Heavyweight thermal mass

[P11036460]

Can anyone inform me as to the best way to create a external wall that is an ICF (insulating concrete formwork) so as to create a heavyweight structure.

Thanks

[ZapBran]

really thick concrete layer not enough?
pop in a couple of thick layers one after another.

not overly familiar with the concept (but I'm an old fella now).

[Marc Jensen]

In one of our previous jobs, we created a large thermal mass in the floor with a thicker than usual concrete floor slab. Make sure that if you intend to get the best performance out of a large thermal mass it should preferably not be insulated from the internal air, such as carpets on the floor slab or internal insulation or particle board/sheet rock linings, as they will reduce the thermal masses ability to act as a 'heat sink'.

Its quite easy to test in IES, just duplicate your construction in question and add some / remove some cladding or finishes till you get the best performance. In our case with direct sunlight onto the slab and decent insulation, it reduced the peak temperature in the rooms by around 10degC (Compared to completely timber construction), but results vary on constructions and WWR.
Also whilst you are there do what Zap said and add multiple layers of concrete, check in the Constructions if the changes have modified the kg/m3 density and if it says whether or not it is heavyweight etc. (I have had some solid concrete walls that IES assumed was Very Lightweight however it clearly should not have been.
Would be great to know how IES calculates the thermal mass of components etc.

Good luck

[JohnLloyd]

I'd guess that they do it the same as iSBEM:

The Km values are calculated by:

For each construction element:

Calculate the contribution of each layer of construction as density (kg/m3) x thickness (m) x specific heat capacity (kJ/(kgK))

Starting from the layer of the construction closest to the space add these values together until any one of the following conditions is satisfied:

the total thickness of layers exceeds 0.1 m

you have reached the mid-point of the construction

you have reached an insulating layer