[Bldg-sim] NECB - MURB Reference Heating Type

Aaron Smith asmith at mreng.ca
Mon Feb 18 08:44:21 PST 2019

Hi Chris,


Thanks for your response.  It would make sense if the Reference Building were also a WLHP but based on AHRI definitions I think a WHLP is pretty clearly not:

a.      an “air-cooled unitary <http://www.ahrinet.org/Certification/AHRI-Certification-Programs/Unitary-Air-Conditioner-Equipment> ” product,

b.      a packaged terminal air conditioner <http://www.ahrinet.org/Certification/AHRI-Certification-Programs/Packaged-Terminal-Air-Conditioners>  or heat pump <http://www.ahrinet.org/Certification/AHRI-Certification-Programs/Packaged-Terminal-Heat-Pumps> , or

c.      a fan coil.


A WLHP is water-cooled unitary product.


If they simply said “unitary” or “air-cooled or water-cooled unitary” then it would makes sense to me that you model an identical system but they specifically state “air-cooled unitary”.



Aaron Smith, P.Eng

Principal, Mechanical Engineer



M&R Engineering Ltd.


From: Chris Hadlock [mailto:cjhadlock at gmail.com] 
Sent: February-18-19 11:27 AM
To: Aaron Smith <asmith at mreng.ca>
Cc: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] NECB - MURB Reference Heating Type


Hi Aaron,


The way I would interpret it is the Reference system will be identical to your Proposed system (i.e. WLHP connected to fossil fuel boiler). If you had a air-source, water-source (i.e. river, lake) or ground-source, then you would have to worry about auxiliary heating (per Section The "through-the-wall" system only applies in the otherwise case (i.e. when your system is not one of the ones listed). 


This is my interpretation - I'd be interested to hear others.




On Sun, Feb 17, 2019 at 10:10 PM Aaron Smith via Bldg-sim <bldg-sim at lists.onebuilding.org <mailto:bldg-sim at lists.onebuilding.org> > wrote:



I’ve got a question about the NECB Reference Building heating system type for Multi-Unit Residential Buildings.  Specifically what should it be when you have water-loop heat pumps connected to a fossil fuel boiler?


Table of the 2015 NECB states that Reference Building HVAC systems for Multi-Unit Residential areas are:


“Where the proposed building or space is heated as well as being cooled with an air-cooled unitary, packaged terminal or room air conditioner (or heat pumps), or fan coils, the reference building or space's HVAC system shall be modeled as being identical to that of the proposed building or space; otherwise, the reference building or space shall use through-the-wall systems.”


I’d consider water-loop heat pumps to be in the “through-the-wall systems” category so the cooling would be air-cooled DX.  It doesn’t describe the heating source for “through-the-wall systems” but says that the energy type of the reference building’s heating system shall be identical to the energy type of the proposed building’s heating system.  The code considers heat pump to be an energy type so I think it should be an air-source heat pump.  I’m just not sure about the auxiliary heat – electric resistance or hot water?


I tried running this in CAN-QUEST but got some errors.  When I run a 4-storey office building with WLHP, the reference building is coming out as air-source heat pump with electric resistance heat so I’m leaning toward using that.  I can see there being an argument for hot water auxiliary heat though based on the proposed building having a fuel-fired boiler (to avoid fuel switching).





     Aaron Smith, P.Eng

    Principal, Mechanical Engineer




     t: (902) 422-7393

     f: (902) 423-4945

     e:  <mailto:asmith at mreng.ca> asmith at mreng.ca

     www.mreng.ca <http://www.mreng.ca/>  


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