Posted by nicksanspam on February 5, 2004, 2:40 pm
...150m x 2m, or a 22 foot cube :-)
Nice simple rules...
A large enough multifamily building might be even simpler, with no solar
collection, just internal heat gains spread around with a hydronic floor
loop. Googling on Russian apartment heating, I found out Moscow walls are
typically 14" of concrete, about R3, with no other insulation, and 10% of
the floorspace is poorly-caulked double pane windows which residents seal
up with newspapers etc in October and unseal in the spring. Energy has
long been underpriced and district heating is poorly managed, with little
incentive to conserve. How big would a building with R20 walls and no air
leakage or windows have to be to stay 70 F indoors on a 30 F day, if each
family used 600 kWh/month and occupied 2,000 ft^2 of floorspace?
Googling on Swedish air leakage, I found a 1999 UK report that mentioned the
world's tightest voluntary standard, Canada's IDEAS (post R2000) 0.15 m^3/h
per m^2 of envelope, tested at 50 Pa, which translates into a natural air
leakage of about 2.5 cfm, or 0.008 ACH for a 2400 ft^2 1-story house :-)
Posted by Niels Lyck on February 5, 2004, 7:57 pm
Thats what the Germans call a "passive house" - a house ("almost entirely")
heated by the heat loss of the people and acticvities within.
Weatherstripping doesn't do the job, though, as you need a certain (=rather
high) ventilation ratio to keep sound and healthy in there. Ie. there has to
be some kind of advanced heat-recovering mechanical ventilation system in
addition to the very tight building "envelope". Besides, in my opinion, in a
very energy efficient building, you shouldn't accept an electricity
consumption of 600 kWh/flat/month...
I wouldn't WANT to do without the solar stuff, though...
Posted by nicksanspam on February 7, 2004, 2:24 pm
Interesting. Have any been built? How can we find out more?
ASHRAE says 15 cfm/occupant, which might be simple fresh air with no heat
If each family has 4 people in residence 50% of the time, that's 30 cfm. With no
heat recovery, that adds about 30 Btu/h-F of thermal conductance per family.
An L foot cube with R20 walls has a thermal conductance of 6L^2/20 = 0.3L^2, and
it can house N = L^3/(2048x8) families, and 600K kWh/mo is 68.2K Btu/day, so we
68.2KN = 24h(70F-30F)(0.3L^2+30N), which makes L = 120', ie a 15 story building.
That could work, with an air-air heat exchanger.
You may be addicted to this technology :-)
Posted by Niels Lyck on February 7, 2004, 6:18 pm
www.passivhaus.de - shows some examples under "Referenzen - Übersicht". In
German, I'm afraid.
I am not familiar with the terms, but read that, with a very well insulated
house/passive house, heating fresh air would make up a considerable part of
the remaining heating energy need.
so we need
Just joking... but also the "passive houses" use solar thermal, mostly for
Posted by Niels Lyck on February 12, 2004, 11:07 pm
Concerning passive houses:
It turns out the term was invented by swedish Bo Adamson from Lund in 1987
and further developed by the german Wolfgang Feist. The standard prescribes
a heating demand of around 15 kWh/m2/year (including hot water...) and an
electricity demand of around 30 kWh/m2/yr.
Example houses have been built in Sweden, Germany, Austria etc. under the EU
project CEPHEUS. Theres a more thorough description of the Passive haous
standard etc here: