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 (http://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: http://j.mp/EnerPHit.
Source: http://www.scribd.com
