IES-VE User Forum

On a project the client has provided specific weather data that the design is to be completed in accordance to.
I realise that I can input this data into the Design Weather Data tab, which I believe then only applies these values to the CIBSE steady state loads.
As part of the design we need to prove compliance with the clients overheating criteria, which we are doing using the range test function on a dynamic simulation. My question is for the sake of proving something to the client, is there a way that I can get the dynamic simulation to incorporate the client weather data too?
I realise that this will then not be representative of a true annual simulation, but I would like to show the results of a realistic simulation and a simulation including the client’s data.

Is there a possibility this could be done by modifying the weather manually and if so how would you do this?

Thanks in advance.

What exactly is the data that the client gave you?

If the client has given you a specific weatherfile (8760 points, one for each hour over a full year) with all necessary inputs (humidity, temperature, wind, solar radiation, cloud cover, etc), just create a weatherfile with his data in *.epw format.

If the client hasn't given you this data and just said something like "35°C DB 30°C WB", then this is really where you, as the thermal engineer, need to explain to the client that -- although the customer is always right -- dynamic thermal simulation (and indeed real weather) doesn't actually work this way, that the customer doesn't quite know what what he/she wants, and that just giving one point like that will not result in any meaningful information. I'd suggest to find somewhere in your existing weatherfile a point which closely matches with the customer's requirements.

And yes, you can edit the weather file but it's really a bad idea when it's just to satisfy a misguided customer requirement.

The client has provided a specific summer and winter temperature that the design should be based on.
I have no problems doing this and have explained the implications such as the performance of the system when the weather exceeds the data provided.
As part of our works we have to produce an over heating test which is not compliant due to the lower system performance, how ever I wanted to demonstrate that the overheating test passes when the clients data is used as a capping point to the weather file. Firstly this would demonstrate that the system design is adequate to the given specification and requirements and secondly it would confirm our arguments that the clients weather data should be excluded and data used from a creditable sources such as CIBSE.
Whilst the client agrees with our arguments I believe he is failing to grasp the concept or he is worried about the additional costs that he may incur due to the increase of the services loads to comply with a realistic set of weather data.

Could the clients single values be used to cap the existing weather data in a modified weather file?

Thanks again.

You can modify the values in energy plus weather files obtained from the US DOE as they're just standard text files. You can cap it from there. I don't know what format CIBSE provides weather files, but I'm guessing you'll be able to edit those as well.

And yes I have done this before, I had to do it, and every time I underlined that this is a pointless exercise. Often people in your own company will sign up to doing that because they don't understand dynamic thermal simulation (DTS) either

The thing is that, from a cooling standpoint particularly, it doesn't necessarily result in bigger plant to use DTS. Weather wise, it matters not just what the outside air temperature is at a specific point in time, but its duration, and other climate components all combining together for excessively warm conditions. This is because the building will dynamically respond to new climate conditions, and one high point does not necessarily need to be catered for if it is for a sufficiently short duration, depending on the building. This is DTS. However, what your client is telling you to do essentially amounts to a steady-state calculation. Using a dynamic thermal simulation package to do a steady-state calculation doesn't make much sense, does it?

You need to educate your client. If your client won't hear anything it's most likely because he/she has a box to tick and doesn't want to think beyond this, which is frustrating as it's completely unnecessary from a technical standpoint, but that's reality unfortunately. So if your client won't hear it, I wouldn't suggest modifying your weatherfile, it will be a waste of time and effort; just go to your weatherfile and pick a time and day where the peak/trough conditions are close enough to the conditions your client has given you.