1

Introduction

1. External shades andscreens

summersunrise

summersunset

winter sunset

winternoon

summernoon

Adelaide HomesDesign Guide 3 - Shading

N

Protecting windows and walls from excessive solar gain in the summer can greatly reduceover-heating. Properly designed retractable or movable shades will provide this protectionwhile also allowing the sun's heat to access the home during cold winter days.

Homes are lit by the sun from differentangles and at various intensities dependingon the time of the day, the time of the year,and the home's orientation. While the sun'sradiation is most welcome in the coldwinter days, in the hot summer season thehome needs to defend itself from the heat.Shades provide efficient summer protectionand, at the same time, they allow solar heatto enter the home when needed.

In the morning and late afternoon, the sunis low in the sky and shines on the east orwest sides of the home. At noon, the sun isat its highest position in the sky and is duenorth, but the angle of the sun's rays ismuch lower and they are much weakerduring winter when we want them to enterthe home than during summer when theyshould be fended off.

Shades can be external, internal orintermediate. They can be fixed, rotating,sliding, folding, retracting, horizontal orvertical, manually driven, or motorized.They have different performances anddifferent impacts on home efficiency.

Overhangs

Well-designed overhangs can shadesouth-facing windows from the highsummer sun and allow the low winter sunto penetrate the home. They can be eavesof the roof, horizontal structural extensionsabove windows, or simple awnings.

The wall and roof insulation is the first lineof defense, preventing the massiveconstruction (brick or concrete) fromaccumulating too much heat in summer andhelping to hold the collected heat insideduring winter. The weakest points in thehome are glazed surfaces.

There are various types of glazing andshading that can modify a window'sperformance, and they should be chosen inaccordance with the window orientation.

2

Overhangs are not effective on east andwest facing windows where the sun shinesat low angles.

Sliding shutters

78°31°

window

shade

Trellises

An eave that protectsa north window fromthe high summer sunwill allow low-angledwinter sun to passthrough.

The width of a horizontalshade above a windowshould extend beyond thewindow's width.

Diffuse light

Only half of the radiation that arrivesat a window is direct radiation. Theother half arrives from diffuse andreflected sunlight. While overhangscan effectively protect from directsun, they still let 50% of heat inside.

A trellis is a verticalnet-like structurethat supportclimbing plants. Asan additional wall,they can shadewhole façades orjust particularwindows. They aregood for shadingeast- andwest-facingwindows.

Pergolas

Attached to a home, a pergola can shadethe whole façade. Though its horizontalsurface serves as a shading element, variousrollups (see below) or light curtains can beadded to make it efficient even in the lowmorning and evening sun.

External rollup shades

Made from clothmaterial, these can blocksunlight in variousamounts, depending onmaterial thickness andopacity. Easily movedand rolled up, they allowflexibility in adjusting thehome to seasonalconditions, but they canbe damaged in storms.

Shutters

Shutters can be wooden or metal,horizontally or vertically sliding or folding,and with or without insulation. Casting vividpatterns on a façade, they can contribute tothe home's aesthetics and attractiveness.

3

Folding shutters.

Folding shutters.

Opened louvres Closed louvres

Louvres

Louvres are verticalshading elementsplaced in front of awindow. Their fins canbe horizontal orvertical, and can befixed or adjustable tofollow the sun's path.They can either bepositioned parallel tothe sun's rays to let thegreatest amount ofheat inside, completelyclosed, or anything inbetween.

Perforated Screens

Perforated metal screens are typically madefrom aluminum, or galvanized or stainlesssteel. They can be perforated in geometricor more decorative patterns, adding depthor uniformity to a building.

Screens are ideal forwindows on all sidesas they reduce heatwhile providingenough light, a senseof closeness andintimacy, and naturalventilation. They comein various beautifulpatterns, making eachfaçade unique.

Landscaping

When leaves fall from trees in winter, theyallow direct solar radiation to reach thehome. On the other hand, in the hotsummer days dense treetops make aperfect natural shade.

2. Internal shades

4

Sun heat

Visible light

Internal shadesintercept solarradiation after ithas passedthrough awindow, whichis why they arenot as effectiveas externalshades.However, theyare the first tostop anycollected heatfrom escaping in winter.

To block unwanted solar heat that hasalready passed through the window, theshades should have a reflective surface onthe outer face to return as much sunlightas possible.

Adjustable shades

Shading systems can be designed to followthe sun's path rather than being fixed. Thiscan be done manually, or by automaticmotor-driven mechanisms that respond to apre-set schedule or to prevailing weatherconditions. This automation makes accessto hard-to-reach windows (such as thoseabove a bathtub or counter) unnecessaryand saves time for occupants by controllingall window shades at the same time.

Controllable shades can be programmedwith solar tracking based on the home'slatitude and longitude and the directions ofits façades.

Photovoltaic shades

Photovoltaic cells can beincorporated into glass louvres ofthe external sun shades, either onthe reverse side or laminatedbetween two glass sheets. Whilereducing the amount of sunlightentering, they can generateelectricity for the home.

A word about windows

One sheet of 3-4mm transparent glassadmits around 88% of solar radiation.Double-glazed windows contain 2 layers ofglass separated by an air gap and so willadmit around 80%. For good winterinsulation, it is recommended that the gapbetween two sheets be at least 12mm.

For the purpose of shading and limiting theamount of heat passing through thewindow, glass panes can be coated with athin transparent film with the ability toreflect the radiation. This only works in onedirection.

3. Recomended types of

5

shading in Adelaidevisiblelightinfrared

(heat)

infrared(heat)

inside inside

Summer sun at noon

Winter sun at noon

Reflective coating on the outer side of theglass pane will fend off the solar radiation,keeping the interior cool in the summer, butit will also prevent heat from entering thehome in winter, when it is needed most.

Low-E glass (low-emissivity glass) will blockradiant heat from passing through awindow, depending on which side it ispositioned. Low-E glass on the outer side ofa window will prevent overheating insummer, while on the inner side it will helpany collected heat to remain in the homeduring winter.

In Adelaide and the surrounding areas, it isrecommended to have low-E glass on theinternal side. Heat will be kept inside duringwinter, and during summer it can bereleased by opening windows.

Shading heat absorbers

Excessive heat can be brought into thehouse by any winds that have passed oversurfaces with a great ability to absorb solarheat. Directly sunlit asphalt drive ways,concrete, hard paved patios, sand or stonesurfaces will absorb sunlight and radiate itas heat. Whenever possible, these surfacesshould be shaded either by pergolas or bydense greenery.Home owners should also take into accountthat all smooth and reflective surfaces (suchas water or metal) can reflect the sun's rays.Any sunlight that initially reflected off thewindows may be bounced right backtowards them, so these surfaces should beplaced away from the house.

Colors

White surfaces reflect all visible light,while black surfaces absorb allvisible light. Colors can also have agreat impact on shading.Dark-colored surfaces on the groundcan absorb heat and then radiate it,but they will not reflect direct sunrays through windows. Flat roofsshould be painted white to helpreflect the sun's heat away.

North side

Short horizontal extensions on the northside can efficiently protect the wholefaçade from direct summer sun, allowinglow-angled winter sun to enter the home.When combined with movable shades suchas shutters, blinds or awnings, the northfaçade can be protected from reflected sunheat too.

6

ArchitecturalEnergy Efficient Homeswww.endurobuilders.com.au

eaves linetrellispergola

N

EW

pergola trellis

It is not recommended to have a porch onthe north side, as its depth will shade offthe sun in winter.

Tree shadow

Trees, with their dense leaves andconstant evapotranspiration, createareas of cooling shadow. In the winterseason when leaves have fallen, barebranches can still create a shadow thatdecreases heat gain on the northwindows by almost 30%. For thatreason, it is not advisable to uselandscaping as shading for the northwindows.

East and west side

Lit by the low-angled sun in the earlymorning and late afternoon, the east andwest sides of the home are defendable byvertical shades such as blinds, shutters,louvres or rollup shades. Though verandasor pergolas can provide some benefit, it isrecommended to install vertical shades onthe perimeter. Rollups, blinds or lightcurtains can make the whole space morecomfortable in summer.

East window

A ten-square-meter east-facing windowcan permit around 100,000 BTU toenter on a sunny summer day. That isthe equivalent of a home furnacerunning for a couple of hours, and willresult in overheating. The situation willbe even worse on the west-facingwindow where the heat will beamplified by the already-high afternoontemperatures.

Landscaping is an effective way of shadingeast and west sides of a home, whether bya group or rows of high trees or denseclimbing plants and vines on trellises orpergolas. Bear in mind that retractableshades on the roof of a pergola are moreadjustable in response to environmentchanges.

South side

As south-facing windows receive a verysmall amount of the summer heat, theyhave no need for sunshades. It is, however,advisable to install shutters with insulationfor protection from winds and heat loss inwinter.

CALL NOW TO DISCUSS YOURNEW HOME: 0438 909 920