diff --git a/src/app/app.ts b/src/app/app.ts
index 3dd4f76b..0ec70068 100644
--- a/src/app/app.ts
+++ b/src/app/app.ts
@@ -6,9 +6,13 @@ import { TemplateSet } from "./template_set";
 
 // reimplement dev mode stuff see last change in 0f7a8289a6fb8387c3c1af41c6664b2a8448758f
 
+export interface Env {
+  [key: string]: any;
+}
+
 interface Config {
   dev?: boolean;
-  env?: { [key: string]: any };
+  env?: Env;
   translatableAttributes?: string[];
   translateFn?: (s: string) => string;
 }
@@ -21,7 +25,7 @@ See https://github.com/odoo/owl/blob/master/doc/reference/config.md#mode for mor
 export class App<T extends typeof Component = any> extends TemplateSet {
   Root: T;
   props: any;
-  env: any = {};
+  env: Env = Object.freeze({});
   scheduler = new Scheduler(window.requestAnimationFrame.bind(window));
   root: ComponentNode | null = null;
 
@@ -36,9 +40,8 @@ export class App<T extends typeof Component = any> extends TemplateSet {
       this.dev = config.dev;
       console.info(DEV_MSG);
     }
-
     if (config.env) {
-      this.env = config.env;
+      this.env = Object.freeze(Object.assign({}, config.env));
     }
     if (config.translateFn) {
       this.translateFn = config.translateFn;
diff --git a/src/component/component.ts b/src/component/component.ts
index 5b717481..e5726ff0 100644
--- a/src/component/component.ts
+++ b/src/component/component.ts
@@ -1,3 +1,4 @@
+import type { Env } from "../app/app";
 import type { ComponentNode } from "./component_node";
 
 // -----------------------------------------------------------------------------
@@ -9,10 +10,10 @@ export class Component {
   static style: string = "";
 
   props: any;
-  env: any;
+  env: Env;
   __owl__: ComponentNode;
 
-  constructor(props: any, env: any, node: ComponentNode) {
+  constructor(props: any, env: Env, node: ComponentNode) {
     this.props = props;
     this.env = env;
     this.__owl__ = node;
diff --git a/src/component/component_node.ts b/src/component/component_node.ts
index b34e261c..d8fcbcc2 100644
--- a/src/component/component_node.ts
+++ b/src/component/component_node.ts
@@ -1,4 +1,4 @@
-import type { App } from "../app/app";
+import type { App, Env } from "../app/app";
 import { BDom, VNode } from "../blockdom";
 import { Component } from "./component";
 import {
@@ -83,6 +83,7 @@ export class ComponentNode<T extends typeof Component = any> implements VNode<Co
   renderFn: Function;
   parent: ComponentNode | null;
   level: number;
+  childEnv: Env;
   children: { [key: string]: ComponentNode } = Object.create(null);
   slots: any = {};
   refs: any = {};
@@ -101,7 +102,9 @@ export class ComponentNode<T extends typeof Component = any> implements VNode<Co
     this.parent = parent || null;
     this.level = parent ? parent.level + 1 : 0;
     applyDefaultProps(props, C);
-    this.component = new C(props, app.env, this) as any;
+    const env = (parent && parent.childEnv) || app.env;
+    this.childEnv = env;
+    this.component = new C(props, env, this) as any;
     this.renderFn = app.getTemplate(C.template).bind(this.component, this.component, this);
     if (C.style) {
       applyStyles(C);
diff --git a/src/hooks.ts b/src/hooks.ts
new file mode 100644
index 00000000..55a941d5
--- /dev/null
+++ b/src/hooks.ts
@@ -0,0 +1,41 @@
+import type { Env } from "./app/app";
+import { getCurrent } from "./component/component_node";
+
+// -----------------------------------------------------------------------------
+// useRef
+// -----------------------------------------------------------------------------
+
+/**
+ * The purpose of this hook is to allow components to get a reference to a sub
+ * html node or component.
+ */
+export function useRef<T extends HTMLElement = HTMLElement>(name: string): { el: T | null } {
+  const node = getCurrent()!;
+  return {
+    get el(): T | null {
+      return node.refs[name] || null;
+    },
+  };
+}
+
+// -----------------------------------------------------------------------------
+// useEnv and useSubEnv
+// -----------------------------------------------------------------------------
+
+/**
+ * This hook is useful as a building block for some customized hooks, that may
+ * need a reference to the env of the component calling them.
+ */
+export function useEnv<E extends Env>(): E {
+  return getCurrent()!.component.env as any;
+}
+
+/**
+ * This hook is a simple way to let components use a sub environment.  Note that
+ * like for all hooks, it is important that this is only called in the
+ * constructor method.
+ */
+export function useSubEnv(envExtension: Env) {
+  const node = getCurrent()!;
+  node.childEnv = Object.freeze(Object.assign({}, node.childEnv, envExtension));
+}
diff --git a/src/index.ts b/src/index.ts
index 72d41ca2..4d3a3a37 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -31,11 +31,9 @@ export const blockDom = {
   html,
 };
 
-// import { makeBlockClass } from "./_old_bdom/element";
 import { App } from "./app/app";
 import { Component } from "./component/component";
 import { getCurrent } from "./component/component_node";
-// import { getCurrent } from "./b_node";
 
 export { App, Component };
 
@@ -57,7 +55,7 @@ export { Portal } from "./misc/portal";
 export { Memo } from "./misc/memo";
 export { css, xml } from "./tags";
 export { useState } from "./reactivity";
-export { useRef } from "./refs";
+export { useRef, useEnv, useSubEnv } from "./hooks";
 export const utils = { EventBus, whenReady, loadFile };
 
 export {
diff --git a/src/refs.ts b/src/refs.ts
deleted file mode 100644
index ac1fc44f..00000000
--- a/src/refs.ts
+++ /dev/null
@@ -1,18 +0,0 @@
-// -----------------------------------------------------------------------------
-// useRef
-// -----------------------------------------------------------------------------
-
-import { getCurrent } from "./component/component_node";
-
-/**
- * The purpose of this hook is to allow components to get a reference to a sub
- * html node or component.
- */
-export function useRef<T extends HTMLElement = HTMLElement>(name: string): { el: T | null } {
-  const node = getCurrent()!;
-  return {
-    get el(): T | null {
-      return node.refs[name] || null;
-    },
-  };
-}
diff --git a/tests/components/__snapshots__/concurrency.test.ts.snap b/tests/components/__snapshots__/concurrency.test.ts.snap
index 931f5fb2..e96638c9 100644
--- a/tests/components/__snapshots__/concurrency.test.ts.snap
+++ b/tests/components/__snapshots__/concurrency.test.ts.snap
@@ -1132,7 +1132,7 @@ exports[`rendering component again in next microtick 2`] = `
     let b2;
     const v1 = ctx['onClick'];
     let d1 = [v1, ctx];
-    if (ctx['env'].flag) {
+    if (ctx['env'].config.flag) {
       b2 = component(\`Child\`, {}, key + \`__2\`, node, ctx);
     }
     return block1([d1], [b2]);
diff --git a/tests/components/__snapshots__/higher_order_component.test.ts.snap b/tests/components/__snapshots__/higher_order_component.test.ts.snap
index 8ce47ed9..42051371 100644
--- a/tests/components/__snapshots__/higher_order_component.test.ts.snap
+++ b/tests/components/__snapshots__/higher_order_component.test.ts.snap
@@ -63,10 +63,10 @@ exports[`basics can select a sub widget  3`] = `
   
   return function template(ctx, node, key = \\"\\") {
     let b2,b3;
-    if (ctx['env'].flag) {
+    if (ctx['env'].options.flag) {
       b2 = component(\`Child\`, {}, key + \`__1\`, node, ctx);
     }
-    if (!ctx['env'].flag) {
+    if (!ctx['env'].options.flag) {
       b3 = component(\`OtherChild\`, {}, key + \`__2\`, node, ctx);
     }
     return multi([b2, b3]);
diff --git a/tests/components/__snapshots__/hooks.test.ts.snap b/tests/components/__snapshots__/hooks.test.ts.snap
index 060da9c8..b829c6d3 100644
--- a/tests/components/__snapshots__/hooks.test.ts.snap
+++ b/tests/components/__snapshots__/hooks.test.ts.snap
@@ -66,6 +66,21 @@ exports[`hooks can use onWillStart, onWillUpdateProps 2`] = `
 }"
 `;
 
+exports[`hooks can use sub env 1`] = `
+"function anonymous(bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, component } = bdom;
+  let { withDefault, getTemplate, prepareList, withKey, zero, call, callSlot, capture, isBoundary, shallowEqual, setContextValue, toNumber } = helpers;
+  
+  let block1 = createBlock(\`<div><block-text-0/></div>\`);
+  
+  return function template(ctx, node, key = \\"\\") {
+    let d1 = ctx['env'].val;
+    return block1([d1]);
+  }
+}"
+`;
+
 exports[`hooks can use useComponent 1`] = `
 "function anonymous(bdom, helpers
 ) {
@@ -80,6 +95,21 @@ exports[`hooks can use useComponent 1`] = `
 }"
 `;
 
+exports[`hooks can use useEnv 1`] = `
+"function anonymous(bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, component } = bdom;
+  let { withDefault, getTemplate, prepareList, withKey, zero, call, callSlot, capture, isBoundary, shallowEqual, setContextValue, toNumber } = helpers;
+  
+  let block1 = createBlock(\`<div><block-text-0/></div>\`);
+  
+  return function template(ctx, node, key = \\"\\") {
+    let d1 = ctx['env'].val;
+    return block1([d1]);
+  }
+}"
+`;
+
 exports[`hooks mounted callbacks should be called in reverse order from willUnmount callbacks 1`] = `
 "function anonymous(bdom, helpers
 ) {
@@ -95,6 +125,35 @@ exports[`hooks mounted callbacks should be called in reverse order from willUnmo
 }"
 `;
 
+exports[`hooks parent and child env 1`] = `
+"function anonymous(bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, component } = bdom;
+  let { withDefault, getTemplate, prepareList, withKey, zero, call, callSlot, capture, isBoundary, shallowEqual, setContextValue, toNumber } = helpers;
+  
+  let block1 = createBlock(\`<div><block-text-0/></div>\`);
+  
+  return function template(ctx, node, key = \\"\\") {
+    let d1 = ctx['env'].val;
+    return block1([d1]);
+  }
+}"
+`;
+
+exports[`hooks parent and child env 2`] = `
+"function anonymous(bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, component } = bdom;
+  let { withDefault, getTemplate, prepareList, withKey, zero, call, callSlot, capture, isBoundary, shallowEqual, setContextValue, toNumber } = helpers;
+  
+  return function template(ctx, node, key = \\"\\") {
+    let b2 = text(ctx['env'].val);
+    let b3 = component(\`Child\`, {}, key + \`__1\`, node, ctx);
+    return multi([b2, b3]);
+  }
+}"
+`;
+
 exports[`hooks two different call to willPatch/patched should work 1`] = `
 "function anonymous(bdom, helpers
 ) {
diff --git a/tests/components/concurrency.test.ts b/tests/components/concurrency.test.ts
index 914720ba..c9257d0a 100644
--- a/tests/components/concurrency.test.ts
+++ b/tests/components/concurrency.test.ts
@@ -587,7 +587,7 @@ test("rendering component again in next microtick", async () => {
     static template = xml`
           <div>
             <button t-on-click="onClick">Click</button>
-            <t t-if="env.flag"><Child/></t>
+            <t t-if="env.config.flag"><Child/></t>
           </div>`;
     static components = { Child };
 
@@ -595,14 +595,15 @@ test("rendering component again in next microtick", async () => {
       useLogLifecycle(steps);
     }
     async onClick() {
-      this.env.flag = true;
+      this.env.config.flag = true;
       this.render();
       await Promise.resolve();
       this.render();
     }
   }
 
-  await mount(Parent, fixture);
+  const env = { config: { flag: false } };
+  await new App(Parent).configure({ env }).mount(fixture);
   expect(fixture.innerHTML).toBe("<div><button>Click</button></div>");
   fixture.querySelector("button")!.click();
   await nextTick();
diff --git a/tests/components/env.test.ts b/tests/components/env.test.ts
index 9ba9e6f5..a014b29e 100644
--- a/tests/components/env.test.ts
+++ b/tests/components/env.test.ts
@@ -8,17 +8,6 @@ beforeEach(() => {
 });
 
 describe("env handling", () => {
-  test("keeps a reference to env", async () => {
-    const env = {};
-    class Test extends Component {
-      static template = xml`<div/>`;
-    }
-    const app = new App(Test);
-    app.configure({ env });
-    const component = await app.mount(fixture);
-    expect(component.env).toBe(env);
-  });
-
   test("has an env by default", async () => {
     class Test extends Component {
       static template = xml`<div/>`;
@@ -27,8 +16,23 @@ describe("env handling", () => {
     expect(component.env).toEqual({});
   });
 
+  test("env is shallow frozen", async () => {
+    const env = { foo: 42, bar: { value: 42 } };
+    class Test extends Component {
+      static template = xml`<div/>`;
+    }
+    const component = await new App(Test).configure({ env }).mount(fixture);
+    expect(Object.isFrozen(component.env)).toBeTruthy();
+    expect(component.env).toEqual({ foo: 42, bar: { value: 42 } });
+    expect(() => {
+      component.env.foo = 23;
+    }).toThrow(/Cannot assign to read only property 'foo' of object/);
+    component.env.bar.value = 23;
+    expect(component.env).toEqual({ foo: 42, bar: { value: 23 } });
+  });
+
   test("parent env is propagated to child components", async () => {
-    const env = {};
+    const env = { foo: 42, bar: { value: 42 } };
     let child: any = null;
 
     class Child extends Component {
@@ -43,9 +47,7 @@ describe("env handling", () => {
       static components = { Child };
     }
 
-    const app = new App(Test);
-    app.configure({ env });
-    await app.mount(fixture);
-    expect(child.env).toBe(env);
+    await new App(Test).configure({ env }).mount(fixture);
+    expect(child.env).toEqual(env);
   });
 });
diff --git a/tests/components/higher_order_component.test.ts b/tests/components/higher_order_component.test.ts
index 45c633f2..ffb63f4c 100644
--- a/tests/components/higher_order_component.test.ts
+++ b/tests/components/higher_order_component.test.ts
@@ -58,19 +58,17 @@ describe("basics", () => {
     class Parent extends Component {
       static template = xml`
             <t>
-              <t t-if="env.flag"><Child /></t>
-              <t t-if="!env.flag"><OtherChild /></t>
+              <t t-if="env.options.flag"><Child /></t>
+              <t t-if="!env.options.flag"><OtherChild /></t>
             </t>
           `;
       static components = { Child, OtherChild };
     }
-    const env = { flag: true };
-    const app = new App(Parent);
-    app.configure({ env });
-    const parent = await app.mount(fixture);
+    const env = { options: { flag: true } };
+    const parent = await new App(Parent).configure({ env }).mount(fixture);
     expect(fixture.innerHTML).toBe("<span>CHILD 1</span>");
 
-    env.flag = false;
+    env.options.flag = false;
     await parent.render();
     expect(fixture.innerHTML).toBe("<div>CHILD 2</div>");
   });
diff --git a/tests/components/hooks.test.ts b/tests/components/hooks.test.ts
index 9a36d527..2088ba13 100644
--- a/tests/components/hooks.test.ts
+++ b/tests/components/hooks.test.ts
@@ -5,6 +5,8 @@ import {
   useRef,
   useState,
   useComponent,
+  useEnv,
+  useSubEnv,
   onMounted,
   onPatched,
   onWillStart,
@@ -12,7 +14,7 @@ import {
   onWillPatch,
   xml,
   onWillUnmount,
-} from "../../src";
+} from "../../src/index";
 import { makeTestFixture, nextTick, snapshotEverything } from "../helpers";
 
 let fixture: HTMLElement;
@@ -163,27 +165,30 @@ describe("hooks", () => {
     });
   });
 
-  test.skip("can use useEnv", async () => {
-    expect.assertions(2);
+  test("can use useEnv", async () => {
+    expect.assertions(3);
     class Test extends Component {
       static template = xml`<div><t t-esc="env.val"/></div>`;
       setup() {
-        //expect(useEnv()).toBe(this.env);
+        expect(useEnv()).toBe(this.env);
       }
     }
-    await mount(Test, fixture);
+    const env = { val: 1 };
+    await new App(Test).configure({ env }).mount(fixture);
+    expect(fixture.innerHTML).toBe("<div>1</div>");
   });
 
-  test.skip("can use sub env", async () => {
+  test("use sub env does not pollute user env", async () => {
     class Test extends Component {
       static template = xml`<div><t t-esc="env.val"/></div>`;
       setup() {
-        //useSubEnv({ val: 3 });
+        useSubEnv({ val2: 1 });
       }
     }
-    const component = await mount(Test, fixture);
+    const env = { val: 3 };
+    const component = await new App(Test).configure({ env }).mount(fixture);
     expect(fixture.innerHTML).toBe("<div>3</div>");
-    expect(component.env).not.toHaveProperty("val");
+    expect(component.env).not.toHaveProperty("val2");
     expect(component.env).toHaveProperty("val");
   });
 
@@ -198,22 +203,20 @@ describe("hooks", () => {
     await mount(Test, fixture);
   });
 
-  test.skip("parent and child env", async () => {
+  test("parent and child env", async () => {
     class Child extends Component {
       static template = xml`<div><t t-esc="env.val"/></div>`;
-      super() {
-        //useSubEnv({ val: 5 });
-      }
     }
 
     class Parent extends Component {
       static template = xml`<t t-esc="env.val"/><Child/>`;
       static components = { Child };
       setup() {
-        //useSubEnv({ val: 3 });
+        useSubEnv({ val: 5 });
       }
     }
-    mount(Parent, fixture);
+    const env = { val: 3 };
+    await new App(Parent).configure({ env }).mount(fixture);
     expect(fixture.innerHTML).toBe("3<div>5</div>");
   });