Hello,
I am currently working on a LEED NCv2009 project which includes a small building ~1,150sf, and has 200sf of regularly occupied space. The remainder of the building is restroom and storage area. The entire building is naturally ventilated with permanent louvers (always open) located at the top of each wall all the way around the building. The regularly occupied area also complies with natural ventilation requirements of ASHRAE 62.1 via appropriately sized operable windows and the building is located within a block of the ocean in a temperate climate. We are running into difficulty achieving the 10% minimum energy cost savings required for EAp2 as there is little energy usage, aside from process, in the building without an HVAC system. We basically have interior and exterior lighting (façade and site), a hot water heater and receptacle. We are using EnergyPro and T-24.
Questions:
1) Since there is no heating or cooling, we do not have to model either. Correct? It is my understanding that if there was heating we would have to also model cooling or vice versa, however if the building is not conditioned we do not have to model either.
2) Do we have to provide any information for unmet heating and cooling hrs if we are not claiming savings for natural ventilation?
3) Any other general suggestions for modeling this scenario to achieve the requirements of EAp2??
Thanks!
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Anil Bhari
Min engineering inc3 thumbs up
May 23, 2013 - 5:29 pm
According to Table G3.1.10 , you have to simulate, even if no cooling and heating system exist in building. In this case your baseline case and Proposed case HVAC system will be similar.
In your case if your building is residential than your baseline system will be System 2, if it is commercial than your baseline system will be system 4. For proposed case you have to use similar system that you have used for Baseline case.
Basic fundamental behind similar system is that you can show saving from envelop, lighting, HWH (if your envelop, interior lighting is more efficient than baseline) .
Hope this info helps you.
Good luck
Chad Coleman
Project ManagerMay 23, 2013 - 6:50 pm
Thanks Anil!
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5909 thumbs up
May 23, 2013 - 7:26 pm
1. I am not sure of the T24 rules but it certainly makes sense to not model systems that do not exist and are identical. Even in 90.1 there is a work around to the requirement that Anil mentions - just change the temperature settings so the fake systems do not run.
2. No you do not.
3. Implement lighting and service hot water saving measures! Are you claiming any hot water demand reduction?
Chad Coleman
Project ManagerMay 23, 2013 - 7:49 pm
Thanks for the response Marcus!
1. We attempted to fake the systems with the temperature set points, however this apparently is not possible in EnergyPro. We ended up discussing this with EnergySoft who confirmed this would not be an option.
2. Thank you for confirming. This is good news.
3. I have a note to confirm that we are claiming hot water demand reduction, however am unsure right now. We are seeing some savings from the service hot water and may be able to capture some additional savings by switching to a more efficient unit. Lighting has been the Achilles heel for the project. From the beginning we were counting on efficient lighting to pull us through and achieve the minimum 10% savings, then the County requested additional lighting for safety measures and we are back to the drawing board with little room to work (without adding additional energy usage).
Jean Marais
b.i.g. Bechtold DesignBuilder Expert832 thumbs up
May 24, 2013 - 2:54 am
The standard is intended to regulate mainly conditioned spaces. IMO if the space is not conditioned, it has no "real" setpoint to meet. So the heating setpoint could be -50 deg C and the cooling setpoint could be +100 deg C. I have no problem with this for unconditioned spaces, unless they are regulary occupied...in which case I believe the intent of the standard is to anticepate that dissatisfied users will retrofit conditioning systems if they are often dissatisfied. For naturally ventilated spaces the upper bounds could be 28-32 deg C and the lower bounds at say 15 deg C. Check out AM10 to back up wild claims like this.
There are no envelope requirements for unconditioned spaces, meaning baseline = designcase. It's going to be hard to show enough savings.
Chad Coleman
Project ManagerMay 24, 2013 - 11:39 am
Thank you Jean, I appreciate the suggestion to look at AM10. The project is located near the ocean in Southern California and the occupied portion is essentially a concession area which will serve the public at a park with a water fountain / feature. A majority of the time the weather in this area does fall between 15 and 32 deg C, and the concession area will likely not be open if it is below 15 deg C. There may be 2 times a year when the temperature is above 90 degrees F this close to the ocean.
I agree that it is going to be difficult to show enough savings as currently designed. We have discussed including AC in the building to take advantage of energy savings from the envelope and AC ...however it seems counterintuitive to include AC in a building to achieve energy savings for LEED. If we thought that thermal comfort was a real concern it would be a different story. I think that going back to the owner and discussing the lighting one more time may be appropriate, however I wanted to make sure that we would not run into problems with unmet hrs before asking for design changes. Alternatively, maybe looking into the thermal comfort and pursuing savings via exceptional calculations for natural ventilation is appropriate?
Jean Marais
b.i.g. Bechtold DesignBuilder Expert832 thumbs up
May 27, 2013 - 4:25 am
Re: via exceptional calculations for natural ventilation
In my experience, unless you have moterized automatic window/vent control to fractionally modulate the openings, regulating the temperature and or room air quality with windows/vents is very hard to proove with a simulation program.
I am currently attempting to do so (i.e. mimick building user behaviour for opening and closing windows) and it is very time intensive and shows pretty erratic behaviour. Especially in winter, due to cold outdoor temps, the room air temperature swings are huge. In 10 min the temp can drop from 22 degC to 17 deg C by opening windows when it is -2 outside. Wind plays a role, air speed plays a role, air quality plays a role.
This particular project has huge internal mass and internal gains, meaning even without heating, the zone overheats in winter if the windows remain closed. If you open a window the room overcools quickly, and as soon as you close the window, it overheats just as fast. I'm having to split the windows in each zone into 2 groups to "modulate" the total opening area (as windows have at most just 3 settings (closed, open, tip).
And I'm still testing and tuning...
If you go this route, good luck.
I suggest doing the baseline AC in both models (where none are planned).
Luana Bertoletti
Sustentech37 thumbs up
July 23, 2013 - 9:28 am
Hi,
I also have the same doubt as Chad Coleman: "Since there is no heating or cooling, we do not have to model either. Correct? It is my understanding that if there was heating we would have to also model cooling or vice versa, however if the building is not conditioned we do not have to model either."
However, according to "Appendix D - Advanced Energy Modeling for LEED - v2" an example is described in which no mechanical heating or cooling is intended fot the building concerned but the energy modeling is done considering a hybrid system (natural+mechanical ventilation). Why was this example modeled this way?
Regards,
Luana Eid
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5909 thumbs up
July 23, 2013 - 10:08 am
You do not have to model heating or cooling in unconditioned spaces.
The natural ventilation example in Appendix D describes an exceptional calculation methodology for demonstrating savings for naturally ventilated spaces. It compares a conditioned space to a naturally ventilated space to demonstrate that similar comfort conditions will be present. You could model the "uncondtioned" spaces without HVAC in both models but if you had no HVAC in both cases you would not show any "savings" for natural ventilation.
Luana Bertoletti
Sustentech37 thumbs up
July 23, 2013 - 10:38 am
Thank you Marcus!