How should I paint my roof white?

[Guy Dawson]

I see that Prof Chu says we should paint our roofs white to help combat climate change.

We have a 1930s semi with a normal pitches roof with dark grey concrete tiles on it. It sure does get hot in the loft during the summer.

Any recommendations as to what I can use to paint (I assume) the tiles white?

Guy

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[Andrew Gabriel]

I would start by making sure your loft insulation is up to spec. That helps summer and winter.

[Guy Dawson]

Already done.

Guy

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4.4>5.4 4.4>5.4 4.4>5.4 The Reality Check's in the Post! 4.4>5.4 4.4>5.4

[The Natural Philosopher]

I want to paint all my trees white. Is this what god invented birdshit for?

[Stuart Noble]

You need insulation between the rafters if you want the loft cool in summer.

[meow2222]

Whitewash is traditional. Its basically chalk in glue, and gradually washes off in winter. If you want it to last longer then diluted lime putty, but it needs 2 or 3 coats. In principle you could use masonry paint, but then you'd have to actually get up there and make sure there was no splash or overpaint. The lime paints thats not a problem with, any spill is just hosed off, and a floor brush can be used for painting.

NT

[Guy Dawson]

It's not so much the keeping the loft cool but the reflection of sunlight back into space to avoid heating the atmosphere.

Prof Chu's point is that a lot of solar heating is caused by building being heated by the sun and radiating the heat back into the atmosphere.

If the sunlight could be reflected back into space by white surfaces then we'd help slow global warming.

-------------------------------------------------------------------- Guy Dawson I.T. Manager Crossflight Ltd [e-mail]

[Stuart Noble]

White tarmac too maybe.

[Guy Dawson]

That's also suggested!

Guy

-- -------------------------------------------------------------------- Guy Dawson I.T. Manager Crossflight Ltd [e-mail]

[Dave Osborne]

Well, you could try googling for "roof tile paint"

e.g.

even "solar reflective paint"

e.g.

[Fredxx]

For good reflectivity, they ought to at least start out white.

[Andy Dingley]

Extensive green roof (or brown roof) is better.

Admittedly a bit hard to retrofit to a 45=B0 slope, but it's what I'm doing with my sheds (which are 3=D7 the house roof area).

[Andrew Gabriel]

White is a definition which relates to visible light. I suspect far more energy is present in the infrared, and it's more important that it's reflective in the infrared than the visible. Sheet copper would probably be quite good if it didn't tarnish, or some type of plasticised film version. At a former workplace, we had the roof painted to reduce solar gain, and IIRC, the paint looked green.

[Guy Dawson]

Guy

-- -------------------------------------------------------------------- Guy Dawson I.T. Manager Crossflight Ltd [e-mail]

[Donwill]

Surely we should be trying to collect this energy and substitute it for fossil fuels rather than attempt to reflect it back through our atmosphere to space. I think that makes more sense don't you?

Don

[Guy Dawson]

Indeed. However the systems are quite expensive still.

Rather than doing nothing and waiting for the perfect solution we can still do something useful...

Guy

[Fredxx]

It's not a coincidence that the suns energy is concentrated in the visible spectrum. The peak is in fact at green.

Reflecting the near infrared is a complete waste of time, it is generally not transmitted through the atmosphere, and if we do manage to reflect the re-radiated near infrared energy, it would only be absorbed again by the atmosphere. Infrared reflecting paints are next to useless.

[Bob Mannix]

Indeed, the greenhouse effect works because visible/uv energy comes from the sun through the atmosphere (or greenhouse glass) (mostly) and is absorbed by the earth and re-radiated as infra-red, which the atmosphere (or green-house glass) doesn't let out again (mostly). So white or silver reflectors would work best in terms of cooling the earth.

[PeterC]

With black lines?

[Donwill]

Expensive to who? yourself? The planet? The planet wont care one way or another, it will survive. However the human species that has inflicted itself on the other species which inhabit this planet will probably destroy itself competing for resources. We have the ability and arrogance to reckognise when other species need culling, yet we are blind to our own faults and untrammelled ambitions.

I suggest you go and read James Lovelock's "The Vanishing Face of Gaia" that could be useful to you.

Don