Hi there, sorry for the long intro and thank you in advance for any feedback,
We're trying to specify our Climate data file for LEED simulation purposes. Our client is developing a LEED-NC project on a site located about 21km north of Cusco, Peru. As per the EnergyPlus website, the closest data file is from Cusco (of course). Such database specify HDD/CDD as falling under zone 4 according to "Table B-3 Zones International Climate".
However, our own specific microclimate studies for the site, which is nearly 1,000 mt lower than Cusco and presents milder conditions, demonstrate that actual HDD/CDD on site coincide with those of zone 3 (CCD: 1636 and HDD: 1763, belonging to zone 3C - Marine). Of course we're using such site-specific conditions for HVAC projects and energy efficiency in general. The problem is that 3C-Marine is defined as to having dry hot seasons versus wet cold seasons whereas in our case, it's exactly the opposite (wet hot season versus dry cold season).
In sum, energy efficiency measures in general, and HVAC sizing in particular, will respond to 3C-zone type conditions, but we don't want to be forced to use 4A zone-type for baseline conditions. We like comparing apples to apples.
So, can we stick to 3C zone-like microclimate conditions, for both proposed AND baseline models (complying with both CDD andHDD but not complying with humidity conditions from Appendix B), or do we have to forcefully use 4A zone requirements for the baseline model (complying with humidity conditions and CDD but not with HDD)?
I know, I'm confused too. Any help is gratefully appreciated.
Jean Marais
b.i.g. Bechtold DesignBuilder Expert832 thumbs up
July 24, 2012 - 2:20 am
I've tried this and it came back as no. For compliance with ASHRAE 90.1, you're better off looking up the climate zones for your location direct from the Standard.
Many of the statistical weather data files have auto-generated climate zones, but watch out! They do not always match that as defined by ASHRAE for the location. This is because statistical weather data is averaged for energy modelling purposes and may not have the extreme weather periods needed for the definition of HDD and CDD.
Dispite the fact that HDD and CDD can fluxtuate up to 40% year to year, the chosen climate zone has large impacts for your performance vs the baseline case model based on this.
It is one of those "sticky" points which is not fully addressed at the current time.
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5909 thumbs up
July 24, 2012 - 10:10 am
You should use the weather file that most closely represents the weather on your site. As Jean indicates measuring HDD/CDD for a short period of time can be misleading so the selection should be based on long term weather data. If using a Marine climate make sure it complies with the criteria in Appendix B2 and not just the HDD/CDD in Table B-4.
Esteban Undurraga
Managing PartnerMinus S.A.
9 thumbs up
July 24, 2012 - 7:36 pm
Jean and Marcus, your feedbacks are much appreciated.
As mentioned, the closest and only weather data we found is for Cuzco, which is not in the standard. it's the one provided by Energy Plus (HDD/CDD matching Ashrae 4 and A-moist). All we did to it later, was to refine it as per site-specific topographic conditions and altitude, obtaining new HDD/CDD matching a slightly different zone (as per Table B-4 AND App B2 = Zone 3C). So I believe it can still be considered as a long-term weather data, right?.
Is this an acceptable methodology? If not, then 4A it is for our baseline and therefore the proposed model will be penalized for using site-specific conditions (3C).
Sorry, but am i missing something? Sticky point indeed.
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5909 thumbs up
July 25, 2012 - 4:21 pm
I can't tell if your weather data is long term without far more information. So I do not know if it is acceptable or not. If you can conclusively demonstrate that the weather is most appropriately 3C then you should make the case to the reviewer when submitting for LEED. Fully explain how you refined it and provide them with your data to support the refinement. If you can justify your changes then the reviewer should accept them.
Esteban Undurraga
Managing PartnerMinus S.A.
9 thumbs up
July 25, 2012 - 4:42 pm
Thanks Marcus. Hopefully a well explained and documented narrative backing up such site-specific weather database should do the job.
Will maintain the forum updated on the success (or not) of this matter.