# Inside / Outside of a shared wall between two zones

Hi there. Simple question.

I have a wall construction which is asymmetrical, it has insulation on the outer layer and thermal mass on the inner layer. How is this treated when I assign this construction to a shared wall between two zones? Which one gets the inner side of the construction? Or does EP calculate as both having the inner side towards each zone?

Thanks!

A or B?

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For internal walls the shared wall has to have the same construction. In the calculation process it relates to each of the walls â€śindependentlyâ€ť, meaning that the first layer of the wall is on the â€śexternalâ€ť side of the wall.
So the answer is that non of your options is right. You are missing option C, in which option A has to sub-cases. The one you draw is correct for Zone 2 and you need a sub-case where you mirror the section for Zone 1.

-A.

Thank you,

Wouldnâ€™t my drawing A) be right for Zone 1 calculations? (Inside layer towards the zone and outside layer towards the outside farther away from the zone? and Mirror that for Zone 2 calculations?

I guess it would be better to make a symmetrical construction in this cases where walls are shared?

You are right. For internal walls you need to have a construction that is symmetrical for both sides (say, plaster+brick+plaster). In this way you donâ€™t have to worry about your question since it will fit both conditions/zones.
-A.

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