Your Answered Questions about Passive House
Prof. Wolfgang Feist Dispels Myths about Passive Housing
1. You can’t open the windows
in a passive house (PH).
On the recommendation of the PHI
(Passive House Institute) every passive house has windows
which can be opened.
The technical ventilation system brings fresh air in, so you
won’t ever find
any stale air in the house, even if you don’t open the
windows for an extended
period e.g. during cold rainy weather. (That there is a lack
of sufficient
ventilation in a lot of buildings, even new ones, is the
reason why we
recommend ventilation systems.
Yes,
You can open windows!
2. Due to mechanical
ventilation there is a draught.
The ventilation of the living
space "ventilates" just as much as is necessary for first-class
indoor air quality, and this is just fresh air (normally no
return air – this
is quite different from the mechanical systems used for air
conditioning e.g.
in the US; much, much lower air flows). It’s best to build
air exhausts at
ceiling height, and therefore from as little a distance as 30
cm away from the
valves the air flow will no longer be noticeable; you will
not feelany draughts
in passive houses. (Of course, it has to be airtight, too –
and the insulation
has to be good enough in order to avoid free convection due
to too high temperature
differences. Both is taken care of in Passive houses – both
is in the very
definition of the standard.)
3. A Passive House has no
heating.
As a rule a passive house needs
only a small heating installation, one, which is not longer
important and no longer
expensive at all. But it isn’t a ‘zero heating energy house’.
The remaining
energy requirement for heating is so small, however, that it
does not hurt –
not the wallet and not the environment, it’s less than 10%
what existing
buildings use in average. Yes, a passive house (as a rule)
has heating.
4. A PH is always rather
"clumsy".
Where does such a statement come
from? There are thousands of passive houses in different
shapes and sizes: from
partial hip roof houses, to those like truncated cylinders
and cones, to those
in Wankel-piston form. Architectural design is free (well, we
do not have
anti-gravity, ever) There is a wide variety available.( Just have a look on the winners of the Passive House
Architectural Price).
5. The technology is still in
development.
A passive house doesn’t require
as much technology as a conventional house! The only special
technology which
is needed is mechanical ventilation with heat recovery, and
this has been
successfully used in Canada and Scandinavia for more than 50
years. The core of
the passive house technology is just very good insulation –
tried and tested
for a longtime. The roots trace back several centuries – always with very
good experience. So why wasn’t it used even more frequently?
One answer is just:
Cheap oil (at least it was perceived cheap, because we
avoided looking at the
consequences). And, yes, there is ongoing development, it’s going to be
even easier, even better and even cheaper in the future –
like we have seen in
the development of mobile phones in the decades passed –
although phones are
cheaper and better now, these have been tried and tested for
more than a
decade.
6. You can only build a PH on
a sunny site.
Well, this opinion might be the
result of a mix-up with the "passive solar" approach. You
will find
passive houses on inner-city premises with the house facing
north. A shaded
site is no excuse not to build a passive house. Yes, a sunny
site is an
advantage. Yes, having windows to the south is very nice. But
crucial is only
the energy balance. What we use to calculate this balance, is
PHPP.
And: The designers soon realised, there are a lot of options.
One should only try.
7. A PH is much more expensive than a conventional house – it
doesn’t
pay off.
Our last
inquiry showed 4 to 8% more investment was required initially
– and well
experienced architects even have built Passive Houses with no
higher
construction costs to ordinary contemporary buildings (https://j.mp/reallyCost).
You also have to factor in higher financial aid due to the
positive
environmental nature of the house. The most impressive result
comes
later: residents will save between 800 and 1500 Euros in
running costs every
year. If you calculate this over the lifecycle of the house,
you will see that
you really can’t afford a less efficient house.A special
topic within this is
the added investment of “thick insulation” – yes, passive
houses as a rule in
cold climates need quite thick insulation. Now: Insulation
turns out to be one
of the cheapest tools to save energy, these are very small
investments. And the
“first cm” pay back extraordinarily well – but even the last
ones of a passive
house insulation do, because these are still near enough to
the very flat
optimum and these help to save additional investment costs in
the heat
distribution system and all systems connected.
8. A PH is always cold.
There is only one thing I
recommend to do: go and visit a passive house. Inhabitants of
passive houses
like the warmth; we have measured temperatures between 22 and
24° C in winter.
This is affordable, as heating a passive house doesn’t cost a
lot; in fact,
just some 100 to 200 each year – this is, what others often
pay each month.
Even if energy prices will skyrocket – paying your heating
bill will still be
affordable in a passive house.
9. Separate rooms can’t have
different temperatures in a PH.
That is up to the inhabitants:
most users don’t really need cold side rooms, it costs little
to keep them warm
– so what’s the problem? If you need, there are many
solutions depending on
what your requirement is (to open a window from time to time
is an easy one, of
course not the most efficient, but still possible and
allowed). A cool sleeping
room, a cool wine cellar can both be built into a passive
house, if required.
Almost anything is possible.
10. You can’t redevelop an
old house into a PH.
This is generally true, but it’s
only half the story: you can build passive house technology
into an old
building – it takes good exterior insulation, triple glazing
and ventilation
with heat recovery. You won’t in most cases reach the energy
standard of a
passive house (with its 15 kWh/(m2a)), but you will get
between 20 and 35
kWh/(m²a). Be clear about this though: real passive house
redevelopments are
possible, even for bigger properties. Now there is a
certification offered for
refurbishment using the Passive House concept: https://j.mp/EnerPHit.
Source: https://www.scribd.com
