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REAL ESTATE
AND
NEW YORK, DECEMBER 9, 1916
RELATION OF HEIGHT AND AREA TO SUNSHINE
Statement by Herbert S. Swan and George W.
Tuttie, of the Staff of the Committee on City Plan
BUILDING requirements in Manhat¬
tan have in the past been so lax
that it is safe to say that a preponderat¬
ing majority of rooms in the existing
shops, factories, offices and apartments
receive absolutely no direct sunshine
on the shortest day in the year.
The height and area regulations now
being considered will have the tendency
of remedying this condition. Bv limit¬
ing the height of buildings with refer¬
ence to the street width and by requiring
all windows to open out on either streets
or open spaces of a prescribed size the
zone plan will provide a larger _ supply
of direct sunshine not only in the interior
of all new residence and business build¬
ings, but also in the streets.
The following paper shows the relation
of these provisions to the duration and
quantity of direct sunshine obtained un¬
der different conditions at New York
City (40° North Latitude) as on Decem¬
ber 21.
At noon, on the shortest day of the
year, the shadows of different sky¬
scrapers envelope large areas. The
Adams Express Building, which is 424
feet high, casts a shadow 875 feet in
length; the Equitable Building, which is
493 feet high, one 1,018 feet in length;
the Singer Tower, which is 546 feet high,
one 1,127 feet in length; and the Wool-
worth Tower, which is 791 feet high, one
1,635 feet in length.
The effect of skyscrapers casting shad¬
ows from a sixth to a third of a mile
in length on surrounding property is
well illustrated in the case of the Equit¬
able Building. Its shadow, which at noon
on December 21 is about one-fifth of a
mile in length, completely envelops an
area of 7.59 acres. The ground area of
the Equitable Building is only 1.14 acres'.
The shadow cuts off all sunshine from
the Broadway facade of the United
States Realty Building, which is twenty-
one stories high. The New York Title
& Mortgage Company Building, four¬
teen stories high, and the Washing¬
ton Life Insurance Building, nineteen
stories high, are both completely
shaded. The south side of the Singer
Tower is shaded to a height of twenty-
seven stories. Tlie nearest part of the
City Investing Building 400 feet away is
in shadow for twenty-four of its twenty-
six stories. Even part of the New York
Telephone Building north of Cortlandt
street is shadowed by the Equitable
Building. For almost a fiftli of a mile
this giant skyscraper casts its shadow.
The area cut off by it from all noonday
sunlight extends to within 100 feet of
Fulton street.
Cedar street, the street immediately
north of the Equitable Building, has an
average width of 34 feet between Broad¬
way and Nassau street. The height of
the Equitable Building is 14J/2 times the
width of this street. On a north and
south street of this width in New York,
uniformly improved on both sides with
buildin.gs having a height equal to that
of the Equitable Building, only 9.31 per
cent, of the windows would receive any
direct sunshine at noon on the shortest
day in the year. On north and south
streets only the windows nearest the top
for a distance equal to .1.35 times the
width of the street would receive direct
sunshine at noon on December 21 at
New York (40° North Latitude). The
windows in tlie first thirty-four stories
nearest the ground would receive abso¬
lutely no direct sunlight, Direct sun¬
shine would only enter those windows in
the four stories nearest the top. Not a
single window within 447 feet of the
street level would receive a ray of direct
sunshine.
The Equitable Building is, of course,
an cxtren-.e case. But even in much
lower buildings a considerable number of
the windows on north and south streets
receive absolutely no direct sunshine at
the winter solstice. Up to a height equal
to 1.35 times the width of such a street
posite side of the street, 28 per cent, of
the sunshine period on a north and south
street is cut off by the thickness of the
wall in which the window is set. Where
the opposite buildin.gs rise to a height
above the window equal to .2 times the
width of the street, 35 per cent, of the
sunshine period is cut off; where it rises
to a height .4 times the width of the
street, 44 per cent, is cut off; .6 times, 54
per cent.; .8 times, 65 per cent.; 1.0 times,
77 per cent.; and 1.35 times 100 per cent.
Time af which sun is eclipsed by given- height of bi/llding
in terms of street widtf)
Streetmcif/i.-%^ -^^
.Oi Oft Ns ^ *0 '^
. '.....
Hours before or offer noon.
VOLUME, or SUIV8mN£ ADM/nZD BY W/NDOW.
Calculated for gi\ten room with window open¬
ing on north and south street. Latitude 40'N.
all the windows (assuming they fulfill the
standard requirements described below)
receive some sunshine. If the street,
liowever, is improved witli buildings one
and one half times the street width in
height only 90 per cent, of the windows
obtain direct sunshine. If the height be
increased to two times the street width
the proportion receiving direct sunshine
is reduced to 67.5 per cent. The number
of windows receiving direct sunshine on
north and south streets with buildings of
different heights is as follows: Two and
one-half times, 54 per cent.; three times,
45 per cent.; four times, 34 per cent.; five
times, 27 per cent.; and six times, 22.5
per cent.
In this connection it must be remem¬
bered that all windows receiving "sunlight
do not obtain the same amount. Even
though there be no buildings on the op-
This is for a wall 14 inches thick. For a
thicker wall the percentage would in
each case be more; for a thinner wall
less.
A window in a north and south street
situated in a position where the height
of the Iniildings opposite it is .2 times
the width of the street above its center
level receives direct sunlight for a period
the length of which is only 72 per cent,
of that received by an unobstructed win¬
dow; where the Iieight of the buildings
opposite is .4 times, SO per cent.; .6 times,
ZZ per cent.; .8 times, 21 per cent.; and
1.0 times, 12 per cent.
The duration of the sunshine period
of tlie facade and in the rooms on a
north and south street at the winter sol¬
stice is shown in the following table for
different points below the top of the op¬
posite buildings: