NC v2.2 SSc7.2: Heat Island Effect—Roof

I would say yes. You should check the LEED interpretation rulings, if this has happened before. Otherwise I would submit as special circumstances since your roof doesn't create a heat island effectHeat island effect refers to the absorption of heat by hardscapes, such as dark, nonreflective pavement and buildings, and its radiation to surrounding areas. Particularly in urban areas, other sources may include vehicle exhaust, air-conditioners, and street equipment; reduced airflow from tall buildings and narrow streets exacerbates the effect.. So you do achieve the intent of the credit.
However be careful to just say it's all covered by solar panels. You will need to show that in drawings and be precise. If you have areas not covered by them for maintenance access or else, these than have to comply with the credit requirements.

Pal, I think this will be hard to find, in part because higher-SRIThe solar reflectance index (SRI) is a measure of a material's ability to reject solar heat, as shown by a small temperature rise. Standard black (reflectance 0.05, emittance 0.90) is 0 and standard white (reflectance 0.80, emittance 0.90) is 100. For example, a standard black surface has a temperature rise of 90_F (50_C) in full sun, and a standard white surface has a temperature rise of 14.6_F (8.1_C). Once the maximum temperature rise of a given material has been computed, the SRI can be calculated by interpolating between the values for white and black. Materials with the highest SRI values are the coolest choices for paving. Because of the way SRI is defined, particularly hot materials can even take slightly negative values, and particularly cool materials can even exceed 100. roofing may cause glare, which can be a problem on sloped roofs. Let us know if you come up with anything.

SRIThe solar reflectance index (SRI) is a measure of a material's ability to reject solar heat, as shown by a small temperature rise. Standard black (reflectance 0.05, emittance 0.90) is 0 and standard white (reflectance 0.80, emittance 0.90) is 100. For example, a standard black surface has a temperature rise of 90_F (50_C) in full sun, and a standard white surface has a temperature rise of 14.6_F (8.1_C). Once the maximum temperature rise of a given material has been computed, the SRI can be calculated by interpolating between the values for white and black. Materials with the highest SRI values are the coolest choices for paving. Because of the way SRI is defined, particularly hot materials can even take slightly negative values, and particularly cool materials can even exceed 100. is dependant on the suface's ability to reflect Solar Spectrum IR in particular. Covering a hight SRI surface with other material does not make sense, unless you are expecting that material to radiate in the near-IR range ?

You may wish to read the research papers from the American Concrete Pavement Association on the effect of the colour of aggregates on the SRI of pavements.

You have asked an interesting question, and i think you will find a light coloured ballast stone could help. How to prove this without coslty Lab measurements is another thing ...

I was going to ask similar question to Lauren - does anyone know a light-colored gravel supplier that would fulfill SRIThe solar reflectance index (SRI) is a measure of a material's ability to reject solar heat, as shown by a small temperature rise. Standard black (reflectance 0.05, emittance 0.90) is 0 and standard white (reflectance 0.80, emittance 0.90) is 100. For example, a standard black surface has a temperature rise of 90_F (50_C) in full sun, and a standard white surface has a temperature rise of 14.6_F (8.1_C). Once the maximum temperature rise of a given material has been computed, the SRI can be calculated by interpolating between the values for white and black. Materials with the highest SRI values are the coolest choices for paving. Because of the way SRI is defined, particularly hot materials can even take slightly negative values, and particularly cool materials can even exceed 100. requirement for a low-sloped roof? I'm looking for one i Europe, but shipping such material from the USA is also an option.

The thing is that I'm not sure gravel has high reflectance... the stones are not flat and usually have polygonal shapes, so if we take the principle "angle of incidence equals the angle of reflection", the rays can be reflected towards the deeper layer of the roof, not to the atmosphere. Please, correct me if I'm wrong...

I will take it as low slope as the reference show ≤2:12 (equal or lower). if 2.1:12, it will be a steep sloped roof, as the pitch is 0.1 steeper.

I agree with Jason. Rounding is generally not a part of LEED—so once you're over 2, you're steep.

If this wasn't working for the project in some way, it's possible GBCI would allow a different view—I just wouldn't bank on it.

Carrie, does the v2.2 form not do this calc for you? I would avoid uploading the 2009 form unless it was absolutely necessary.

Adam, it's a weighted average. We have a spreadsheet in our Documentation Toolkit (above) that you might find is a useful tool for exploring this. That should also make the calcs transparent.

Blake, you're being asked for that since you're using the Option 3 path that combines green roof and high-SRIThe solar reflectance index (SRI) is a measure of a material's ability to reject solar heat, as shown by a small temperature rise. Standard black (reflectance 0.05, emittance 0.90) is 0 and standard white (reflectance 0.80, emittance 0.90) is 100. For example, a standard black surface has a temperature rise of 90_F (50_C) in full sun, and a standard white surface has a temperature rise of 14.6_F (8.1_C). Once the maximum temperature rise of a given material has been computed, the SRI can be calculated by interpolating between the values for white and black. Materials with the highest SRI values are the coolest choices for paving. Because of the way SRI is defined, particularly hot materials can even take slightly negative values, and particularly cool materials can even exceed 100. areas. I think the LEED  Online template is just not smart enough to recognize when you're entering green roof areaRoof area is the area of the uppermost surface of the building which covers enclosed Gross Floor Area, as measured when projected onto a flat, horizontal surface (i.e. as seen in Roof Plan view). ‘Roofs’, or portions of roofs, covering unenclosed areas (e.g. roofs over porches and open covered parking structures) are not included in the areas used to evaluate compliance with SSc7.2, though they may be applicable to SSc7.1., and when you're entering SRI area, for which reflectance would be relevant. I would look for a way to "trick" the form to not requiring this information, and explain in the narrative what you did.

Maura, here's an article from RealLifeLEED that is a useful starting place in understanding SRIThe solar reflectance index (SRI) is a measure of a material's ability to reject solar heat, as shown by a small temperature rise. Standard black (reflectance 0.05, emittance 0.90) is 0 and standard white (reflectance 0.80, emittance 0.90) is 100. For example, a standard black surface has a temperature rise of 90_F (50_C) in full sun, and a standard white surface has a temperature rise of 14.6_F (8.1_C). Once the maximum temperature rise of a given material has been computed, the SRI can be calculated by interpolating between the values for white and black. Materials with the highest SRI values are the coolest choices for paving. Because of the way SRI is defined, particularly hot materials can even take slightly negative values, and particularly cool materials can even exceed 100. values on copper roofs. I think you'll find two things that don't work in your favor, a) the SRI value will be very low, and b) you'll need to test it to verify a value for your LEED documentation.

http://www.reallifeleed.com/2009/08/sri-values-for-copper-roofing-old-vs...

Thanks! We thought the zinc coating would raise the SRIThe solar reflectance index (SRI) is a measure of a material's ability to reject solar heat, as shown by a small temperature rise. Standard black (reflectance 0.05, emittance 0.90) is 0 and standard white (reflectance 0.80, emittance 0.90) is 100. For example, a standard black surface has a temperature rise of 90_F (50_C) in full sun, and a standard white surface has a temperature rise of 14.6_F (8.1_C). Once the maximum temperature rise of a given material has been computed, the SRI can be calculated by interpolating between the values for white and black. Materials with the highest SRI values are the coolest choices for paving. Because of the way SRI is defined, particularly hot materials can even take slightly negative values, and particularly cool materials can even exceed 100....

It might... you never know. But you won't know, or be able to document the credit, without some data.  Too bad the manufacturer is holding back. Sounds like they just don't have the data themselves.

That depends, is the space underneath the roof heated or cooled? If so, the roof is to be considered under Heat Island EffectHeat island effect refers to the absorption of heat by hardscapes, such as dark, nonreflective pavement and buildings, and its radiation to surrounding areas. Particularly in urban areas, other sources may include vehicle exhaust, air-conditioners, and street equipment; reduced airflow from tall buildings and narrow streets exacerbates the effect. - Roof. That would also be the case if the space is underground.
If the spaces underneath the roof are not conditioned, it will be parking under cover under credit:"Heat Island Effect - Non-Roof". So to make it count, it needs to have a minimum of SRIThe solar reflectance index (SRI) is a measure of a material's ability to reject solar heat, as shown by a small temperature rise. Standard black (reflectance 0.05, emittance 0.90) is 0 and standard white (reflectance 0.80, emittance 0.90) is 100. For example, a standard black surface has a temperature rise of 90_F (50_C) in full sun, and a standard white surface has a temperature rise of 14.6_F (8.1_C). Once the maximum temperature rise of a given material has been computed, the SRI can be calculated by interpolating between the values for white and black. Materials with the highest SRI values are the coolest choices for paving. Because of the way SRI is defined, particularly hot materials can even take slightly negative values, and particularly cool materials can even exceed 100. 29 or vegetated green roof.

I would interpret the Reference Guide has being specific about green roofs being the sole EP path here. I think if the intention was to allow an SRIThe solar reflectance index (SRI) is a measure of a material's ability to reject solar heat, as shown by a small temperature rise. Standard black (reflectance 0.05, emittance 0.90) is 0 and standard white (reflectance 0.80, emittance 0.90) is 100. For example, a standard black surface has a temperature rise of 90_F (50_C) in full sun, and a standard white surface has a temperature rise of 14.6_F (8.1_C). Once the maximum temperature rise of a given material has been computed, the SRI can be calculated by interpolating between the values for white and black. Materials with the highest SRI values are the coolest choices for paving. Because of the way SRI is defined, particularly hot materials can even take slightly negative values, and particularly cool materials can even exceed 100. path, it would have been stated that the EP path is simply a "100%" version of the regular credit.

Has anyone found anything different on their projects?

The definition of a green roof has been a moving target with GBCI reviewers and depends on the version of the reference guide you use. First Edition NC2.2 Reference Guide is not clear on this point. The Third Edition apparently clarifies the definition of a green roof. The 2009 Reference Guide specifically refers to a "vegetated roof system" for SS7.2EP. From a LEED Review Team we recently received the following clarification:

The project team is correct to assume the credit was denied because 100% of the roofing material was only high-albedoAlbedo is synonymous with solar reflectance. and not vegetative. The LEED NCv2.2 Reference Guide, Third Edition defines green roofs as vegetated surfaces that reduce heat island effectHeat island effect refers to the absorption of heat by hardscapes, such as dark, nonreflective pavement and buildings, and its radiation to surrounding areas. Particularly in urban areas, other sources may include vehicle exhaust, air-conditioners, and street equipment; reduced airflow from tall buildings and narrow streets exacerbates the effect. by replacing heat-absorbing surfaces with plants, shrubs, and small trees that cool the air through evapotranspiration (or evaporation of water from leaves). As submitted, the project has not demonstrated exemplary performanceIn LEED, certain credits have established thresholds beyond basic credit achievement. Meeting these thresholds can earn additional points through Innovation in Design (ID) or Innovation in Operations (IO) points. As a general rule of thumb, ID credits for exemplary performance are awarded for doubling the credit requirements and/or achieving the next incremental percentage threshold. However, this rule varies on a case by case basis, so check the credit requirements. for SSc7.2: Heat Island Effect, Roof.

LEED allows you to exclude mechanical systems and other appurtenances from this credit, so if it is more like a mechanical system or a similar appurtenance (solar array) then you could say there is some precedent for excluding it. It's not clear-cut, however.

A couple thoughts. One, if you want to exclude it and only include the small portion of the remaining roof for this credit, are you down a path of following the letter of the requirements, but not the intent? Perhaps this isn't the most appropriate credit for the project.

Two, would it be more appropriate to consider it as a "non-roof" surface and see if the SRIThe solar reflectance index (SRI) is a measure of a material's ability to reject solar heat, as shown by a small temperature rise. Standard black (reflectance 0.05, emittance 0.90) is 0 and standard white (reflectance 0.80, emittance 0.90) is 100. For example, a standard black surface has a temperature rise of 90_F (50_C) in full sun, and a standard white surface has a temperature rise of 14.6_F (8.1_C). Once the maximum temperature rise of a given material has been computed, the SRI can be calculated by interpolating between the values for white and black. Materials with the highest SRI values are the coolest choices for paving. Because of the way SRI is defined, particularly hot materials can even take slightly negative values, and particularly cool materials can even exceed 100. requirements and technologies for parking would be more appropriate?

Nicholas, have you gone any further with this situation? A similar question just came up on our v2009 forum... that made me curious to hear more on your situation.

If the buiding were adjacent to your project and shading it, this would not be allowed. It's very possible that the same rule would apply here, strange as it may seem.

LEED is certifying your building only, and there is no guarantee that the other building will always be there to provide the shade.

I'm curious what your LEED boundary looks like? Might be kind of tough to exclude the other building. Have you discussed this with GBCI?

Anyone else have thoughts?

Do you really mean loam, and not some kind of gravel surface? Seems odd, since loam will tend to grow weeds in no time. Just checking, since this obviously affects SRIThe solar reflectance index (SRI) is a measure of a material's ability to reject solar heat, as shown by a small temperature rise. Standard black (reflectance 0.05, emittance 0.90) is 0 and standard white (reflectance 0.80, emittance 0.90) is 100. For example, a standard black surface has a temperature rise of 90_F (50_C) in full sun, and a standard white surface has a temperature rise of 14.6_F (8.1_C). Once the maximum temperature rise of a given material has been computed, the SRI can be calculated by interpolating between the values for white and black. Materials with the highest SRI values are the coolest choices for paving. Because of the way SRI is defined, particularly hot materials can even take slightly negative values, and particularly cool materials can even exceed 100..

Let's see... here are some answers.

1) You have discretion here. LEED Online says: "Upload the project roof plan(s) or drawing(s) depicting project roof areaRoof area is the area of the uppermost surface of the building which covers enclosed Gross Floor Area, as measured when projected onto a flat, horizontal surface (i.e. as seen in Roof Plan view). ‘Roofs’, or portions of roofs, covering unenclosed areas (e.g. roofs over porches and open covered parking structures) are not included in the areas used to evaluate compliance with SSc7.2, though they may be applicable to SSc7.1. and highlighting the location and quantity of specific roofing materials areas and/or vegetated roofing systems as applicable.

2) I would say that you have the discretion to count overhangs as non-roof (if over the ground), or perhaps not include them at all if over other roof surfaces. If treating overhangs differently in your calculations or specifications has no effect, I might not bother to do this, though.

3) I don't know. I think this would vary based on the depth and the surface underwater. Anyone? This wikipedia page was a start, but not that helpful. Try LBNL and let us know if you find out.

4) Yes.

5) That would really vary among vegetation types and seasons and I'm not sure counting it as an SRIThe solar reflectance index (SRI) is a measure of a material's ability to reject solar heat, as shown by a small temperature rise. Standard black (reflectance 0.05, emittance 0.90) is 0 and standard white (reflectance 0.80, emittance 0.90) is 100. For example, a standard black surface has a temperature rise of 90_F (50_C) in full sun, and a standard white surface has a temperature rise of 14.6_F (8.1_C). Once the maximum temperature rise of a given material has been computed, the SRI can be calculated by interpolating between the values for white and black. Materials with the highest SRI values are the coolest choices for paving. Because of the way SRI is defined, particularly hot materials can even take slightly negative values, and particularly cool materials can even exceed 100. surface is the right method. Either it qualifies as a green roof, or you probably need to count the pavers under the tree. Mara's comment on SSc7.2 for v2009 gives some nuance on this.

Your suggestion is great—we'll work to incorporate it in the future.

1) Thanks, I might try a composite as the project is also split in phases and this way it's easier for everyone to see the full picture.
2) thanks
3) that's a tricky one, but since the water is over uncondtioned space anyway, I don't have to count it. However in the 'Get it done section' it talks about a swimmingpool but doesn't address how to deal with it. Aside from the reflectivity of water, it does absorb the heat, thus it could be considered as beneficial towards the intent of the credit. If it's a waterfeature that moves the water constantly, it would even be better.
4) thanks
5) thanks

A follow up on if water features are roofs: CIRs dated 2/7/2006 and 5/23/2005 are for LEED NC2.1 and deals with the non-roof credit, but it's feasable that it would also apply to NC2.2 and apply to roofs as well. it says that water feature are excluded from calculations for non-roofs:
http://www.usgbc.org/LEED/Credit/CIRDetails.aspx?RequirementID=13

Ben,
We are working on a project that has a similar condition to the one you described above. Could you please explain your final approach and if it was approved by GBCI.
How did you account for the water feature on the roof? Is the Pool / water feature area part of the denominator?

Thanks,