Check calculation of interior area

[PRemmen]

What is the problem?

• For some archetype buildings (especially residentail with one floor) the calculated interior (floor+wall+ceiling) seems to be very high ( e.g. 1 Floor , net leased area around 150 results in almost 400 m² interior walls).

Why do we want to solve it?

• especially for residential buildings the inner walls do have an effect on the total heating demand

How do we want to solve it?

• check if the calculation works as expected
• after that: write unit tests

[StanleyRisch]

The calculation of the interior area is calculated (in the thermalzone) as followed:

   for floor in self.floors:
        floor.area = (
            (  self.parent.number_of_floors - 1) /
            self.parent.number_of_floors) * self.area
    for ceiling in self.ceilings:
        ceiling.area = (
            (self.parent.number_of_floors - 1) /
            self.parent.number_of_floors) * self.area

    for wall in self.inner_walls:
        typical_area = self.typical_length * self.typical_width

        avg_room_nr = self.area / typical_area

        wall.area = (avg_room_nr * (self.typical_length *
                                    self.parent.height_of_floors +
                                    2 * self.typical_width *
                                    self.parent.height_of_floors))

with typical_length=3 and typical_width=6 for usage=living in UseCondition.xml

[StanleyRisch]

Does anyone have an idea where I can find the origin of the calculation above?

Until now I looked into the teaser documentation and into IWUs Paper (
Projekt: „Entwicklung eines vereinfachten,
statistisch abgesicherten Verfahrens zur
Erhebung von Gebäudedaten für die Erstellung
des Energieprofils von Gebäuden“
Kurztitel: „Kurzverfahren Energieprofil“).

But couldn't find any calculation for the interior walls.

The typical_length and typical_width varies accoarding to SIA's Nutzungsbedingungen
fur die Energie- und Gebäudetechnik where it is defined as 4m and 4m.

[PRemmen]

@mlauster may help your here @mla-srs

What we could do in a first step to check the values if they make sense at all

[mlauster]

@mla-srs, @PRemmen, sorry for missing this issue. The calulation are based on DIN 277-3 (I assume this only contains definitions of terms), SIA 2024 and the paper from Hillebrand for Retrofit Matrix (Evaluation Tool and Retrofit Matrix for Office Buildings. In: EON Energy Research Series 4 (2012). Let me know if I should provide a copy of this.
But according to your example, @PRemmen, with one floor (so no ceilings or floors), given three rooms leads to a height of floors of 14.8 m. Even seven rooms (20 m² each) leads to a height of floors of 6.3 m. Am I getting something wrong?

Edit: With the correct calculation of typical_area, what leads to 8 rooms, the height of floors is 5.55 m, still quite high.

Edit: Find a mistake in my calculations, 8 rooms and 15 m wall length, leads to 3.33 m height of floors, that sounds reasonable...

Are you shure that 400 m² isn't a realistic value?

[mlauster]

Of course, what is not considered is, that not all rooms in the house have three interior walls. In particular for small houses, there might be more rooms with less than three interior walls, since they contain a corner of exterior walls or span an entire side of the house. In such cases, the estimation might be too high. This will mainly affect single family dwellings (SFD). We could distinguish the building types in the calculation and consider only two or one and a half interior walls for (SFD). Does that sound like a reasonable approach for you?

[PGorzalka]

How about this approach? Given that it is quite straightforward, I wonder if there is any reason it was not used before:

1. calculate number of rooms (as before)
2. total wall area wall_area = (avg_room_nr * (2 * self.use_conditions.typical_length * height_of_floors + 2 * self.use_conditions.typical_width * height_of_floors))
3. substract all outer walls, windows and vertical roof parts from the result to get interior wall area