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<DIV><STRONG><FONT size=2 face="Courier New">RT <</FONT></STRONG><A
href="mailto:ArchiLogic@yahoo.ca"><STRONG><FONT size=2
face="Courier New">ArchiLogic@yahoo.ca</FONT></STRONG></A><STRONG><FONT size=2
face="Courier New">> writes:</FONT></STRONG></DIV><STRONG><FONT size=2
face="Courier New"></FONT></STRONG><STRONG><FONT size=2
face="Courier New"></FONT></STRONG><STRONG><FONT size=2
face="Courier New"></FONT></STRONG><STRONG><FONT size=2
face="Courier New"></FONT></STRONG><STRONG><FONT size=2
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face="Courier New"></FONT></STRONG><STRONG><FONT size=2
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<DIV><BR><STRONG><FONT size=2 face="Courier New">> Once a house is well
insulated/air-sealed and its massing, orientation and <BR>> landscaping
have been reasonably well considered, the building heat load <BR>> will
be so minimal that occupancy gains and solar gains should provide <BR>>
most of it (speaking "typical"-sized houses, say 1600 - 2800 sf) in Cold
<BR>> Climate Regions, say, > 7500 HDD/yr)</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New"></FONT></STRONG> </DIV>
<DIV><STRONG><FONT size=2 face="Courier New">Bullshit.</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New"></FONT></STRONG> </DIV>
<DIV><STRONG><FONT size=2 face="Courier New">Then again, Sustainable
Building Industry Council ma</FONT></STRONG><STRONG><FONT size=2
face="Courier New">sonry </FONT></STRONG><STRONG><FONT size=2
face="Courier New">salesmen </FONT></STRONG><STRONG><FONT size=2
face="Courier New">say</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New">reasonably well considered
lukewarm sunspaces </FONT></STRONG><STRONG><FONT size=2
face="Courier New">with </FONT></STRONG><STRONG><FONT size=2
face="Courier New">LOTS of </FONT></STRONG><STRONG><FONT size=2
face="Courier New">thermal mass</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New">(</FONT></STRONG><STRONG><FONT
size=2 face="Courier New">bricks, </FONT></STRONG><STRONG><FONT size=2
face="Courier New">according to SBIC</FONT></STRONG><STRONG><FONT size=2
face="Courier New"> Brick Institute </FONT></STRONG><STRONG><FONT size=2
face="Courier New">of America </FONT></STRONG><STRONG><FONT size=2
face="Courier New">members :-) can </FONT></STRONG><STRONG><FONT size=2
face="Courier New">give</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New">a max
60% </FONT></STRONG><STRONG><FONT size=2 face="Courier New">solar heating
</FONT></STRONG><STRONG><FONT size=2 face="Courier New">fraction, even here
</FONT></STRONG><STRONG><FONT size=2 face="Courier New">in PA,
</FONT></STRONG><STRONG><FONT size=2 face="Courier New">with a mere 4954
FHDD.</FONT></STRONG> </DIV>
<DIV><STRONG><FONT size=2 face="Courier New"></FONT></STRONG> </DIV>
<DIV><STRONG><FONT size=2 face="Courier New">Then again, "most" can leave a lot.
If a department store sells </FONT></STRONG><STRONG><FONT size=2
face="Courier New">a $1000 </FONT></STRONG><STRONG><FONT size=2
face="Courier New">shirt</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New">with a 60% discount, it's
still </FONT></STRONG><STRONG><FONT size=2 face="Courier New">a $400
shirt. Direct </FONT></STRONG><STRONG><FONT size=2 face="Courier New">gain
</FONT></STRONG><STRONG><FONT size=2
face="Courier New">houses </FONT></STRONG><STRONG><FONT size=2
face="Courier New">with minimal</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New">fuel bills in cold climates cost a
lot, because windows </FONT></STRONG><STRONG><FONT size=2
face="Courier New">on living </FONT></STRONG><STRONG><FONT size=2
face="Courier New">spaces lose</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New">heat on cloudy days. It's better to
focus on absolute </FONT></STRONG><STRONG><FONT size=2 face="Courier New">fuel
consumption than</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New">fractional
</FONT></STRONG><STRONG><FONT size=2
face="Courier New">savings.</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New"></FONT></STRONG> </DIV>
<DIV><STRONG><FONT size=2 face="Courier New">If cloudy days are like coin flips
(a reasonable assumption, according to my</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New">TMY2
simulations) </FONT></STRONG><STRONG><FONT size=2 face="Courier New">a
house that can keep itself warm for </FONT></STRONG><STRONG><FONT size=2
face="Courier New">N </FONT></STRONG><STRONG><FONT size=2
face="Courier New">cloudy </FONT></STRONG><STRONG><FONT size=2
face="Courier New">days in a row</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New">has a 1-2^-N solar heating
fraction, eg 50% for 1 day, </FONT></STRONG><STRONG><FONT size=2
face="Courier New">75% for 2, </FONT></STRONG><STRONG><FONT size=2
face="Courier New">and so on... </FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New">90% requires -ln(1-0.9)/ln(2) = 3.3
days, 95% </FONT></STRONG><STRONG><FONT size=2 face="Courier New">requires
</FONT></STRONG><STRONG><FONT size=2
face="Courier New">4.3...</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New"></FONT></STRONG> </DIV>
<DIV><STRONG><FONT size=2 face="Courier New">A direct gain house in Minneapolis
(7981 FHDD) in December will cool from</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New">70 to 60
F in </FONT></STRONG><STRONG><FONT size=2
face="Courier New">-RCln((60-17.9)/(70-17.9)) </FONT></STRONG><STRONG><FONT
size=2 face="Courier New">= 0.213RC cloudy hours,
wh</FONT></STRONG><STRONG><FONT size=2 face="Courier New">ere
</FONT></STRONG><STRONG><FONT size=2 face="Courier New">RC</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New">is the house time
</FONT></STRONG><STRONG><FONT size=2 face="Courier New">constant in hours, so a
95% solar fraction requires </FONT></STRONG><STRONG><FONT size=2
face="Courier New">RC</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New">= 4.3x24h/0.213
</FONT></STRONG><STRONG><FONT size=2 face="Courier New">= 484
</FONT></STRONG><STRONG><FONT size=2 face="Courier New">hours = C/G, where C is
the house thermal mass </FONT></STRONG><STRONG><FONT size=2
face="Courier New">in</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New">Btu/F and G is
</FONT></STRONG><STRONG><FONT size=2 face="Courier New">the house
</FONT></STRONG><STRONG><FONT size=2 face="Courier New">conductance in Btu/h-F
(with nicely cancelling</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New">units: C/G = (Btu/F)/(Btu/h-F)
= h.) </FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2
face="Courier New"> </FONT></STRONG> </DIV>
<DIV><STRONG><FONT size=2 face="Courier New">A 40'x60' house fully-loaded
with room temperature thermal mass might </FONT></STRONG><STRONG><FONT size=2
face="Courier New">have</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New">a 6" </FONT></STRONG><STRONG><FONT
size=2 face="Courier New">floorslab with 6"/12"x40x60x25 = 30K Btu/F
plus 2(40+60)x8x5 = 8K Btu/F</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New">hollow concrete block walls, with C
= 38K Btu/F and G = C/484 = 78 Btu/h-F.</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New"></FONT></STRONG> </DIV>
<DIV><STRONG><FONT size=2 face="Courier New">With A ft^2 of U0.25 south
</FONT></STRONG><STRONG><FONT size=2 face="Courier New">windows with 50% solar
transmission (a low U-value</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New">to maximize cloudy
</FONT></STRONG><STRONG><FONT size=2 face="Courier New">day heat storage)
</FONT></STRONG><STRONG><FONT size=2 face="Courier New">and
</FONT></STRONG><STRONG><FONT size=2 face="Courier New">820 Btu/ft^2 of
sun on the south wall,</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New">24h(70-17.9)(0.25A+Gmax) = 410A
makes A = 12.8Gmax, where Gmax only includes</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New">the ceiling and wall and
ventilation conductances and 0.25A+Gmax < 78, which</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New">makes Gmax < 5.7 Btu/h-F, with A
= 72 ft^2 of south windows.</FONT></STRONG><STRONG><FONT size=2
face="Courier New"> <STRONG><FONT size=2 face="Courier New">In a
perfectly </FONT></STRONG></FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New"><STRONG><FONT size=2
face="Courier New">airtight </FONT></STRONG></FONT></STRONG><STRONG><FONT size=2
face="Courier New"><STRONG><FONT size=2 face="Courier New">house,
</FONT></STRONG></FONT></STRONG><STRONG><FONT size=2
face="Courier New"><STRONG><FONT size=2 face="Courier New">a 30 cfm 90% ERV
adds about </FONT></STRONG></FONT></STRONG><STRONG><FONT size=2
face="Courier New"><STRONG><FONT size=2 face="Courier New">0.1x30 = 3 to
</FONT></STRONG><STRONG><FONT size=2 face="Courier New">Gmax,
</FONT></STRONG><STRONG><FONT size=2 face="Courier New">leaving
2.7</FONT></STRONG></FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New"><STRONG><FONT size=2
face="Courier New">for walls </FONT></STRONG></FONT></STRONG><STRONG><FONT
size=2 face="Courier New"><STRONG><FONT size=2
face="Courier New">and ceiling, eg 5928 ft^2 of 5928/2.7 = R2196 walls and
ceiling,</FONT></STRONG></FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New"><STRONG><FONT size=2
face="Courier New">eg R5/inch </FONT></STRONG></FONT></STRONG><STRONG><FONT
size=2 face="Courier New"><STRONG><FONT size=2 face="Courier New">Styrofoam
walls and ceiling, 36.6 feet
thick :-)</FONT></STRONG></FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New"><STRONG><FONT size=2
face="Courier New"></FONT></STRONG></FONT></STRONG> </DIV>
<DIV><STRONG><FONT size=2 face="Courier New">> the remaining auxiliary
heating requirement will be so small that</FONT></STRONG></DIV>
<DIV><STRONG><FONT size=2 face="Courier New">> a wee woodstove is quite
adequate as the auxiliary heat source.</FONT></STRONG></DIV><STRONG><FONT
size=2 face="Courier New">
<DIV> </DIV>
<DIV>After a few cloudy days, the wee woodstove needs to supply all the house
heat.</DIV>
<DIV>How much wood do you have to feed it over a 7981 FHDD Minniapolis winter,
if</DIV>
<DIV>the house walls are less than 36 feet thick? :-)</DIV>
<DIV><BR>> True, one could probably get close to 100% of the building's heat
load <BR>> from occupancy/solar gains by making the house look
like one of Nick <BR>> Pine's wet dreams, but curiously enough, most
people seem to like having <BR>> windows on their homes and have their
houses look like houses rather than <BR>> Grade 6 science experiments
gone awry.</DIV>
<DIV> </DIV>
<DIV>It's fun to live in science experiments gone awry :-)</DIV>
<DIV> </DIV>
<DIV>Nick</DIV></FONT></STRONG></BODY></HTML>