I am using IES VE to model hotel type rooms that each have a separate bathroom. The bathrooms do not have any heating equipment, cooling equipment or thermostats in them. But they have exhaust system which exhausts at about 8 ACH with the make up air coming from the conditioned adjoining apartment. This makes the bathrooms 'indirectly conditioned'.
The set point for the conditioned apartment is 24 Celsius, so obviously the make up air into the bathroom is at around this temperature. Given that there are some heat loads from lights etc in the bathrooms, the space will obviously end up at a temperature above 24 C.
My question is - in terms of calculating the 'unmet hours', these bathrooms will often fall outside the temperature setpoint for the main rooms. Increasing size/flow rates of the air conditioning equipment in the main rooms will not assist in achieving this, as the main rooms are maintaining temperature already.
Do I need to:
1. Exclude these bathrooms etc from the 'unmet hours' calculation as they are not directly conditioned to maintain a setpoint temperature.
2. Model these bathrooms with baseline air-conditioning equipment in both the proposed and the baseline model so that they are able to maintain temperature even though this does not represent what will be really implemented. (There is something in the reference guide about using a baseline system if no heating or cooling plant is proposed for a space, but I have currently presumed this refers to a whole building or a whole area rather than an individual room within a building.)
3. Change the model thermal zoning to include the apartment and the bathroom as a single thermal zone so that the model mixes the air completely across both the apartment and the bathroom and thus maintains temperature in both spaces. The problem with this is that the proposed equipment sizing may not cover all of the load in this now larger space, in which case the whole space may struggle to maintain temperature.
In Australia, we would use option 1 for our modelling, but I can't find anything in the ASHRAE 90.1 that describes this. Your help is much appreciated.
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5909 thumbs up
June 18, 2013 - 9:37 am
Definitely not 1 or 2.
Typically a single residential unit or grouping of several units are modeled as a thermal block. I would not treat the bathroom as a separate zone. I would assume that you would size the systems to account for the bathroom exhaust. So #3 is the best of the options above.
Phillip Cook
WGE5 thumbs up
June 18, 2013 - 10:49 am
Thanks a lot Marcus. I will update my model. That was a really helpful answer.
On a related note, we have a kitchen and laundry in this same building that have large exhaust and heat loads. We are not conditioning these areas to remain within a set point temperature. In the kitchen, we will supply make up air from an evaporative cooler which will help keep the space cool but will not guarantee 24 C. In the laundry we will just have exhaust with make up from outside. How would you treat these areas as the will also have large unmet hours? Would these meet ASHRAE 90.1 requirements?
Phil
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5909 thumbs up
June 18, 2013 - 11:49 am
Is there a reason you would be trying to maintain he same level of comfort in these spaces as in the units? You can adjust temperatures as long as the settings are the same in both cases.
Phillip Cook
WGE5 thumbs up
June 27, 2013 - 3:22 pm
So, what set point do I use for an indirectly conditioned space in a commercial building?
They obviously don't have a thermostat in them and the mechanical engineer has not actually specified a temperature set point for these spaces. Will LEED ask me to prove / justify my set point selections for these spaces or is it simply enough that both spaces are treated the same in the baseline and the proposed?
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
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June 27, 2013 - 3:35 pm
You will not be asked for those temperature set points. Just use your best judgement and make sure they are identical in the baseline and proposed.
Francesco Passerini
engineer90 thumbs up
November 8, 2013 - 10:46 am
Marcus wrote: “Typically a single residential unit or grouping of several units are modeled as a thermal block.”
Table G3.1. 7 states: “a. The space use classification is the same throughout the thermal block”.
Does it mean that a bathroom that is used only by the occupants of a sleeping room can be considered as part of “hotel/motel guest rooms” (tab. 9.6.1)?
Best Regards
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5909 thumbs up
November 8, 2013 - 11:29 am
Yes the space use classification is the same.
Yes in a hotel you use the LPD for the whole room including the bathroom. You do not need to use the restroom LPD separately.
Francesco Passerini
engineer90 thumbs up
November 8, 2013 - 11:44 am
Thank you. I'm not a native English speaker, but I think that a bathroom that is used only by the occupants of a sleeping room is not a "restroom", is it?
Actually, because of LEED Interpretation 5253 in dwelling units the lighting power is considered process power. And the rooms that include provisions for "living, sleeping, eating, cooking, and sanitation" are considered "dwelling units". In the hotel that I'm considering some rooms include provisions for cooking while some other rooms don't. I would consider the LPD in them in a different way. We have asked a clarification from the reviewers. Regards
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5909 thumbs up
November 8, 2013 - 12:51 pm
I think that is correct. In English we tend to refer to a restroom as a public/multi-user facility.
Be careful. I think that interpretation applies to multi-family residential LPD. If it is a hotel then that interpretation does not apply. Since there is a hotel guest rooms LPD in Table 9.6.1 that would apply and it is therefore not process.