Energy modeling requires that each space have at least **one** wall/surface. In order for the model to be accurate you should enter all surfaces through which a significant amount of heat is gained or lost. Conditioned spaces may have surfaces adjacent to Outdoors, Ground or unconditioned spaces defined on Spaces/Rooms screen. Unconditioned spaces may have surfaces adjacent to Outdoors and Ground. **No surfaces between conditioned rooms (interior partitions) may be entered**. Data input on the screen starts with selection the **space** for which the surface is being entered. Choose any space that you described on the Spaces/Rooms screen from the Surfaces In drop down box. Click the Next and Previous buttons to switch between spaces. The buttons are disabled if there is only a single space in the project.

- Before leaving the screen use
**Next**and**Previous**buttons to go through all the spaces in the project and make sure that at least one surface is entered for each space. - You do not have to enter each physical surface in the space separately. For example, for the basement you may choose to enter all four below-grade walls as a single surface, since exposure is not relevant. In this case use basement perimeter instead of wall length.

The Description field allows the user to specify the surface construction. You can either select constructions from the list of typical constructions or from TREAT Surface Library. The list of typical constructions in the combo box may be customized by editing **Surface Constructions** tab of **Preferences** that are accessible from **Project Group** menu. Select <Library> at the end of the list to open TREAT Surface Library.

The Walls/Surfaces screen allows you to enter a number of inputs including a **Description, Code, Type, Adjacent to, Exposure, Length ft., and Height ft.**

**Descriptions: **

Hold the cursor over the description input in the Input Area to view the complete wall description if the text is cut off. The **R-value** in the description is the overall thermal resistance of the surface including framing and excluding air film.

**Code: **

This field is filled out automatically after the surface construction is selected. It can be used as a shortcut to enter surface descriptions without opening the library. When you start entering a new surface you may go directly to this field and enter the code. Surface construction will be displayed as soon as you move to the next field.

**Note:** **You may use surfaces that you have already entered for the space as a reference for the surface code of the new surfaces.**

**Type: **

This input allows you to select the type of surface; inputs include wall, ceiling, sloped or flat roof, etc.

**Adjacent To: **

This field can be set to Outdoors and Ground or, if the surface is in conditioned space, it may also be adjacent to any unconditioned space that you have entered on Spaces screen.

**Note:**A typical walk-out basement has a portion of the wall below grade and the other portion above grade. Such a wall should be entered as two different surfaces, one adjacent to Ground and one adjacent to Outdoors. You must enter correct dimensions (length and height) and elevation for each section of the wall.

**Exposure: **

This field refers to the direction a surface is facing and must be filled in for all exterior surfaces except for horizontal ones (surfaces with zero tilt). Set exposure to NA for such surfaces.

**Note:**It is important to enter the accurate exposure for each above grade exterior wall because it has a strong influence on infiltration and window solar gains.

**Length** and **Height: **

These inputs define dimensions of the wall for heat loss and infiltration calculations. *For horizontal surfaces such as floors and ceilings use Height field to enter width.* The product of length and height must be equal to the gross surface area. TREAT will use door and window areas entered on the following screens to calculate the net surface area.

**Note:**Height of the wall is used to calculate stack effect. If multiple stories are modeled as a single space and the height of the wall is entered as the ceiling height of one floor times the number of floors, then the infiltration losses for the space may be exaggerated, because internal partitions between the stories are ignored.

Use the **Advanced Inputs** button to edit surface name, tilt, elevation, overhang, side fins and albedo.

**Name:**

This optional input that can be used to further describe a surface.

**Elevation:**

The Elevation equals the height of the bottom edge of the surface above space floor. It is used to calculate stack effect. Elevation of the floor is 0. Elevation of the ceiling is equal to the ceiling height. Elevation of a typical wall that goes from floor to ceiling is 0.

**Tilt:**

The angle of the surface from horizontal in degrees. Enter 90 for a vertical wall, 0 for floors and horizontal ceilings and any number in between for a sloped ceiling.

**Overhang** and **Side Fin Depth:**

These inputs are used for exterior walls to model the effect of solar gain on energy consumption. TREAT assumes that the overhang is located at the top of the wall at a right angle to the wall. Left and right side fins are located at the corresponding edge of the wall at the right angel to the wall.

#### TREAT uses the following logic for modeling surfaces adjacent to ground:

#### Walls

- TREAT attaches 0.68′ layer of soil to walls that are 1ft high or less. Temperature of surrounding soil is assumed to be equal to the ambient air temperature for the hour.
- TREAT attaches layer of soil equal to Wall Height × 0.77 to walls that are between 1 and 3 feet high. Soil temperature is assumed to be equal to the ambient air temperature for the hour.
- Below grade walls that are more than 3 feet high are modeled as two separate walls. First wall is 3′ high, has 2.31′ layer of soil attached to it, and loses heat to ambient air temperature, Second wall is (WallHeight-3) feet high and has 3′ layer of soil attached to it. Temperature of surrounding soil is assumed to be equal to average annual air temperature.
- Slabs are modeled as two separate surfaces. First surface is 3′ wide slab perimeter ring. It has 3′ layer of soil attached to it. Temperature of surrounding soil is assumed to be equal to the ambient air temperature. The second surface is of the same area as the remaining section of the slab and has 3′ layer of soil attached to it. The temperature of surrounding soil is assumed to be equal to the average annual air temperature.
- Losses are calculated from 3′ perimeter ring around the slab. 9′ layer of soil is attached to the perimeter wring and the temperature of surrounding soil is assumed to be equal to average annual air temperature. Layers of soil are attached to the surface in order to model insulating properties of soil. Thickness of the soil layer is selected to approximate the length of heat flow path through ground. For the typical building configurations the algorithm produces results that are very close to heat loss coefficients specified in ASHRAE Fundamentals starts on page 21.

#### Slab on Grade:

- Slabs are modeled as two separate surfaces. First surface is 3′ wide slab perimeter ring. It has 3′ layer of soil attached to it. Temperature of surrounding soil is assumed to be equal to the ambient air temperature. The second surface is of the same area as the remaining section of the slab and has 3′ layer of soil attached to it. The temperature of surrounding soil is assumed to be equal to the average annual air temperature.

#### Slab below Grade:

- Losses are calculated from 3′ perimeter ring around the slab. 9′ layer of soil is attached to the perimeter wring and the temperature of surrounding soil is assumed to be equal to average annual air temperature. Layers of soil are attached to the surface in order to model insulating properties of soil. Thickness of the soil layer is selected to approximate the length of heat flow path through ground. For the typical building configurations the algorithm produces results that are very close to heat loss coefficients specified in ASHRAE Fundamentals starts on page 21.