IES and PHPP modelling

[Anonymous]

Just wondering if anyone has used IES to model Passivhaus designs?
I've been carrying out some basic parametric testing for both and found that adjustments to the glazing g-values in PHPP when comparing with IES are particularly sensitive. For what is in essence the same model (geometry, spec, location etc.) it seems that when modelling the same g-values, the difference in solar gains is almost 30 per cent!

Does anyone else have any experience with this?

P.S This post was destined for the technical forum, but i haven't got around to fully signing up yet!

“which i will do ofcourse” 🙂

Thanks Mike

[Nick Grant]

Not got PHPP to hand but g is just a factor, half the g, half the gain. Only thing that might vary between PHPP and IES would be utilisation factor.

Obviously absolute results might be different as shading etc probably give diffrent results but in terms of sensitivity to g . . . .

[Anonymous]

Ok thanks for the pointers Nick

[Mark Siddall]

The frame fraction can be pretty high at time – over 50% in some/many cases with small windows. What is the frame fraction of the window area? Is it about 30%? PHPP takes the frame area into account, but does IES? Also, could the shading reveal be another factor that may not be picked up in IES, unless they are specifcally modelled.

…Just a thought.

Mark

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