ENERGY EFFICIENCY ADDENDUM
Cool roofs key in sustainable and affordable homes in South African
By Denise Lundall , project officer , Energy Efficiency Cool Surfaces at SANEDI
Energy efficiency and building materials are high on the list in any conversation about affordable housing solutions . This is because when it comes to constructing a building , capital expenditure and operational expenditure are vital considerations . There ’ s no point using low-cost materials if it will lead to high-cost maintenance .
With climate change set to see African temperatures
on the rise , prominent considerations when looking at building an affordable house in South Africa include cooling and ventilation ; and energy efficient methods of achieving this . While it is difficult to think of this issue in the dead of winter , a common challenge in our country is not the heating of our buildings for a few months , but the cooling of these buildings for most of the year . Essentially , the question is : How cool can we get this house without using electrical technology ?
The answer most often lies in proper insulation , and there are building standards which necessitate this . A well-insulated house is very energy efficient and will need very little additional heating and cooling . Furthermore , insulation amounts to a minimal portion of a building ’ s construction cost and requires minimal to no insulation .
However , considering the South African context , there are some problems with relying on insulation alone for cooling our homes . A simple solution lies in cool roofing technology – a passive cooling method which involves coating the roof of a building with a heat-reflective and highly durable substrate . Use of this energy efficient material can help overcome three challenges presented by relying on insulation alone . Insulation is most effective at retaining heat even though it has historically been widely used for both heating and cooling . Cool coatings perform at a magnitude of three times better than insulation for a fraction of the cooling cost . Return on investment for insulation to achieve the same quality of cooling as a cool coat membrane does takes 17 to 19 years and would require three to four times the regulation insulation thickness to achieve . Cool coatings cannot insulate against cold .
Firstly , because much of the required insulation in a house lies in the ceiling , it often goes unchecked with little enforcement of the required building standards related to insulation . This leads to losses on energy efficiency , colder homes in winter and hotter homes in summer .
Secondly , many of our citizens can hardly afford a house , let alone an insulated house . Think of the informal settlements across the country where the norm is corrugated iron . These homes are extremely hot , often uninhabitable in the peak of the day . These can be cooled inexpensively with cool coatings .
Lastly , Africa is hot . While cool roofing technology doesn ’ t replace insulation , it can certainly aid to cooling homes even more . There is nothing to lose when deciding to coat your roof with this membrane . Studies have proved that insulation and cool roofs perform better together and are not in competition .
FINFORUM
THE COOL ROOFING REVOLUTION FOR AFFORDABLE HOUSING
Energy efficiency should be at the front and centre of any affordability strategy in this era of economic depression . Here , I am referring to the efficiency of materials and not energy efficient appliances . On an individual building scale , cool surfaces improve the thermal comfort of occupants in buildings without mechanical air-conditioning . Even better , it substantially reduces the cost of building maintenance as it is waterproof , fire retardant , inexpensive , and low-tech .
The cool membrane itself is relatively easy to make and quick to deploy . It essentially involves mixing your baseline material ( water-based paint ) with titanium dioxide – commonly used as the UV filtering ingredient in sunscreen . Titanium dioxide – one of the additives of the final blend – is a great material because it is non-toxic , odourless , and absorbent . Other additives allow the pigment to even disperse , allow for waterproofing , fireretardation and dust-resistance . Applied to surfaces , it provides brightness , hardness , acid resistance , and UV protection – properties which lend it perfectly to applications for cool roofing . The coating has superb longevity and can last up to 25 years depending on the quality of the additives .
The South African National Energy Development Institute ( SANEDI ) is encouraging South Africans to manufacture cool coatings for roofs , walls and roads , establishing new industries and job opportunities . Furthermore , the institute is one of ten global teams awarded a USD100 000 grant by the Million Cool Roofs Challenge to deploy this technology in their country . Rollout has begun , with substantial cooling achieved in many informal settlements around South Africa . However , this material is by no means limited to rural shacks – any home will reap efficiency and economic rewards by implementing cool roofing .
The important insulation in a house lies in the ceiling .
www . saaffordablehousing . co . za NOVEMBER - DECEMBER 2020 11