diff --git a/cara/apps/calculator/report_generator.py b/cara/apps/calculator/report_generator.py
index 2f73c05d..261dd8d8 100644
--- a/cara/apps/calculator/report_generator.py
+++ b/cara/apps/calculator/report_generator.py
@@ -29,11 +29,80 @@ def model_start_end(model: models.ExposureModel):
     return t_start, t_end
 
 
-def calculate_report_data(model: models.ExposureModel):
-    resolution = 600
+def fill_big_gaps(array, gap_size):
+    """
+    Insert values into the given sorted list if there is a gap of more than ``gap_size``.
+    All values in the given array are preserved, even if they are within the ``gap_size`` of one another.
+
+    >>> fill_big_gaps([1, 2, 4], gap_size=0.75)
+    [1, 1.75, 2, 2.75, 3.5, 4]
+
+    """
+    result = []
+    if len(array) == 0:
+        raise ValueError("Input array must be len > 0")
+
+    last_value = array[0]
+    for value in array:
+        while value - last_value > gap_size + 1e-15:
+            last_value = last_value + gap_size
+            result.append(last_value)
+        result.append(value)
+        last_value = value
+    return result
+
+
+def non_temp_transition_times(model: models.ExposureModel):
+    """
+    Return the non-temperature (and PiecewiseConstant) based transition times.
+
+    """
+    def walk_model(model, name=""):
+        # Extend walk_dataclass to handle lists of dataclasses
+        # (e.g. in MultipleVentilation).
+        for name, obj in dataclass_utils.walk_dataclass(model, name=name):
+            if name.endswith('.ventilations') and isinstance(obj, (list, tuple)):
+                for i, item in enumerate(obj):
+                    fq_name_i = f'{name}[{i}]'
+                    yield fq_name_i, item
+                    if dataclasses.is_dataclass(item):
+                        yield from dataclass_utils.walk_dataclass(item, name=fq_name_i)
+            else:
+                yield name, obj
 
     t_start, t_end = model_start_end(model)
-    times = np.linspace(t_start, t_end, resolution)
+
+    change_times = {t_start, t_end}
+    for name, obj in walk_model(model, name="exposure"):
+        if isinstance(obj, models.Interval):
+            change_times |= obj.transition_times()
+
+    # Only choose times that are in the range of the model (removes things
+    # such as PeriodicIntervals, which extend beyond the model itself).
+    return sorted(time for time in change_times if (t_start <= time <= t_end))
+
+
+def interesting_times(model: models.ExposureModel, approx_n_pts=100) -> typing.List[float]:
+    """
+    Pick approximately ``approx_n_pts`` time points which are interesting for the
+    given model.
+
+    Initially the times are seeded by important state change times (excluding
+    outside temperature), and the times are then subsequently expanded to ensure
+    that the step size is at most ``(t_end - t_start) / approx_n_pts``.
+
+    """
+    times = non_temp_transition_times(model)
+
+    # Expand the times list to ensure that we have a maximum gap size between
+    # the key times.
+    nice_times = fill_big_gaps(times, gap_size=(max(times) - min(times)) / approx_n_pts)
+    return nice_times
+
+
+def calculate_report_data(model: models.ExposureModel):
+    times = interesting_times(model)
+
     concentrations = [
         np.array(model.concentration_model.concentration(float(time))).mean()
         for time in times
@@ -212,7 +281,7 @@ def manufacture_alternative_scenarios(form: FormData) -> typing.Dict[str, mc.Exp
     return scenarios
 
 
-def comparison_plot(scenarios: typing.Dict[str, dict], sample_times: np.ndarray):
+def comparison_plot(scenarios: typing.Dict[str, dict], sample_times: typing.List[float]):
     fig = plt.figure()
     ax = fig.add_subplot(1, 1, 1)
 
@@ -244,7 +313,7 @@ def comparison_plot(scenarios: typing.Dict[str, dict], sample_times: np.ndarray)
     return fig
 
 
-def scenario_statistics(mc_model: mc.ExposureModel, sample_times: np.ndarray):
+def scenario_statistics(mc_model: mc.ExposureModel, sample_times: typing.List[float]):
     model = mc_model.build_model(size=_DEFAULT_MC_SAMPLE_SIZE)
     return {
         'probability_of_infection': np.mean(model.infection_probability()),
@@ -258,7 +327,7 @@ def scenario_statistics(mc_model: mc.ExposureModel, sample_times: np.ndarray):
 
 def comparison_report(
         scenarios: typing.Dict[str, mc.ExposureModel],
-        sample_times: np.ndarray,
+        sample_times: typing.List[float],
         executor_factory: typing.Callable[[], concurrent.futures.Executor],
 ):
     statistics = {}
@@ -309,8 +378,7 @@ class ReportGenerator:
             'creation_date': time,
         }
 
-        t_start, t_end = model_start_end(model)
-        scenario_sample_times = np.linspace(t_start, t_end, 350)
+        scenario_sample_times = interesting_times(model)
 
         context.update(calculate_report_data(model))
         alternative_scenarios = manufacture_alternative_scenarios(form)
@@ -323,7 +391,7 @@ class ReportGenerator:
             'level': 'Yellow - 2', 
             'incidence_rate': 'lower than 25 new cases per 100 000 inhabitants',
             'onsite_access': 'of about 8000', 
-            'threshold' : ''
+            'threshold': ''
         } 
         return context
 
diff --git a/cara/dataclass_utils.py b/cara/dataclass_utils.py
index 3915b9e8..0b261afd 100644
--- a/cara/dataclass_utils.py
+++ b/cara/dataclass_utils.py
@@ -43,3 +43,24 @@ def replace(obj, **changes):
     new = dataclasses.replace(obj, **changes)
     object.__setattr__(obj, '__dataclass_fields__', orig)
     return new
+
+
+def walk_dataclass(model, name=""):
+    """
+    Recursively walk a dataclass instance, generating (name, obj) pairs for
+    attributes and decending into nested dataclasses.
+
+    >>> list(walk_dataclass(obj), 'my_obj')
+    [('my_obj.attr_a', <dataclass instance>), ('my_obj.attr_a.sub_attr', <dataclass instance>)]
+
+    """
+    if name:
+        name = name + '.'
+    if not dataclasses.is_dataclass(model):
+        raise TypeError(f'Not a dataclass based model: {type(model)}')
+    for field in dataclasses.fields(model):
+        obj = getattr(model, field.name)
+        fq_name = f'{name}{field.name}'
+        yield fq_name, obj
+        if dataclasses.is_dataclass(obj):
+            yield from walk_dataclass(obj, name=fq_name)
diff --git a/cara/tests/apps/calculator/test_report_generator.py b/cara/tests/apps/calculator/test_report_generator.py
index 91c6a02c..c18fdd45 100644
--- a/cara/tests/apps/calculator/test_report_generator.py
+++ b/cara/tests/apps/calculator/test_report_generator.py
@@ -2,10 +2,13 @@ import concurrent.futures
 from functools import partial
 import time
 
+import numpy.testing
+import numpy as np
 import pytest
 
-from cara.apps.calculator.report_generator import ReportGenerator, readable_minutes
 from cara.apps.calculator import make_app
+from cara.apps.calculator.report_generator import ReportGenerator, readable_minutes
+import cara.apps.calculator.report_generator as rep_gen
 
 
 def test_generate_report(baseline_form):
@@ -38,3 +41,50 @@ def test_generate_report(baseline_form):
 )
 def test_readable_minutes(test_input, expected):
     assert readable_minutes(test_input) == expected
+
+
+def test_fill_big_gaps():
+    expected = [1, 1.75, 2, 2.75, 3.5, 4]
+    assert rep_gen.fill_big_gaps([1, 2, 4], gap_size=0.75) == expected
+
+
+def test_fill_big_gaps__float_tolerance():
+    # Ensure that there is some float tolerance to the gap size check.
+    assert rep_gen.fill_big_gaps([0, 2 + 1e-15, 4], gap_size=2) == [0, 2 + 1e-15, 4]
+    assert rep_gen.fill_big_gaps([0, 2 + 1e-14, 4], gap_size=2) == [0, 2, 2 + 1e-14, 4]
+
+
+def test_non_temp_transition_times(baseline_exposure_model):
+    expected = [0.0, 4.0, 5.0, 8.0]
+    result = rep_gen.non_temp_transition_times(baseline_exposure_model)
+    assert result == expected
+
+
+def test_interesting_times_many(baseline_exposure_model):
+    result = rep_gen.interesting_times(baseline_exposure_model, approx_n_pts=100)
+    assert 100 <= len(result) <= 120
+    assert np.abs(np.diff(result)).max() < 8.1/100.
+
+
+def test_interesting_times_small(baseline_exposure_model):
+    expected = [0.0, 0.8, 1.6, 2.4, 3.2, 4.0, 4.8, 5.0, 5.8, 6.6, 7.4, 8.0]
+    # Ask for more data than there is in the transition times.
+    result = rep_gen.interesting_times(baseline_exposure_model, approx_n_pts=10)
+
+    np.testing.assert_allclose(result, expected, atol=1e-04)
+
+
+def test_interesting_times_w_temp(exposure_model_w_outside_temp_changes):
+    # Ensure that the state change times are returned (minus the temperature changes) by
+    # requesting n_points=1.
+    result = rep_gen.interesting_times(exposure_model_w_outside_temp_changes, approx_n_pts=1)
+    expected = [0., 1.8, 2.2, 4., 4.4, 5., 6.2, 6.6, 8.]
+    np.testing.assert_allclose(result, expected)
+
+    # Now request more than the state-change times.
+    result = rep_gen.interesting_times(exposure_model_w_outside_temp_changes, approx_n_pts=20)
+    expected = [
+        0., 0.4, 0.8, 1.2, 1.6, 1.8, 2.2, 2.6, 3., 3.4, 3.8, 4., 4.4, 4.8,
+        5., 5.4, 5.8, 6.2, 6.6, 7., 7.4, 7.8, 8.
+    ]
+    np.testing.assert_allclose(result, expected)
diff --git a/cara/tests/conftest.py b/cara/tests/conftest.py
index e69b44c5..9499dfcf 100644
--- a/cara/tests/conftest.py
+++ b/cara/tests/conftest.py
@@ -1,4 +1,6 @@
 from cara import models
+import cara.data
+import cara.dataclass_utils
 
 import pytest
 
@@ -33,5 +35,20 @@ def baseline_exposure_model(baseline_model):
             activity=baseline_model.infected.activity,
             mask=baseline_model.infected.mask,
         ),
-        fraction_deposited = 1.,
+        fraction_deposited=1.,
     )
+
+
+@pytest.fixture
+def exposure_model_w_outside_temp_changes(baseline_exposure_model: models.ExposureModel):
+    exp_model = cara.dataclass_utils.nested_replace(
+        baseline_exposure_model, {
+            'concentration_model.ventilation': models.SlidingWindow(
+                active=models.PeriodicInterval(2.2 * 60, 1.8 * 60),
+                inside_temp=models.PiecewiseConstant((0., 24.), (293,)),
+                outside_temp=cara.data.GenevaTemperatures['Jan'],
+                window_height=1.6,
+                opening_length=0.6,
+            )
+        })
+    return exp_model
diff --git a/cara/tests/test_dataclass_utils.py b/cara/tests/test_dataclass_utils.py
index ec0da382..270066ee 100644
--- a/cara/tests/test_dataclass_utils.py
+++ b/cara/tests/test_dataclass_utils.py
@@ -1,6 +1,6 @@
 import dataclasses
 
-from cara.dataclass_utils import nested_replace
+from cara.dataclass_utils import nested_replace, walk_dataclass
 
 
 @dataclasses.dataclass(frozen=True)
@@ -25,3 +25,15 @@ def test_nested_replace():
     inst = One(1, two=Two(3, Four(4)))
     new_inst = nested_replace(inst, {'two.four': Four(5)})
     assert new_inst == One(1, two=Two(3, Four(5)))
+
+
+def test_walk():
+    inst = One(1, two=Two(3, Four(4)))
+    expected = [
+        ('inst.one', inst.one),
+        ('inst.two', inst.two),
+        ('inst.two.three', inst.two.three),
+        ('inst.two.four', inst.two.four),
+        ('inst.two.four.four', inst.two.four.four),
+    ]
+    assert list(walk_dataclass(inst, name='inst')) == expected
diff --git a/cara/tests/test_known_quantities.py b/cara/tests/test_known_quantities.py
index 1556df75..89c0268d 100644
--- a/cara/tests/test_known_quantities.py
+++ b/cara/tests/test_known_quantities.py
@@ -312,7 +312,7 @@ def test_concentrations_hourly_dep_temp_vs_constant(month, temperatures, time):
 )
 def test_concentrations_hourly_dep_temp_startup(month, temperatures, time):
     # The concentrations should be the zero up to the first presence time
-    # of an infecter person.
+    # of an infected person.
     m = build_hourly_dependent_model(
         month,
         ((0., 0.5), (1., 1.5), (4., 4.5), (7.5, 8), ),