Looking on the internet,
one will find many different oppinions. Some state that Passive
Houses would never pay-off, while others promise that you can
make over "200,000 Euro" profit with a single family Passive
In short, both statements
are wrong. Under the present economic conditions in Germany
and Austria Passive Houses pay-off, if they are competently
planned and built. Getting rich overnight should not be expected;
but investment in the Passive House is more secure than the
alternatives. Those wanting "fast money" should try elsewhere
(... of course the chances to lose much money are then naturally
greater as well).
An example analysis of a single family house
The house in the
left column performs much better than a typical new German single
family house with 149 m² floor space. It is not a Passive House
- it could easily be built as a passive house though. In order
to do this, the following details would have to be improved:
- The external
wall insulation is to be increased to 300 mm; the brick-work
is reduced to 115 mm lime sandstone; thus the external wall
is only slightly thicker (around 25 mm) than it was before
(see Abb. 2).
- In the roof
the insulation under the rafters is increased from 100 to
225 mm; there is still 140 mm between the rafters with thermal
conductivity of 0.035 W/(mK).
- On the slab
on ground instead of tatol150 mm now 250 mm of EPS insulation
boards with heat conductivity 0.035 W/(mK) are used.
The measures were
taken to be suitable within typical Central European climate.
In Northern and Eastern Europe the insulation should be even
better; in Western Europe less insulation will be needed. In
a hot climate the measures are somewhat different, there will
be further information about Passive Houses in hot climates
published at this website later.
To a large extent
thermal bridge-free details already existed in the
house. Apart from increasing the insulation levels and installing
the windows outside before the brick-work no changes are necessary.
In place of the timber beam structure used as the second floor
in the original building, the Passive House uses a concrete
floor which has a substantially smaller structure height, and
is more economical. Using this floor system, it is possible
to gain usable height on the interior while maintaining the
same exterior dimensions of the house, despite the somewhat
thicker roof. Also the floor space can be increased somewhat
(approx.. 1 m²); however, this increased floor area is not included
in the computation in order to not complicate the comparison
by a change of the reference areas.2)
Also we do not consider the cost saving due to the simpler floor
All external walls
have plaster on the inside, the roof systems keep air tightness
foils, which are covered with the interior plaster at all joints
to the exterior walls. Previous experiences show that an airtightness
of n 50 =0.4h
-1 is attainable. There are
no extra costs associated with this. In fact it reduces costs
because the higher airtightness protects against building damage
- the repair of which is multiples more expensive than the one
time investment into a high-quality airtight shell. In addition
the improved health for the occupants of the dwelling is not
taken into account.
- The windows implemented
in place of the original Double pane windows are 3-pane-double-low-e
(with insulated edges) in a Passive House suitable frames
Thus the window U-value is on average 0.75 W/(m²K) including
the thermal bridge of the installation. The average g-value
of the glazings is 0.54.
Passive Houses uses a ventilation
system with a heat recovery of 92%. The air distribution
layout is seen in Fig. 3 and 4.
detail improvements described above it is possible to meet the
Passive House level of energy consumption. On solution will
be, that the existing heating system (boiler in a store room)
could be maintained. However it would go even more economical
to replace it and the ventilator with a compact unit (already
drawn in in the h-w-area). This would eliminate the oil tank,
the fire-place and the boiler. The heat distribution piping
and radiators can be eliminated - the compact unit can supply
the heat directly to the supply air; only in the bathroom on
the second floor there must be an extra heating element, this
in order to be able to quickly increase the temperature in the
bathroom when desired.
What does it cost?
The improved building
components require the installation of additional insulation,
better windows (triple pane with two low-e coatings), insulated
window installation and a heat recovery ventilator and its associated
- Additional thermal
insulation in wall, roof and slab on ground:
- Passive House
windows: 5,400 €
- Ventilation with heat recovery:
- Savings from smaller oil tank, boiler;
elimination of radiators: -1,400 €
(we do not count the additional usable area)
- Sum of additional
capital outlay: 14.000 €
In order to remain on the safe side, we will round this up to 15,000 €. In any case, a Passive House single family home can be created for this amount which is about an 8% increase in construction costs compared to the German average.
We asume that the
house is financed by a mortgage. In this case, the interest
rate in Germany is 4.7% and with a repayment of capital of 1.6%,
that sums up to an annuity of 945 €.
If a Passive House
is built, the owner can qualify for the German Federal States
Bank "Building Ecologically" credit for the "Passivhaus".
This loan has a 100% disbursement and only 2.10% interest (as
of the end of April 2006). Each unit qualifies for 50,000 €,
in this case a single family house. Savings from the reduced
interest rate amounts to approximately 880 € annually!
Thus the additional expenses to make this house a Passive House
are nearly offset by the savings in interest. How it looks in
later years is treated further down.
It gets even better:
Instead of using approximately 13,300 kWh fuel oil or natural
gas, the Passive House needs only approx.. 2290 kWh fuel for
heating and 350 kWh electicity for the ventilation system. This
saves 715 € per year using today's fuel costs, the electricity
for the ventilation system adds approximately 65 € per
year in electricity costs.
Passive House Cost Balance (149 m²)
- initial comparison -
Additional investment *) of 15,000 €compared with a standard
Additional mortgage annuity (bank)
|Reduced interest (1. Year)
|Heating energy savings of 11,000 kWh/a:
|Heating energy cost saving with 65 Ct/Liter h-oil
electricity cost for ventilation with 18 Ct/kWh (German
Initial savings of (each year)
*) Example. According to
experience the investment can be smaller.
Does cost alone make it worthwhile?
building a Passive House, expenses are reduced considerably
compared to a "normal house", even if energy costs do not increase
in the future. Therefore the Passive House is economically attractive
- even if the net yield is not enormously high, as is sometimes
promised. But the owner of a Passive House benefits from a few
Joy of life!
With the Passive
House, energy consumption is so small that the family will no
longer be concerned with energy price increases. The house is
practically independent of imported energy. It can even be completely
independent through the use of renewable energy. For example:
if a heat pump compact mechanical system and an Renewable Electricity
Supplier are selected (or by purchasing a share of a wind-generat
or wood pellet heating is used or...).
But there is more:
In a Passive House there are no moldy walls, no drafts, no cold
feet. Fresh air is delivered continuously, minimizing indoor
As Robert Hastings stated at the 8. Passive House
Conference: "Passive Houses minimize environmental impacts and maximize the joy of life".
Because the consequences of climate change affect everyone, the family can enjoy the decreased environmental impact of the home. The emissions from a Passive House which contribute to global warming are reduced by a factor of 4 compared to "normal" new buildings. These contributions to environmental
protection are multipled with each family that decides to build an energy-efficient new building or rennovate an existing building.
So far these are
individual advantages - however doesn't the community benefit
if new jobs are created in the region and import of energy sources
from unstable parts of the world is reduced? Consider the passive
house depicted above, which costs approximately 14,000 euro
more than a usual new building. Of this 14,000 euro, 75% will
go to local builders. The remaining 25% goes to purchase materials
predominantly of regional origin. That creates jobs - it even
"pays off". The community saved the costs of international tensions
which need not be discussed here, they can be seen in the newspaper
on any given day. This also contributes to the joy of life,
because "securing energy resources" does not only cost money.
the Longer Term, only Energy Efficiency Saves Money
Above all, it is
the energy conservation which reduces costs in the longer run.
Without it, when the promotional interest credits expire, one
could experience high expenses. It is recommended to use the
incentives for proven energy-efficiency measures, e.g. what
has been specified above, thermal insulation, windows and the
ventilation system. The fact: That these measures save energy
in practice has been proven by measurements (see Passive
house practice results).
The following table shows the annual average result of the predicted
ownership costs over a 30 year period seen in Fig
7. There is another benefit seen in Fig. 7: After 30
years you continue to profit from reduced energy costs because
the components of the Passive House continue to work as long
as the house exists.
Table showing annual predicted ownership costs over 30 years:
Passive house cost balance
- Predicted ownership costs over 30 years nominally -
| Additional investment
*) compared with a standard house 15,000 €
cost (annuity to
due to reduced interest rates
by KfW. "ESH40/Passivhaus")
|Annual heating energy saving of 11000 kWh/a:
|Average heating energy cost savings over 30 years (nominal price increase 1,6 % per year):
|Additional cost of electricity for ventilation
Annual cost savings of
*) Example. According to experience the investment
can be also smaller.
Incentive frorm KfW credit ESH40/Passivhaus conditions
at the end of of April 2006.
Interest (nominal) 2.1 %p.a. 100% disbursement, 30 year running
time, here: none years without repayment. Calculatory service
life: 30 years, calculation interest 4.7 % per annum (mortgage
loans, nominally, effectively)
Fuel price: 6,5 €Ct/kWh(real), electricity 18 €Ct/kWh, energy
price increase equal inflation rate of 1,6% per annum (nominally).
Method: The vcapital values of all financial stream are nominally
determined and converted into constant values over 30 years
(annuity). The used components have a life cycle period, which
can be expected, far over 30 years (up to wearing parts which
can be changed simply, from which there are no more in the Passive
House than with conventional buildings). Maintenance costs are
almost unchanged, if changed, lower than "nortmal".
to evtl. Changes with the boundary conditions:
This side was updated at the end of of April 2006.
Prices for energy, interest rates and the conditions for
incentives are subject to change over time. Such changes, however, have only a small influence on the core statement ("yellow table") Why?
- Economic effectiveness of a building is not determined by
current market condintions, but instead by the conditions which
will occur over the lifetime of the building (which is more
than 30 years).
- In this period "much can happen". But the interest rate on
the mortgage can be held at a comparatively low level over the
next 20 to 30 years. Does anyone believe that energy will be
cheaper in the next few decades than it is now? Thus the most
important parameters are relatively stable even if current fluctuations
occasionally give another impression.
- The incentives from KfW are intended to offset the current
market difference between the costs of Passive Houses and "normal
houses" so this incentive can be expected to remain in the future
as long as it is needed.
- The (nominal) market interest rate is strongly influenced
by the inflation rate. This results in the stable core statement
of the "yellow table" remaining approximately constant, even
if the values change nominally. All values cannot be predicted
to "within a few euro exactly". However, the risk is highest
for owners who build houses with high energy consumption.
link leads to basic information about Passive Houses.
Dr. Wolfgang Feist,
director of the PHI
Link to the homepage of the
Passive House Institute:
(last changed: 6.05.2007 / author Dr. Wolfgang Feist;
to David Stecher for proof reading of the 1st edition
Passive House Institute;
unchanged copy is permitted, please give reference to this page)