IES-VE User Forum

Hi guys

wondering should we model ground temperature or not? is I only considered apply ground temp if the building below grade.

also how can i determine when should i model a ceiling void in the model. sometimes i saw people not included ceiling void in the physical model.

any advice pleasE?

Hi there

Whether you include the ground temperature depends on what sort of analysis you are doing and how accurate you really need to be. If you do not include it, IES will assume that the ground and below grade walls are exposed to external air temperature, even if built below the 0m line.

So, for example, if you are carrying out a steady state heating load calculation you might decide to not include the ground temperature in order to provide a slight safety margin (since the ground adjacency will be set at something like -4degC rather than 8 or 10 and will therefore increase your heat losses for some rooms).

However, if you are carrying out a bespoke energy analysis to show compliance with some sort of planning target you might want to squeeze every kWh out of the results and so adding the ground temperature might be advantageous.

As for including ceiling voids as a separate zone, I generally only do that if the void is particularly deep or if you do not wish to apply construction thicknesses but do want the room volume more accurately represented. Otherwise, just setting the void as part of the overall ceiling construction should be sufficient.

Also, if you are building a compliance model under UK Part L2A I think the iSBEM technical guide uses the convention that ceiling voids should be included as part of the main space and so I'd tend not to make them separate in this case.

CP