> For the complete documentation index, see [llms.txt](https://docs.ladybug.tools/fairyfly-primer/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.ladybug.tools/fairyfly-primer/components/0_create/ff_boundary.md).

# FF Boundary

![](/files/kghMGReIAIdTRq25o8E2)

Create Fairyfly Boundary.

### Inputs

* **geo \[Required]**

Planar Polyline or Line geometry representing the boundary.

* **name**

Optional text for the name of the boundary. If unspecified, a generic one will be automatically assigned.

* **temperature \[Required]**

A number for the temperature at the boundary in degrees Celsius. For NFRC conditions, this temperature should be 21C for interior boundary conditions and -18 C for winter exterior boundary conditions.

* **film\_coeff \[Required]**

A number in W/m2-K that represents the convective resistance of the air film at the boundary condition. Typical film coefficient values range from 36 W/m2-K (for an exterior condition where outdoor wind strips away most convective resistance) to 2.5 W/m2-K (for a vertically-oriented interior wood/vinyl surface). For NFRC conditions, this should be 26 for exterior boundary conditions and around 3 for interior boundary conditions.

* **rad\_env**

The optional output of the "FF Radiant Environment" component, which can be used to customize the radiant properties of the boundary (if they differ from the input \_temperature and standard emissivity of 1 or if there is additional solar heat flux along the boundary).

* **u\_factor\_tag**

An optional text string for to define a U-Factor tag along the boundary condition. This tag is used tell THERM the boundary on which a net U-Value shall be computed. Typical values to input here, which are recognizable in LBNL WINDOW include the following.

```
* Frame

* Edge

* Spacer

* ShadeInETag

* ShadeOutETag

* SHGC Exterior
```

* **rgb\_color**

An optional color to set the color of the material when it is imported to THERM. All materials from the Fairyfly Therm Library already possess colors but materials from the HB-Energy material lib will have a randomly-generated color if none is assigned here.

### Outputs

* **report**

Reports, errors, warnings, etc.

* **boundaries**

Fairyfly boundaries. These can added to Fairyfly models and used in THERM simulation.