Space Parameters - Specified Supply Airflow.

[juanquis_avila]

Hi everyone,

I'm struggling with some issue extracting information from a certain space parameter (Specified Supply Airflow CFM).

For example, a single space has got 2400 CFM within Specified Supply Airflow in Revit but when I get the parameter value through Revit API the value is like 1 or 0.40 which doesn't make sense since the value in revit is 2400CFM.

Thank you very much for your help.

Juan Avila

[juanquis_avila]

Hi everyone,

I'm struggling with some issue extracting information from a certain space parameter (Specified Supply Airflow CFM).

For example, a single space has got 2400 CFM within Specified Supply Airflow in Revit but when I get the parameter value through Revit API the value is like 1 or 0.40 which doesn't make sense since the value in revit is 2400CFM.

Thank you very much for your help.

Juan Avila

[jeremy_tammik]

You need to be aware that all Revit API data and parameter values are provided in internal Revit database units, not in the project units displayed in the user interface:

Read one of the very first posts by The Building Coder from September 2008:

https://thebuildingcoder.typepad.com/blog/2008/09/units.html

As you can see, I was confronted with the same question pretty early on.

Here are many other unit-related articles by The Building Coder:

https://thebuildingcoder.typepad.com/blog/units

[jeremy_tammik]

You need to be aware that all Revit API data and parameter values are provided in internal Revit database units, not in the project units displayed in the user interface:

Read one of the very first posts by The Building Coder from September 2008:

https://thebuildingcoder.typepad.com/blog/2008/09/units.html

As you can see, I was confronted with the same question pretty early on.

Here are many other unit-related articles by The Building Coder:

https://thebuildingcoder.typepad.com/blog/units

[juanquis_avila]

Hi Jeremy. Thank you very much for your response.

It seems like the problem is not about units. When I get the value from "Specified Supply Airflow" space parameter, I can tell that revit api it's retrieving this value with CFM unit, same unit I see on my revit side but values are not matching between revit desktop and revit api. 

[juanquis_avila]

Hi Jeremy. Thank you very much for your response.

It seems like the problem is not about units. When I get the value from "Specified Supply Airflow" space parameter, I can tell that revit api it's retrieving this value with CFM unit, same unit I see on my revit side but values are not matching between revit desktop and revit api. 

[jeremy_tammik]

Sounds like a misunderstanding to me.

[jeremy_tammik]

Sounds like a misunderstanding to me.

[juanquis_avila · Accepted solution]

Dear Jeremy,

Thank you very much for your answer.

Let me show you the whole picture. As you can see in the enclosed picture, values between revit api and revit are not matching. Within revit I can say that suplly airflow for that space is 55 CFM but in revit api I see that paremeter value as 0.91 CFM. I've checked and units are set to be CFM.

Thank you so much for your kind assistence. 

[juanquis_avila · Accepted solution]

Dear Jeremy,

Thank you very much for your answer.

Let me show you the whole picture. As you can see in the enclosed picture, values between revit api and revit are not matching. Within revit I can say that suplly airflow for that space is 55 CFM but in revit api I see that paremeter value as 0.91 CFM. I've checked and units are set to be CFM.

Thank you so much for your kind assistence. 

[jeremy_tammik · Accepted solution]

You have set CFM as display units in the user interface.

You cannot modify the internal database unit. It is fixed.

So, your snapshot shows that 1.0 internal database unit equals 55.03 / 0.917 CFM (or maybe 0.917 / 55.03 CFM?).

Please study The Building Coder explanations of units:

https://thebuildingcoder.typepad.com/blog/units

Here is the first one, for starters:

https://thebuildingcoder.typepad.com/blog/2008/09/units.html

I am repeating myself...

[jeremy_tammik · Accepted solution]

You have set CFM as display units in the user interface.

You cannot modify the internal database unit. It is fixed.

So, your snapshot shows that 1.0 internal database unit equals 55.03 / 0.917 CFM (or maybe 0.917 / 55.03 CFM?).

Please study The Building Coder explanations of units:

https://thebuildingcoder.typepad.com/blog/units

Here is the first one, for starters:

https://thebuildingcoder.typepad.com/blog/2008/09/units.html

I am repeating myself...

[manuel.solis.lopez · Accepted solution]

Internal Units for Air Flow are not Cubic Feet per Minute but Cubic Feet per Second. The Revit Documentation is quite clear: Units 
Just Convert from internal units to the wished output unit.

Space space;
double c0 = UnitUtils.ConvertFromInternalUnits(space.DesignSupplyAirflow, UnitTypeId.CubicFeetPerMinute);

[manuel.solis.lopez · Accepted solution]

Internal Units for Air Flow are not Cubic Feet per Minute but Cubic Feet per Second. The Revit Documentation is quite clear: Units 
Just Convert from internal units to the wished output unit.

Space space;
double c0 = UnitUtils.ConvertFromInternalUnits(space.DesignSupplyAirflow, UnitTypeId.CubicFeetPerMinute);

[juanquis_avila]

Dear Jeremy,

Thank you very much for your patience and help. I've been working for several time with these parameters and is the first time I deal with this unit problem. I will take my time to study the links you have shared 😄 thank you very much.

cheers 😄

[juanquis_avila]

Dear Jeremy,

Thank you very much for your patience and help. I've been working for several time with these parameters and is the first time I deal with this unit problem. I will take my time to study the links you have shared 😄 thank you very much.

cheers 😄