[Bldg-sim] Thermal Blocks in Multifamily Residential Buildings
Joe Huang
yjhuang at whiteboxtechnologies.com
Mon Oct 26 14:49:49 PDT 2015
I thought I'd add my two-bits here, because back in the late 1980's (showing my age
here...) I did a project for the Gas Research Institute to develop prototypical
multi-family building models in which by necessity I took virtually the same approach as
mentioned in Table G3.1-9.
I categorized all multi-family spaces into seven categories:
top, middle, and bottom floors (differences here should be obvious)
middle- and end-units, where middle-units have adjoining units on two sides while
end-units have them only on one.
internal hallways
The following drawing shows how the 16 prototypical MF buildings are modeled:
In order to get rid of directional bias in solar loading, all spaces are modeled with
equal amounts of exterior walls and windows in each of the cardinal orientations
(Horrors! Don't try to do a DrawBDL sketch of the model - but hey, we're talking here of
prototypical buildings. If you're doing a real building, then you should distinguish the
units by orientation - but otherwise the approach works fine).
What I like about this modular approach is that it makes it extremely easy to tweak the
numbers of floors and apartment units, just by changing the multipliers applied to each
space type.
For those interested, the full GRI report is available on my web site here.
<http://www.whiteboxtechnologies.com/PAPERS/89_YJH_Multifamily_Prototypes_GRI-88-0239.pdf>
Joe
Joe Huang
White Box Technologies, Inc.
346 Rheem Blvd., Suite 205A
Moraga CA 94556
yjhuang at whiteboxtechnologies.com
http://weather.whiteboxtechnologies.com for simulation-ready weather data
(o) (925)388-0265
(c) (510)928-2683
"building energy simulations at your fingertips"
On 10/26/2015 12:08 PM, Maria Karpman wrote:
>
> 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
> *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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