Above Grade Envelope

There are four different locations in OptiMiser where various components related to an attic or ceiling might be modeled.

Attics:

- On the Attics page the Attic Areas are used to model any ceiling that forms a boundary between a conditioned space and an unconditioned buffer space such as an unconditioned attic. Including:
  - The floor of standard full unconditioned attics
  - The flattened peak of a conditioned attic
  - The floor of the unconditioned space behind a knee wall (which forms the ceiling to the room below)
- When moving the thermal boundary of an attic space from the attic floor and knee walls to the roof deck and gable walls, use the Encapsulate checkbox on the improved side. Encapsulate makes the following changes:
  - Improved attic controls now represent the roof deck
  - Improved knee wall controls now represent gable/cheek walls
  - Be sure to set improved areas appropriately for the new surfaces
  - Use the Ducts checkbox, if ducts are being brought inside the conditioned space

Knee Walls:

- Knee walls are vertical boundaries between a conditioned space and an unconditioned buffer space that is also bounded by roof slope and the ceiling of the floor below.
- Knee walls are modeled using special Knee Wall sections on the Attic page.
- It is preferable to model a knee wall in association with the attic area that represents the floor of the space behind the knee wall.
- When moving the thermal boundary behind a knee wall, set improved area of that knee wall to zero or use the Encapsulate checkbox on the associated Attic area, as described above.

Ceilings:

- The Ceilings page is used to model any ceiling that forms a boundary between a conditioned space and the outdoors (i.e. roofs). Including:
  - Standard vaulted ceilings
  - Flat roofs
  - Roof slopes of a conditioned attic space
  - Roof slopes of the space behind a knee wall (but only if insulated)

Walls:

- The Walls page is used to model any wall above the foundation that forms a boundary between the conditioned space and the outdoors. Including:
  - Main floor exterior walls
  - Gable walls of existing conditioned attics
  - Cheek/gable walls behind knee walls (but only if they are insulated)
- Be sure to hand calculate exterior wall area, when the building has finished attic space, lots of vaulted ceilings, or other unusual geometry

The wall height should be the average floor-to-ceiling of all exterior walls.

Multiple Attic Areas

We only have controls to describe two open cavity attic spaces, so you will need to combine some areas. The approach would depend on what you are improving.

Here is a forum article with a spreadsheet that can be used to combine above grade envelope areas: 

https://optimiserenergy.com/forums/topic/what-do-i-do-when-there-are-more-wallsceilingsfloors-than-optimiser-supports/

Here's a post on the various types of attic/ceiling spaces: https://optimiserenergy.com/forums/topic/where-to-put-attics-knee-walls-slopes-vaults-cheek-walls-etc/

Modeling "misaligned" insulation and worse

Since we have not been able to find a technical definition for the term "misaligned" as it is applied to insulation, we have mapped it to a Grade III installation quality. A Grade III installation has gaps or voids covering 5% of the insulated area. In the PC version, this is modeled in the parallel path calculations view able using the ||Path buttons on the detailed envelope component pages.

If the actual installation that you are modeling is worse than Grade III, then you should set the quality to Grade I and manually modify the R-value of the insulation itself. If the insulation is so poorly installed that it is making little to no contact with the interior cavity surface then you should model it as uninsulated. If there are significant portions of contact and no-contact, then follow these steps (some functionality available in PC version only):

- Model both insulated and uninsulated scenarios and record the Assembly R-values (reported on the ||Path popups) for each scenario
- Estimate the area and compute the UA=Area/AssemblyR for each scenario
- Sum the UA values, divide by the total area, and invert the number (1/x) to determine the properly weighted average Assembly R-value
- Enter this value in the Assembly R control or increment the Insul R control until the correct Assembly R-value is calculated

Attic Continuous Insulation

Cavity insulation in excess of the joist depth is automatically applied continuously. Currently this is done for all insulation types. 

What is the correct way to handle the Pitch, Rise and Run specifications for the attic space?

For Attics, the pitch is intended to represent the pitch of the thermal boundary (e.g. the attic floor). In the vast majority of cases, the pitch and rise will be zero. One exception to this is a scissor truss roof. We consider this to be an "Attic" because there is an open buffer space above the insulation layer.

When defining the windows for a compass direction wall and there is a mixture of window types there, what is the best way to represent that?

On the detailed Windows screen there is a button labeled Windows 2. That button accesses another screen just like the main screen where you can define a second window type and assign areas to the four directions. There is also a button labeled Add Skylights, Windows or Doors that accesses a third screen on which you can define four more unique glazing areas.

How handle partially insulated basements?

For basement walls please see the following post:
https://optimiserenergy.com/forums/topic/what-do-i-do-when-a-basement-wall-is-only-partially-insulated