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Cool Roofs for Green Architecture: Six Basic Things to Know

 

Cool roofs are not tricky. They are what they claim to be: roofs that are cool in temperature. So although the concept is simple, the result is a very powerful tool for architects in the growing need and desire for greener buildings.

1. The Basics

Cool roofs stay cool by doing two things:

a) reflecting heat from the sun (called solar reflectance).

b) quickly re-emitting any heat that is absorbed (called thermal emittance).

In essence, the goal of a cool roof is to reduce the amount of heat entering the building. As seen in the diagram below, these two properties, solar reflectance and thermal emittance are what determine if a roof is technically cool.

cool roof diagram

Diagram courtesy of the lovely people at the Cool Roof Rating Council.

 

2. Cool Roofs Are Not A New Idea

There's a lot of technical jargon you can get into when it comes to cool roofs. Leave that to us architects. In principal, cool roofs work because:

architects cool roof colors

Get it? White roofs absorb less heat than dark-colored roofs. A cool roof only absorbs 10-15 percent of the sun's heat versus 90 percent heat absorption for a  traditional dark roof.

The beauty of cool roofs is that they're a low-tech concept. Long before the days of electricity and air conditioning, warm-climate areas used light colors in their buildings to reduce heat gain. I think I even wrote something about this last year called Environmental Architecture in Greece.

Historical Green Architecture

In Santorini, Greece, cool roofs (and walls) are not a new idea.

However, since people don't always want white roofs, some smart scientist types have figured out a way to have cool roofs with darker colors by utilizing special highly reflective coatings. Cool roofs are versatile, coming in all types of materials that can be applied to a home just as easily as to an office or industrial building.

 

3. Cost

Inevitably, the first question we get after we describe a green feature to a client is "That's great, but is it more expensive?" Thankfully, for cool roofs, the answer is "not really." The added cost for a cool roof can be as little as 15 percent. This minor increase is far outweighed by the projected 20 percent or more savings in air conditioning cost (source). Besides, knowing you have a cool roof and are helping the environment will make you feel warm and fuzzy inside.

Compared to other green building features with high upfront costs, such as solar panels, cool roofs are an affordable option.

 

4. It's Not Just About You

Don't be selfish when selecting a new roof. Having a hot roof not only increases your cooling costs, it also affects the world around you through an ugly phenomenon called heat island effect. 

heat island effect

Diagram of Urban Heat Island Effect, courtesy of Lawrence Berkeley National Laboratory

Heat island effect occurs as result of the numerous heat-absorbing surfaces that cities contain such as dark colored roofs, streets and seas of parking lots. This effect overheats urban areas, increasing the demand for air conditioning and electricity. Another not-so-fun aspect of heat island effect is that it's known to increase smog formation.

 

5. For Remodels Too

Whereas many green building features are better suited for new construction or extensive remodels, cool roofs are a viable option for any remodel or simple re-roofing.

On our recent remodel of the Fashion Square Car Wash, we specified a cool roof to reduce the air conditioning loads and heat island effect from the surrounding paved areas.

cool roof start

The re-roofing of the Fashion Square Car Wash started out looking very similar to a typical roof. So far, not very cool.

los angeles architects cool roof

That's a little better.

los angeles architects cool roof

Now there's a cool roof.


So in this case, the roofing was pretty standard, but in the end it was covered with a white coating to increase its reflectivity.

 

6. Location, Location Location

There is a fair amount of debate as to whether cool roofs are beneficial in all climate zones. For us here in Los Angeles and other warm climates (hey Texas, Nevada and Arizona), it's a no-brainer: cool roofs work. The worry in cooler climates is that cool roofs don't allow for thermal gain in the winter. The good news is that there are numerous studies that have shown that cool roofs are effective in just about any climate.

 

heat island map

Potential net energy savings from changing roof reflectivity. Savings are measured in dollars. Note that the net savings are the savings of cooling energy use less the penalties of heating energy use. Image courtesy of the Heat Island Group.

 

If you have any thoughts on cool roofs, feel free to leave a comment or send us a fancy form message.

 

 

Using Old Jeans to Keep Your House Warm

 

One of the major components the energy efficiency of any building is insulation. Insulation is critical to maintaining comfortable indoor temperatures by either keeping the heat in or out of a building.

Green Insulation

As sustainability gains momentum in the building industry, new products are available that rethink insulation. One of these is recycled denim insulation. Yes, old jeans. One of the leading manufactures of this green product is UltraTouch.

 

recycled insulation jeans  safe green insulation

It even looks like your old jeans. (images from UltraTouch & Victor Insulation)

Don't Eat the Pink Stuff

UltraTouch Natural Cotton Fiber Insulation is targeted as a replacement for traditional fiberglass insulation - the typically yellow or pink soft looking stuff you see between the studs during construction. Yes, you're probably also picturing the pink panther. If you haven't had the pleasure of handling traditional fiberglass insulation, don't. It's not pleasant stuff to to touch (itchy) or breath (can cause respiratory problems). I definitely wouldn't wear pants made of the stuff. UltraTouch on the other hand is made of safe, easy to handle, recycled denim.

green building products

UltraTouch comes in rolls and is easily installed. 

Product Info

So aside from this obvious point that it the product is safer for people to install, here are a few other interesting factoids:

  • The insulation is 85% post industrial recycled fibers.
  • Has acoustic ratings approximately 30% better than traditional insulation. Less outside or neighborly noise.
  • The cotton fibers are treated for fire resistance - Class A rating.
  • No VOC concerns - those little particles you don't want to breath.
  • Good mold resistance.
  • Obviously helps with LEED certification points.

Cost

A common question, as with most green products, is does it cost more? Well, yes, it does. How much more depends on the size of your project and the construction market. However, the short and long term benefits of this product far outweigh the upfront costs. 

At Modative, we are now specifying this or similar products instead of traditional fiberglass insulation. If you are concerned about the cost, we're happy to help you compare the cost of this green product to traditional insulation.



 

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