2 identical models (except zoning) BUT different results

[Tom_McGrath]

Any comments / observations welcome on the following:

I'm comparing two identical models with the only difference being the zoning of the space to obtain a temperature profile.

The basic building is a one floor building with a pitched roof.

The first model is created as a one zone and the second model in layers of 0.4m with holes separating the layers.

When comparing the peak roof surface temperatures I get a 17 degree difference between the models, with the layered model being much higher. Solar irradiance on the roof should be identical, therefore the only thing that I can attribute to this is higher convection and radiation heat loss from the roof for the single zone model.

If this assumption is correct, why would this be and also is there a way in IES of showing this?

Just to add these peak surface temperatures occur at different times of the year

[Marc Jensen]

Hi,

I have had a little experience with this.

With my model I found that my biggest issue was due to the internal gains and ventilation etc all not being per m2.

I had 1 person per space. rather than 1 person / 10m2.

First thing i would do is check your internal gains if any then check with the holes you have placed if you are getting any heat transfer or flow through them.

Next thing i would do is widen your slices up to around 1m. I have found less than that can maybe cause issues. On my side or IES...

Now check you roof temperature. If you have large amounts of slices there is the possibility of compounding errors. However I am not sure how IES calculates each slice. So dont quote me on that!

Good Luck