diff --git a/Package.swift b/Package.swift
index e7e18f9..17a1719 100644
--- a/Package.swift
+++ b/Package.swift
@@ -1,26 +1,23 @@
 // swift-tools-version: 6.2
-// The swift-tools-version declares the minimum version of Swift required to build this package.
 
 import PackageDescription
 
 let package = Package(
-    name: "swift-manual-d",
-    products: [
-        // Products define the executables and libraries a package produces, making them visible to other packages.
-        .library(
-            name: "swift-manual-d",
-            targets: ["swift-manual-d"]
-        ),
-    ],
-    targets: [
-        // Targets are the basic building blocks of a package, defining a module or a test suite.
-        // Targets can depend on other targets in this package and products from dependencies.
-        .target(
-            name: "swift-manual-d"
-        ),
-        .testTarget(
-            name: "swift-manual-dTests",
-            dependencies: ["swift-manual-d"]
-        ),
-    ]
+  name: "swift-manual-d",
+  products: [
+    .library(name: "swift-manual-d", targets: ["swift-manual-d"]),
+    .library(name: "ManualDCore", targets: ["ManualDCore"]),
+  ],
+  targets: [
+    .target(
+      name: "swift-manual-d"
+    ),
+    .target(
+      name: "ManualDCore"
+    ),
+    .testTarget(
+      name: "swift-manual-dTests",
+      dependencies: ["swift-manual-d"]
+    ),
+  ]
 )
diff --git a/Sources/ManualDCore/ComponentPressureLosses.swift b/Sources/ManualDCore/ComponentPressureLosses.swift
new file mode 100644
index 0000000..d796d99
--- /dev/null
+++ b/Sources/ManualDCore/ComponentPressureLosses.swift
@@ -0,0 +1,7 @@
+import Foundation
+
+public typealias ComponentPressureLosses = [String: Double]
+
+extension ComponentPressureLosses {
+  public var totalLosses: Double { values.reduce(0) { $0 + $1 } }
+}
diff --git a/Sources/ManualDCore/CoolingLoad.swift b/Sources/ManualDCore/CoolingLoad.swift
new file mode 100644
index 0000000..f018e9e
--- /dev/null
+++ b/Sources/ManualDCore/CoolingLoad.swift
@@ -0,0 +1,13 @@
+import Foundation
+
+public struct CoolingLoad: Codable, Equatable {
+  public let total: Double
+  public let sensible: Double
+  public var latent: Double { total - sensible }
+  public var shr: Double { sensible / total }
+
+  public init(total: Double, sensible: Double) {
+    self.total = total
+    self.sensible = sensible
+  }
+}
diff --git a/Sources/ManualDCore/EquipmentInfo.swift b/Sources/ManualDCore/EquipmentInfo.swift
new file mode 100644
index 0000000..4019c07
--- /dev/null
+++ b/Sources/ManualDCore/EquipmentInfo.swift
@@ -0,0 +1,17 @@
+import Foundation
+
+public struct EquipmentInfo: Codable, Equatable {
+  public let staticPressure: Double
+  public let heatingCFM: Int
+  public let coolingCFM: Int
+
+  public init(
+    staticPressure: Double = 0.5,
+    heatingCFM: Int,
+    coolingCFM: Int
+  ) {
+    self.staticPressure = staticPressure
+    self.heatingCFM = heatingCFM
+    self.coolingCFM = coolingCFM
+  }
+}
diff --git a/Sources/ManualDCore/Room.swift b/Sources/ManualDCore/Room.swift
new file mode 100644
index 0000000..2dd6b2c
--- /dev/null
+++ b/Sources/ManualDCore/Room.swift
@@ -0,0 +1,20 @@
+import Foundation
+
+public struct Room: Codable, Equatable {
+  public let name: String
+  public let heatingLoad: Double
+  public let coolingLoad: CoolingLoad
+  public let registerCount: Int
+
+  public init(
+    name: String,
+    heatingLoad: Double,
+    coolingLoad: CoolingLoad,
+    registerCount: Int = 1
+  ) {
+    self.name = name
+    self.heatingLoad = heatingLoad
+    self.coolingLoad = coolingLoad
+    self.registerCount = registerCount
+  }
+}