# [EnergyPlus_Support] Re: Calculation of Phase Change Material (PCM) amount

```Hi,

I have no specific experience on PCM modelling but I was wondering if your problem could not just be solved by adding a layer in the construction assembly that will represent the properties of your PCM amount and another layer that will play the role of the usual sensible thermal mass and resistance. So say if I take your example with the standard board, you use your manufacturer breakdown in amount of conventional and PCM material and make a two layer equivalent model.

Of course I would benchmark this method against a normal model with usual material and one with fully assigned PCM to see how it behaves.

Aymeric

--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "wgorrissen" <wgorrissen@...> wrote:
>
>
> so, if I understand correctly, when using PCM one merely applies a enthalpy temp curve to a material (the material being defined in the typical manner). So this means that EnergyPlus will see the material as being made up in it entirety of the PCM material (if the h-T curve is for the actual PCM). So if I am applying PCM to standard wall board of thickness .019 m and density of 800 kg/m3 then I am basically indicating that the material contains 15 kg/m3 of the PCM.
>
> Is this correct?
>
> and if it is correct which property should l vary in order to get the correct amount of PCM in the material if i have the material properties of the actual PCM rather than the complete wall board product.
>
> ideally (i think) i would want to vary the enthalpy temp curve but this seems to be the most complicated. so, that leaves me with either changing the thickness or the density. if i understand correctly how E+ works, by changing either of these proportions I will alter the sensible storage due to the mass of the product and if i change the thickness i will lose some thermal resistance.
>
> is this correct, has any one come across this issue before?
>
> thanks,
>
> Will
>

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