diff --git a/cara/tests/test_known_quantities.py b/cara/tests/test_known_quantities.py
index 10243f91..fc563071 100644
--- a/cara/tests/test_known_quantities.py
+++ b/cara/tests/test_known_quantities.py
@@ -183,5 +183,18 @@ def test_piecewiseconstantfunction_vs_interval():
     interval = models.SpecificInterval(present_times=[(8,16)])
     assert interval.transition_times() == fun.interval().transition_times()
     for t in [0,1,8,10,16,20.1,24]:
-        assert fun.interval().triggered(t) == interval().triggered(t)
+        assert fun.interval().triggered(t) == interval.triggered(t)
+
+
+def test_windowopening():
+    w1 = models.WindowOpening(active=models.SpecificInterval([(0,24)]),
+                inside_temp=293.15,outside_temp=283.15,
+                window_height=1.,opening_length=0.6)
+    w2 = models.WindowOpening(active=models.SpecificInterval([(0,24)]),
+                inside_temp=293.15,outside_temp=273.15,
+                window_height=1.,opening_length=0.6)
+    npt.assert_allclose(w1.air_exchange(models.Room(volume=68),10.),
+                        3.7393925,rtol=1e-5)
+    npt.assert_allclose(w2.air_exchange(models.Room(volume=68),10.),
+                        5.3842316,rtol=1e-5)