Hi,
This has been bogging us for a while, as we cannot figure out how to
interpret the various issues in ASHRAE 90.1.
If in a multifamily building the residential units are only heated but
not cooled in the actual design (climate is North Europe), how does the
baseline get modeled? I suppose Systems #9 and #10 (Heating Only) would
be out of the question as these are intended for ancillary spaces. So it
would have to be System #1 or #2, but with cooling as well?
More importantly, would the Proposed residential units be modeled with
additional cooling using identical systems as in Baseline?
Thank you in advance,
?mer Moltay, LEED AP BD+C, ASHRAE BEMP, ASHRAE CPMP
Mimta EcoYapi, LEED Proven Provider
Hekimsuyu Cad. 559. Sk.
No:39 34255 Kucukkoy Istanbul Turkey
Tel: 90-212-617-2296
Fax: 90-212-617-2297
Mobile: 90-533-957-1394
www.eco-yapi.com
www.buildingenergymodels.com
Mr. Moltay,
Hoping to get a discussion started.....
I agree that Systems 9 & 10 are inappropriate. I suspect that there is a natural ventilation cooling scheme, since it's unlikely that a multi-family building will have "nothing" for cooling.
If that's true, you do have a cooling system, it's just not a mechanical system. The Baseline system would then be System #1 or #2 and your challenge for the Proposed system will be to demonstrate that it maintains proper control of temperatures and ventilation.
ps, You do not need to maintain typical temperature setpoints for, say an enclosed shopping center. If the owner agrees that 30C is acceptable as a cooling setpoint, then model that.
James V Dirkes II, PE, BEMP, BCxP
Team Lead - Building Performance
616 450 8653
Foresight Management
https://fsmgmt.co/
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To follow up on this, I have some input.
I'm assuming you are using ASHRAE 90.1-2010, in which case, you would use System #1 or #2 with cooling in the Baseline model and the Proposed system as designed with the System #1 or #2 cooling system included in the Proposed model. This assumes that the residential spaces are considered "conditioned" as defined in section 3.2 of ASHRAE 90.1-2010 (using Table 3.1 the heating output of the Proposed system would need to be greater than or equal to the value listed for the climate zone). Then the cooling setpoint can be pretty much what you want as long as it's the same in both the Baseline and Proposed. This means that even though cooling is required to be included in the models, it is not likely to be used very often between the cold climate and having the ability to set a high cooling setpoint.
If the spaces are not considered "conditioned" and are instead "semiheated" then you don't need to include cooling in either model, but the Baseline Case system would be the same as the Proposed Case other than heating and motor efficiency improvements.
Per 90.1-2016 Appendix G, table G3.1 (10.d), the proposed case should be modeled with the same cooling system as the baseline when the proposed design does not have a cooling system. For northern Europe, you are looking at system 1 (PTAC plus boiler). Assuming there is no cooling load, the cooling system would have no impact on your energy use. But if there is a cooling load in the baseline and not in the proposed (due to cooling load-reducing features), then the proposed design will get credit for it.
Rahul