Cool Homes: White Roofs and the need for solar reflectance

Is Global Warming caused by heat retained in our homes & other buildings & can white roofs cool our planet?

The more I read about carbon and global warming, the more I think that a big part of global warming is the rise and rise of urban and city sprawl with buildings and roads that absorb and trap solar heat, and don’t allow that heat to escape.

Solar reflectance is a different solution to Global Warming.

Switching the lights off will save carbon dioxide production and reduce greenhouse gases that trap heat from the sun. Got that, but is their more to it than that?

What about our homes, our commercial building and our roads and pavings? They soak up and trap heat.

Our buildings absorb heat and slowly release that heat.

Sustainablity experts have long held that thermal mass, the ability to hold solar heat and release it over night is a good thing, because we won’t need to rely on heating.

Is that really true in the total scheme of Global Warming? Many are now saying that this is a bad idea even in countries with cold winters.

Thermal mass holds heat that causes more cooling power to be used.

But what about when we want to cool down.

Having thermal mass is a bad idea in Summer, because the home is hot long after the sun has gone down. Brick walls and concrete roof tiles roofs stay hot for hours, and this would mean more air-conditioning, and cooling is far more expensive than heating.

I am a believer of  white roofs

Long before the White Roof Alliance was formed I had a business in the nineties that restored mainly concrete tiled roofs. The coating I used were not sold as “insulating”, and most of the roofs we resprayed were not white. But the overwhelming testimonials I received from customers proved to me that these coatings made the homes cooler in Summer and warmer in Winter. So insulation was a factor, maybe because it kept the concrete dry, and therefore made the substrate a better insulator.

Is solar reflective more important than the colour white”

My point of difference in a crowded markerplace was that I completed by roofs with a clear highly reflective glaze coat. This was an extremely expensive poduct, and kept its glaze for many years, unlike normal roof coating.

I promoted this as “self cleaning” as the shiny surface prevented dust and soil buildup over time.

People with white iron roofs were asking me “If I had also installed insulation as well” because the temperatures of the homes were far more comfortable to come home to after a hot day.

I had never heard of solar reflectance in those days, but I did know that a dull surface absorbs more heat than a reflective one, regardless of colour. And that dark colours absorb more heat than lighter colours. It is becoming apparent that solar reflectivity is as important as insulation.

WhiteRoofAlliance.org becomes GlobalCoolCities.org

I Googled white roofs to research my theory that this was a big part of the global warming problem and White Roof Alliance was a name that sprang up.

This site name was recently changed to Global Cool Cities. The name change was for three logical reasons that I can see.

1. Firstly, white roofs was a “commodity/product” based name, but global cool cities is a “benefit/solution” based name.
2. Secondly, the solution need not be white, but must be solar reflective. That is durable solar reflectivity is the paramount attribute.
3. Thirdly, the problem is not just roofs, its all structures, including walls, bridges, pavings and roads.

Increasing building solar reflectivity delivers immediate results in reducing Global Warming.

Taking Carbon gases out of the atmosphere will take years and the heat builds up every day. Results in carbon gas reduction will not be seen for years after any action is taken.

But retro coating our homes’ roofs, walls and pavings will give immediate results in reflecting heat that would otherwise be stored. It will also provide more time to reduce carbon emissions.

The effect of solar reflectance on the average pitched home roof needs to be quantified, but it would be considerable, and the Australian Government needs to look at giving grants for this work as another spoke in the sustainability wheel, based on what their findings are of the benefits in reducing Global Warming:

1. On a clear day reflected solar heat can be as high as 80% effective in returning that heat to space, thus reducing the build up of heat. This compares with just 4% at present with some of our roofing.
2. By reflecting the solar heat away from roofs, walls, and paving we would cool the homes and reduce the need for cooling.
3. It is my experience that sealing the roof concrete and brick walls, also reduces moisture ingress, and that aids the insulating effect during cold wet months, keeping the home warmer and drier in winter.

The benefits of Solar reflectance happen instantly , like switching off a heater or light bulb.

Collectively they would make a huge difference, and the Australian Government needs to consider this.

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