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Special roof coatings are saving electricity and energy in hot climates and can help utilities reduce peak demand.

Thermal cooling coatings can help reduce the indoor temperatures of buildings to below ambient. ( not needing air conditioning )
Architects are using special coatings to cool off buildings in hot climates, but until recently there was little research on the measured cooling-energy savings of these roofs.

Over the past two years, however, researchers in Florida and California have examined the impact of these roof coatings on air-conditioning energy use in retrofits of monitored homes. Simulation analysis suggests that a specially coated roof can cut a building’s cooling load by 10-60%. The higher numbers are associated with uninsulated roofs.

Cooling coatings are increasingly being used for manufactured homes in the Southeast, based on homeowner reports that such coatings can reduce summer air conditioning costs. Until now, however, no investigation in a cooling-dominated climate examined the effect of coated roof on time-of-day air conditioning electrical demand in occupied residential buildings–important information for utilities where summertime peak demand is a concern.

One of the earliest whole-building studies that measured cooling-energy savings from cool roof coatings was performed by the Mississippi Power Company. The utility monitored two identical side-by-side single-story commercial office buildings after the roof of one had been covered with a cooling coating. Both existing buildings had R-11 roof insulation. The results of the experiment? Summertime air conditioning was reduced by 22% in the building with the reflective roof coating.

More recently, researchers at LBL measured very significant cooling-energy savings from applying cooling coatings to three buildings in central California . At one site, energy demand for space cooling was nearly eliminated. But regardless of the potential of cooling roof coatings in California, Florida’s higher humidity and nighttime temperatures make prospects for near elimination of space cooling energy use in that state very unlikely.

 

 

The Sno-Coat™ range is a range of advanced roof cooling paint that acts as a radiation barrier for buildings.

There are three versions of Sno-Coat™ to choose from, each with their own valuable properties to suit every customers needs.

The products in our range can reduce internal temperatures to below ambient, leading to significant cost savings on air conditioning and other electrical appliances such as fans, fridges and freezers.

Reducing electricity consumption not only saves money, but also contributes to environmental sustainability, aiding in the fight against global warming.

Depending on the building, air temperatures measured inside can drop by up to 15 degrees centigrade and temperatures of roof sheets or walls can drop by up to 35 degrees centigrade.

 

The Sno-Coat™ range is suitable for use on steel, IBR, Harveytile, cement fibre, asbestos, concrete and shingle roofs

Some examples of ideal uses for the Sno-Coat™ range are shopping centres, hotels, churches, farming warehouses, homes, factories, schools, office buildings and hospitals.

We recommend the use of the Sno-Coat™ range on any building that is in need of cooling and thermal shock protection. 

 

 

 

Typically payback periods vary between 2 to 5 years depending on the structure type and size. Factors taken into account to determine this are size of building, height of roof, roof material, ceiling, air conditioning, heating, electricity tariffs, climate.

 

 

SABS TESTS CONDUCTED AND RESULTS OBTAINED

Thermal Insulation Coating.
Test report 7222/ 2090038/v 76

Product was tested for:
Heat absorption of air inside treated and non-treated containers.
Adhesion of thermal coating.

Test methods:
Adhesion – requirements in accordance with SABS ISO 2409 : 1992
Two containers – one coated one non-coated.
Inside temperatures measured with thermocouple at 1 hour intervals
Between 11:00 and 15:00.

Test window:
12 April 2002

Results:
Adhesion – 100 % adhesion, no loss.
Inside Temp – Temp in coated container is always lower than uncoated by approx. 18%.
As ambient temp. drops air in coated container drops slower than uncoated container confirming insulating properties.

 

Sno-Coat™ is a wet in the can paint on coating with thermal insulating, rust preventing and other properties.

Can reduce air conditioning installation and running costs by up to 25%

 Reduces thermal shock by up to 50%

Increases rust onset and degradation time by up to 300%

Prolongs substrate life by up to 300%

Increases live carry capacity by at least 25% (Chicken house)

Decreases heat stress mortality by more than 90% (Chicken house)

Summer inside temperatures decrease by up to 30%

Roof substrate temperatures drop by up to 50%

Excellent waterproofing properties.

Aesthetically pleasing.

Table 1: Solar Reflectance Index (SRI) for Typical Roofing Materials

         Example SRI Values 

    for Generic Roofing

Solar

Reflectance

Infrared

Emittance

Temperature

Rise

Solar

Reflectance Index (SRI)

                      Gray EPDM

0.23

0.87

68F

21

      Gr            Gray Asphalt Shingle

0.22

0.91

67F

22

                     Unpainted Cement tile

0.25

0.9

65F

25

                     White Granular Surface

                      Bitumen

0.26

0.92

63F

28

                      Red Clay Tile

0.33

0.9

58F

36

                     Light Gravel on Built-Up Roof

0.34

0.9

57F

37

                    Aluminium

0.61

0.25

48F

56

                   White-Coated Gravel on built-up roof

0.65

0.9

28F

79

 

 

 

 

 

                   White EPDM

0.69

0.87

25F

84

                   White Cement Tile

0.73

0.9

21F

90

                   Sno-Coat – 1 Coat

0.8

0.91

14F

100

 

 

 

 

 

                   Sno-Coat 2 Coats

0.85

0.91

9F

107

Source: LBNL Cool Roofing Material Database. These value are for reference only and are not for use as substitutes for actual manufacturer data

 

An Initial Experiment

In the summer of 1991 we conducted a preliminary experiment in Merritt Island, Florida. Our first test building (Site #0) was a 1,800 ft2 detached single-family, single-story home of conventional concrete-block construction. The pitched roof faced north-south, with plywood decking covered by green/gray asphalt shingles.

The home’s attic was well insulated with approximately two inches of fiberglass covered by an additional six inches of cellulose insulation, yielding a thermal resistance of about R-25. Air infiltration from the attic area into the conditioned interior (a common problem due to duct leakage), had been largely eliminated in a previous audit and retrofit.

Beginning in May 1991, we submetred the home’s air conditioner while maintaining a constant thermostat setting of 79deg.F. We also recorded the underside roof deck, attic air, and living room temperatures.

When we applied the cooling coating on September 5 of that year, the roof’s reflectivity increased from 0.22 to 0.73.2 Spot measurements under full sun at midsummer had shown shingle surface temperatures of 160-170deg.F, prior to the roof treatment, compared to 110deg.F after we applied the coating. Analysis assuming an 81deg.F average summer temperature indicated that a cooling roof coating would reduce energy consumption by 10% (35 kWh versus 39 kWh per day).

Yet this test house probably understated the savings, since most existing Florida residences have fairly poor attic insulation and attic air frequently leaks into the conditioned interiors. Therefore, we obtained more “typical” residences for the detailed experiments we conducted the following year.

View a Full 5 house study for Sno-Coat™

 

Costs are in AUS$
Multiply by 19 for ZAR

Use a rule of thumb of about 600 Btu per square meter of floor area to be air conditioned

9000 Btu of cooling output equates to 2.64 Kw of cooling wattage which requires 1000 watts of electrical input which will cost about R0.75 cents per hour.

The above electrical consumption costs don`t take into account maintenance or initial installation costs which can increase the above savings by a factor of 3

1 Kg of air is about 850 liters in volume

The specific heat capacity of air is about 1 –  i.e it requires about 1 KJ to  heat 1 Kg of air by 1 deg.C
1 KJ is approx. .95 BTU

Air conditioning costs calculator

Air conditionng electric running costs

 http://michaelbluejay.com/electricity/cooling.html

 

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Cosmo-Dec Everlasting Coatings originated in 1991, with a single product – Therma-Masta™.

Knowledge gained from manufacturing this complex and unique product allowed us to formulate new and innovative products such as Fire-Guard™, Aqua-Mite™, Aqua-Therm™, Clean-Air, etc. for specialty applications.

To-day, 3 decades on we manufacture more than 80 different types of construction chemicals out of our factory in Pretoria, Gauteng.

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coatings for metal

A frequent question concerns payback of cool roofing. There are several angles on the answer, but generally speaking, cooling coatings are most appropriate when one is re-roofing. If the coating is applied to an existing roof that is in otherwise pristine condition, the cost equation is straightforward. The typical coverage of a cooling coating is 25 ft2 per gallon,(0,6 sq. meters per liter) (Sno-Coat® gives 6 square meters per liter reducing the application cost factor by a factor of 10!!!!

This makes a massive difference to these calculations and results) based on an application of two coats to a target thickness of 40 mils.

Cost for the material from vendors varies by 50% or more but averages about $60 per 5-gallon container when purchased in quantity. It is important to keep in mind that roof area is generally considered greater than building floor area, particularly with a steep roof pitch. For instance, a typical 1,500 ft2 home may have 2,200 ft2 of roof to be covered. The application then requires 90 gallons of coating material for a materials cost of approximately $1,100.

The cost of labor for installation depends greatly on the roof surface, on whether the coating is to be rolled on or sprayed, and on labor rates. A typical labor cost might be approximately 50cents per ft2 for the required two applications. Thus the overall application would cost about $1 per ft2, or approximately $2,200 for a typical home. With annual energy savings in Florida of $35-$140, the payback times are long–usually lasting longer than the roof itself.(With the exception of Sno-Coat®)

A completely different scenario emerges if the home is soon in need of re-roofing, however. Here the roof coating (which essentially creates a new weatherproof surface) might be seen as a way of extending the life of the roof by 5 to 10 years at half of the cost of re-roofing. The energy savings then become a side benefit.

For new homes, the situation is even more interesting. Here it is often possible to choose roofing types–such as metal roofing, tile roofing, or metal or ceramic shingles–that can be specified in a reflective white at significant additional cost.

Unfortunately, no truly reflective asphalt roofing shingles yet exist for the residential market, but this situation may change as researchers work with the roofing industry to develop new products and spread the word about the energy benefits to help create a market for the materials. For commercial buildings, a variety of reflective roofing materials are already available: Hypalon, white EPDM, and PVC single-ply membranes.

Once such products are widely available for the residential market, the economics may be significantly altered as the cost of reflective roofing becomes inconsequential.

Notes

1. Reflectivity or albedo is the hemispherical reflectivity integrated over a particular wavelength band of the electromagnetic spectrum. For the purposes of this article, the terms reflectivity and albedo are used interchangeably and refer to the wavelengths encompassing the range of solar irradiance from 0.28 to 2.8 microns.

2. Surface solar reflectivity is measured using a precision spectral pyranometer with the device alternately faced upward towards the sun and downward towards the roof to determine the ratio of incident to reflected solar radiation.

 

Temperatures after using Sno-Coat™

Below are tables that show the temperature differences between roofs with and without Sno-Coat™

temperatures are in deg. F. Attic air means ceiling void air.

Temperatures are in deg. F. Here the roof surface temperature reaches 37 deg. C. In South Africa this can reach
to 65 deg. C ( 149 deg. F) This is where Sno-Coat truly comes into it`s own resulting in impressive cost savings.
Estimated to be R1,50 per deg. temp. difference per hour per 100 square meters of air-conditioned space.
Based on R1,56 per kwh. For a 60,000 square meter air-conditioned shopping centre at a average temp drop of 5 deg. C
this equates to a saving of About R5,000-00 per hour.
Over a 5 year period, savings amount to R330-00 per square meter, about 10 times the cost of the original coating contract.

The above temperatures are in deg. F (Average about 74,5) this relates to only 23,61 deg. Celsius. Yet at these temperatures 
only slightly above room temperature , there are huge electrical savings in air conditioning and appliance
electrical consumption as seen above.

In typical South African conditions where temperatures indoors frequently
reach over 30 deg. C, the electrical savings are massive. Bearing in mind that the higher the ambient temperatures the more effective Sno-Coat™ becomes.

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