Hi,
I work on a Core & Shell project based in Paris and i have a question about ASHRAE 90.1 Standards, and more especially on the possibility to derogate to certain requirements. On this project, 3 labels are targeted : HQE / WELL / LEED
My question if about the Requirement 5.5.4.1 that said the SGHC must be < 0.4 for every windows. In the case of our project, there are 2 patios of 7 floors, with a low access to natural lightning. The study we did, according the HQE requirements, oblige us to use extra clear glazing (with SGHC > 0.4) . If not, the HQE certification wont be possible.
Could you confirm, in this case, that we can derogate to LEED requirements, and could you also explain how di we need to justify this derogation.
In a general way, if there are other requirements of ASHRAE 90.1 that can't be meet, how do we justify it ?
Thank you for your help.
Regards,
Guillaume
Jean Marais
b.i.g. Bechtold DesignBuilder Expert832 thumbs up
October 1, 2019 - 5:56 am
There is no requirement for SHGC <= 0.4. That's just for the baseline building... so your building is measured against the baseline building.
Waleed AlGhamdi
Sustainability EnablerEskew+Dumez+Ripple
20 thumbs up
October 2, 2019 - 10:24 am
Like Jean said, it's a "prescriptive" requirement. If you're doing LEED, chances are you're following the performance path and don't need to meet all prescriptive requirements (though you still need to meet all "Mandatory" requirements).
Having said that, you can still get pretty good daylight but also with low SHGC with coated glazing (Low-E). LSG (light to solar gain ratio, could also have other acronyms) is a measure of how much visible light you can get to how much solar gain is let through. In 90.1 2016 the minimum is 1.10, which ensure good visible light while blocking solar gain. Some products have LSG up to 2.30 and even more. For example, Viracon VNE13-63 has a VLT of 67%, which is pretty good, and a SHGC of 0.29, also pretty good when compared to 0.40 applicable to most moderate climate zones like Paris. Also note that the SHGC allowance increases if the glazing has permanent external shading on it, which reduces the solar gain on the glazing.
I'm not familiar with HQE, does it require VLT that's considerably more than 65%?
Guillaume Rose
October 2, 2019 - 4:07 am
In HQE there is no requirements on the VLT. There are only objectives on the daylight autonomy in your building.
Sara BENLOUBA
Green building managerConfidential
13 thumbs up
February 5, 2020 - 11:00 am
Hello Jean, hello Waleed,
Could you tell me if it's if it is mandatory that the thermal coefficients of my building comply with table 5 - 5.3 of ASHRAE 90.1 which governs the performance of each type of envelope?
I'm lost, I'm on a project outside the United States.
Waleed AlGhamdi
Sustainability EnablerEskew+Dumez+Ripple
20 thumbs up
February 5, 2020 - 11:25 am
Sara,
Table 5-5.3 is a "prescriptive" requirement, not a "mandatory" requirement.
All buildings wanting to comply with 90.1 must comply with ALL MANDATORY requirements, regardless of compliance path. There are two paths for compliance in the standard: Prescriptive Path and Performance Path.
In your post above, you identify Table 5-5.3 as "Mandatory" when it is in fact "Prescriptive", so if you're following the performance path, you don't need to follow all of them. Needless to say, following them are minimum best practice, and if you don't meet too many prescriptive requirements, you won't be able to comply with the standard using the performance path.
Sara BENLOUBA
Green building managerConfidential
13 thumbs up
February 5, 2020 - 12:48 pm
Many thanks walid,
You saved the whole design team. We thank you all for your help.
I understand that I am confusing the normative and the prescriptive ... could you tell me how I can clearly make the difference?
Can I consider as mandatory provisions only the points below?
5.4
6.4
7.4
8.4
9.4
10.4
there are others points?
Many thanks
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5909 thumbs up
February 5, 2020 - 1:16 pm
Yes all the mandatory provisions are in Sections X.4 as you indicate above.
Eduardo Vidal Kume
energy and building physics expertATP sustain
1 thumbs up
May 20, 2020 - 9:57 am
What about sections 5.8.1.1 through 5.8.1.9 ? It says in mandatory provision 5.4.1 that insulation should comply with those when prescribed by 5.5 or 5.6.
Cam Fitzgerald
3 thumbs up
May 20, 2020 - 10:40 am
Hi Eduardo,
Section 5.6 defines the options for envelope performance trade-off with other building components. When using the performance path from Appendix G (energy modleing), the referenced Appendix C calculations are accounted for in the modeling.
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5909 thumbs up
May 20, 2020 - 4:30 pm
Sections 5.8.1.1 through 5.8.1.9 address characterisitics of the insulating materials. So Section 5.4.1 means that when insulation is prescribed in Section 5.5 or 5.6 it must comply with those characterisitics. So these mandatory provision are associated with prescriptive requirements. I suppose they are a cross over of sorts.
Gustavo De las Heras Izquierdo
LEED Expert185 thumbs up
November 14, 2023 - 7:26 pm
That's right Sara and Guillaume,
As a matter of a fact, the credit requires the following:
As you can see, the projects need to comply ONLY with mandatory provisions of ASRHAE 90.1, and be more efficient than an energy model that follows the Appendix G. Consequently, you have plenty of flexibility to design your envelope and MEP systems. Some of the U-values might be more efficient than the baseline (other U-vaues may not be more efficient).... The same applies with MEP systems, for example some spaces might have a LPD be more efficient than the baseline (other spaces may not be more efficient)...etc.
The energy model will serve to verify that the WHOLE design is more efficient than the baseline building, but you do NOT need to be more efficient than the baseline on every single item. In your example, your project may perfectly have a glass with a SHGC less efficient than the baseline (greater than 0.40).
I hope that helps!
Francesco Emanuele Contaldo
April 10, 2024 - 12:13 pm
Hi,
as far as I understood, only previsions provided in chapter 5.4 have to be considered mandatory, while, for instance, building envelope performances represented in chatper 5.5, and connected tables, are prescriptive.
So, for instance, although 5.4.1 references value in chapter 5.5 for thermal insulation, I do not mandatory have to respect those minimal values, but I can consider the whole building in order to achieve targetted energy consumptions reductions.
I pose this question because I am designing the refurbishment of a historical building in Rome and I cannot add thermal insulation to external walls, so, if I am right in reading this conversation, I can pursue LEED certification even if I cannot reach minimum insulation values for external walls of conditioned spaces stated in chapter 5.5.
Thanks in advance for your attention and support
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5909 thumbs up
April 11, 2024 - 12:38 pm
That is a correct interpretation.