EBOM 2009 SSc7.2: Heat Island Reduction—Roof

Angelica, I haven't seen this problem. It sounds like there could be a math error embedded in the form. I would send an email to GBCI about it, but I would otherwise proceed with submitting the form for the credit.

Mauricio, this strategy is not a "preapproved" strategy for this credit, which is not to say that it wouldn't work. I would encourage you to submit documentation showing how effective it will be, but I would not count on earning the credit in this way.

I wouldn't see a helipad meeting this standard. Seems like it could easily have a reflective coating, anyway?

It has a Sherman Williams white coating, but the paint is not tested, and the company is not about to go test it either. Do you think the white coating would pass regardless? It's been there for years now.

Andy, I doubt it. You would be expected to get the paint tested by sending a sample to the lab. That is the standard approach for this credit, even if it can be a pain.

We should get at least 1 point without excluding the helipad, but could get 2 if they were to exclude it (as a backup IO pt.) We'll keep you posted on the outcome.

Solar panels do help you with SSc7.2, in the sense that they are considered appurtenances and are not counted as part of your 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.. So use of solar panels effectively reduces the area that you need to consider for other measures.

does anyone know if the same applies to a green roof application as well?

Denise, green roofs are a key way to earn SSc7.2. I'm not sure if that's your question, though -- can you clarify?

sorry, i meant for option 1 of ssc7.2. If I go the reflective materials route, am i able to not count green roof and photovoltaic panels as part of my 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.?

Denise, Option 3 is a combination of Options 1 or 2. So it's not either/or.

To clarify,

We have existing solar roof shingles which cover approximately 50% of our roof. Are solar shingles still considered appurtenances? Because of the slope and the weight load we cannot do the green roof option, though we are considering the white roof option for the other portion of it.

Thanks!

That should work - your solar shingles in this case would be considered mechanical equipment, which you subtract from your 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., and use white/ 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. roof for 75% of the remainder.

It may be acceptable to mark up or alter the drawings, as long as you a) have permission from the architect as well as the client for the specific use or changes, and b) make it clear which information is yours.

We've had LEED reviewers who suggested we hide or turn off unnecessary information in the drawings or make it very obvious where the relevant LEED info was. Their priority is more for efficient review and are less concerned with format formalities. Anecdotally, I'd say that LEED submissions need to "clear, complete, and credible," (to coin a phrase) but there are no legal or policy guidelines for format, title blocks, or attribution.

Many architects will remove their stamp from the title block of drawings submitted for LEED and provide a disclaimer "For LEED Documentation - Not Intended for Construction" to make it clear that these are not Construction Documents, which become part of a legal contract between the general contractor and owner.

You might consider adding a key note with date and LEED purpose to the title block or notes area and then use revision clouds, color circles, or highlighting, etc to make the LEED specific information on the drawings more obvious. With permission, you could also use the original drawings as "backgrounds" for your own photoshoped sheet, and make your markup and highlighting clearly your own.

Jorge, we don't have a sample. I think it can be pretty simple, though.

I think you would have to test the glass, if there isn't a manufacturer you can get specs from. There is so much variation in the performance of glass.

Jutta,
I am not exactly sure what you mean by heat reflectance, do you mean thermal reflectance? Either way, heat reflectance is not the same as solar reflectance or albedoAlbedo is synonymous with solar reflectance.. Albedo is the ratio of total-reflected to incident electromagnetic radiation from the sun. This is a measure over all wavelengths of light.

It is likely that this product is still a cool roof product with such a high thermal emmitance level, but you will have to determine the solar reflectance of the material to be able to accurately calculate 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..

many thanks for the response and i understand the point you make.

unfortunately the data sheet simply states "heat reflectance" and "emittance" - as above - and also has a value for thermal conductivity (0.09 W/m°K).

are there any other resources we could consult to help us calculate 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. correctly with the information that we have available?

indeed all products that we have been able to source so far (we are located in South Africa) only provide, if at all, values for heat reflectance and emittance.

we are being pushed to make a decision on the coating and really do not want to lose the point on documentation, if it seems that we may be quite close!

many thanks!

Can you ask the manufacturer to clarify, or offer better data?

This may simply be a language issue, where what they are calling "heat reflectance" is in fact "solar reflectance."

Many thanks! have done so and it was indeed simply a language issue and the test reports have now confirmed the values. Such is the excitement of working on projects outside the US!

Appurtenances such as HVAC equipment, etc., can be excluded from the calculations. Good news for your project.

Does this mean if the building 100' x 100' for example = 10,000 sq/ft total roof surface, you will use 10,000 sq/ft as your total roof sq/ft. even though your roof may only be really covered by 50% 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. membrane and the other 50% HVAC appurtenances, etc...??

When you're documenting this credit in LEED Online, the form asks you to provide 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)." So, you're not entering total roof area, you're entering total roof area that is eligible for consideration under the credit. You're also uploading a roof plan and other documentation. Make sense?

That makes perfect sense Tristan. What doesn't make sense is that when LEED asks for the SF (from LEED;Note that in the table below, 'Square footage' refers to the actual area of roof covered by 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. surface) and then asks for "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) (sf):"
and then I calculate I get a number of 243.55%. Because my the overall SF is 5932 sf and the number excluding the appurtenances is
2591.75 I come out with that strange number.

LEED's response was this;
Response: The information provided above indicates that the area of White EPDM (5932 sf) exceeds the total roof area (2591 sf). This information would indicate that the reported square footages may be incorrect and would indeed result in > 100%. Perhaps the numbers are switched? Also, please note that the calculation for the SRI compliant area is weighted based on the SRI value. Therefore, when using high SRI materials, it is possible that this calculation will demonstrate > 100% compliant roof area.

I guess what they are saying is that it is okay to have a 200+% number. Does that make any sense to you? If it does I have completed this credit.

You didn't mention 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. values, but if they're higher than the minimum requirements, it's not surprising that the weighted value would generate a weird-looking percentage number.

Just to be sure....table SSc7.2-1 asks for the total square footage of the reflective material. And THEN it asks for the total square footage of the roof MINUS the solar panels, skylights and mechanical equipment. I have entered in the relective material square footage which is a larger number than the square footage minus the appurtenances. And this will be okay? Shall I upload a spreadsheet with all the square footage numbers in it (total roof, roof minus LEED-allowed appurtenances, roof minus terrace and other "non-roof" surfaces, etc)?

Andrea, I don't see how the SF of your reflective material could be larger than the SF of the applicable 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.. It implies that some of the area you are counting as appurtenances actually has relfective roofing on it. Or am I misunderstanding something?

Exactly, Tristan. Our RTU-1 rooftop unit (5794 square feet) actually has the reflective roofing on it. I should be okay, right? I uploaded a very clearly labeled Google Earth map.

Yes, that sounds okay. Hopefully everything is clear to the reviewer and you don't have any difficulties.

Wayne, there's no shading option for this credit. The white glass must 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 of Option 1. (See above for more.)

A commitment to purchase a compliant roof system does not meet the credit requirements of SSc7.2. This is a great opportunity to integrate the roof replacement into the LEED EB Recertification plan/strategy. The replacement may impact energy efficiency (EAc1), in addition to SSc7.2.

Cara, I don't have definite answers to any of your very good questions, but I did find some interesting resources. A fairly recent note in the Cool Roofs Rating Council newsletter that makes it sound like ballasted roofs are gaining acceptance as "cool" roofs. Also, a study from ORNL that may be behind some of this recognition.

I'm not sure where this leaves you, except perhaps with some encouragement that you're on a reasonable path.

Just to clarify a bit further, while white ballasted roofs are showing evidence of performing as well as other "cool roof" systems, the USGBC does not recognize any flat roof material under a 78 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 the SScr7.2 LEED credit. This is because the intention of the credit for micro-climate development is not met by materials that do not meet this threshold.

Just to echo what is stated above - we submitted 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 about a ballasted roof referencing the ORNL study and the CRRC information, and the response to the CIR confirmed that although the ballasted roof performs as well or better than a white roof for energy purposes, it does not meet LEED's requirements, because of the micro-climate issues listed above. It still may be better to use a ballasted roof in some situations, and forgo this particular LEED point.

Rashid, you will need documentation showing that the paint or whatever else you apply is actually 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.. You can't simply claim the credit by using a white color, since SRI values vary so much even with materials that may appear to be simlar colors. Also, keep in mind that SRI factors in emissivityEmissivity is the ratio of the radiation emitted by a surface to the radiation emitted by a black body at the same temperature. which is different than reflectivity. Polished aluminum, for example, is highly reflective but very poorly emissive.

Thanks tristan for your comments. In case if we couldn't find a coating which has data sheets to show compliance of that having a suitable 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. will it be sufficient if we check a sample with lab and show the compliance or does our test has to be done to a sample of the roof material which is after applying the paint..please post your comments.