EPS slab with foil face on both sides

[P11036460]

Hi,

Am after some help to create an EPS slab with foil facing material on both sides. I though i would be a simple aluminium layer added to either side. is this right it seems to simple? anyone with a thickness for such a materiel if this is the case.

[Marc Jensen]

Hi P,

I take it you mean a floor slab with EPS foil faced insulation.

You can build your own construction by either starting from scratch or finding a similar construction created for your region, this is usually needed for the inside and outside emissivity and resistances.

I have built a construction that adds a 1mm thick layer of foil on each side of the EPS. The total R Value and U Values do not change. The thermal mass and mass change ever so slightly but its so small that it could be attributed to calculation accuracy.

Now I dont know the ins and outs of the simulation that you will be using, however I think that you can safely ignore the foil on the EPS, providing that the supplier of the foam does not have a large variance between foiled and unfoiled insulation panels....

Let me know what the difference is between them, it is worth calling up the manufacturer and asking why you should go for foil and if there are any performance improvements.

[P11036460]

Cheers Marc

I thought this would be the solution. However, IES wont let me insert a aluminium layer with a thickness of less than 0.1mm and looking at manufactures details the thickness of 0.006mm is required, or in your experience is 0.1mm sufficient to simulate the foil.

Ta

[P11036460]

Hi again,

another issue I'm facing is that the wall construction with aluminium on either side for the EPS is greater than the 10 allowed layers for the construction, can you combine the 3 structure foil-EPS-foil to make one? perhaps make a new material?

Mark

[Marc Jensen]

The foil in IES has such a small impact that I would leave it out, starting from the foil that is wedged against concrete or timber etc.

I don't think that you can combine 3 different materials.


What the NZ standard wall and floor constructions do are they have bridged insulation that has the Insulation and the Timber battens etc all included in one construction.

Now you want to keep your external surfaces, bridging materials and internal surfaces marked out clearly in IES,(not merged) this is due to the emissivity and surface resistances etc...

If you substitute your wall with an identical unit with the same R Value (U Value), Thermal Mass (Mass) and thickness (Only if you modelled internal volumes) they should perform nearly the same. In New Zealand we have a dedicated standard to calculate the thermal resistance (R Value) of parts of buildings... Find those calculations, follow through them and get a total R Value using them.

You can use online calculators such as this to get your R value if you are too lazy to calculate them:

http://www.designnavigator.co.nz/CRC.php

Depending where you are in the world your inside and outside surface (Rsi and Rso) values will be slightly different so pay attention to them.



Pretty much you can cut your wall down to 4 or so constructions and have quite accurate results.

Good Luck!