[BLDG-SIM] Garage Heating

[JRR]

The idea that  "It would seem the heat rate off the floor could increase 
momentarily when a draft of cold air hits a warm floor" is dead wrong. 
The concrete acts as a huge thermal flywheel. THIS IS RADIANT HEAT. 
There should be a separate hydronic heat zone the first 4 feet inside 
the doors, set hotter than the rest of the floor. It should be fired up 
several hours before the business opens. Do you have perimeter thermal 
breaks < 1 inch XPS foam > around the slab ? Do you have 2 inch XPS foam 
on the outside of the footings  at least 24 inches below grade? What is 
the door height vs inside ceiling height? Ceiling fans installed? What 
direction do the doors face?  <Solar: South = good>   What direction do 
the doors face?  <Wind: Winter Prevalent Direction Leeward = good>  
External wall fins / fencing to control wind installed? You have ignored 
many details .......
JRR

Chris Jones wrote:

> Fred
> I did some analysis for a very large warehouse with 10 bay doors on 
> one side.  The design assumed two "zones".  The interior zone which 
> included the envelop loads from roof, walls, slab edge, windows, etc.  
> The zone also heated the required ventilation air.  This was done by a 
> gas fired roof top unit.  The second zone was the area adjacent the 
> bay doors.  The problem I had was in determining first the depth from 
> the doors affected by the doors opening and second the average air 
> change rate per hour for occupied hours.  Radiant gas fired heating 
> tubes at the ceiling were used.  These heat up fairly quickly.  The 
> mechanical designer thought he had designed a large enough system but 
> the dock workers complained that they were too cold during the worst 
> days of winter.  I was called in after the fact and from my research I 
> agreed with the designers assumptions for average air change per 
> hour.  Do you have any additional thoughts about this kind of facility?
>
>
>
> At 14:38 13/05/2005, you wrote:
>
>> All;
>> I simulated an existing 5-bay garage and attached 2000 sf offices in 
>> Colorado, and calibrated a DOE-2 model with real weather and bills. 
>> Infiltration must be about 65% of the annual building heat load, even 
>> with fairly bad walls. The owner wants to build another one with 
>> minor changes. The garage is heated with overhead low-intensity tube 
>> heaters with a combined output of 200 Btuh/sf. The high capacity can 
>> also handle some ventilation, if anyone ever turned it on. When it is 
>> cold and the doors are opened the thermostats will kick all these 
>> heaters on. With bay doors on each side, the room is probably over 
>> 100 ac/hr for an hour per day and there are a few more hours with 
>> just one door open, depending on occupant behavior.
>>
>> I notice that radiant hydronic in-floor heat is installed in repair 
>> garages at 35 Btuh/sf at design conditions, much lower than my 
>> system. It would seem the heat rate off the floor could increase 
>> momentarily when a draft of cold air hits a warm floor, but is 
>> limited over time to the much smaller boiler capacity. So is some of 
>> the claimed savings from in-floor heat in these types of spaces just 
>> from less "recovery capacity," and less output during periods of 
>> extreme airflow.  I suppose I could "simulate" this by merely 
>> reducing the capacity while leaving the infiltration schedule the 
>> same, and I would just show more hours with loads not met. My old 
>> standby DOE-2 has limitations for this type of situation obviously. 
>> These peak infiltration events are subhourly; my workaround is to 
>> group them into an hour, and the calibration to monthly bills is 
>> actually quite good.
>>
>> Does anyone know of comparisons between similar buildings with these 
>> two types of "radiant" heat, or have experiences with actual 
>> installations, or other programs. The setpoint is already down at 60F 
>> so I'm not going to "simulate" one system as better than another by 
>> changing the setpoint down.
>>
>> -- 
>> Fred W. Porter
>> Senior Engineer
>> Architectural Energy Corp.
>>
>>
>>
>>
>> ======================================================
>> You received this e-mail because you are subscribed to the 
>> BLDG-SIM at GARD.COM mailing list.  To unsubscribe from this mailing 
>> list send a blank message to BLDG-SIM-UNSUBSCRIBE at GARD.COM
>>
>>
>
>
> Chris Jones, P.Eng.
> 14 Oneida Avenue
> Toronto, ON M5J2E3
> Tel. 416 203-7465
> Fax. 416 946-1005
>
>
> ======================================================
> You received this e-mail because you are subscribed to the 
> BLDG-SIM at GARD.COM mailing list.  To unsubscribe from this mailing list 
> send a blank message to BLDG-SIM-UNSUBSCRIBE at GARD.COM
>
>



======================================================
You received this e-mail because you are subscribed 
to the BLDG-SIM at GARD.COM mailing list.  To unsubscribe 
from this mailing list send a blank message to 
BLDG-SIM-UNSUBSCRIBE at GARD.COM