lect. 8 sun path

8/10/2019 Lect. 8 sun path

1/13

Sun Path Diagram


2/13

Sun Path

Sun pathrefers to the apparent significantseasonal-and-hourly positional changes of the

sun (and length of daylight) as the Earth rotates,

and orbits around the sun.

The relative position of the sun is a major factor in

the heat gainof buildings and in the performance

of solar energysystems.
http://en.wikipedia.org/wiki/Sunhttp://en.wikipedia.org/wiki/Solar_gainhttp://en.wikipedia.org/wiki/Solar_energyhttp://en.wikipedia.org/wiki/Solar_energyhttp://en.wikipedia.org/wiki/Solar_gainhttp://en.wikipedia.org/wiki/Sun


3/13

Sun Path

Accurate location-specific knowledge of sun pathand climatic conditions is essential for

economic decisions about solar collectorarea,

orientation,

landscaping,

summer shading, and

the cost-effective use of solar trackers.
http://en.wikipedia.org/wiki/Solar_collectorhttp://en.wikipedia.org/wiki/Solar_trackerhttp://en.wikipedia.org/wiki/Solar_trackerhttp://en.wikipedia.org/wiki/Solar_collector


4/13

Importance of Sun Path By analysing the impact of the sun on a site, as well

as the buildings location, the spatial arrangement,orientation, window placement, daylight access andother design features, the designer can take fulladvantage of passive solar design features and

increase the energy efficiency and comfort of thebuilding. assessing a site for sun

sun paths

altitude and azimuth solar radiation

building material durability

shade

sites with limited solar gain

locating information


5/13

Assessing a site for sun

When assessing a site for sun, consider: the time during the day that the site receives

sunlight

the suns path at different times of the day and year

how the sites shape, slope and orientation affect

solar access

how obstructions such as adjacent buildings, trees

and landforms will impact on the site and the

potential design the owners lifestyle for example, when they want

to have sun or shade.


6/13

Sun paths

The simplest way to assess the passage of sunacross a site is by observation.

A site visit can also help identify site-specific

conditions such as the impact of a tree or a

ridgeline.

Sun path diagrams provide a broader overview of

sun on a site as they map the path of the sun

across the sky at different times during the day

throughout the year.

They can help establish the position of the sun

relative to a site and can be used to determine

the effect of shadows cast by buildings, trees andlandforms on and around the site.


7/13

Altitude and azimuth The position of the sun with respect to an observer is

commonly represented by two anglesaltitude and

azimuth.

Altitude is the angle of the suns rays compared with thehorizon. At sunrise and sunset, the altitude is zero, and

in the southern hemisphere, the maximum altitude of the

sun at any specific location occurs at solar noon on

21/22 December (longest days of the year).

Azimuth (sometimes known as bearing) is the direction

of the sun as shown on a compass. Sun bearings at

sunrise and sunset at different latitudes are available

from Land Information astronomical information.
http://www.linz.govt.nz/docs/hydro/nautical-info/astro/true-bearing-sr-ss.pdfhttp://www.linz.govt.nz/docs/hydro/nautical-info/astro/true-bearing-sr-ss.pdf


8/13

Solar radiation

Solar or ultraviolet (UV) radiation is the energyfrom the sun. The amount of solar radiation

available on a site depends on the latitude and

the sunlight hours received.


9/13

Building material durability

UV radiation affects the durability of manymaterials. Colours fade, plastic-based materials

may become brittle, timber moves and twists, and

expansion and contraction from heating and

cooling places stress on many materials, so theeffect of UV radiation over a buildings lifetime

must be considered.

Select materials with a higher UV index number

(when available) as they are more resistant to UVdegradation (such as fading).


10/13

Shade Shadeis often required in the summer, especially

in hot areas of our country. Obstructions on a sitemay block sunlight access at times when it isrequired.

When considering sunlight and building design,assess the impact of obstructions in the future aswell as the present. For example, a small tree onan adjacent site may grow into a large one thatblocks sun, a building may be erected on acurrently vacant site or an existing building maybe demolished and replaced by a larger one.

Alternatively, existing trees may be retained forsummer shade.
http://www.level.org.nz/passive-design/controlling-temperature/shade/http://www.level.org.nz/passive-design/controlling-temperature/shade/


11/13

Sites with limited solar access

South and west-facing, sloping sites have limitedsolar access.

It is difficult to utilise effective passive solar

design features on these sites, and they should

generally be avoided.

Where it is not possible to avoid or the site is an

otherwise desirable one (e.g. if it has excellent

views), careful consideration of design including

building location (e.g. locate as high as possible

on the site), orientation and use of

skylights/clerestories can maximise the benefits

of solar access.


12/13

Locating information information about sunshine hours and mean

temperatures is available from local meteorologicalagencies/Dept. (IMD).

Aerial photographs can provide information about thebuildings and vegetation on adjacent sites and mayprovide some limited information about the impact ofsun on a site.

This will depend on the age of the photo as in olderphotos, trees may have grown.

Aerial images can be obtained from local councils,Google Earth, Etc..

Sun impact information is also available:

by carrying out an on-site survey to establish levels ofadjacent buildings and site features.

obtaining plans of neighbouring buildings from localcouncils.
http://www.localgovt.co.nz/http://earth.google.com/http://earth.google.com/http://www.localgovt.co.nz/


13/13

Sun Path Diagram for Mumbai

lect. 8 sun path

Documents