Heliodon Discussion

Horizontal shading is effective for excluding light to enter the house
as the shade prevents the light from the sun entering the house. This is true
when the sun is above the actual shading. This happens during the spring and
summer seasons as shown by the results of the experiment as the shade always
caused less area of the room to be lit compared to when there is no shade.
During winter, the shade had no effect on the solar gain apart from one result
as the sun was below the shade.

Horizontal shading is needed to ensure that throughout
the year a balance of solar gain and solar exclusion is achieved. Southern
facing facades can use a fixed shading method to exclude the sun most of the
time. During the winter the sun is lower therefore would penetrate the building
but wouldn’t be a problem in terms of heat gain. For Eastern and Western
facades wouldn’t benefit from a fixed shading method so would be more suitable
to use a movable shading system. This would be needed because the altitude of
the sun is much lower. (Coltinfo.co.uk, n.d.)

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Solar gain can also be beneficial as the sun can heat up
the building and provide natural light. A passive building design can be used
to maximise heat gain. An example of a design that allows the blockage of the
summer sun but allows the gain of the winter sun is a brise soleil which is a
common item used to achieve horizontal shading. (Designingbuildings.co.uk,
2017)

From the results we can see that shading is optimal for
the months where the sun is higher than the shade and not when the sun is
closer to the horizon, when it is lower than the shade. This means horizontal shading
is useful in the UK as solar gain is common which can be excluded easily. A
negative of using a horizontal shading method would be the aesthetic appearance
when used on the building as it would have to be extended to exclude the lower
winter sun. View restriction also can occur when looking out of the opening as
the horizontal shading blocks the view looking above. To achieve optimum exclusion of solar gains in the summer the orientation
of the building needs to be well thought out as it is one of the main ways to
exclude solar gain in the summer. To do this a site analysis is needed. This
can be used to determine factors which can affect solar gain such as the
position of the sun throughout the year and the topographical features which
could optimise or worsen performance of the building. (http://www.greenspec.co.uk,
n.d.) During the summer, solar
gains in a building occurs on East and West facing walls as seen from the
results. The highest amount of solar gains occurred at 0800 and 1600. With the
shade the amount of solar gain was reduced considerably. This means we can use
a shade on East and West facing walls to reduce solar gains in summer. This
wouldn’t affect the solar gains in the winter as the sun is lower predominately
lower than the shade therefore the results only lower a small amount. Using an
orientation for passive heating would allow the exclusion of solar gains in the
summer but allows sunlight to enter during the winter. (Brinkley, 2013) The building may find benefit from neighbouring buildings which can block
the East and West sun. The buildings on the East would block the morning sun
whereas the buildings on the West would block the evening sun. Having a
building either side allows the least amount of solar gain overall but if only
one side can be blocked from the sun, it should be the East side as the morning
sun could cause solar gain to remain in the building throughout the day. (http://www.greenspec.co.uk,
n.d.)  

A simple method that can be used to optimise the orientation to exclude
solar gains in the summer is by having openings mainly on the north facing
façade as the sun rises in the East and sets in the West. Having south facing
openings on a south facing façade would maximise solar gain, so not having any
would lead to the exclusion of the main source of solar gain. Passive Solar Design is
achieved with the sun in mind to ensure that the building does not overheat or
heat at all. Factors such as the suns path, how much heat the building will
need and the solar strength are all considered to ensure maximum optimisation (Roaf, Fuentes and Thomas,
2005).  Optimisation for buildings in the winter
would mean the building would take advantage of the low sun path. This can be
done through passive solar design and strategic solar design. Southern facing windows would be used to absorb solar energy
during the winter. This would mean that during the summer there would also be
solar gain but this can be prevented by using shading or overhang as the sun is
at a higher latitude then that of the winter sun, where the winter sun will not
be affected by the overhang or shading. Shading would be achieved by using
trees in the surrounding environment to the buildings advantage. Deciduous
trees will block out the sun in the winter as the leaves will block solar gain.
In the winter, there will be no leaves and so the sun will reach the building
and cause solar gain. It should be noted that the trees should be placed in a
way to ensure that the low sun penetrates the tree and it is close enough to
the building to block the higher summer sun. To avoid major effects ion the
summer sun, only a few trees should be planted as the sun will be able to
filter through. (http://www.greenspec.co.uk,
n.d.) Windows can be used to take
advantage of the low sun during the winter. 
Using the design shown on (3) we can see that the winter sun is low
enough for the building to absorb solar gain through the window. The summer sun
is higher and so the building will remain cooler. This is a great way to
maintain the aesthetic appearance of the building and achieve solar gain in the
winter. (Greenpassivesolar.com,
n.d.) Determining the size of the window or openings can be optimised for the
winter sun using a Stereographic Sun Path diagram. From this we can see that an opening
from 140 degrees to 220 degrees will gain the most solar energy during the
winter from 09:00 – 15:00. This opening will also gain the summers sun within
the same time but not before or after the times stated. (Stereographic Sunpath
Diagram, Latitude 53N, 2011) 

Direct
gain systems are commonly used as a form of passive solar design. The roof,
walls and floors in the building can be designed to remain insulated at a high
level which will absorb the solar energy that the building is exposed to. The
building acts as a form of thermal storage. The energy is slowly released at night
when there is no solar gain. (Roaf, Fuentes and Thomas, 2005).  Using this system is important
during the winter when there is less time for the building to absorb solar
energy. Solar gain would want to be achieved in winter due to the lower
temperatures and not in the winter as this would cause overheating in the building
by the lower sun. The winter sun is lower than the summer sun and a direct
system can be made intelligently to maximise solar gain in winter using the
system and other methods to block the summer sun. Using a typical passive
system as shown in (3), with an overhang maximises winter solar gains and
blocks the summer sun from entering the building to prevent overheating.  Direct solar gain can also be achieved by
using mass walls and trombe walls which are fairly common. Both revolve around
using a form of glazing and a large thick masonry wall that is painted a dark
colour which absorbs heat. The heat passes through the glazing and is absorbed
into the wall through convective heat transfer. The heat is released at night
to warm the inside of the building. (Roaf, Fuentes and Thomas, 2005).  

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