The effect depends on the temperature difference inside and outside and the changing air mass /air mass in the building, but also the changing air mass/total mass of the building. The large mass of the building, furniture, people, equipment what has the targeted temperature won't allow the relatively small mass of cold air to have huge impact.

The effect is rather the decreased comfort in the building especially around the doors.

Hi Robert,

Thanks very much for your answer. Actually in my case, the inside and outside temperature difference is Quite high (25 degree c). The wind pressure is high too. The space I am simulating is not massive in compaison to the opening. Yet, I don't get the result I expect from the simulation.

Dear Elham

Probably you are using the building with air conditioning system always on. When the doors are opened in the thermal balance you do not have the effects of the natural ventilation (infiltration - observing temperature and pressure difference). Maybe DesignBuilder and Energy Plus do not be the appropriate tool for your goal. To consider the pressure difference in the thermal balance you must use AirflowNetwork.

Maybe the way for your simulation would be to calculate the air changes per hour observing the temperature and pressure differences. I can send to you per E-mail simple equations for the calcultaions. Later you can simulate the building with the air conditioning system, the doors opened, and the infiltration configured based on the results of the natural ventilation (your calculations).

Dear Eduardo,

Thanks very much for your answer. I will look into AirflowNetwork. Could you please kindly send me the equations you mentioned? Here is my Email: [email protected]

Thanks again and good luck!

Dear Elham,

It is really interesting problem. It would be interesting to see what is final solution that was used to handle your problem.

Have faced this problem several times. Following points helped me to understand the problem better and arrive to solution in IES VE tool.

1. The heat loss is caused by [air flow rate] which is dependent on [A] hole size ( resistance or coefficient) and [B] pressure difference between inside and outside. (See work of Max Sherman Max Howard Sherman to get deeper understanding). You need to make assumptions about A and B - is it constant, variable, dependent on weather? For initial ques constant assumption across simulation will work fine.

2. Overall amount of air going thru the opening depends on time, for how long it is open. As the doors can have open and closed state, those states should be included in the model (occupant behaviour plays important role in it ...). Probably it may depend on occupant movement. Some building codes in Finland and Lithuania determines the duration of open doors according to the building type.

Initial assumption of average flow on occupied hours may be better than ignoring this aspect.

3. Despite the complicated explanations, simple t scheduled air flow rate from outside to specific building zone (connected to outside) would represent the phenomena and would be enough to reflect it on the model. Probably the idea of your study is to get predictions on energy consumption and not to build complicated physical representation which may produce the same accuracy as simple empiricism based solution (See Mr. Eduardo Gralla post)

In case you would need some validation example or field data - these sources should be useful:

Article A Field Investigation of Air Infiltration Rates through Auto...

Conference Paper Investigation of Air Exchange and Ocupancy Rates in Big-Box ...

Realy nice and detailed work from Chalmers, Sweden:

http://publications.lib.chalmers.se/records/fulltext/184752/184752.pdf

Hope that this information will help you.

Good luck with your work.

Hi Karolis,

Awesome. I will go through the publications you shared. Thank you!

I will update this question by sharing the interesting points I've figured out, shortly.

Cheers!

hi Elham,

Heat losses in door openings can be very high and you need to simulate it based on the the actual working physical conditions.

Considering:

Ventilation efficiency( ability for a climate separation to reduce infiltrations) over the door opening:

- temperature difference

- Building stack effect

- Wind pressure

- heating source for the climate separation

- opening time, traffic, etc.

- Opposed door openings in the building creating a very high draught effect.

Without a efficient climate separation you have hot air escaping from the building and cold air entering the building(in the heating cycle). an example, in cold stores rooms this can account for anything between 20 to 40% of the compressor load.

You would need a tried and tested software simulation programme of a door air curtain performance, can provide you with information regarding

the same. If you wish please feel free to contact and send your e-mail. Also see attached paper below.

Climate separation can change its ventilation efficiency(reduction of losses in the door due to infiltrations,etc) during daily use, seasonal use,etc.you will need to simulate a seasonal performance based on unit efficiency given in all working conditions.

Best of luck with your solution.

Hi Paul,

Many thanks fir your comment. I will read the chapter you shared. Could you please give me your Email address?

Is there any specific sotware you use for energy simulation (and particularly the effect of door opening)?

Hi Elham,

Yes we have a software to simulate, it is in house software developed by our specialist manufacturer.No commercial interest here but do not know a reliable independent software which has been tested and verified. The efficiency of a climate separation will depend on the available technologies, a cheap option will give around 40% and an efficient option can go up to 90%, this means 90% of savings in door loss.

I can give you data of the software and manufacturing company in the UK.

you can contact me at: [email protected]

Building energy simulation programmes I think do not have this possibility and simulating a hole in the building will not be sufficient, you need to do a separate calculation and input the data as a seasonal heat load in the building energy software, but with calculated values in kw/h of thermal load.

Ciao,

Thanks very much everyone!

I found out how to model door opening in DesignBuilder and got 40% increase in the energy consumption as I expected. If anyone has a similar problem, I would be happy to help.

Hi Elham,

I can confirm you that we have also had energy savings to 40%, and inclusive more.

regards,

Paul....

hi Elham,

To clarify the above answer what I meant is that when we apply an efficient climate separation technology in a door opening we can achieve more than 40% energy savings which by deduction implies that when there is no climate separation the loss increases by 40% as you mention.

Regards,

Paul, that was what I got from your message and it is very interesting. Thank you very much for sharing it with me.

Sorry for late reply. However expecting this reply would be resourceful to others with same question.

In EnergyPlus "AirflowNetwork:MultiZone:Zone" object define the ventilation control mode to temperature for the zones you had doors/windows. Dont forget to define the temperature setpoint schedule along with minimum vent opening factor and deltaC details based on your required control logic.

After that go to "AirflowNetwork:MultiZone:Surface" object and set ventilation control mode to "ZoneLevel" for the surfaces representing your doors/windows. Finally you can set the infiltration level and discharge coefficients for doors/windows in "AirflowNetwork:MultiZone:Component:DetailedOpening" object.