,

Login