diff --git a/envbuilder.go b/envbuilder.go
index 670c40d8..659de424 100644
--- a/envbuilder.go
+++ b/envbuilder.go
@@ -123,6 +123,10 @@ type Options struct {
 	// to using a devcontainer that some might find simpler.
 	DockerfilePath string `env:"DOCKERFILE_PATH"`
 
+	// CacheTTLDays is the number of days to use cached layers before
+	// expiring them. Defaults to 7 days.
+	CacheTTLDays int `env:"CACHE_TTL_DAYS"`
+
 	// DockerConfigBase64 is a base64 encoded Docker config
 	// file that will be used to pull images from private
 	// container registries.
@@ -557,6 +561,10 @@ func Run(ctx context.Context, options Options) error {
 				logf(codersdk.LogLevelInfo, "%s", scanner.Text())
 			}
 		}()
+		cacheTTL := time.Hour * 24 * 7
+		if options.CacheTTLDays != 0 {
+			cacheTTL = time.Hour * 24 * time.Duration(options.CacheTTLDays)
+		}
 
 		endStage := startStage("🏗️ Building image...")
 		// At this point we have all the context, we can now build!
@@ -578,7 +586,7 @@ func Run(ctx context.Context, options Options) error {
 			CompressionLevel: 3,
 			CacheOptions: config.CacheOptions{
 				// Cache for a week by default!
-				CacheTTL: time.Hour * 24 * 7,
+				CacheTTL: cacheTTL,
 				CacheDir: options.BaseImageCacheDir,
 			},
 			ForceUnpack:       true,
@@ -931,20 +939,23 @@ func OptionsFromEnv(getEnv func(string) (string, bool)) Options {
 		if env == "" {
 			continue
 		}
+		e, ok := getEnv(env)
+		if !ok {
+			continue
+		}
 		switch fieldTyp.Type.Kind() {
 		case reflect.String:
-			v, _ := getEnv(env)
-			field.SetString(v)
+			field.SetString(e)
 		case reflect.Bool:
-			e, _ := getEnv(env)
 			v, _ := strconv.ParseBool(e)
 			field.SetBool(v)
+		case reflect.Int:
+			v, _ := strconv.ParseInt(e, 10, 64)
+			field.SetInt(v)
 		case reflect.Slice:
-			v, ok := getEnv(env)
-			if !ok {
-				continue
-			}
-			field.Set(reflect.ValueOf(strings.Split(v, ",")))
+			field.Set(reflect.ValueOf(strings.Split(e, ",")))
+		default:
+			panic(fmt.Sprintf("unsupported type %s in OptionsFromEnv", fieldTyp.Type.String()))
 		}
 	}
 
diff --git a/envbuilder_test.go b/envbuilder_test.go
index 55cfea90..84c476a0 100644
--- a/envbuilder_test.go
+++ b/envbuilder_test.go
@@ -23,11 +23,13 @@ func TestSystemOptions(t *testing.T) {
 	opts := map[string]string{
 		"INIT_SCRIPT":            "echo hello",
 		"CACHE_REPO":             "kylecarbs/testing",
+		"CACHE_TTL_DAYS":         "30",
 		"DEVCONTAINER_JSON_PATH": "/tmp/devcontainer.json",
 		"DOCKERFILE_PATH":        "Dockerfile",
 		"FALLBACK_IMAGE":         "ubuntu:latest",
 		"FORCE_SAFE":             "true",
 		"INSECURE":               "false",
+		"GIT_CLONE_DEPTH":        "1",
 		"GIT_URL":                "https://github.com/coder/coder",
 		"WORKSPACE_FOLDER":       "/workspaces/coder",
 	}
@@ -37,10 +39,12 @@ func TestSystemOptions(t *testing.T) {
 	require.Equal(t, "echo hello", env.InitScript)
 	require.Equal(t, "kylecarbs/testing", env.CacheRepo)
 	require.Equal(t, "/tmp/devcontainer.json", env.DevcontainerJSONPath)
+	require.Equal(t, 30, env.CacheTTLDays)
 	require.Equal(t, "Dockerfile", env.DockerfilePath)
 	require.Equal(t, "ubuntu:latest", env.FallbackImage)
 	require.True(t, env.ForceSafe)
 	require.False(t, env.Insecure)
+	require.Equal(t, 1, env.GitCloneDepth)
 	require.Equal(t, "https://github.com/coder/coder", env.GitURL)
 	require.Equal(t, "/workspaces/coder", env.WorkspaceFolder)
 }