How Can Roofing Cool Down your House or Building?

What does cool down your house have to do with roofing? Summer is here. It’s hot in Woodland Hills, Pasadena and most local cities. The beach towns like Santa Monica and Malibu might be cooler but can you cool your home with your roofing? There are a few ways to help control the temperatures inside your house, and yes, chief among these is via your roof.

If you have a flat roof, assuming it’s a smooth surface (and not a gravel roof) – you can paint it with white elastomeric roof paints that reflect the sun. This isn’t rocket science and certainly can be a DIY project but it is hard work and, surprisingly, it’s easy to get it wrong and waste a ton of money – the paint is not cheap.

Having done a few hundred of these I have found a few things that can help you produce a job well done, whether you do it yourself or hire a professional roofer, like J and J Roofing, my company.

First of all, the roof doesn’t necessarily have to be washed but it does need to be clean and the cleaner, the better. For example, if you recently had rains, your roof is probably pretty clean and if you brush out any sediment (from puddles) and use a blower, you should be fine, otherwise, hose it down and let it dry until at least the next day.

It takes two coats and I use a roller with a thick nap which holds more paint.  There’s no real technique here, just try to be even with it and if you see a wavy pattern, you’re probably trying to lay down too much. Do not try to do this with one coat of paint, no matter who tells you different.

First of all, every single manufacturer recommends two coats and I have found through much experience it’s absolutely necessary. One coat is just not thick enough. Nor can you really lay
one coat down, properly, thick enough.  I have tried, believe me. You’ll just end up with a wavy coat that attracts dirt.

Generally, you want to figure on using at least two gallons per square (a square being 10×10 feet, and is how roofing products are often measured). I personally recommend about 2.2 – 2.5 gallons per square. You really can tell the difference and at three gallons, it will last a very, very long time (10 years or more).  So for example, on a 1500 square foot roof, I would lay down about 1.5 gallons per 100 square feet, on the first pass.  Then use the balance, about 0.8 gallons per 100 square foot, on the second pass the following day (or, several days if it’s not hot and dry out).  So, in total, I’d use around 35 gallons. It comes in 5 gallon pails.

There are quite a few brands of the paint and your best bet is to go to an actual roofing supply yard. We use Burbank Roofing Supply, for example. You don’t necessarily have to buy the most expensive one or the most reflective one – they are all pretty close in terms of the ability to reflect the sun. I would say you’d get an overall better job by buying a less expensive product, and using more of it, than using less of a superior product.  My favorite brands are Sunshield (by United Coatings), Tropical, and APOC (APOC usually is the most expensive).


In the years that follow, try to keep it clean, and hose it down a couple times just before and during the summer. Of course, if it gets dirty it tends to lessen its ability to reflect the sun.
Matt Glass is one of the owners of J and J Roofing a Los Angeles Roofing Contractor. He enjoys sharing his roofing knowledge with anyone who wants to know… J and J Roofing services most of Southern California from homes in Woodland Hills, Pasadena to beach cities like Santa Monica and Malibu.