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18 Comments
SRI compliant paints
What if we apply a paint, for instance lets say we apply White color paint which is not a specific reflective coating on our roof. Will we able to claim the credit?
If not, do we specifically need to make the roof by a 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. material or by a specific reflective coating to meet the credit needs?
Please forward your ideas....Thanks
Tristan Roberts replied Editor – LEEDuser, BuildingGreen, LLC Mar 25 2010
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.
RASHID HAMEEN replied Mar 26 2010
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.
Ballasted Roofs SRI?
Has anyone had luck getting a good 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. rating out of existing ballasted roofs? Apart from sending this to a lab, are there any charts or other information to use? Has anyone successfully gotten this credit when their building has a majority of light-colored ballasted roofs?
Tristan Roberts replied Editor – LEEDuser, BuildingGreen, LLC May 28 2010
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.
BKSK Architect replied BKSK Architects Jun 01 2010
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.
Jonathan Weiss replied Aug 16 2010
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.
What if the roof doesn't requiring replacing?
Our project's roof does not meet the credit requirements. The owner is willing to spec a compliant roofing system; however, the roof is in good conditions and still has 7 years left on its warranty. Is a commitment to purchase a compliant roofing system once the roof requires replacement a valid compliance path? I'm guessing based on Kim's experience above that this is not likely a possibility. It seems a bit 'counter-green' to replace a roofing system that is still in good working order.
Natalie Bodenhamer replied Green Building Consultant, CTG Energetics, Inc Jun 01 2010
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.
Shaded roof
If the shaded roof area exceeds the 75% does that meet the requirement of this credit. I have a building that has an architectural crown of white glass that shades over 75% of the roof surface at any given time.
Tristan Roberts replied Editor – LEEDuser, BuildingGreen, LLC Aug 05 2010
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.)
75% COMPLIANCE area
Our roof is 100% covered with White EPDM material. On top of that material are the HVAC units. There are also a couple of vents and a hatch opening for roof access. All these things add up to 56.5% of the roof area. Does this forfiet me from getting credit SS c 7.2? Since I do not have 75% of the roof clear of obstructions? Thanks.
Tristan Roberts replied Editor – LEEDuser, BuildingGreen, LLC Aug 30 2010
Appurtenances such as HVAC equipment, etc., can be excluded from the calculations. Good news for your project.
material specification
where we are located, 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 not a common terminology and we are currently in the process of specifying an SRI compliant roof coating for a roof which is currently undergoing repainting/repair.
the product we are looking at gives us the following data:
heat reflectance: >99%
emittance: 0.88
if i assume that heat reflectance equates to solar reflectance, we can achieve an SRI of over 126. Are my assumptions correct? or is heat reflectance not the same as solar reflectance?
all the other information contained in the data spec for this particular product indicate that this is a cool roof product - but since it is not a US product, the terminology is a bit confusing to us.
many thanks!
Jacob Arlein replied Director of Energy Services, Environmental Building Strategies Aug 31 2010
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..
Jutta Berns-Mumbi replied Aug 31 2010
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!
Tristan Roberts replied Editor – LEEDuser, BuildingGreen, LLC Aug 31 2010
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."
Jutta Berns-Mumbi replied Sep 01 2010
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!
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