# Blower Pressure Converter

![](/files/-Mihpe9xV-3DBRM3-Fv1)

![](/files/-Mihpe9ztCugbjAZB-U-) - [\[source code\]](https://github.com/ladybug-tools/honeybee-grasshopper-energy/blob/master/honeybee_grasshopper_energy/src//HB%20Blower%20Pressure%20Converter.py)

Convert infiltration flow per exterior area measured at a particular blower door pressure to flow per exterior area measured at a typical building pressure.

This is accomplished by computing a normalized-area air mass flow coefficient that is derived the power law relationship between pressure and air flow. Cqa = Qblow / dPblow^n And then using the coefficient to approximate air flow at typical building pressure. Qbldg = Cqa \* dPbldg^n

where: Cqa: Air mass flow coefficient per unit meter at 1 Pa \[kg/m2/s/P^n] Qblow: Blower-induced volumetric air flow rate per area \[m3/s/m2] dPblow: Blower-induced change in pressure across building envelope orifice \[Pa] Qbldg: Typical building volumetric air flow rate per area \[m3/s/m2] dPbldg: Typical building change in pressure across building envelope orifice \[Pa] d: Air density \[1.2041 kg/m3] n: Air mass flow exponent \[0.65]

## Inputs

* **infilt\_per\_exterior \[Required]**

  A numerical value for the intensity of air flow induced by blower pressure in m3/s per square meter of exterior surface area. 
* **blower\_pressure**

  A number representing the pressure differential in Pascals (Pa) between indoors/outdoors at which the specified \_infilt\_per\_exterior occurs. Typical pressures induced by blower doors are 75 Pa and 50 Pa. (Default: 75). 
* **bldg\_pressure**

  The reference air pressure difference across building envelope under typical conditions in Pascals. (Default: 4). 

## Outputs

* **infilt**

  The intensity of infiltration in m3/s per square meter of exterior surface area at the input *bldg\_pressure*. 
* **C\_qa**

  Air mass flow coefficient per square meter at 1 Pa \[kg/m2/s/P^n]. 


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