A rooftop doubt dispeller

[[email protected]]

This fall, it looks like PGW may finally shut off the gas for 40,000
non-paying customers in Philadelphia. What would they do for space heat
and showers and cooking?

An equilateral A-frame on a flat Phila roof with a $200 12'x16' Dynaglas
polycarbonate south wall might collect 0.9x16(6x620+12cos(30)1000)
= 203.2K Btu of sun and lose 6h(Tg-34)12x16/R1 = 1152Tg - 39.2K on
an average January day, where Tg (F) is the A-frame air temp. If it
collects Q Btu/day of useful heat, Tg = 210.4-Q/1152.

If a north wall reflects 0.9x16(6x620+0.9x12cos(30)1000) = 188.4K Btu
into a polyethylene film Tw (F) water duct on the floor and it loses
6h(Tw-Tg)1.5x12x16 = 1728(Tw-Tg), Q = 188.3K-1728(Tw-(210.4-Q/1152))
= 691(319-Tw). Tw = 100 F makes Q = 152K Btu (45 kWh for PV fans
per day, with Tg = 79 F. How can we distribute this heat?

If ridge R of the A-frame reflects direct sun rays S from the horizon
vertically down onto edge Q of a duct that extends 6' to the south from
base B of the north wall, the ridge needs a 45 degree north wall slope.
Two north slopes might join at J, like this, viewed in a fixed font:

R ---
U .
. 45
(xo,yo) J . . . . <-- S south -->
. |
y . . .
. beta 10.4' = 12'cos(30)
^ . . .
| L. |
| . . .
| .
| 45 . beta alpha
----O----------B--------------Q--------------N--> x

| 4.4' | 6' | (not to scale)

| 10.4' |

With a beta degree tilt at bottom B, reflected ray angle BJQ = beta,
so alpha = 180-2beta. If x=y along line OR, tan(beta) = xo/(xo-4.4),
so xo = 4.4tan(beta)/(tan(beta)-1) = 10.4tan(beta)/(tan(beta)+1), ie
beta = 67.96 degrees, which makes the lower slope L = 7.97' and the
upper slope U = 4.25'. We might make L = 8' and U = 4', with 4'x8'
double-foil polyisocyanurate boards and a low vertical wall at B.

This would reduce the heat losing surface and raise the solar collection
efficiency in times of direct sun, with 2 suns from B to Q, so we might
produce 2 kW of electrical power with 1 kW of standard PV panels under
that 6'x16' of duct. Polyethylene and water and glass have similar
refractive indices, so the ducts might transmit most of the sun to
the PVs. When I put a water-filled duct on a PV panel, the output
current decreased 6%, in a crude experiment. Can we make 3 suns?

A draindown EPDM bladder with an upper constraint (eg welded-wire fence)
from Q to N might collect diffuse sun, with warm water naturally
thermosyphoning up through the BQ duct when available.

Nick

 

[Vaughn Simon]

This fall, it looks like PGW may finally shut off the gas for 40,000
non-paying customers in Philadelphia. What would they do for space heat
and showers and cooking?

While it would be wonderful if all that gas didn't get burned because it
was replaced by "green" solar heat, I doubt if those 40,000 non-paying customers
(probably mostly renters) in Philadelphia have the wherewithal, the enterprise,
and the technology to design and build a custom heating system for themselves.

Vaughn

 

[[email protected]]

While it would be wonderful if all that gas didn't get burned because
it was replaced by "green" solar heat, I doubt if those 40,000 non-paying
customers (probably mostly renters) in Philadelphia have the wherewithal,
the enterprise, and the technology to design and build a custom heating
system for themselves.

Me too, even if it were legal...

Nick

I know of some local folks, Amish, who had a baby at home a couple of
years ago. Babies born at home nowadays are no big deal; most of the
Amish have a midwife deliver their babies. All of my six children were
born at home. However, a local county health worker decided to put a stop
to this practice and charged the young Amish couple with child abuse for
not having their baby born in a hospital.

Here we have an otherwise happy young couple who just had a beautiful baby,
and some poor, deluded authority figure was actually telling them he'd
have their baby taken away and put in a foster home if they didn't tell him
who delivered the kid. This is a true story. The couple gave him the name
of their midwife, a highly respected and eminently qualified woman who
has now delivered over one thousand babies. She was promptly arrested.
To make a long story short, the local magistrate threw the charge
(practicing medicine without a license) out, the authorities actually
appealed, then the higher court threw the charges out.

What does this have to do with compost? Composting humanure is like
having babies where and how you want them, or educating your kids
alternatively. It's behavior out of the mainstream of Western society.
It may be something different, and different things can scare people when
they don't know anything about them, especially those people who have
oatmeal for brains and have somehow gravitated into a position of
authority. Whether it's legal or not often isn't the issue. The Amish
story is one of many in which the basic rights of humans have been
subverted by the ignorance and the misuse of authority by others.

Ideally, laws are made to protect society. Laws requiring septic waste and
sewage disposal systems are supposedly designed to protect the environment,
the health of the citizens and the water table. This is all to be commended
and conscientiously carried out by those who produce sewage, a waste
material. If you don't produce sewage, you have no need for a sewage
disposal system, and laws pertaining to sewage disposal are not your
concern. The number of people who produce compost instead of sewage is
so minimal that few if any laws have been enacted to regulate the practice.
The thermophilic composting of humanure is not a threat to society, it
produces no pollution, does not threaten the health of humans or
contaminate the ground water or environment. Unfortunately, this fact
is not understaood by many people, and ignorance is a problem.

It would be hard to intelligently argue that a person who produces no
sewage must have a costly sewage treatment system. What would they do
with it? That would be like requiring someone who doesn't own a car to
have a garage. And it would be very difficult to prove that composting
humanure is threatening to society, especially given the facts as
presented in this book. On the other hand, Galileo, the astronomer, was
arrested as a heretic and forced to renounce his theory that the Earth
revolves around the sun. Sure, that was three hundred years ago. But
sometimes I think the consciousness of our society as it relates to
human manure is still back in the middle ages.

One way to dispel the darkness of ignorance is with the light of knowledge.
Knowledge is best gained by experience. Therefore, I'd like to hear from
any of you readers about your composting experiences. You may be able to
add to the body of knowledge, and I may someday revise and update this book
to include the experiences of others. So don't hesitate at any time to
write to the address at the front of this book and let me know how it's
going for you. I'd welcome any feedback at all.

If you're concerned about your local laws, go to the library and see what
you can find about regulations concerning compost. Or also inquire at your
county seat or state agency as statutes, ordinances and regulations vary
from locality to locality. Where I live septic system permits aren't
required for new home construction, but the next county is two properties
over and people there are required to have septic system permits before
they can build a new dwelling. This is largely due to the fact that the
water table tends to be high in my area, and septic systems don't always
work, so sand mounds are required by law for sewage disposal. Now, if you
don't want to dispose of your manure but want to compost it instead (which
will certainly keep it out of the water table, not to mention raise a few
eyebrows at the local municiapal office), you may have to stand up for
your rights.

In Pennsylvania, the state legislature has enacted legislation "encouraging
the development of resources recovery as a means of managing solid waste,
conserving resources, and supplying energy." Under such legislation the term
"disposal" is defined as "the incineration, dumping, spilling, leaking, or
placing of solid waste into or on the land or water in a manner that the
solid waste or a constituent of the solid waste enters the envirnoment, is
emitted into the air or is discharged to the waters of the Commonwealth"
(Pennsylvania Solid Waste Management Act, Title 25, Chapter 29A). Further
legislation has been enacted in Pennsylvania stating that "waste reduction
and recycling are preferable to the processing or disposal of municipal
waste," and further stating "pollution is the contamination of any air,
water, land or other natural resources of this Commonwealth that will create
or is likely to create a public nuisance or to render the air, water, land,
or other natural resources harmful, detrimental or injurious to public
health, safety or welfare..." (Pennsylvania Municipal Waste Planning,
Recycling and Waste Reduction Act (1988), Title 53, Chapter 17A. In view of
the fact that the thermophilic composting of humanure involves recovering
a resource, requires no disposal of waste, and creates no environmental
pollution, it is unlikely that any one who conscientiously engages in
such an activity would be successfully convicted of criminal activity.

From The Humanure Handbook, by J. C. Jenkins, third printing, c. 1994.
Jenkins Publishing/POB 607/Grove City PA 16127

 

[Harry Chickpea]

On the other hand, Galileo, the astronomer, was

arrested as a heretic and forced to renounce his theory that the Earth
revolves around the sun.

FWIW, that is the popular snippet that was promulgated by Protestants
who wanted to impress the abuses of the Catholic church on their
children. The actual events may have had that end result, but Galileo
was a bit of a prick, who had ample opportunity to present his work
and proof to that church before he was forced to renounce. The
church, in that case, was more receptive to change than many of the
churches today, who insist on creationism, etc.. It is simply safer
for an author to repeat the Galileo media bite than risk the wrath of
providing more current examples.

The author further displays ignorance with the statement "But
sometimes I think the consciousness of our society as it relates to
human manure is still back in the middle ages." In the middle ages,
people threw their shit out second story windows into the street. It
was the understanding of the causes of epidemics and disease that
forced sanitation to become law.

Anyone promoting change in society often fails to recognize that what
they consider a lofty goal or common sense often does not work when
placed into the hands of people without goals or common sense. IE:
Landscape at a courthouse was in the news recently. Seems as though
the existing landscape plants were being destroyed by people relieving
themselves in the bushes around the building. IE: A recent
investigative report by a local tv station on restaurant ice in the
Miami area found that about half of the tested samples of ice
contained fecal coliform; this caused by employees not following basic
sanitation rules.

Humanure might be fine for people who understand how to handle it
properly, but to repeal sanitation laws is much closer to going back
to the middle ages and shit out the window than I would care to go.

 

[surfnturf]

the existing landscape plants were being destroyed by people relieving
themselves in the bushes around the building. IE: A recent

Electric fence would solve this.

investigative report by a local tv station on restaurant ice in the
Miami area found that about half of the tested samples of ice
contained fecal coliform; this caused by employees not following basic
sanitation rules.

For some reason, it seems hand washing is now out of fashion. But we worry
about chlorine residual in city water and avian flu. Hmmm. Perhaps we are
approaching a serious public health disaster which will once more focus us
on the basics.

Humanure might be fine for people who understand how to handle it
properly, but to repeal sanitation laws is much closer to going back
to the middle ages and shit out the window than I would care to go.

We have enough humanure in our modern approach to analytical thinking. I'll
have to agree with Harry on this. let's work to improve public health, not
make it worse.

And vaccinate your children while you're at it!

surfnturf

 

[Mary Fisher]

Let em rub their legs together for heat and maybe that will keep
them from reproducing too.
They may not have money for gas, but I'm positive they have money for
cigarettes.

And only mucky people have showers.

Mary

 

[[email protected]]

An equilateral A-frame structure on a flat roof with a tension anchor
through an access hatch with a $200 12'x16' Dynaglas polycarbonate south
wall might collect 0.9x16(6x620+12cos(30)1000) = 203.2K Btu and lose
6h(Tg-34)12x16/R1 = 1152Tg-39.2K on an average January day, where Tg (F)
is the A-frame air temp. If it collects Q Btu/day of useful heat,
Tg = 210.4-Q/1152.

If the north wall reflects 0.9x16(6x620+0.9x12cos(30)1000) = 188.4K Btu
into a draindown polyethylene film duct on the floor containing Tw (F)
water and it loses 6h(Tw-Tg)1.5x12x16 = 1728(Tw-Tg), Q = 691(319-Tw).
Tw = 100 F makes Q = 152K Btu (45 kWh) per day, with Tg = 79 F. We could
store warm water in a large unpressurized tank in the basement (like
a circular swimming pool) and use it to preheat water for showers and
heat a few rooms with fan-coil units.

To increase the solar collection efficiency and decrease the absorber cost,
we could make the north wall with lower and upper segments L and U for
moderate solar concentration with reflected rays rl and ru from the upper
edges of the segments having a common focal line F, like this, viewed in
a fixed font like Courier:

. <------------------------- sun

 

[dew]

[email protected] wrote

An equilateral A-frame structure on a flat roof

How many of your houses have flat roofs ?

with a tension anchor through an access hatch with a $200
12'x16' Dynaglas polycarbonate south wall might collect
0.9x16(6x620+12cos(30)1000) = 203.2K Btu and lose
6h(Tg-34)12x16/R1 = 1152Tg-39.2K on an average
January day, where Tg (F) is the A-frame air temp.
If it collects Q Btu/day of useful heat, Tg = 210.4-Q/1152.

If the north wall reflects 0.9x16(6x620+0.9x12cos(30)1000) = 188.4K
Btu into a draindown polyethylene film duct on the floor containing
Tw (F) water and it loses 6h(Tw-Tg)1.5x12x16 = 1728(Tw-Tg), Q =
691(319-Tw).

 

[[email protected]]

How many of your houses have flat roofs ?

Almost all of them.

Nick

 

[dew]

Almost all of them.

Don't believe it.

 

[dew]

Hi dew;




Well, what does your roof look like?

Irrelevant.

 

[[email protected]]

How many of your houses have flat roofs ?

About 300,000.

http://www.citypaper.net/articles/092800/sl.slant.shtml

Philadelphia's low-income housing stock essentially consists of brick boxes
with flat black tar roofs. In the best of times these roofs have a short
life span, currently carrying a warranty of only five years. On an extremely
hot day, the temperature on these black roofs can exceed 175 degrees,
transferring much of that heat to the upper stories and occupants inside.
These homes literally become brick ovens, radiating heat inside to their
occupants and outside to the street.

The Energy Coordinating Agency (ECA) is a local nonprofit corporation that
has been working to solve the energy problems of low-income people since
1984. The ECA is currently using a relatively new roof coating material to
help solve the problem of excess heat build up in homes: white, acrylic,
elastomeric roof coatings have an extremely high reflectance and typically
reduce the cooling load in buildings by 22 percent...

Nick

 

[dew]

About 300,000.

Bugger all of the total in fact.

http://www.citypaper.net/articles/092800/sl.slant.shtml

Philadelphia's low-income housing stock essentially
consists of brick boxes with flat black tar roofs.

Pity few of those are individual houses.

And even with those with flat roofs, **** all of them
have basements where your water pool can go anyway.

In the best of times these roofs have a short life span, currently
carrying a warranty of only five years. On an extremely hot day,
the temperature on these black roofs can exceed 175 degrees,
transferring much of that heat to the upper stories and occupants
inside. These homes literally become brick ovens, radiating heat
inside to their occupants and outside to the street.

Mindlessly silly stuff.

The Energy Coordinating Agency (ECA) is a local nonprofit
corporation that has been working to solve the energy problems of
low-income people since 1984. The ECA is currently using a
relatively new roof coating material to help solve the problem of
excess heat build up in homes: white, acrylic, elastomeric roof
coatings have an extremely high reflectance and typically reduce the
cooling load in buildings by 22 percent...

Pity your silly scheme was for heating.

 

[[email protected]]

That's the approximate number of houses with flat roofs in Philadelphia.
A lot were built in the 1800s. About 40,000 of them may end up with their
gas disconnected this winter.

Bugger all of the total in fact.

Rod, is that you? What's "Bugger all of the total in fact" in English?

http://www.citypaper.net/articles/092800/sl.slant.shtml

Pity few of those are individual houses.

Most have common walls, which is good for heating.

And even with those with flat roofs, **** all of them
have basements where your water pool can go anyway.

Almost all of them have basements. That's where the coal bin is.

Mindlessly silly stuff.

It's exaggerated, and flat roofs radiate heat to the sky vs the street, but
there is a correlation between high outdoor temperatures and mortality, esp
among older and poorer people.

This also stops leaks and doubles the roof lifetime.

Pity your silly scheme was for heating.

These houses need both. Heating becomes easier after ECA does white roofs
and R40 attic insulation and airsealing. They also install whole-house
fans which can keep the houses comfortable for all but 2 weeks or so in
summertime, if they are properly operated. With a desiccant, the rooftop
structure might also help with cooling and dehumidification.

Nick

 

[Rod Speed]

That's the approximate number of houses with flat roofs in
Philadelphia.
A lot were built in the 1800s. About 40,000 of them may end up with
their gas disconnected this winter.


Rod, is that you? What's "Bugger all of the total in fact" in
English?

A small percentage of the total.

http://www.citypaper.net/articles/092800/sl.slant.shtml

Most have common walls, which is good for heating.

Irrelevant to whether the scheme you proposed is viable there.

Almost all of them have basements. That's where the coal bin is.

Pity its impractical to use that to heat the
individual units with what you proposed.

It's exaggerated,

Its mindlessly silly.

and flat roofs radiate heat to the sky vs the street, but
there is a correlation between high outdoor temperatures
and mortality, esp among older and poorer people.

Irrelevant to your silly scheme which was about HEATING.

This also stops leaks and doubles the roof lifetime.

Irrelevant to your silly scheme which isnt very useful because
there are so few individual houses with flat roofs and basements.

These houses need both. Heating becomes easier after ECA does white
roofs and R40 attic insulation and airsealing. They also install
whole-house fans which can keep the houses comfortable for all but 2
weeks or so in summertime, if they are properly operated. With a
desiccant, the rooftop structure might also help with cooling and dehumidification.

Irrelevant to your silly scheme which isnt very useful because
there are so few individual houses with flat roofs and basements.

 

[[email protected]]

A small percentage of the total.

No. It's probably more than 90% of the houses that may end up disconnected.
In past years, PA's governor has come up with about $20 million to pay
the gas bills ($500 each) of the 40K customers who haven't paid, but
that seems less likely to happen this year.

No. Most are single family row houses.

Irrelevant to whether the scheme you proposed is viable there.

No. Common brick walls have lots of thermal mass and lose little heat
to the outdoors, which makes solar heating these houses easier.

Pity its impractical to use that to heat the
individual units with what you proposed.

Not according to simuilations with hourly historical TMY2 Philadelphia
weather data.

Irrelevant to your silly scheme which isnt very useful because
there are so few individual houses with flat roofs and basements.

No. Almost all of them have flat roofs and basements.

Nick

After weatherization and more insulation and airsealing, a 30'x40'x16' high
row home with brick common walls and a flat roof and a basement might have
10,000 Btu/F of thermal mass and a thermal conductance of 175 Btu/h-F, with
R40 roof insulation and R20 wall insulation and 0.2 air changes per hour...

National Renewable Energy Laboratory (NREL) long-term average weather data
indicates that January is the worst-case month for solar house heating in
Philadelphia, when 620 Btu/ft^2 falls on the ground and 1000 falls on
a south wall on an average 30.4 F day with a 37.9 F average daily max.
NREL's Philadelphia hourly Typical Meteorological Year (TMY2) weather
data file is useful for solar house heating simulations.

The simulation below uses NREL's TMY2 weather data file to estimate
the natural gas consumption for space heating a house like the one above
with a) no solar heat (117 therms per year), b) a 4x48 ft^2 air heater
on a south wall with a $50 fan and a $20 thermostat (39 therms), and
then adds c) a $100 differential thermostat (24 therms), d) R20 exterior
wall insulation (11 therms), and e) an 8x48 ft^2 air heater (3 therms.)

The air heater might be 4 4'x12' $50 sheets of Dynaglas single-wall
corrugated clear polycarbonate greenhouse roofing material mounted on
a frame on a south brick wall, with a layer of dark window screen (about
25 cents/ft^2 in 4' rolls) behind it to reduce reradiation loss and 1/2"
single-foil 4'x8' polyisocyanurate Dow Super Tuf-R boards ($9.48 each
at Home Depot) glued to the wall with foam from a can, with the foil
side facing the wall and the other side facing out. The 8'x24' frame
might be pressure-treated 1x6 boards ($3.70/8') glued on edge to bricks
with foam from a can, with corner reinforcing. Lasko's $50 2470 cfm 90 W
16" window fan could circulate warm air through the house when the air
heater is warm and the house needs heat, with a wide temperature range
(50 to 80 F below) to maximize storage efficiency.

With 64' of pressurized fin-tube ($2/ft) near the top and a $100 low-power
circulation pump, this air heater could also provide significant year-round
domestic water heating. But it would have limited applicability, for houses
with large south walls with few windows. It might save $200 per year in
natural gas at a cost of $2000, including labor.

20 DAYSTART=0'display start time (days)
30 DS=DAYSTART*24'display start time (hours)
40 RANGE=8760'display range (hours)
50 LINE (0,0)-(639,349),,B:XDF=640/RANGE:YDF=3.88
60 FOR TR=50 TO 80 STEP 10'temp ref lines
70 LINE (0,349-YDF*(TR-10))-(639,349-YDF*(TR-10)):NEXT
80 AROOF=30*40'roof area (ft^2)
90 RROOF=40'roof R-value (F-h/Btu)
100 GROOF=AROOF/RROOF'roof conductance (Btu/h-F)
110 AWALL=2*30*16'wall area (ft^2, excluding common and basement)
120 RWALL=20'wall R-value (F-h/Btu, including windows)
130 GWALL=AWALL/RWALL'wall conductance (Btu/h-F)
140 ACH=.2'air infiltration (house volumes per hour)
150 GAIR=ACH*30*40*24/60'air infiltration conductance (Btu/h-F)
160 GH=GROOF+GWALL+GAIR'house conductance (Btu/h-F)
170 CH=10000'house thermal mass (Btu/F)
180 AHA=8*48'air heater area (ft^2)
190 TMIN=50'min house temp (F)
200 TMAX=80'max house temp (F)
210 TH=TMIN'initialize house temp (F)
220 OPEN "ecayear" FOR INPUT AS #1:LINE INPUT#1,H$
230 FOR H=1 TO 8760'hours of typical (TMY2) year
240 INPUT#1,MONTH,DAY,HOUR,TDB,WIND,TDP,IGLOH,SS,WS,NS,ES
250 Q=-(TH-TDB)*GH'heatflow into house (Btu/h)
260 TH=TH+Q/CH'house temp before heating (F)
270 IF TH>TMAX GOTO 330'no heat required
275 IF MONTH>=5 AND MONTH<=9 GOTO 330'no summer solar heat
280 QS=.9*SS*AHA-(TH+10-TDB)*AHA/1'available solar heat
290 IF QS<0 GOTO 320'no solar heat available
300 TH=TH+QS/CH'house temp with solar heat (F)
310 IF TH>TMAX THEN TH=TMAX'limit upper house temp
320 IF TH<TMIN THEN GASHEAT=GASHEAT+(TMIN-TH)*CH:TH=TMIN'gas heat to Tmin
330 PSET(XDF*(H-DS),349-YDF*(TDB-10))
340 PSET(XDF*(H-DS),349-YDF*(TH-10))'plot house temp (F)
350 IF DAY=1 AND HOUR=.5 THEN LINE (XDF*(H-DS),349)-(XDF*(H-DS),345)'months
360 NEXT H
370 CLOSE #1
380 PRINT GASHEAT/100000!

117.16 therms with no solar heat (AHA=0 in line 180),
38.82 therms with a 4x48 ft^2 solar air heater,
24.16 therms with a differential thermostat,
10.68 therms with R20 wall insulation, and
2.84 therms with an 8x48 ft^2 solar air heater.

Nick

 

[dew]

No.

Fraid so.

It's probably more than 90% of the houses that may end up disconnected.

Dont believe that those are individual houses with
basements where what you propose is viable.

In past years, PA's governor has come up with about $20 million
to pay the gas bills ($500 each) of the 40K customers who
haven't paid, but that seems less likely to happen this year.

Its unlikely those would have the cash to do what you propose.

No. Most are single family row houses.

With basements ?

No. Common brick walls have lots of thermal mass and lose little heat
to the outdoors, which makes solar heating these houses easier.

Pity thats only a tiny subset of the total houses.

Not according to simuilations with hourly
historical TMY2 Philadelphia weather data.

I wasnt talking about the weather data, the
impracticality is with how you propose to heat it.

No. Almost all of them have flat roofs and basements.

Still a tiny subset of all houses.

 

[[email protected]]

NREL says the long term average 24-hour outdoor temp is 76.7 F with
a 67.2 F daily min and w = 0.0133 in July in Phila, so a house with
lots of thermal mass would be close to the 24-hour average, with no
ventilation, ignoring internal heat gains and sun into windows.

A structure that heats domestic water in summertime with 8 ft^2 of gable
vents 10' above a roof and 8 ft^2 of basement or first-floor windows with
passive one-way dampers and a 24' height difference and a dT (F) indoor-
outdoor temp difference might make Q = 16.6x8sqrt(24dT) = 651sqrt(dT) cfm
of passive airflow, removing about QdT Btu/h of heat. If dT=10 F, 2060 cfm
would flow (like a whole house fan), removing about 20,600 Btu/h of heat
(like 4 window ACs.)

A low-income row house with an improved 175 Btu/h-F thermal conductance
and average temp T (F) in 81 F air for 12 hours and 72 F air at night and
a 12h(81-T)175 Btu daily gain that equals a 12h(T-72)175+12h(651(T-72)^1.5)
night loss would have T = 72+(0.538(T-72)^(2/3) = 73.4 vs 76.5 F with no
ventilation, closer to the daily min than the 24-hour average. The TMY2
simulation below says the average house temp from June through August
would be about 69 vs 74 F, with a max 79 vs 82 F when it's 95 F outdoors.
These differences would increase with internal and solar heat gains.

10 CLS:KEY OFF:SCREEN 9
20 DAYSTART=100'display start time (days)
30 DS=DAYSTART*24'display start time (hours)
40 RANGE=4000'display range (hours)
50 LINE (0,0)-(639,349),,B:XDF=640/RANGE:YDF=3.88
60 FOR TR=50 TO 100 STEP 10'temp ref lines
70 LINE (0,349-YDF*(TR-10))-(639,349-YDF*(TR-10)):NEXT
80 GH=175'house conductance (Btu/h-F)
90 CH=10000'house thermal mass (Btu/F)
100 'AV=8'vent area (ft^2)
110 H=24'vent height diff (ft)
120 KV=16.6*AV*SQR(H)'vent coefficient
130 TH=70'initialize house temp (F)
140 OPEN "ecayear" FOR INPUT AS #1:LINE INPUT#1,H$
150 FOR H=1 TO 8760'hours of typical (TMY2) year
160 INPUT#1,MONTH,DAY,HOUR,TDB,WIND,TDP,IGLOH,SS,WS,NS,ES
170 Q=(TDB-TH)*GH'conductive heatflow into house (Btu/h)
180 DT=TH-TDB'indoor-outdoor temp diff (F)
190 IF DT<0 THEN DT=0'no passive airflow
200 CFM=KV*SQR(DT)'passive airflow
210 Q=Q-CFM*DT'heatflow into house (Btu)
220 TH=TH+Q/CH'house temp before heating (F)
230 IF MONTH <6 OR MONTH >8 GOTO 280
240 N=N+1'accumulate summer hours
250 IF TDB>TDBMAX THEN TDBMAX = TDB
260 IF TH>THMAX THEN THMAX = TH
270 THA=THA+TH'accumulate average house temp (F)
280 PSET(XDF*(H-DS),349-YDF*(TDB-10))'plot outdoor temp (F)
290 PSET(XDF*(H-DS),349-YDF*(TH-10))'plot house temp (F)
300 IF DAY=1 AND HOUR=.5 THEN LINE (XDF*(H-DS),349)-(XDF*(H-DS),345)'months
310 NEXT H
320 CLOSE #1
330 PRINT N,THA/N,THMAX,TDBMAX

summer --- indoor temp--- outdoor
hours average maximum max (F)

2208 73.72266 81.52365 95 w/o passive ventilation (line 100)
2208 68.71685 78.68447 95 w/ passive ventilation

Nick

 

[[email protected]]

NREL says the long term average 24-hour outdoor temp is 76.7 F with
a 67.2 F daily min and w = 0.0133 in July in Phila, so a house with

Is that the TMY2 data from
http://rredc.nrel.gov/solar/old_data/nsrdb/tmy2/ ?

That data is awkward to parse. The "tgz" download is a gz of a text file,
and the sample c code for decoding isn't valid. Seems like too much
trouble for old data from a station 60 miles from here.

Did you find it somewhere else?

 

[[email protected]]

Is that the TMY2 data from

http://rredc.nrel.gov/solar/old_data/nsrdb/tmy2/ ?

No. That's just long-term monthly average data from NREL's "Blue Book."
My Phila TMY2 hourly weather data came from NREL's TMY2 CD-ROM, which
is most likely the same as the web site data. NREL also sells 3 CD-ROMs
that cover 30 year's worth of hourly weather data for all US locations.

That data is awkward to parse.
Awww.

The "tgz" download is a gz of a text file,
and the sample c code for decoding isn't valid.

Perhaps you need a better language like BASIC

Nick