Roof

A space’s roof can play a big role on PD. Several el- ements of roof natural ventilation have been used to provide adequate PV. These elements are part of archi- tecture which are distinguished from other ventilation concepts. Also, the cost of implementation is simple without affecting ventilation performance. Many ap- proaches have been adopted to provide PV through harnessing the PV and PL into the building. Most of these approaches were results of traditional architecture.

A trickle advice is one of devices of PV which has been used to minimise energy consumption. This technique has been used commonly in Europe. Trickle dvice can be in the roof in some cases to accurately control the air inlet and outlet, as shown in Figure 4:32. Usually, it is interoperable with the skylight to provide PV to the space; and for the skylight to oper-

ate safely the gap around the complete perimeter should be between 5-10mm (The National Domelight Company, 2009).

At the same time, the roof should be well-insulated in order to decrease the temperature loss from the interior building. In addition to that, the accuracy of shape and slope angle can help to remove water when it is raining. Considering the orientation of the roof also helps to optimise ventilation.

Wind scope is one of PDS. Wind scoops and wind cowls are synonymous with each other. Wind cowl can be defined as a general name for roof structure ventilation (Khan et al, 2008). Wind scoop is a device which collects outside air inside a space,

Figure 4:30: Trickle advice (The National Domelight Company, 2009)

Figure 4:31: The different level of scoop in Pakistan (McDonough, 2002).

which is the reverse function of wind towers. In this case, the building’s roof is an essential part of the building in which to install this system. Sometimes it can be installed in the landscape to provide the air into the building through embedded ducts (Kleiven, 2003). There are many case studies which have applied wind scoops such as houses in Hyderabad in Pakistan from 500 years ago (see Figures 4:33 and 4:34). The process was to catch the air pressure and direct it to the space. The wind scoop’s location is above the roof of the housing because it needed to be higher to accurately catch the re- quired wind speeds. Wind scoops can also be provided in another way: through a tube in the ground, which will supply the place (McDonough, 2002).

Figure 4:32: The widespread use of wind scoop to the same direction (McDonough, 2002) BIM (2011) point out the importance of the location of roof venti-

lators, skylight and vent shafts. Some of these elements are dual function (interoperable) and can be used for natural illumination and ventilation, such as skylight, clerestory and light tube. These elements should be focused on in terms of the security and accura- cy of their installation. A skylight is defined as a horizontal open- ing on the roof to provide lighting (Baker, 1993). Garcia et al (2002) claimed that there are benefits from opening a skylight to provide ventilation to the space. This means that this element (sky- light) can perform two functions, so it is interoperable. This is the same as the situation with duct ventilation which combines heating and ventilation in the same element. The main function of a clere- story is to allow the sunlight to light the space. Also, it can be used to provide ventilation to the space, which meansinteroperability of two functions of PD. Garcia et al (2002) confirmed that a clerestory allows ventilation to enter into the space. They are defined as the tilted or vertical openings and their place is on the roof of a build- ing, as shown in Figure 4:35. Usually, a clerestory is vertical or a tilted opening from the roof. Its function is similar to the roof

Figure 4:33: Clerestory (American Institute of Architects, 2009).

Figure 4:34: Clerestory and roof monitor (Garcia-Hansen et al, 2002)

monitor’s function in terms of illuminating the space as well as ventilation and heating (Garcia- Hansen et al, 2002), as presented in Figure 4:36. In gen-

eral, a saw tooth is used to light the space through the roof. In some cases it can be used as ventilation when it involves window opening. Kacira et al (1998) concluded that the ventilation of the building can enter through the windward side openings and cross the greenhouse from one side to another. In case the windward openings are

closed, the saw tooth can vent the space through its opening and exit through the same opening. Kaci- ra et al (1998) confirm that the best accuracy of efficiency function is in the first case when the windward side is opening. In the second case, the average amount of ventilation can decrease from 80% to 90%, as shown in Figure 4:37.

This system is placed on the roof and includes the sloping roof and vertical glass to allow natural light to enter into the space to optimise its function. Then the vertical glass window needs to be shad- ed: usually the sloop roof extends to shade it. The extension is used as

an overhang against direct sun (Natural Frequency, 2011).

A skylight can be defined as an opening area which is placed on a horizontal place or slope roof, as per Baker et al (1993); and this is illus- trated in Figure 4:38. Its main function is to provide PL, but it has another function which is ventilation in some situations, where it needs to be movable. The problem is in summer it needs to adapt some shad- ing devices to mitigate the sunshine. PV and PL techniques are usually developed separately; however, in some techniques they are interoper-

able in order to achieve demands of both lighting and ventilation. Skylight and sun pipe are good in- stances. This element can be transparent in order to allow PL into spaces; especially those previously unreached by PL. Bouchet and Fontoynont (1996) claimed that there is interoperability between EU feelings and PL as well as the fact that PV is able to change EU feelings. This means PL and PV can affect the EUs’ performance.

There are many systems and approaches which can be classified as sun pipe. Kim and Gon (2010) divided the sun pipe system into different categories, as shown in Table 4-5. Figure 4:39 shows the Figure 4:37: Sun pipe combi-

nation system (RH and Construction, 2009).

Figure 4:35: Saw tooth air movment (Kacira et al, 1998)

Figure 4:36: Skylight (Garcia-Hansen et al, 2002)

sun vent pipe which involves two pipes as follows. The channel is used to provide air flow to the space and out of the space. The entrance is used to allow an amount of sun to enter the space and the top of the pipe is covered by a transparent dome where the pipe surface is covered by material film (Oliveira, 2001). Seaside Primary School in Lancing, West Sussex is a good example of this type of combination, as presented in Figure 4:40 (RH and Con-

struction, 2009). Bansal et al (1993) confirmed that the solar chimney plays a big role in providing air ventilation. They also identified the value of air flows by three factors as follows: geometry of collec- tor, cross-section of the duct, and the extent of the performance parameters of the air collectors.

Roof overhang is one of the strategies which can be part of ventilation and PL. Ahsan (2009) indi- cated that roof overhang can enhance indoor air quality through providing shading and changing the air flow direction. In addition to that, its size can be enhanced to protect the walls from radiation as well as the surface openings. It has been confirmed that it needs to be made using lightweight materi- als with high reflectivity. PV panels are widely used to store solar access (ARUP, 2012). The Department of Education, Northern Ireland (DENI) and corp creator (1998) concentrated on the im- portance of evaluating the security of the roof lighting and selection of glazing to avoid overheating.

BIM (2011) clarified that the roof glazing should be very well insulated to mitigate heat loss. There are several methods of PV such as roof garden, roof pond and thermal insulation. The perfor- mance of the trombe wall is lower than that of the solar roof design in hot climates where the temperature is very high. In a simple sense, this is because the roof solar collector can optimise higher air temperature (Awbi, 1998). In terms of the concrete slab, it can be added to the insulation layer by taking into account the gap between the two. This can affect the thermal performance in the summer time. The roof insulation can help to mitigate the harsh solar heat (Dimoudi, Lykoudis and Androut- sopoulos, 2006).

The heating system for both air and water is installed to suit EU needs as a source for both heating and cooling systems (Chan, Riffat and Zhu, 2010). This reflects the importance of the EU at the de- sign stage and how they must be considered and taken into account as well as other functions. Roof monitors and clerestoreys have the same function. Roof monitors can be defined as a high portion of the roof which is open from north and south directions. The main function is to allow lighting to enter into the low level of the space in order to increase the luminance level, plus allowing PV through the open window (Garcia-Hansen et al, 2002). Using a ventilated double roof is one of the roof solutions for providing optimum PV. This should be accurate to help the air enter between the different layers of the roof without entering the space, as shown in Figure 4:41 (Gut and Ackerknecht, 1993).

Figure 4:38 : Seaside Primary School in Lancing, West Sussex (RH

Type No Sub-Type Description Photo Natu ral v en tilatio n an d d ay lig h t- in g

1 Sun Catcher This can provide day lighting and ventila- tion from different directions. The technical details can provide stack venti- lation and natural buoyancy.

2 Movement sun catcher

This technical approach compacts both sun catcher systems. It is preferable to apply it in small spaces.

3 Solar This technique combines three systems together: fluorescent light, sun pipe and natural ventilation. It is often used for utility area and bathrooms.

Day

lig

h

tin

g 1 Sun pipe There is no limit in length or number of bends. This technique is 98% reflective tube. Day lig h tin g ( B rig h ten up)

1 Solatube 160 DS The tube length is six metres and the light coverage area is between 14 and 19 m2.

2 Solatube 190 DS The tube length is 9 metres and the light coverage area is between 23 and 28 m2.

Day lig h tin g (So la- Ma ster )

1 Solatube 21-C The round tube is converted to a square diffuser on installation.

2 Solatube 21-O This technique is distinguished by not having a finished ceiling and by a less obtrusive roof opening.

Day lig h tin g (So laM aster

) 1 Rigid This system differs from the others by its _{bright, white light and flexibility.}

2 Flexible This system is similar to the Rigid one but it is quick and easy to install.

Day lig h tin g (R ec tan g le sh ap e)

1 Rigid Its length is around 1950mm and 4mm tough glass is used for the top dome. 2 Flexible Its length is around 1950mm and 4mm

tough glass is used for the top dome.

The case study of Hyderabad looks at a traditional system. Wind scoops have been installed in the shopping mail (Blue Water shopping centre) in Kent in the UK using modern ma- terials (aluminium as well as transparent to provide lighting), as presented in Figure 4:42. The main function is to direct air

to the space to create high efficiency in the mall (McDonough, 2002). Elmualim (2006) pointed out that the design of wind scoops in the mall was

based on the traditional approach used in Kent houses, as shown in Figure 4:43. This approach was developed until it became the architectural standard for buildings around Kent. The designers must ac- curately predict the height of windscoops to provide the correct amount of air which cannot be provided

through the window. Also, the scoops should all be on the same side of the building, and all directed at the prevailing wind.

Qatar University has included this technique to combat the harsh climate in Qatar. The designers chose this method in order to add another value to the building, which is aesthetic value, as shown in Figure 4:44 (Sayigh et al, 1998). The spread and conver- gence of wind catchers give the impression that its role is to guard from the harsh conditions (Al-Shaali, 2002). The designer uses the wind catcher to provide PV into the university spaces. Also, other aspects such as courtyards were included. All of these aspects have

led to high levels of efficiency because they are installed in the suitable positions. Opening the wind catchers from each side enables accurate provision of wind into the building. Duct ventilation is in- stalled in the roofs to accurately provide air ventilation; usually it is interoperable between the roof and the centre of the building or space. On the top of the duct a

fan is installed to draw air into the building (Odeh, 2006). The duct was installed to achieve two functions which are fluid transport and heat recovery. In some cases, the chimney can be used based on the method of its installation (Manz et al, 2000). For example, when the warm air rises in the place it will be replaced

by cool air through this technique. Usually, it is used in bathrooms and kitchens (Greenspec, 2010), as shown in Figure 4:45.

Some roofs or their elements can be suitable for one level or for many in case the building has courtyards or lobbies. In other cases, roofs and their elements cannot help other storeys or space. For

Figure 4:39: Double roof ventilation (Gut and Ackerknecht, 1993)

Figure 4:41: Traditional wind scope (Elmualim, 2006)

Figure 4:40: The spread of windscoops on the roof of shopping mail on Kent, UK (McDonough, 2002)

Figure 4:42: Section explaining wind movement through the build-

this reason, there are several measurements that should be accurate and suitable when designing the building roof. The angle and shape of the roof should be suitable and accurate for optimum PV and PH. Both the United States Department of Energy (2000) and Ahsan (2009) referred to the importance of the roof angle and its shape; how it can help to admit lighting to the interior building. The Faculty of Design building of Newcastle University used a saw toothed roof to provide optimum PL (Prasad and Fox, 1996), as shown in Figure 4:46. Roof angles can be effective in PV, especially with regard to accurate orientation to the pre- vailing wind. Biwole et al

(2008) investigated the impact of angle of slope on the degree of temperature and the air movements on the channel exits. They found that the temperature decreases and the air velocity increases when the angle of the roof rises. In terms of PV, Susanti et al (2008) confirm that increased roof slope can affect the accuracy of the PV which means decreasing the degree of temperature.

As can be seen from the discussion above, the sloping surface is very important in the provision of PV and PH. For this reason, it can be said that accuracy of the roof angle must be taken into account during the design process to see if it is possible to apply and ensure that it complies with local regulations.

Code End User factors References

AD1 Use roof elements for stack effect venti- lation

The National Domelight Company (2009), Khan et al (2008), Kleiven( 2003), McDonough (2002)

AD2 Use skylight, light tube and clerestory for natural illumination

BIM (2011), Baker (1993), Garcia et al (2002), Kacira et al (1998), (Natural Frequency, 2011), Baker et al (1993), Bouchet and Fontoynont (1996), Kim and Gon (2010), Oliveira (2001), RH and Construction (2009), Bansal et al (1993), Ahsan (2009), ARUP (2012), De- partment of Education, Northern Ireland (DENI), corp creator (1998), BIM (2011)

AD3 Use solar roof collectors on the south- oriented surfaces

Awbi (1998), Dimoudi, Lykoudis and Androutsopoulos (2006), Chan, Riffat and Zhu (2010), Garcia-Hansen et al (2002).

AD4 Use double roof and wall construction for ventilation within envelope

Gut and Ackerknecht (1993) AD5 Use ventilated roof to lower summer

gains through roof

McDonough (2002), Elmualim (2006), Sayigh et al (1998), Al-Shaali (2002), Odeh (2006), Manz et al (2000), Greenspec (2010)

AD6 Use of an appropriate shape and angle of the roof for optimum ventilation and thermal comfort

United States Department of Energy (2000), Ahsan (2009), Prasad and Fox (1996), Biwole et al (2008), Susanti et al (2008)

Table 4-6: End user Factors passive design functionality: Roof end user factors

Figure 4:43: Duct ventilation (Odeh, 2006 and Greenspec,

2010).

Figure 4:44: Saw tooth roof of The Design Faculty building of New- castle University (Prasad and Fox,