Honeybee R-Value with Air Films Component Problem


Hi there,

I am using the RValueAirFilms component to consider airfilms in a glazing construction I am doing. I looked inside the component and it is adding 0.17 R-Value (I would imagine it is SI). However this doesnt seem right. 0.17 air film would be a typically used R-Value in IP units. Can anyone else share their thoughts on this? Or am I looking incorrectly?


        if surfaceType_ == None or surfaceType_ == 0 or surfaceType_ == 1 or surfaceType_ == 2 or surfaceType_ == 3:
            #Get the value of R-Value added to the air film.
            if surfaceType_ == None:
                addedR = 0.17
                print "Default surface type set to an exterior wall."
            elif surfaceType_ == 0: addedR = 0.17
            elif surfaceType_ == 1: addedR = 0.26
            elif surfaceType_ == 2: addedR = 0.14
            elif surfaceType_ == 3: addedR = 0.21
            #Caluculate the new values.
            RValue_SI = 1/_uValue_SI
            newRValue_SI = RValue_SI + addedR
            newUValue_SI = 1/newRValue_SI
            newRValue_IP = newRValue_SI * 5.678263337
            newUValue_IP = 1/newRValue_IP


As being involved a little bit in the discussion towards creating this component, i’m the one that provided the data to @chris, back then.
The table below is the source of the data (i translated it to english. It is used for our local thermal insulation standard and is based in ISO 6946-2003, which unfortunately i don’t have). The units are SI:

As for the source you gave, it is weird to have such a source that don’t mention the units of the numbers. Indeed seems to be IP, but you can’t be sure …



That is interesting. Im still confused. The source I gave mentions at the top of the table IP units. ASHRAE 90.1 2010 (IP) which I have also utilizes 0.17 R-Value for exterior air films, and this is the Imperial Units version.


@jholguin71 ,
Keep in mind that the 0.17 in @AbrahamYezioro 's component refers to the combination of both interior and exterior air films. The 0.17 in the IP version of ASHRAE 90.1 only refers to the exterior film and you see in your image that the interior film adds an additional R-0.68 for a total IP R-value of R- 0.85. And R-0.85 IP roughly equals R-0.17 SI so the two standards are in general agreement.


That makes a lot of sense! The fact both were 0.17 was a confusing coincidence :slight_smile: Thank you!