IES-VE User Forum

Hi there,

I currently am doing a project using IES, and have set up heating profile to have a central heating system activate whenever the temperature within each space falls below 19 degrees. Without any cooling I run the simulation and this appear to work correctly.

The building is also to be naturally cooled//ventilated, which I have been trying to achieve through MacroFlo. I have set up a modulating profile for the window openings, using the formula (ta>21) - for any window to open if the temperature inside the space reaches 21 degrees. The problem then arises when I run the simulation at this point, with all openings applied to the building. The heating demand suddenly increases by a factor of 5, and heating is required in spaces even though the internal temperature is well above 19 degrees.

Does anyone have any ideas as to why this may be the case? I'm new to using this software so unsure where to begin. I have trie changing all sorts of paramaters such as the opening threshold, as well as the opening profile with no luck. Prehaps it is an issue with the heating profile? For this I am using a modulating profile with the temperature within the space to be a minimum of 19 degrees.

Any help would be very much appreciated!

Make sure when you use a formula profile in this way for a MacroFlo Opening type that you also set the opening threshold temperature to be 0 so the profile controls the opening.

Also you should take care to ensure that you have your simulation timestep and reporting interval to a low enough time interval so you can see the effects dynamically as using simple greater than or less than operators tends to result in a fluctuating window (switching regularly from open to closed across each small time period). I would usually say use a RAMP profile so you can include a dead-band and stagger the opening & closing a little bit.

I would also say a good advice for building up any opening profile is to do it a bit at a time then you can run the sim for that section and check it performs as you require before adding the next part. Although this case is simple if it is not performing as you require then you would do well to follow this practice for troubleshooting.