buildings usually have an existing heat dirtribution system
and there is no reason not to use the very same system after
renovation. With the renovation the heat requirement is
reduced, then the system temperatures can also be reduced.
Therefor, high efficiency boilers and heat pumps can then
be used. Good thermal insulation and high efficency mechanical
equipment go hand in hand.
building before upgrades
Location: 4 Jean Paul Place, WBG Nuernberg
building - with Passive House components
The modernization included very good thermal
insulation of all exterior surfaces, new windows and balanced
ventilation with heat recovery.
Planning by Dr.
Burkhard Schulze Darup.
shows that increasing insulation levels minimizes problems
associated with thermal bridges such as condensation. The
following diagrams illustrate this. If the wall is well insulated,
as seen on the right, the moisture problems in the room are
eliminated. You can find additional details on the this project
in the document: "Modernization of Old Buildings" [ AkkP 24
building - situation at the front without insulation
Example of conditions one usually finds in a partially modernized
building: New windows were installed, but no insulation was
added to the exterior walls. Under winter boundary conditions
(outside -5°C; inside 20°C) the resultant surface temperatures
within the dwelling range down to 9°C: Behind a cabinet against
an outside edge, the temperatures can drop below 5°C. At these
low temperatures air will hold very little moisture. Therefore
the relative humidity rises to high values, good conditions
for mould growth.
In the uninsulated old building mould damage is caused
by the increased humidity.
insulated (200 mm) building after renovation
The concept that better insulation reduces
the danger of mold growth is not limited to the case shown
here. By increasing the insulation of the wall, interior surface
temperatures rise. Systematic investigations show that adequate
insulation all critical connection points raises surface temperatures
high enough so that the relative humidity remains under 80%
everywhere and therefore problems with humidity are
Source: [ AkkP 24 ]
site picture: Installation of 200 mm of thermal insulation.
In each case, a strip of non combustible mineral wool
insulation is placed over the windows. (photo:
site picture: The old exterior plaster is primed before
the insulation is placed against it, also note how the
insulation fits tightly under the window sill. (photo:
Contrary to popular
prejudices, it is beneficial, when rennovating, to make the
building very airtight. Unsealed gaps and
cracks allow water to get into the wall when it condenses
out of the air passing throught the wall. The planning
principles for new buildings can successfully be transferred
to the modernization of old buildings. In implemented renovations,
the attained airtightness has been surprisingly good. Therefore,
we must refer to how important controlled ventilation of dwellings
becomes: "Those who demand airtightness, must also
provide sufficient ventilation."
building - often extremely leaky
wooden windows; Timber
beam attic floor; ribbed
slab for main floor.
this old building an air leakage of 4.9h -1 was
measured. Is it possible to improve such an old building
to the same airtightness as a new high-quality building?
(additional information in: [ AkkP 24 ].)
building with good airtightness
It is! The air tightness
level formed by a priming the old external plaster (the insulation
is seen in the bottom of the middle photo), the floor was
made airtight by an airtightness barrier (right photo; important:
the thermal insulation installed on top of the airtightness
The air leakage after the renovation was with 0.35 h-1.
a careful thermal bridge free modernization the
windows often remain the most significant
weak point. It has been shown, however, that high comfort
levels and the elimantion of condensation is achieved when
the Passive House windows are used and the window installation
is done using Passive House methodology.
building - old, poorly insulated and leaky windows
wooden windows; leaky and poorly insulating - replacement
interior surfaces of an old window (here between 12 and 14°C)
lead to wasted energy and make the occupant feel cold through
radiative losses (IR-image: Feist, in the PHI office space)
house window - the best choice
The new window installed: A
warm window with triple glazing, warm-edge spacers and
a highly insulated frame. This window will be considered to
be high performance for the next 50 years.
contrast, Passive House windows have high internal surface
temperatures: Both for the glazing (here: 17 °C) and
at the framework. This creates good comfort for the occupants
in the room.
Feist, in the Passive
House Darmstadt Kranichstein)
sufficient fresh air is a main focus in rennovating an old
building. The typically recommened "twice daily intermittant
ventilation" is not sufficient for the removal of room air
pollutants. With highly airtight building envelope, the safeguarding
of the necessary ventilation
of dwellings is an indispensable component of a responsible
renovation. This statement applies to the modernized of old
building even more than with new buildings: Adequate
air exchange must be ensured.
The most important task in cold climates is dehumidifying
from kitchen, bathrooms and toilet rooms. An exhaust register
must be located in all rooms where humidity is generated.
The amount of fresh air brought in should not be too high,
however, because then the air can possibly become "too
dry". Information about ventilatoin for good comfort and
health can be found here: [ AkkP 30 ].
with the heating energy balance of old buildings are the high
losses through the exterior walls (see the portion with the
balance in the following diagram on the left side). It is
particularly important then, not only from the building design
viewpoint, but also from an energy-economic perspective, to
improve the thermal resistance in the walls. The often expressed
view not to add insulation to the exterior walls of old buildings,
is wrong. That the exterior walls must be better insulated
comes not only from an energy perspective but also from a
in door air quality one (See the paragraph above over mould
avoidance by good thermal insulation).
During the demonstration
projects in Ludwigshafen and Nuernberg the heating energy
requirement was reduced to under 30 kWh/(m²a). Old buildings
thus experience a factor 8 improvement. Such drastic improvements
were not considered to be realistic until recently, even in
the building industry. The results of measurement from the
demonstration projects, documented in [ AkkP 24 ], show that
there is a strong relationship between values determined through
computer simulation and the measured results.
balance of the old building (before) 2)
The high specific
losses through the exterior walls (blue) and the attic cover
(light red) are remarkable. Solar gains play nearly no role,
because the losses are so high. These high losses have to
be balanced by the heating system (red), which amounted to
a an energy consumption of more than 200 kWh/(m²a) (20-litre
house) before the renovation.
balance after the successful renovation 2)
balance of the renovated building is much better. Due to the
good thermal insulation, the losses are diminished to very
small values. The values of the Solar and internal Heat gains
changed very little, but now they counteract nearly half of
the losses. As a result, the heating energy requirement is
very small after the renovation: The modeled energy consumption
is 27.4 kWh/(m²a) (2,7-Liter-Haus) resulting in energy
savings of 87%.
the exemplary renovation at the building Jean Paul place 4,
described here, was actually accomplished in Nuernberg with
the presented quality, the measured results for heating energy
consumption can now be compared with the modeled results.
The actual measured heating energy consumption for the first
year was 26.9 kWh/(m²a) - which confirms the modeled results.
The graph below compares the modeld results with the measured:
measurements documented in this diagram were performed
by the Munich Institut FIW. The results of measurement for
the whole building are represented as blue squares. The monthly
values during the first year after the modernization add up
to 26.9 kWh/(m²a), in the second year
it was 24 kWh/(m²a). Measured consumption is even smaller
than the modeled amount (PHPP
computation, as red columns represented). The renovation reduced
heating energy consumption in this building by a factor 8:
Remaining consumption is extremely small, it amounts to only
about 12% of the original value. Note the significant variation
between the values of individual dwellings: This is due to
different living habits of the inhabitants (e.g. different
thermostat settings, having windows open during the winter).
Despite this, it can be seen that even then, energy consumption
remains low, the largest individual consumption is approximately
40 kWh/(m²a), still more than 80% less the average consumption
in the building prior to renovation. You find a discussion
about opening windows here: "may
one open the windows in a Passive House?" (German)
the meantime additional examples of renovations using passive
house components were implemented. Among them also the following
example of a Passive House renovation of the GAG in Ludwigshafen
(PHIB: Passive house in the building stock).
Old Building in Ludwigshafen
A Passive House