A friend in the US has sent me details of passive housing, reproduced
below. Comments, anyone?

Published: December 26, 2008

DARMSTADT, Germany - From the outside, there is nothing unusual about
the stylish new gray and orange row houses in the Kranichstein District,
with wreaths on the doors and Christmas lights twinkling through a
freezing drizzle. But these houses are part of a revolution in building
design: There are no drafts, no cold tile floors, no snuggling under
blankets until the furnace kicks in. There is, in fact, no furnace.

The Energy Challenge

Articles in this series are examining the ways in which the world is,
and is not, moving toward a more energy efficient, environmentally
benign future.

In Berthold Kaufmann's home, there is, to be fair, one radiator for
emergency backup in the living room - but it is not in use. Even on the
coldest nights in central Germany, Mr. Kaufmann's new "passive house"
and others of this design get all the heat and hot water they need from
the amount of energy that would be needed to run a hair dryer.

"You don't think about temperature - the house just adjusts," said Mr.
Kaufmann, watching his 2-year-old daughter, dressed in a T-shirt, tuck
into her sausage in the spacious living room, whose glass doors open to
a patio. His new home uses about one-twentieth the heating energy of his
parents' home of roughly the same size, he said.

Architects in many countries, in attempts to meet new energy efficiency
standards like the Leadership in Energy and Environmental Design
standard in the United States, are designing homes with better
insulation and high-efficiency appliances, as well as tapping into
alternative sources of power, like solar panels and wind turbines.

The concept of the passive house, pioneered in this city of 140,000
outside Frankfurt, approaches the challenge from a different angle.
Using ultrathick insulation and complex doors and windows, the architect
engineers a home encased in an airtight shell, so that barely any heat
escapes and barely any cold seeps in. That means a passive house can be
warmed not only by the sun, but also by the heat from appliances and
even from occupants' bodies.

And in Germany, passive houses cost only about 5 to 7 percent more to
build than conventional houses.

Decades ago, attempts at creating sealed solar-heated homes failed,
because of stagnant air and mold. But new passive houses use an
ingenious central ventilation system. The warm air going out passes side
by side with clean, cold air coming in, exchanging heat with 90 percent
efficiency.

"The myth before was that to be warm you had to have heating. Our goal
is to create a warm house without energy demand," said Wolfgang Hasper,
an engineer at the Passivhaus Institut in Darmstadt. "This is not
about wearing thick pullovers, turning the thermostat down and putting
up with drafts. It's about being comfortable with less energy input, and
we do this by recycling heating."

There are now an estimated 15,000 passive houses around the world, the
vast majority built in the past few years in German-speaking countries
or Scandinavia.

The first passive home was built here in 1991 by Wolfgang Feist, a local
physicist, but diffusion of the idea was slowed by language. The courses
and literature were mostly in German, and even now the components are
mass-produced only in this part of the world.

The industry is thriving in Germany, however - for example, schools in
Frankfurt are built with the technique.

Moreover, its popularity is spreading. The European Commission is
promoting passive-house building, and the European Parliament has
proposed that new buildings meet passive-house standards by 2011.

The United States Army, long a presence in this part of Germany, is
considering passive-house barracks.

"Awareness is skyrocketing; it's hard for us to keep up with requests,"
Mr. Hasper said.

Nabih Tahan, a California architect who worked in Austria for 11 years,
is completing one of the first passive houses in the United States for
his family in Berkeley. He heads a group of 70 Bay Area architects and
engineers working to encourage wider acceptance of the standards. "This
is a recipe for energy that makes sense to people," Mr. Tahan said. "Why
not reuse this heat you get for free?"

Ironically, however, when California inspectors were examining the
Berkeley home to determine whether it met "green" building codes (it
did), he could not get credit for the heat exchanger, a device that is
still uncommon in the United States. "When you think about passive-house
standards, you start looking at buildings in a different way," he said.

Buildings that are certified hermetically sealed may sound suffocating.
(To meet the standard, a building must pass a "blow test" showing that
it loses minimal air under pressure.) In fact, passive houses have
plenty of windows - though far more face south than north - and all can
be opened.

Inside, a passive home does have a slightly different gestalt from
conventional houses, just as an electric car drives differently from its
gas-using cousin. There is a kind of spaceship-like uniformity of air
and temperature. The air from outside all goes through HEPA filters
before entering the rooms. The cement floor of the basement isn't cold.
The walls and the air are basically the same temperature.

Look closer and there are technical differences: When the windows are
swung open, you see their layers of glass and gas, as well as the
elaborate seals around the edges. A small, grated duct near the ceiling
in the living room brings in clean air. In the basement there is no
furnace, but instead what looks like a giant Styrofoam cooler,
containing the heat exchanger.

Passive houses need no human tinkering, but most architects put in a
switch with three settings, which can be turned down for vacations, or
up to circulate air for a party (though you can also just open the
windows). "We've found it's very important to people that they feel they
can influence the system," Mr. Hasper said.

The houses may be too radical for those who treasure an experience like
drinking hot chocolate in a cold kitchen. But not for others. "I grew up
in a great old house that was always 10 degrees too cold, so I knew I
wanted to make something different," said Georg W. Zielke, who built his
first passive house here, for his family, in 2003 and now designs no
other kinds of buildings.

In Germany the added construction costs of passive houses are modest
and, because of their growing popularity and an ever larger array of
attractive off-the-shelf components, are shrinking.

But the sophisticated windows and heat-exchange ventilation systems
needed to make passive houses work properly are not readily available in
the United States. So the construction of passive houses in the United
States, at least initially, is likely to entail a higher price
differential.

Moreover, the kinds of home construction popular in the United States
are more difficult to adapt to the standard: residential buildings tend
not to have built-in ventilation systems of any kind, and sliding
windows are hard to seal.

Dr. Feist's original passive house - a boxy white building with four
apartments - looks like the science project that it was intended to be.
But new passive houses come in many shapes and styles. The Passivhaus
Institut, which he founded a decade ago, continues to conduct research,
teaches architects, and tests homes to make sure they meet standards. It
now has affiliates in Britain and the United States.

Still, there are challenges to broader adoption even in Europe.

Because a successful passive house requires the interplay of the
building, the sun and the climate, architects need to be careful about
site selection. Passive-house heating might not work in a shady valley
in Switzerland, or on an urban street with no south-facing wall.
Researchers are looking into whether the concept will work in warmer
climates - where a heat exchanger could be used in reverse, to keep cool
air in and warm air out.

And those who want passive-house mansions may be disappointed. Compact
shapes are simpler to seal, while sprawling homes are difficult to
insulate and heat.

Most passive houses allow about 500 square feet per person, a
comfortable though not expansive living space. Mr. Hasper said people
who wanted thousands of square feet per person should look for another
design.

"Anyone who feels they need that much space to live," he said, "well,
that's a different discussion."

--
Graeme

On Tue, 6 Jan 2009 06:53:11 +0000 someone who may be Graeme
wrote this:-

A friend in the US has sent me details of passive housing, reproduced
below. Comments, anyone?

PassivHaus http://www.passivhaus.org.uk





--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

In message , David Hansen
writes
On Tue, 6 Jan 2009 06:53:11 +0000 someone who may be Graeme
wrote this:-

A friend in the US has sent me details of passive housing, reproduced
below. Comments, anyone?

PassivHaus http://www.passivhaus.org.uk

Thanks, yes, I have read the site, which is extremely interesting. I
wondered whether anyone had any experience, or comments? My main
concern is fresh air within the house, but I like open windows.
--
Graeme

On 6 Jan, 08:35, Graeme wrote:
In message , David Hansen
writes

On Tue, 6 Jan 2009 06:53:11 +0000 someone who may be Graeme
wrote this:-

A friend in the US has sent me details of passive housing, reproduced
below. *Comments, anyone?

PassivHaus http://www.passivhaus.org.uk

Thanks, yes, I have read the site, which is extremely interesting. *I
wondered whether anyone had any experience, or comments? *My main
concern is fresh air within the house, but I like open windows.
--
Graeme

If very low thermal mass, house could take ages to heat up after
opening a door etc.
Air locks may be required !

Lack of building space is a problem over here (planning regs etc).
A super-insulated house may take up more space since the walls may be
thicker.
Not compatible with squeezing tiny boxes into a space.
However, if I was building a new house on a good sized plot (self-
build etc), I would
certainly build it will very high levels of insulation.
Currently still doing up my old 9" solid brick walled house. Now
there's a comparison !
Simon.

Graeme wrote:
In message , David Hansen
writes
On Tue, 6 Jan 2009 06:53:11 +0000 someone who may be Graeme
wrote this:-

A friend in the US has sent me details of passive housing, reproduced
below. Comments, anyone?

PassivHaus http://www.passivhaus.org.uk

Thanks, yes, I have read the site, which is extremely interesting. I
wondered whether anyone had any experience, or comments? My main
concern is fresh air within the house, but I like open windows.

I think its a very intersting idea: my own calculations showed that with
low occupancy rates, ad a crap location, you would need either some
heating, or a massivley complex heat exchanger to get venitalion without
heat loss. Because ventilation is calcualted on a per room size, not per
person absis..so the regulations deny the possibility on a large room
with low occupancy.



Ventilation turns out to be the key: Modern insulation regulations now
have so little heat loss that the ventilation losses start to dominate.

I haven;t thought it through, but a heat exchanger/heat pump that
coooled outgoing air and pumped the heat into incoming, would provide
maybe a 4:1 factor on the cccupants body heat etc. So there is scope here.

An interesting puzzle for the mathematicians.

Compare the energy used by an incandescent lightbulb, with the energy
loss through a window capable of providing the same input of light ;-)

Over a typical 24hour period..in midwinter..

On Tue, 06 Jan 2009 11:26:55 +0000 The Natural Philosopher wrote :
Ventilation turns out to be the key: Modern insulation regulations
now have so little heat loss that the ventilation losses start to
dominate.

Very much so, which is why pressure testing of new dwellings was
made compulsory in E&W in 2006

I haven;t thought it through, but a heat exchanger/heat pump that
coooled outgoing air and pumped the heat into incoming, would
provide maybe a 4:1 factor on the cccupants body heat etc. So
there is scope here.

An interesting puzzle for the mathematicians.

Been done, and in the latest version of SAP, which underpins
Building Regs for new homes. What you're describing is mechanical
ventilation with heat recovery (MVHR) which can recover up to 90% of
the heat from air being extracted from the dwelling, this heat
pre-heating cold air coming in. The system is set up to provide a
controlled 0.5ach ventilation rate, air being fed into living areas
and extracted from kitchens and bathrooms.

For this to work, you do need to be able to build to a much greater
degree of airtightness than has been normal in the UK, otherwise you
are running a fan and the air leaks out rather than being extracted
via the heat exchanger.

--
Tony Bryer, 'Software to build on' from Greentram
www.superbeam.co.uk www.superbeam.com www.greentram.com

Graeme wrote:

But new passive houses use an ingenious central ventilation system. The
warm air going out passes side by side with clean, cold air coming in,
exchanging heat with 90 percent efficiency.

I've never understood this, I must admit.

If the air going out is at 20 degrees, and the air coming at 20, I can
understand that we might be able to make them both 10 degrees (which I
presume would be 50% efficiency) but not that we could do any better
than that.

Daniele

On Jan 6, 1:13 pm, (D.M.
Procida) wrote:
Graeme wrote:
But new passive houses use an ingenious central ventilation system. The
warm air going out passes side by side with clean, cold air coming in,
exchanging heat with 90 percent efficiency.

I've never understood this, I must admit.

If the air going out is at 20 degrees, and the air coming at 20, I can
understand that we might be able to make them both 10 degrees (which I
presume would be 50% efficiency) but not that we could do any better
than that.

Daniele

The air inside is at 20, but the air outside is at (eg) 0, not 20.

If you just blow a fan, the air coming in is at 0, and the air going
out is at 20.

If you blow a fan through a heat exchanger, the air that eventually
gets in to the house has heated up to 18, and the air that finally
leaves the ventilator has cooled down to 2 (assuming 90% efficiency).

Martin Bonner wrote:

If the air going out is at 20 degrees, and the air coming at 20, I can
understand that we might be able to make them both 10 degrees (which I
presume would be 50% efficiency) but not that we could do any better
than that.

The air inside is at 20, but the air outside is at (eg) 0, not 20.

Sorry - I meant the air coming in is at 0 degrees.

If you just blow a fan, the air coming in is at 0, and the air going
out is at 20.

If you blow a fan through a heat exchanger, the air that eventually
gets in to the house has heated up to 18, and the air that finally
leaves the ventilator has cooled down to 2 (assuming 90% efficiency).

OK, but I don't understand how this is possible (without the help of
Maxwell's Demon).

If 1kg of hot air meets 1kg of cold air, I can't imagine a mechanism
that would do better than make them both warm.

That is, I can understand how air at 20 degrees could be used to make
air at 0 degrees 10 degrees warmer, but not how air at say 4 degrees
could be used to make air at 16 degrees 2 degrees warmer.

How do we make the heat jump salmon-like up the gradient?

Daniele

D.M. Procida wrote:
Martin Bonner wrote:

If the air going out is at 20 degrees, and the air coming at 20, I can
understand that we might be able to make them both 10 degrees (which I
presume would be 50% efficiency) but not that we could do any better
than that.

The air inside is at 20, but the air outside is at (eg) 0, not 20.

Sorry - I meant the air coming in is at 0 degrees.

If you just blow a fan, the air coming in is at 0, and the air going
out is at 20.

If you blow a fan through a heat exchanger, the air that eventually
gets in to the house has heated up to 18, and the air that finally
leaves the ventilator has cooled down to 2 (assuming 90% efficiency).

OK, but I don't understand how this is possible (without the help of
Maxwell's Demon).

If 1kg of hot air meets 1kg of cold air, I can't imagine a mechanism
that would do better than make them both warm.

That is, I can understand how air at 20 degrees could be used to make
air at 0 degrees 10 degrees warmer, but not how air at say 4 degrees
could be used to make air at 16 degrees 2 degrees warmer.

How do we make the heat jump salmon-like up the gradient?

Daniele

cross-flow heat exchanger


NT

(D.M. Procida) wrote:

If 1kg of hot air meets 1kg of cold air, I can't imagine a mechanism
that would do better than make them both warm.


Surely there is one: a heat pump. But a mere "heat exchanger" would not
do any more than you say.

I suspect something has been lost in translation.

D.M. Procida wrote:

That is, I can understand how air at 20 degrees could be used to make
air at 0 degrees 10 degrees warmer, but not how air at say 4 degrees
could be used to make air at 16 degrees 2 degrees warmer.

How do we make the heat jump salmon-like up the gradient?

OK - I think I have worked out hwo it could be done.

Two rows of air represented below, the row of air coming in on top and
the row of air leaving below it. The numbers represent the remperature
of a block of air.

Inside it's 4 degrees outside it's 0.

In --- 0 0 0 0
Out 4 4 4 4 ---

As the rows move past each other, heat jumps from the hot row to the
cold one. As the cold row moves leftwards, it becomes progressively
warmer, since more heat has jumped onto it, and the opposite is true of
the hot row.

So there's always a gradient from the hot air to the colder air, and the
trick is to make sure that as the cold air warms up it's brought towards
air that's warmer still, and eventually we end up with a steady state
like:

In --- 3 2 1 0
Out 4 3 2 1 ---

where the air that is allowed to leave has already given up most of its
heat to the fresh air coming in.

You don't need Maxwell's demon, or heat with salmon-like properties.

How cunning.

Daniele

On Tue, 6 Jan 2009 14:07:44 +0000 someone who may be
(D.M. Procida) wrote
this:-

That is, I can understand how air at 20 degrees could be used to make
air at 0 degrees 10 degrees warmer, but not how air at say 4 degrees
could be used to make air at 16 degrees 2 degrees warmer.

Is the latter a situation which is going to arise? If the air inside
is at 4 C then something has gone badly wrong with the design. I
have been inside buildings which are heated by the sun and
occupants/equipment rather than a heating system, they don't get so
cold that the internal air is at 4 C.



--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

On Jan 6, 2:35 pm, (D.M.
Procida) wrote:
D.M. Procida wrote:
That is, I can understand how air at 20 degrees could be used to make
air at 0 degrees 10 degrees warmer, but not how air at say 4 degrees
could be used to make air at 16 degrees 2 degrees warmer.

How do we make the heat jump salmon-like up the gradient?

OK - I think I have worked out hwo it could be done.

Two rows of air represented below, the row of air coming in on top and
the row of air leaving below it. The numbers represent the remperature
of a block of air.

Inside it's 4 degrees outside it's 0.

In --- 0 0 0 0
Out 4 4 4 4 ---

As the rows move past each other, heat jumps from the hot row to the
cold one. As the cold row moves leftwards, it becomes progressively
warmer, since more heat has jumped onto it, and the opposite is true of
the hot row.

So there's always a gradient from the hot air to the colder air, and the
trick is to make sure that as the cold air warms up it's brought towards
air that's warmer still, and eventually we end up with a steady state
like:

In --- 3 2 1 0
Out 4 3 2 1 ---

where the air that is allowed to leave has already given up most of its
heat to the fresh air coming in.

You don't need Maxwell's demon, or heat with salmon-like properties.

How cunning.

Congratulations! You have just invented (again) the counter current
heat exchanger. http://en.wikipedia.org/wiki/Countercurrent_exchange.
As you say, it's extremely cunning.

Martin Bonner wrote:

In --- 3 2 1 0
Out 4 3 2 1 ---

You don't need Maxwell's demon, or heat with salmon-like properties.

How cunning.

Congratulations! You have just invented (again) the counter current
heat exchanger. http://en.wikipedia.org/wiki/Countercurrent_exchange.
As you say, it's extremely cunning.

Truly ingenious. And countercurrent exchangers exist in nature too - I
have one in my kidneys! How cool is that? It's never cease to be amazed
at what nature manages to come up with.

Daniele

D.M. Procida wrote:

So there's always a gradient from the hot air to the colder air, and the
trick is to make sure that as the cold air warms up it's brought towards
air that's warmer still, and eventually we end up with a steady state
like:

In --- 3 2 1 0
Out 4 3 2 1 ---

where the air that is allowed to leave has already given up most of its
heat to the fresh air coming in.

Um, yeah, that's a heat-exchanger. Pretty much any heat-exchanger (at
least, I don't know why you'd want to build one any other way).

Pete

D.M. Procida wrote:
Martin Bonner wrote:

If the air going out is at 20 degrees, and the air coming at 20, I can
understand that we might be able to make them both 10 degrees (which I
presume would be 50% efficiency) but not that we could do any better
than that.

The air inside is at 20, but the air outside is at (eg) 0, not 20.

Sorry - I meant the air coming in is at 0 degrees.

If you just blow a fan, the air coming in is at 0, and the air going
out is at 20.

If you blow a fan through a heat exchanger, the air that eventually
gets in to the house has heated up to 18, and the air that finally
leaves the ventilator has cooled down to 2 (assuming 90% efficiency).

OK, but I don't understand how this is possible (without the help of
Maxwell's Demon).

If 1kg of hot air meets 1kg of cold air, I can't imagine a mechanism
that would do better than make them both warm.

That is, I can understand how air at 20 degrees could be used to make
air at 0 degrees 10 degrees warmer, but not how air at say 4 degrees
could be used to make air at 16 degrees 2 degrees warmer.

How do we make the heat jump salmon-like up the gradient?

Daniele

Consider an infinitely long coaxial pipe perfectly insulated. The air
comes in down the inside, and goes out up the outside.

The air never mixes.

"Graeme" wrote in message
...
In message , David Hansen
writes
On Tue, 6 Jan 2009 06:53:11 +0000 someone who may be Graeme
wrote this:-

A friend in the US has sent me details of passive housing, reproduced
below. Comments, anyone?

PassivHaus http://www.passivhaus.org.uk

Thanks, yes, I have read the site, which is extremely interesting. I
wondered whether anyone had any experience, or comments? My main concern
is fresh air within the house, but I like open windows.
--
Graeme

This is not new. The house primarily needs to be "superinsulated", even the
front door, and air-tight with a heat reclaim vent system. The dreaded warm
air in the UK. No other country dreads them. The clever ones, like
commercial systems, modulate the incoming air from minimum 10% to 100%,
using re-circ air to maintain heat in the house.

But they do need heat input, but this is negligible and they try to use
incidental heat from TV's, fridges, etc to maximum effect - more efficient
appliances means this will get less as time goes on. Heat input can be a
heater battery in the living room air supply and/or one in the hallway.
Both locally controlled.

Passive oriented to the sun with correctly sized windows and shading to the
angle of the sun helps a lot, the biggest contributor to heat in such a
house, as does insulated shutters. Many people just forget to use the
shutters at night which are also a security feature.

"sm_jamieson" wrote in message
...

If very low thermal mass, house could take
ages to heat up after opening a door etc.
Air locks may be required !

If using forced air that is not a problem.

Lack of building space is a problem over
here (planning regs etc).

The biggest problem. You can buy a kit home from Scandinavia for £25,000 and
1/2 acre of land for £5-6,000, but they will not allow you to build it.

A super-insulated house may take up more space
since the walls may be thicker.

No thicker than the two walls we build now.

Not compatible with squeezing tiny
boxes into a space.

Flats are highly efficient as there is little heat loss if the outside walls
are insulated.

"The Natural Philosopher" wrote in message
...

Ventilation turns out to be the key: Modern insulation regulations now
have so little heat loss that the ventilation losses start to dominate.

You confuse ventilation losses and air leaks.

On Jan 6, 8:57 pm, Pete Verdon
d wrote:
D.M. Procida wrote:
So there's always a gradient from the hot air to the colder air, and the
trick is to make sure that as the cold air warms up it's brought towards
air that's warmer still, and eventually we end up with a steady state
like:

In --- 3 2 1 0
Out 4 3 2 1 ---

where the air that is allowed to leave has already given up most of its
heat to the fresh air coming in.

Um, yeah, that's a heat-exchanger. Pretty much any heat-exchanger (at
least, I don't know why you'd want to build one any other way).

I can't provide a counter example for /heat/ exchangers, but your
lungs are a non-counter current gas exchanger. (Birds on the other
hand use a more efficient and more complex counter current system.)

In article , Martin Bonner wrote:
On Jan 6, 8:57 pm, Pete Verdon
id wrote:
D.M. Procida wrote:
So there's always a gradient from the hot air to the colder air, and the
trick is to make sure that as the cold air warms up it's brought towards
air that's warmer still, and eventually we end up with a steady state
like:

In --- 3 2 1 0
Out 4 3 2 1 ---

where the air that is allowed to leave has already given up most of its
heat to the fresh air coming in.

Um, yeah, that's a heat-exchanger. Pretty much any heat-exchanger (at
least, I don't know why you'd want to build one any other way).

I can't provide a counter example for /heat/ exchangers

I can: http://www.villavent.co.uk/pdf/info-pages-units.pdf
(And the "why" is "because the crossflow is cheaper than counterflow".)

"D.M. Procida" wrote in
message
...
Martin Bonner wrote:

In --- 3 2 1 0
Out 4 3 2 1 ---

You don't need Maxwell's demon, or heat with salmon-like properties.

How cunning.

Congratulations! You have just invented (again) the counter current
heat exchanger. http://en.wikipedia.org/wiki/Countercurrent_exchange.
As you say, it's extremely cunning.

Truly ingenious.

The most common is the plate heat exchanger inside combis. Plate heat
exchangers on some combis are designed not to be so efficient as to drop the
return water so much the boiler cannot raise the temperature on the primary
flow side enough. This also may affect the delta T of the main heat
exchanger and have adverse effects, such as cracking. Long thin high kW
plate heat exchangers extract an amazing amount of heat from incoming water
and are used on heat banks.