[Bldg-sim] Thermal Blocks in Multifamily Residential Buildings

Mon Oct 26 12:30:57 PDT 2015

Sherif,

There is actually a quite simple response to the comment from your appraiser regarding the treatment of Residential spaces within a multi-family building. 

Section 3 of ASHRAE 90.1 defines the term Residential as “spaces within buildings used primarily for living and sleeping.  Residential spaces include, but are not limited to, dwelling units, hotel/motel guest rooms, dormitories, nursing homes, patient rooms in hospitals, lodging houses, fraternity/sorority houses, hostels, prisons, and fire stations.” 

What this means is that all spaces associated with living and sleeping fall under the same use classification from a 90.1 and Appendix G perspective.   In this case the assessor has provided the wrong interpretation of ASHRAE 90.1.  G3.1 7a.  

In my experience the assessor will be reluctant to admit he has made an incorrect interpretation.  Could I suggest that you request an interpretation from the ASHRAE 90.1 committee to help clarify the question for your assessor.  There are two types of interpretations you can request, informal and formal.  The later requires a vote by the full committee and constitutes an official interpretation to the standard while the former is unofficial but is still an answer from 90.1 committee members.  In this case if you can get the assessor to agree to abide by an informal interpretation from 90.1 you could change his mind. 

The Standards section of the ASHRAE website will explain how to submit an interpretation request. 

Cheers,

Mike

Michael Tillou, PE, LEED AP BD+C, ASHRAE BEMP

Associate

Atelier Ten

Environmental Design Consultants + Lighting Designers

45 East 20th Street, 4th Floor

New York NY 10003

T +1 (212) 254 4500 x208

F +1 (212) 254 1259

michael.tillou at atelierten.com

www.atelierten.com

From: Bldg-sim [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Maria Karpman
Sent: Monday, October 26, 2015 3:08 PM
To: 'Nicholas Caton' <ncaton at catonenergy.com>; 'Julien Marrec' <julien.marrec at gmail.com>; 'Sherif Farag' <sherif.sabr at gmail.com>
Cc: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] Thermal Blocks in Multifamily Residential Buildings

Sherif,

I agree with Jim and Julien that each unit can be modeled as a single block, and blocks facing the same exposure can be aggregated. There is an example illustrating that in 90.1 User’s manual which I would reference in your response to the reviewer.

Thermal Blocks in Multifamily

Residential Buildings (Table

G3.1-9)

Multifamily residential buildings are

another special case for the creation of

thermal blocks. In general, each residential

space must be treated as separate thermal

blocks, except that some combinations are

allowed. Units all facing the same

orientation, and having similar conditions

at the top, bottom, and sides, may be

combined. Similar corner units may be

combined, and units with similar roof or

floor loads may be combined (see Figure

G-E).

In addition, 90.1 User’s manual has a case study on applying App G to a mixed use building which includes four floors with apartment units. Apartments in the example are served by four pipe fan coil systems, so I think it is reasonable to assume that each room is a separate HVAC zone (i.e. each room has a fan coil unit, and each unit is independently controlled). The example does not describe the modeled thermal blocks on residential floors, but DOE2 files for the case study are available at ASHRAE website and are attached. I don’t have DOE2.1 so couldn’t open the model, but glancing through INP file it seems that they modeled one thermal block per exposure plus corner units. Hopefully someone on the list can open the model and confirm that. 

Maria 

-- 

Maria Karpman LEED AP, BEMP, CEM

________________

Karpman Consulting

www.karpmanconsulting.net <http://www.karpmanconsulting.net/>  

Phone 860.430.1909 

41C New London Turnpike

Glastonbury, CT 06033

From: Bldg-sim [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Nicholas Caton
Sent: Monday, October 26, 2015 1:52 PM
To: Julien Marrec; Sherif Farag
Cc: bldg-sim at lists.onebuilding.org <mailto:bldg-sim at lists.onebuilding.org> 
Subject: Re: [Bldg-sim] Thermal Blocks in Multifamily Residential Buildings

My strongest advice:  Good reviewers do not consider themselves “un-convincible” but some effectively are when your own time/ability constraints come into play.  Weigh your interactions so far with this individual, and decide if you are better off “biting the bullet” and just doing what’s been asked, as in such a case any discussions on this list won’t change your situation and will only lose you time.

That said…

I expect your simplification to one block per unit is *probably* appropriate, based on my general experience with multifamily projects of varying types.  I’m the sort of personality that tends to err on the side of “too much detail,” and I have constructed residential simulations similar to what your reviewer is prescribing to find the added complexity did not ultimately contribute to my confidence in the results.  

Your reviewer is not incorrect however to point out that the actual design, in reality, does have multiple thermostats and in a literal sense has more than one zone per apartment unit.  Your reviewer and your project are in a grey area.  Take note Sections 7 and 9 are not mutually exclusive: Section 9 prescribes “at least” one zone per multifamily unit in the same sentence that allows for combining all units with a common perimeter orientation to be combined.  I wish I could tell you 90.1 is clear as day on this front and that Section 9 “trumps” Section 7 for multifamily, but I don’t think I can make that case for a reviewer who is convinced otherwise.

Whether the reviewer is “right” or “reasonable” to suggest you break apart the zones and distinguish the occupancy schedules (independent of what 90.1 says) is too context-dependent a question for anyone to answer absolutely over this mailing list (and is ultimately a subjective question anyway), though Julien is asking the right questions to provide an informed opinion.  That you have a multi-zone arrangement in the actual design suggests somebody felt it would at least improve comfort (not necessarily save energy), which in turn suggests you’ve some expected substantial variance in perimeter vs. core loads, possibly internal loads as well.  Whether such skin load variances and/or occupant-borne heat scheduling should have a meaningful impact on system energy consumption is going to depend on the system(s) itself, the occupant density we’re talking about, and perhaps especially just how easily heat propagates between the zones (which drives questions like “how big ARE these apartments?”).

Assuming the reviewer’s directives would take much more time for the full project and you still have a degree of uncertainty yourself, I’d suggest performing a ‘sensitivity study’ on a single apartment unit for your own benefit (and perhaps to ultimately present to the reviewer).  Run the simulation once as you have approximated the combining the actual zones/systems, then again with the prescribed level of detail to match actual zoning, as though you were following the guidance in Table G3.1 section 7. You can still freely combine zones with common “living” vs. “sleeping” designations, as requested.  Ensure you have realistic degrees of inter-zonal thermal transfer for that case.  Also be aware this is a “rabbit hole” problem that can easily be overdone and unnecessarily eat up your time – so don’t feel obligated to go the sidewalk’s edge.  Just test the degree of detail requested by the reviewer and no more.

Critique the results for each run, consider/approximate the “scaled up” impact of the difference in results for the project as a whole, and see if you can demonstrate/convince yourself that ultimately this is not a big deal by quantifying the potential swing in the overall numbers.  

If this is something you feel motivated to try, I would advise first starting a fresh conversation with your reviewer to propose this sensitivity study/exercise (provide context:  explain the time-commitments involved).  If you sense they are not going to accept anything more than the detail prescribed for the full simulation effort, consider it time saved and just “bite the bullet” per my initial advice!

Regards,

~Nick

NICK CATON, P.E.
Owner

Caton Energy Consulting
  306 N Ferrel

  Olathe, KS  66061

  office:  785.410.3317

www.catonenergy.com

From: Bldg-sim [mailto:bldg-sim-bounces at lists.onebuilding.org <mailto:bldg-sim-bounces at lists.onebuilding.org> ] On Behalf Of Julien Marrec
Sent: Monday, October 26, 2015 2:25 AM
To: Sherif Farag
Cc: bldg-sim at lists.onebuilding.org <mailto:bldg-sim at lists.onebuilding.org> 
Subject: Re: [Bldg-sim] Thermal Blocks in Multifamily Residential Buildings

Sherif,

Is it a local incentive program or your national energy code or something?

I don't know quite yet how to convince this person, but if you could give us a few pointers about your project it may help.

Can you describe the HVAC system very briefly? What's your heating and cooling system and how is it controlled? And do the residents have fully manual control over the temperature? Do the residents pay for the utility bills?

Also, how big are your apartments?

Julien

Envoyé de mon iPhone

Le 26 oct. 2015 à 07:31, Sherif Farag <sherif.sabr at gmail.com <mailto:sherif.sabr at gmail.com> > a écrit :

Hi Julien,

No, it is not a LEED project;

I tried to convince the assessor but with no success, any advice? basically he doesn’t agree with my interoperation and wants to see a clear document.

appreciate your help.

Thanks & Regards; 

Sherif

On Oct 26, 2015, at 2:06 AM, Julien Marrec <julien.marrec at gmail.com <mailto:julien.marrec at gmail.com> > wrote:

Is this a LEED project?

Long story short, no I don't think this is a reasonable comment.

One block per apartment is common practice, and you can merge block if their share a similar orientation.

Julien

Envoyé de mon iPhone

Le 25 oct. 2015 à 13:01, Sherif Farag <sherif.sabr at gmail.com <mailto:sherif.sabr at gmail.com> > a écrit :

Dear Modellers;

I am modelled a multifamily residential building with thermal blocks following ASHRAE 90.1:2007 Table G3.1 item 9. but I received a comment from the reviewer asking me to follow Table G3.1 item 7a and justified the comment because the living areas and bedroom areas having different occupancy profiles, he also suggested that (to simplify the profiles) the occupants are in the living space from 1800hrs to 2400hrs and in the bedroom spaces 0000hrs to 0800hrs.

Is this a reasonable comment?

Did anybody here had a similar experience?

I will appreciate your feedback & recommendations.

Thanks & Regards; 

Sherif Farag

Sustainability Consultant

P.O. Box: 127842

Abu Dhabi, UAE

M: +971 55 199 0022 | E: sherif.sabr at gmail.com <mailto:sherif.sabr at gmail.com>  | Skype ID: sherif.farag9

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