Comments on: Sustainable Sites 7.2 – Heat Island Effect – Roof

By: Thomas K. Sinclair

Thomas K. Sinclair — Tue, 10 Aug 2010 11:49:52 +0000

This is a great idea, didn't think of this until I read about it here. I'll had it to my blog

By: Convey

Convey — Fri, 25 Jun 2010 18:27:47 +0000

I’m minded to believe that the thin sedum green roofs that are becoming common in the UK would be less able to reduce the heat island effect than deep planted grass roofs that are more common on the continent. Does anyone have an opinion on this or know of any research that support or dispels my theory?

By: Amy

Amy — Tue, 09 Jun 2009 03:04:32 +0000

hu….I found my answer, haha time for a study break!

By: Amy

Amy — Tue, 09 Jun 2009 02:49:44 +0000

…The answers are A D & F

By: Amy

Amy — Tue, 09 Jun 2009 02:48:44 +0000

I got this question on a practice exam and now I am confused as to if Solar panels are actually included in green roof area calculations, or are they excluded?

A project with a 30,000 sq. ft. building footprint has been designed with a 100% green roof. Renewable energy certificates will provide 25% of the electricity. The project team is revising the design to decrease the size of the green roof by 5,000 sq. ft. and add 5,000 sq. ft. of photovoltaic cells to the roof. What other credits/prerequisites will this design change affect?

A
EA Prerequisite 1 Fundamental Commissioning of the Building
B
EA Prerequisite 2 Minimum Energy Performance
C
EA Credit 6 Green Power
D
SS Credit 6.1 Stormwater Design: Quantity Control
E
SS Credit 7.2 Heat Island Effect: Roof
F
EA Credit 2 On-Site Renewable Energy

Notes:

Adding photovoltaic cells will contribute to EA Credit 2 On-Site Renewable Energy.

Renewable energy systems (wind, solar, etc.) are part of the commissioning process for EA Prerequisite 1.

Decreasing the size of the green roof will alter stormwater quantity, thereby impacting SS Credit 6.1 Stormwater Design.

Green roofs do not include areas with solar energy panels. Since the original design had a 100% green roof, adding solar energy panels will have no effect on SS Credit 7.2 Heat Island Effect.

By: Lule

Lule — Sun, 07 Jun 2009 16:21:15 +0000

also Green roofs are not roof gardens please read below (just in case they mention this in the exam)
“The typical roof garden consists of plants in containers. A green roof is an integrated structure that allows even drainage and more consistent weight distribution across the entire roof.”

By: Lule

Lule — Sun, 07 Jun 2009 16:16:21 +0000

green roof = vegetated roof=vegie roofs
cool roof = high sri value = high abedo value

By: Gail

Gail — Mon, 25 May 2009 11:27:26 +0000

Hi,
Has anyone run across an official definition or official a specification for ‘Vegetated Roof’ or ‘Green Roof’ in any of the LEED material??
Thanks
Gail

By: Reenu

Reenu — Tue, 17 Mar 2009 23:30:24 +0000

If its submitted in the design phase then how come contractor is one of the decision makers??? Plz confirm. Thanks.

By: Brian

Brian — Wed, 26 Nov 2008 13:56:50 +0000

Please remember:

1. A vegetated roof system using fast-growing native and adapted plant species has the potential to contribute to earning which three credits?

A: SSc6.1, Stormwater Design: Quantity Control
B: SSc7.2, Heat Island Effect: Roof
C: EAc1, Optimize Energy Performance

This will help you on the tests…

By: sherif

sherif — Mon, 20 Oct 2008 07:41:32 +0000

Thanks,

By: Pat

Pat — Mon, 20 Oct 2008 07:08:08 +0000

It’s difficult because LEED does not endorse specific products or companies. Different companies will have different materials with different specifications, but they are somewhat easy to find. If you type in “LEED SRI Chart” in google, there are some good prospects there.

I’m sorry I can’t be more specific for you!

By: sherif

sherif — Mon, 20 Oct 2008 07:04:51 +0000

Thanks very much Pat, i will pass over these articles, but do we have any specified clear data about finishing materials that is applied on concrete roofs, with specified SRI values indicated in a table for example

By: Pat

Pat — Sun, 19 Oct 2008 18:16:59 +0000

Hi sherif,

I found this article online that may help you a little further on your question, and explain a little better than I can:

http://www.roofingcontractor.com/CDA/Articles/Cool_Roof/4cfd330bc6f8a010VgnVCM100000f932a8c0____

http://www.coolroofs.org/leed.html

By: sherif

sherif — Sun, 19 Oct 2008 14:29:25 +0000

Hi,
Do i have to apply some kind of a membrane or a special coat to the finshed roof layer to achieve the rates of the SRI, or the finishing materils whatever it is, (marble cement tiles, terrazzo, etc..)can achieve these values at the non slopped roofs, and if so where do i find company names that provide this kind of rates at there materials specifications or cataloges

Sherif

By: Chris

Chris — Sun, 28 Sep 2008 00:59:45 +0000

I can understand a SRI of 78 for a low pitched cool roof, but a SRI of 29% for a steep pitched roof is total greenwashing. Shame on LEED for allowing the big asphalt manufacturers to influence this section. An SRI of 29% does nothing to reduce thermal absorption into a roof. I could live with a solar reflectance of 40 if the roof was high profile concrete or clay and air could be convected out through the ridge caps.

By: Pat

Pat — Mon, 22 Sep 2008 20:58:11 +0000

Gerry,

You’d have to speak to a specialist regarding that matter, possibly a landscape architect or even a mechanical engineer. You’d have to be able to measure temperatures and cooling/heating measurements and compare them to a baseline figure, either before the green roof was applired or to a computer model with baseline conditions. Thanks!

By: Gerry

Gerry — Mon, 22 Sep 2008 01:25:16 +0000

How can i quantify my savings for applying green roof?

By: Brandie

Brandie — Wed, 23 Jul 2008 00:31:22 +0000

Will-

Good question check out Aaron and Pat’s exchange above; you can not get EP for high albedo only veggie!!

Aaron,

You are correct. I checked my resources and one of them was incorrect, and thats the one I put down. I apologize for the mixup. 100% veggie roof = exemplary performance.

By Pat on Feb 29, 2008

By: ahamed

ahamed — Fri, 11 Jul 2008 12:21:44 +0000

Will i qualify for exemploary performance if i use high albedo material for 100% roof?

By: valeria

valeria — Fri, 04 Jul 2008 23:39:55 +0000

Hi
I do see how the formula was followed in the example but I can’t ’see’ how a 100 sf ft roof yields in combination of whatever area sri divided by the required %i and veggie roof area divided its required % exceed the area on that said roof!

I can follow the formula to calculate, but the final value expressed in sf ft is throwing me as far as what it looks like…here, you demonstrated that if you cover only 75% of the roof, (in actuality) in the above combination, the calc is 116..667sf…it loses meaning…when i try to see it on the roof!

I guess it helps in that these sq ft perhaps are only in regards to a ‘threshold’
and not directly the roof, I think I would better grasp if it wasn’t expressed in sq ft…! So are these sf, the ‘good heat island fighter sq ft’ that live soley on the credit letter template?

By: Pat

Pat — Mon, 30 Jun 2008 17:59:54 +0000

Valeria,

I can see where this equation might be confusing, but you have to remember that when you divide by a percentage, the valuve of any number becomes greater.

Just for an example, lets say we have a roof area of 100 SF and we’re using option 3.

If we have 50% (or 50 SF) as SRI, and 25% (or 25SF) as green roof, the equation would look like this:

50SF/0.75 = 66.667 SF
25SF/0.5 = 50 SF

66.667 + 50 = 116.667.

The SRI area (50SF) isn’t greater than 75% (or 75 SF) as per option 1, and the veggie roof (25SF) isn’t greater than 50% (or 50SF), but with the equation, you can see the final calculated number is greater than 100 SF, therefore using 50SF SRI and 25SF veggie roof works for option 3 in this case.

I hope this helps.

By: valeria

valeria — Sun, 29 Jun 2008 21:10:27 +0000

In Option 3, I am having a hard time visualizing the equation….. as to what the roof would actually LOOK like,
when they are saying that the combo of sri and veggie roof need to be equal (fine) or GREATER than the total roof ? how is that possible? pehaps I am not getting the factors .75 and .5 what are they factors of ? I thought the total roof area but combined they are GREATER than the total roof area…

I’m just not seeing it…anyone care to draw me a picture?

(Area of SRI roof/0.75)+(Area of veggie roof/.5)is equal to or greater than Total Roof Area

By: cynthia

cynthia — Fri, 09 May 2008 09:04:31 +0000

same happened with me,,it took me e long half an hour to read and try to grasb.memorize all these standards.. and then thought i’d check ur website first,,such a great relief knowing they’re not required!!

By: Sofia

Sofia — Sat, 26 Apr 2008 20:22:18 +0000

For a very ambitious minute I thought about memorizing all the actual names of the ref. standards for this credit… and then I thought, “this is crazy! look at these names!”

Then, I said to myself, let me see what Pat did in intheleed… cause if Pat “the sleek-LEED-freak” put them there, I must learn them then.

Thank you Pat for liberating me of such torturous and treachorous path!!

By: Sofia

Sofia — Sat, 26 Apr 2008 20:21:36 +0000

For a very ambitious minute I thought about memorizing all the actual names of the ref. standards… and then I thought, “this is crazy! look at these names!”

Then, I said to myself, let me see what Pat did in intheleed… cause if Pat “the sleek-LEED-freak” put them there, I must learn them then.

Thank you Pat for liberating me of such torturous and treachorous path!!

By: Pat

Pat — Fri, 29 Feb 2008 01:12:07 +0000

Aaron,

You are correct. I checked my resources and one of them was incorrect, and thats the one I put down. I apologize for the mixup. 100% veggie roof = exemplary performance.

By: Aaron

Aaron — Fri, 29 Feb 2008 01:06:00 +0000

The first edition NC 2.2 gives exemplary performance as 100% vegetated roof. Just wanted to confirm it really is 100% SRI roofing and not 100% veggie roof. Thanks!