Sunshine - Nissho (English spelling) sunlight

Japanese: 日照 - にっしょう（英語表記）sunlighting

The direct sunlight shining on an object. A term used in meteorological observation. Even if there are thin clouds, if an object casts a shadow, it is considered to have been sunny. In meteorology, sunshine is used as an indicator of weather and cloud cover, and is also widely used in agriculture and construction. An instrument used to measure sunshine is called a sunshine gauge. The total amount of time there is sunshine during a day or a month is called sunshine hours.

Sunshine hours are measured by meteorological offices all over the country, and the results are compiled. According to statistics from 1971 (Showa 46) to 2000 (Heisei 12) by major meteorological offices throughout Japan, the monthly sunshine hours in Sapporo, Hokkaido, are maximum 196.7 hours in May and minimum 86.9 hours in December, in Tokyo the maximum is 180.9 hours in May and minimum 112.9 hours in September, and in Naha, Okinawa the maximum is 243.6 hours in July and minimum 84.6 hours in February.

[Masaji Ohta and Hiroshi Matano]

Buildings and sunlight

In architecture, the term is used to refer to techniques that deal with the strength and direction of direct solar radiation on the earth's surface due to the movement of the sun. It can also simply refer to sunlight. Sunshine is essential to human life, along with clean air and greenery, and in Japan it is especially necessary for homes. It is desirable for one or more rooms in an apartment or condominium to receive at least four hours of sunlight on the winter solstice, and ideally at least six hours. The Building Standards Act stipulates shadow regulations (Article 56-2) to ensure that mid- to high-rise buildings do not cause shade problems for surrounding homes.

[Kunio Matsuura]

Shadow curve and sunlight curve

A shadow curve is the path of the shadow of the tip of a pole placed vertically on the ground (lower diagram in Figure A ), while a sunlight curve is the path of the points where the sunlight incident on observation point O intersects a horizontal plane parallel to the ground (upper diagram in Figure A ). Using the shadow curve, it is possible to draw a shadow diagram of a building or the like, as shown in Figure B. A group of sunlight curves drawn on a single diagram by superimposing sunlight curves with various heights H (see Figure A ) from observation point O to the horizontal plane is called a sunshine chart. A plane of an obstacle such as a building is drawn on this, and the part of the sunlight curve that is equivalent to the building's height H that is on the observation point (point O) side is sandwiched between two straight lines with point O as its vertex, and the time when these two straight lines intersect can be read to determine the time when point O is in shadow due to this building ( Figure C ).

[Kunio Matsuura]

Sunlight adjustment

Sunlight adjustment is a comprehensive planning that takes into account the building's shape, orientation, window opening direction, eaves and sunshades, etc., and the building's purpose, so that it can block sunlight in the summer and utilize sunlight in the winter. There are various methods, including the layout plan of the buildings, the building floor plan, detailed plans for windows, openings, eaves and sunshades, and even the selection of window glass materials. For example, in a housing complex, the spacing between adjacent buildings should be set appropriately so that all units receive 4 to 6 hours of sunlight on the winter solstice, the main openings should be oriented as close to the south as possible to allow more sunlight in the winter and less in the summer, and to further increase this effect, eaves should be installed on openings facing south, and louvers or fins (made up of several boards and not as numerous as louvers) should be installed outside the windows to block sunlight and use reflected light to let in light, and Venetian blinds or vertical louver blinds, which have a similar effect, should be installed indoors.

[Kunio Matsuura]

"Ishihara Shunsuke, 'Evaluation and Standards of Sunshine in Living Environments: Considerations for Solving Sunshine Problems' (1973, Metropolitan Forum)" ▽ "Architectural Institute of Japan, 'Measurement and Consideration of Sunshine' (1977, Shokokusha)" ▽ "Tanaka Osamu and Yanase Masatoshi, 'What You Need to Know About Sunshine Planning' (1985, Kajima Institute Publishing)" ▽ "Yoshimitsu Kiyomitsu, Okura Tadao and Asano Tetsuro, 'Legal Disputes over Sunshine, Views and Noise: Advice for a Comfortable Life in the Neighborhood' (1999, Yuhikaku)" ▽ "Matsuura Kunio, 'Ace Architectural Environmental Engineering 1: Sunshine, Light and Sound' (2001, Asakura Shoten)"

[Reference] | Daylighting | Sunshine meter | Sunlight rights | Sunshade

Shadow curve and sunlight curve (Figure A)
©Shogakukan ">

Shadow curve and sunlight curve (Figure A)

Shadow map of a cubic building (Figure B)
©Shogakukan ">

Shadow map of a cubic building (Figure B)

Sunshine chart (Figure C)
The figure shows an example of how long a building casts a shadow on observation point O (at 35 degrees north latitude on the winter solstice). The blue area formed by the intersection of the building plan (ABCD) and the sunlight curve for building height H = 25m (scale S = 1000) is sandwiched between two straight lines (dotted and dashed lines) with point O as the vertex, and the time of the straight lines is read off, which is the time the building casts a shadow on point O (14:10 to 15:30 in the figure). Note: Based on "ACE Architectural Environmental Engineering I - Sunshine, Light, Sound" by Kunio Matsuura and Daini Takahashi (Asakura Publishing) ©Shogakukan

Sunshine chart (Figure C)

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

Japanese:

太陽の直射光が地物を照射すること。気象観測の用語。薄い雲があっても地物の影ができる程度であれば、日照があったとみなす。日照は気象学では天気や雲量の指標として利用されるほか、農業、建築などに広く利用される。日照を計る器械を日照計という。また、1日中あるいは1か月中などに日照のあった時間を合計して日照時間という。

　日照時間は全国の気象官署で測定されており、その結果がまとめられている。日本各地のおもな気象官署の1971年（昭和46）から2000年（平成12）までの統計によれば、月間の日照時間は北海道の札幌での最大月は5月で196.7時間、最小月は12月で86.9時間、東京での最大月は5月で180.9時間、最小月は9月で112.9時間、沖縄県の那覇(なは)での最大月は7月で243.6時間、最小月は2月で84.6時間となっている。

［大田正次・股野宏志］

建物と日照

建築学では太陽の動きによる地表での直達日射の強さや向きを取り扱う技術に関して用いられる。単に日当りをいうこともある。日照はきれいな空気や緑とともに人間生活に欠かせないもので、日本ではとくに住宅には必要とされている。共同住宅（アパート、マンション）の一つ以上の居室に冬至の日4時間以上、できれば6時間以上の日照を受けることが望ましい。建築基準法では、中高層の建物によって周辺の住宅などに日影(ひかげ)障害を与えないよう日影規制（56条の2）が定められている。

［松浦邦男］

日影曲線と日ざし曲線

日影曲線は、地平面上に鉛直に立てた棒の先端の日影の軌跡であり（図Aの下図）、一方日ざし曲線は、観測点Oに入射する太陽光線が地平面に平行な水平面を切る点の軌跡である（図Aの上図）。日影曲線を用いれば図Bに示すような建物などの日影図を描ける。また、観測点Oから水平面までの高さH（図A参照）を種々変えた日ざし曲線を重ねて一つの図に描いた日ざし曲線群を日照図表とよぶ。これに障害物となる建物などの平面を描き、その建物の高さHに相当する日ざし曲線より観測点（O点）側に出る部分を、O点を頂点とする2直線で挟み、この2直線と重なる時刻を読み取って、この建物によってO点が日影となる時間が求められる（図C）。

［松浦邦男］

日照調整

日照調整は、建物の形、方位、窓開口の向き、庇(ひさし)や日よけなどを、その建物の用途を考慮に入れて、夏季は日射遮蔽(しゃへい)、冬季は日照利用ができるよう年間を通じて総合的に計画すること。その方法は種々あり、建築群の配置計画や建物の平面計画、窓、開口および庇、日よけの詳細な計画、さらには窓ガラスの材料の選択まである。例を示せば、住宅団地において隣棟間隔を適正にとって冬至に全戸4ないし6時間日照を得ること、主要開口部をできるだけ南向きに近くとって、冬季に多く、夏季に少ない日射量とすること、さらにこの効果を増すよう南向き開口に庇を取り付けること、日射を遮蔽するとともに採光のために反射光を利用できるルーバーlouverやフィンfin（数枚の板で構成され、ルーバーほど数が多くないもの）を窓外に設置すること、また同様の効果をもつベネチアンブラインドVenetian blindや縦形ルーバーブラインドを室内に設備することなどがある。

［松浦邦男］

『石原舜介著『住環境における日照の評価とその基準　日照問題解決への考察』（1973・首都圏懇話会）』▽『日本建築学会編『日照の測定と検討』（1977・彰国社）』▽『田中授・柳瀬正敏著『これだけは知っておきたい日照計画の知識』（1985・鹿島出版会）』▽『好美清光・大倉忠夫・朝野哲朗著『日照・眺望・騒音の法律紛争――隣近所快適ライフへのアドバイス』（1999・有斐閣）』▽『松浦邦男著『エース建築環境工学1　日照・光・音』（2001・朝倉書店）』

[参照項目] | 採光 | 日照計 | 日照権 | 日よけ

日影曲線と日ざし曲線〔図A〕

立方体建物の日影図〔図B〕

日照図表〔図C〕
図は、ある建物によって観測点Oが日影となる時間を求める例（冬至における北緯35度地点）である。建物平面図（ABCD）と建物高さH＝25m（縮尺S＝1000）に対する日ざし曲線との交点でできる青色の部分を、O点を頂点とする2直線（一点鎖線）で挟み、その直線の時刻を読みとれば、その時間が建物によるO点の日影時間（図では14時10分～15時30分）となる。注：松浦邦男・高橋大弐著『エース建築環境工学I―日照・光・音―』（朝倉書店）による©Shogakukan">

日照図表〔図C〕

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