CS 2009 SSc7.2: Heat Island Effect—Roof

It use to be a bit more like you describe it, depending the space being conditioned. But with the new definition of 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. the roof above your mechanical room will be included in the calculation, since it's enclosed gross square footageSum of the floor areas of the spaces within the building including basements, mezzanine and intermediate-floored tiers, and penthouses with headroom height of 7.5 ft or greater. It is measured from the exterior faces of exterior walls or from the centerline of walls separating buildings, but excluding covered walkways, open roofed-over areas, porches and similar spaces, pipe trenches, exterior terraces or steps, chimneys, roof overhangs, and similar features. of the building. However form my experience these mechanical rooms a lot of time are more like a enclosure to prevent direct exposure to rain. So those walls often times are lovers all around and no actual wall separating inside from outside. I think in this case I would excluded such an area form the calculation. I hope that helps.

You can deduct both the equipment and the duct work. see also the definition of 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.: http://www.leeduser.com/credit/NC-2009/SSc7.2#comment-16498
In many countries you are required to have gravel strips around and under equipment for fire security and people safety reasons. Even thought I don't think that was the reason for excluding these areas.
Good luck with the project.

You don't have to include the awnings since there don't cover an enclosed space see also this comment with the definition of a roof. http://www.leeduser.com/credit/NC-2009/SSc7.2#comment-16498

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. can vary a lot depending on, what exactly your gravel looks like and is made of. You will need the actual SRI either per manufacturer's data or testing. See also George's question below.

Luis, this gets into some tricky issues which have been discussed in more detail on the NC version of the SSc7.2 forum, but my recommendation is to not try to count the pool for your 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.-compliant surfaces.

For this credit, according to Leed Online, you have to consider total 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. excluding mechanical equipment, photovoltaic panels and skylights. If your project's roof consist of only photovoltaic panels and green roof, in terms of this credit, 100% of this roof is a green roof and therefore you achieve it. Actually you can apply for 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. with this percentage.

The project i'm looking at has a green roof with PVs sitting on a framing system slightly above the vegetative material. Is it possible to include the plan view area of PV in the 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. calculations as on other projects we've seen a better growing result in the shade of the PV than elsewhere . Sun angles etc would also mean that the green area is alos doing its job. The project's ecologist has given the all clear for walk on access for maintenance purposes. thanks

Vivian,
do you have other materials on the roof as well? Or is it only green roof with PV panels? If there is only vegetated surface and PV panels, why do you want to include it?

The reason for excluding mechanical equipment and PV panels from this credit calculation is that it would be contraproductive. HVAC systems are very often situated on the roof, because it is not possible to put it anywhere else. And without it you wouldn't achieve some other more relevant credits...

Yes there are other roof areas - two difference types of roof material and also some other plant enclosures. I'd exclude the plant areas easily enough but if we can include the area of PV within the green roof area on which the PV sits the calculations should be favourable for the 50% vegetative roof area

I see... my guess is that if you wish to do it this way, you will need to submit a CIRCredit Interpretation Ruling. Used by design team members experiencing difficulties in the application of a LEED prerequisite or credit to a project. Typically, difficulties arise when specific issues are not directly addressed by LEED information/guide on this.

Patrick, I would say that depends in part on the function of the underground spaces. Are they conditioned and occupied?

Hi guys.
We have it the same, but on the contrarary. My guess is that if the underground floors serve as a garage, then the "roof" at the ground level can be considered a terrain instead of a roof and we do not have to count that towards achieving SSc7.2. Any comments on this?

Yet I forgot to mention that besides the green "roof" aka vegetated surface above garage there is a portion of asphalt drive way. That is why we want to exclude it.

Yes they are, both conditioned and occupied.

Patrick, in that case I would consider it a roof.

Courtney, as with other existing materials on the project, you would not have to include the roof in your project cost. You could earn the credit by leaving the white roof in place, but you'll have to show that it has  compliant 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. value. That will probably require finding specs from the manufacturer, or testing.

George, skylights are excluded from the calculations for this credit. I think that puts these fins, which you describe as an appurtenanceAn appurtenance is any built-in, nonstructural portion of a roof system, such as skylights, ventilators, mechanical equipment, partitions, and solar energy panels. on the skylight, in a bit of a gray area. Sounds like it would be a good idea to include them, though.

We have had the same issue on our projects. There are no 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 for roofing materials and the only way of getting them is to perform an rather expensive testing. As far as I know and have read so far you will have to prove the actual SRI. You can not use that table. We haven't actually tried a CIRCredit Interpretation Ruling. Used by design team members experiencing difficulties in the application of a LEED prerequisite or credit to a project. Typically, difficulties arise when specific issues are not directly addressed by LEED information/guide or submitted the credit with presume values. So maybe they will except it, but my guess is not.

I would second what Susann says. You have to show actual 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.. I think part of the hope of LEED in general and perhaps in this credit is that manufacturers will be more motivated to provide this kind of information.

In this project, the gravel or cement on the roof is going to be painted white. The white paint is produced locally by manufacturers who do not know what 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. means!

As such, can I use the SRI value for the white coating in Table 1? I do not think that the SRI will vary significantly among white coatings.
Any suggestions?

Thanks!

Again, I think you need to use actual values, not rely on the table. The value for something that appears "white" can in fact vary a lot, especially when it's applied to something like roof ballast.

Does GBCI want to document 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. of materials that have SRI lower than required by this credit as well as of complying materials?
For example, part of roof is covered with bituminous material and part of roof covers high albedoAlbedo is synonymous with solar reflectance. EPDM foil. We have documents only for EPDM foil. In calculations for this credit I intent to use actual SRI for EPDM and for bitumin a value from the table or other sources. Could this be acceptable? Obviously, bitumins do not have high albedo so the manufacturer doesn't even want to test the material for SRI. This sounds logical to me...

Petr, you do not need to document 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. for materials that you are not using to comply with the credit. I hope that answers your question.

I have the same problem in Brazil. Difficulties to obtain 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. value for some materials. One of most respected tech institutes performs SRI test according to ASTMVoluntary standards development organization which creates source technical standards for materials, products, systems, and services E 1980. However, the refletance value is obtained by ANSI/ASHRAE 74-1988 - "Method of Measuring Solar-Optical Proprerties of Materials - E procedure". Emittance is measured according to ASTM C1371, as indicated by the LEED RG.
Can USGBC/GBCI accept SRI values for a material performed ​​in accordance with these standards referenced, using ANSI/ASHRAE Standard, instead of ASTM standard, to determine the reflectance value?
We have not submmited any CIRCredit Interpretation Ruling. Used by design team members experiencing difficulties in the application of a LEED prerequisite or credit to a project. Typically, difficulties arise when specific issues are not directly addressed by LEED information/guide or LEED Interpretation.

The reference Guide page 119, see footnote 2, listes both ASTMVoluntary standards development organization which creates source technical standards for materials, products, systems, and services 1980 and ASTM c1371. So you should be fine. No CIRCredit Interpretation Ruling. Used by design team members experiencing difficulties in the application of a LEED prerequisite or credit to a project. Typically, difficulties arise when specific issues are not directly addressed by LEED information/guide necessary.

Reference Guide CS 2.0 says on page 105: "Default values will be available in LEED-CS v2.0 Reference Guide". I assume this points on the table on page 107. Under the table there is a statement that the values dont replace values of manufacturer data sheet. Strange for me? As we use white coatet gravel on built-up roofA roof covering consisting of several successive layers (each of which is called a "ply"), usually of roofing felt, with mopping of hot asphalt between layers and topped by a mineral-surfaced layer or by gravel embedded in a heavy coat of asphalt. and white cement tiles I would take the values from the table...
For documentation the RG says just to provide a list of materials of 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., but not how to proof this SRI. So I assume that they dont need manufacturer data sheets as proof, right?

You will need the manufacturer data sheets or testing protocols showing 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.. You really can not use data listed in the table of sample data you may find otherwise. Also make sure the manufacturer list the standard under which he has tested the SRI.
Sorry, I know this is hard and expensive if you are working on a non US project. Good luck!

I think you would most likely have to consider this a roof, since it is a horizontal exterior surface over conditioned space. So, I think you would have to count it under SSc7.2. I suppose you could try to to count it under SSc7.1, under the argument that it's more like a non-roof surface, if you thought that would be advantageous, although you'd have to get a CIRCredit Interpretation Ruling. Used by design team members experiencing difficulties in the application of a LEED prerequisite or credit to a project. Typically, difficulties arise when specific issues are not directly addressed by LEED information/guide or hope for the best during review. I certainly couldn't see it being ignored—not clear how you could argue that. If it's occupied space that it would have to have roof above it, right?

I could see it being counted as pedestrian-oriented hardscape under SSc5.2 if you're also earning SSc2.

Thoughts?

We are having the same problem on a football arena. The project has a big area which serves as roof for part of the occupied areas and is the main access of the stadium, functioning as a large circulation area. However, if we specify a material finish with a 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., wouldn't it be unconfortable for the pedestrians since it is a horizontal surface? If we specify an 29 SRI wouldn't it be enough?
Thank in advance for your answer.

Any of these surfaces over conditioned space would be considered a roof and would need to meet 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 accordingly. Although use of roof space for these activities is clearly commendable -- in may receive credit in other areas of LEED -- a dark surface would not meet the intent of this credit. Note that roof covering occupied but not conditioned spaces are not counted in this calculation.

I would not rule out a pedestrian-appropriate high SRI surface -- a lot of products have been developed in the last few years that meet the SRI requirements without feeling highly reflective. The stadium condition is somewhat unusual, though, so I don't know offhand of anything appropriate. You won't likely find products for the play space.

Robert, I believe that a roof is defined as a surface that covers usable interior space. So, for example, a balcony is not a roof, but it sounds like this terrace is a roof.

What about a terrace that is just partially covered by the next floor? One of the projects we are currently working on has this very interesting design: like stacked floors with some with vegetated terraces/balconies, and the next floor overhung partially or completely or opened like a rooftop terrace.

According to your experience, how shall we treat for SSc7.2 the terraces, that are partially covered by the next floor? I am thinking of counting as roof, only the visible part from bird-eye.

Also, a big issue is the open space calcs in SSc5.2: can we included the vegetated balconies, even though they are covered by the next floor.

Any thoughts and considerations would be highly appreciated. Thanks in advance.

In regards to the 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. for SS 7.2 I have looked through all the CIRs and couldn't find a ruling that clarifies this. The general rule you will have to go by is "roof is what covers the building", this excludes a roof covering unconditioned spaces, or spaces open to the outside. So you will have to count your terrace even if it's over shadowed by an overhung.
It does on the other hand side make sense to exclude areas, which are in the shade, similar to SS 7.1 Non-Roof. If you want to do that, you should probably submit a CIR to make sure it's ok for the reviewer.
For SS c5.2 you can included the balconies, if you also comply with SS c2 and the balcony, terrace or roof top needs to accessible for building occupants. So if the access is restricted or it's a private balcony than it doesn't count.

Hi Xavi,

Your square footage numbers should be consistent so I'd either wait and see what your total square footage ends up being or just work to certify the first 80,000 square feet.

Hope that helps,
Lauren

Thanks

The credit requires you to have at least 75% of the roof surface meet 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. requirement. If I understand you correctly, then the mesh is only 20% solid, so this alone would not meet the requirement and at least part of the roof would have to comply. There are several CIRs under earlier versions of LEED that can give guidance on weighted calculations that take the shading into consideration.

Ladders and other appurtenances are not required to meet the SRI requirements.

Thanks Mara for your advice.
Actually, most of the concrete roof slab has M&E equipments and pipes. Since the M&E areas are exempted from this requirements, we would like to exclude the concrete roof slab from 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. Another reason is that gird mesh is located at about more than 10m high above conc slab and the conc slab is well shaded by vertical perforated panels. So, we wonder if the reflectance of the roof slabs will have impact on UHI.
Any comment or suggestion? Thanks,

There are two different questions here (unfortunately). The first is whether or not the roof has much impact on UHI. The second is how you're supposed to treat it for the LEED point. You're probably right that the concrete roof surface doesn't play a big role. For LEED, you still have to document that you're mitigating the UHI effect -- if not by the conventional mechanisms, then by an alternative compliance path that is equally or more stringent. The simplest way to do this is to determine how much of your roof is not M/E equipment, and make at least 75% of that area cool. Part of this strategy may also include making the mesh cool as well (e.g. painting that white).

I definitely recommend checking out the different CRIs for more specific guidance regarding the shading -- you'll better be able to figure out what applies to your circumstance.

As per the Reference Guide, appurtenances are exempt from this calculation, along with mechanical equipment and PV panels. I typically think of parapets as appurtenances, because by definition they are a less significant element associated with the roof. It sounds like that might not be the case for your parapet, however, which leaves this as more of a judgment call.

Do you generally include walking pads on roofs or lump that into the excluded category as well? Thanks

It's my understanding that walking pads are included. There are several walking pad products that meet 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, although you can also require a conventional pad with an added coating. This can be pretty important, as walking pads can potentially make up a significant percentage of 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..

The horizontal surface of the parapet can contribute to heat island. This surface is not an appurtenanceAn appurtenance is any built-in, nonstructural portion of a roof system, such as skylights, ventilators, mechanical equipment, partitions, and solar energy panels. (which would include things like ladders, pipes, antennae, etc.). Intent of the credit should be considered here so you don't get bogged down in meaningless analysis of course.

Usually (big roof and typical parapet), the area of the top of a parapet would not change the outcome of the calculation for this credit, but you would want to look at it if significant. Imagine an 18-24" wide dark painted metal coping around a 2500 sf roof - around 10% of the 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. net of equipment. Might matter...and such buildings have been built. As well - parapet area can exceed walking pad area.