Horizontal shading is effective for excluding light to enter the houseas the shade prevents the light from the sun entering the house. This is truewhen the sun is above the actual shading. This happens during the spring andsummer seasons as shown by the results of the experiment as the shade alwayscaused 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 resultas the sun was below the shade.Horizontal shading is needed to ensure that throughoutthe year a balance of solar gain and solar exclusion is achieved. Southernfacing facades can use a fixed shading method to exclude the sun most of thetime. During the winter the sun is lower therefore would penetrate the buildingbut wouldn’t be a problem in terms of heat gain.
For Eastern and Westernfacades wouldn’t benefit from a fixed shading method so would be more suitableto use a movable shading system. This would be needed because the altitude ofthe sun is much lower. (Coltinfo.
co.uk, n.d.)Solar gain can also be beneficial as the sun can heat upthe building and provide natural light. A passive building design can be usedto maximise heat gain. An example of a design that allows the blockage of thesummer sun but allows the gain of the winter sun is a brise soleil which is acommon item used to achieve horizontal shading.
(Designingbuildings.co.uk,2017)From the results we can see that shading is optimal forthe months where the sun is higher than the shade and not when the sun iscloser to the horizon, when it is lower than the shade. This means horizontal shadingis useful in the UK as solar gain is common which can be excluded easily. Anegative of using a horizontal shading method would be the aesthetic appearancewhen used on the building as it would have to be extended to exclude the lowerwinter sun.
View restriction also can occur when looking out of the opening asthe horizontal shading blocks the view looking above. To achieve optimum exclusion of solar gains in the summer the orientationof the building needs to be well thought out as it is one of the main ways toexclude solar gain in the summer. To do this a site analysis is needed.
Thiscan be used to determine factors which can affect solar gain such as theposition of the sun throughout the year and the topographical features whichcould optimise or worsen performance of the building. (http://www.greenspec.co.
uk,n.d.) During the summer, solargains in a building occurs on East and West facing walls as seen from theresults. The highest amount of solar gains occurred at 0800 and 1600. With theshade the amount of solar gain was reduced considerably. This means we can usea shade on East and West facing walls to reduce solar gains in summer. Thiswouldn’t affect the solar gains in the winter as the sun is lower predominatelylower than the shade therefore the results only lower a small amount.
Using anorientation for passive heating would allow the exclusion of solar gains in thesummer but allows sunlight to enter during the winter. (Brinkley, 2013) The building may find benefit from neighbouring buildings which can blockthe East and West sun. The buildings on the East would block the morning sunwhereas the buildings on the West would block the evening sun. Having abuilding either side allows the least amount of solar gain overall but if onlyone side can be blocked from the sun, it should be the East side as the morningsun 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 excludesolar gains in the summer is by having openings mainly on the north facingfaçade as the sun rises in the East and sets in the West. Having south facingopenings on a south facing façade would maximise solar gain, so not having anywould lead to the exclusion of the main source of solar gain. Passive Solar Design isachieved with the sun in mind to ensure that the building does not overheat orheat at all. Factors such as the suns path, how much heat the building willneed and the solar strength are all considered to ensure maximum optimisation (Roaf, Fuentes and Thomas,2005). Optimisation for buildings in the winterwould mean the building would take advantage of the low sun path. This can bedone through passive solar design and strategic solar design.
Southern facing windows would be used to absorb solar energyduring the winter. This would mean that during the summer there would also besolar gain but this can be prevented by using shading or overhang as the sun isat a higher latitude then that of the winter sun, where the winter sun will notbe affected by the overhang or shading. Shading would be achieved by usingtrees in the surrounding environment to the buildings advantage. Deciduoustrees 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 buildingand cause solar gain. It should be noted that the trees should be placed in away to ensure that the low sun penetrates the tree and it is close enough tothe building to block the higher summer sun. To avoid major effects ion thesummer sun, only a few trees should be planted as the sun will be able tofilter through. (http://www.
greenspec.co.uk,n.d.
) Windows can be used to takeadvantage of the low sun during the winter. Using the design shown on (3) we can see that the winter sun is lowenough for the building to absorb solar gain through the window. The summer sunis higher and so the building will remain cooler. This is a great way tomaintain the aesthetic appearance of the building and achieve solar gain in thewinter. (Greenpassivesolar.com,n.d.
) Determining the size of the window or openings can be optimised for thewinter sun using a Stereographic Sun Path diagram. From this we can see that an openingfrom 140 degrees to 220 degrees will gain the most solar energy during thewinter from 09:00 – 15:00. This opening will also gain the summers sun withinthe same time but not before or after the times stated. (Stereographic SunpathDiagram, Latitude 53N, 2011) Directgain 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 highlevel which will absorb the solar energy that the building is exposed to. Thebuilding acts as a form of thermal storage. The energy is slowly released at nightwhen there is no solar gain.
(Roaf, Fuentes and Thomas, 2005). Using this system is importantduring the winter when there is less time for the building to absorb solarenergy. Solar gain would want to be achieved in winter due to the lowertemperatures and not in the winter as this would cause overheating in the buildingby the lower sun. The winter sun is lower than the summer sun and a directsystem can be made intelligently to maximise solar gain in winter using thesystem and other methods to block the summer sun. Using a typical passivesystem as shown in (3), with an overhang maximises winter solar gains andblocks the summer sun from entering the building to prevent overheating.
Direct solar gain can also be achieved byusing mass walls and trombe walls which are fairly common. Both revolve aroundusing a form of glazing and a large thick masonry wall that is painted a darkcolour which absorbs heat. The heat passes through the glazing and is absorbedinto the wall through convective heat transfer. The heat is released at nightto warm the inside of the building. (Roaf, Fuentes and Thomas, 2005).
