Part J NCC2019 error

Part J NCC2019 Comes into effect on May 1st 2020.

Just a word of warning. There is a slight error in the new Facade calculator, which the ABCB is working on rectifying by May 1st.

The current Conductance and Solar Admittance of a wall/glazing system is calculated in respect to the orientations, North, East, South and West.

The problem is that there is no method of satisfactorily calculating a wall/glazing system that separates a conditioned and unconditioned space, (e.g. a wall between a class 5 office & a class 7b shed).

More to the point there is no way to incorporate a window in these walls without assuming it to be an external wall with a solar admittance value.

The updated ABCB Facade calculator will add an ‘internal’ wall selection with the related windows being assessed for conductance only. However, apparently, the written version of the code won’t be updated unit 2022.


A word to my clients. We have already made this function available on our own calculator so we’re good to go.

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A word to my North American friends. Part J has nothing to do with Manual J. It’s best if you completely ignore this post.