**Summary**

- Basic Perimeter / Core is the default zoning strategy for the web application.
- It automatically divides the building up into zones based on their orientation.

- There are two options for using the perimeter / core zoning strategy.
- Basic, the default, which constraint the model to 5 zones only.
- Detailed, which makes each non-contiguous space into its own zone.

- It is substantially more accurate than one zone per floor for calculating whole building energy and HVAC size.
- If you want to simulate actual spaces from your model it's better to use one zone per room.

**What is Perimeter / Core? **

Perimeter / Core zoning is a zoning strategy that divides each floor plate into roughly 5 zones - a “perimeter” zone for each cardinal coordinate (i.e. north, south, east, west) and a “core” zone. The “perimeter” zones are typically about 4m (15’) deep, but can be adjusted within the Web Application.

**Where Sefaira uses perimeter / core zoning**

- Plugin - Not available
- Web Application - Default setting

**How results will be affected**

For many building designs perimeter / core zoning is a perfectly acceptable zoning strategy to use while making the sorts of decisions Sefaira is designed to help with. For example, HVAC systems can be robustly compared with a perimeter / core zoning strategy and envelope changes will be able to be accurately benchmarked on the basis of their impact on energy and peak loads.

Perimeter / core zoning is not ideal however for more granular sizing because it assumes an entire external facade has the same glazing proportion. For example, if your building has some areas with lots of glass and some areas with no glass facing the same orientation then the localized impacts of those variations will not be captured by perimeter core zoning.

**What are the benefits of using perimeter / core? **

The algorithm interprets the floor plate and divide it up into these five zones. For some buildings this works really well, for buildings with lots of articulation or with many different orientations (e.g. a round building) is can be less effective and can occasionally crash a model.

Sefaira uses perimeter / core zoning because for sizing in particular it is very important to capture the peak loads in each perimeter segment. For example it is not realistic to assume heat gained from direct sun could be shared evenly across a floor plate - realistically it all needs to be dealt with at the perimeter, meaning the cooling equipment at the perimeter needs to have more capacity.

**What is the difference between Basic Perimeter / Core and Detailed Perimeter / Core?**

The image on the left shows the Basic Perimeter / Core zoning strategy which has the five main zones (i.e. a core and four others based on the cardinal directions) while the image on the right shows the Detailed Perimeter / Core zoning strategy. The Detailed Perimeter / Core still automatically divides the building between a perimeter and core, but instead of each cardinal direction being one singular zone, each non-contiguous portion of the perimeter is its own zone.

The advantage of choosing this option is that it will generally provide a more accurate assessment of HVAC sizing for buildings with lots of facade articulation or for projects with more than one building in the model. Expect run times in the Detailed Perimeter / Core to take a little longer than basic, as there are more zones being submitted to EnergyPlus.

**Known Issues**

While the algorithm which automatically creates the perimeter / core can handle a wide range of geometry, there are some known issues which can cause the zones to overlap, which can unintentional add extra square footage to the project.

This can be corrected by decreasing the Perimeter Depth, or by adding the zones as "rooms" and using one zone per room.

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