[Greenbuilding] Stale Air

[Brian Uher]

John S-

Thanks for the thoughts. 

I certainly agree with the CO point and with what I infer from your
comment about independent humidity/ventilation systems - I always
envision this as parallel to the heating/cooling, and that heating and
cooling could be closed circuit (and in fact are such in traditional
residential), while the ventilation/humidity control is open circuit
(outdoor coupled).  I come at this from Passive House in many respects,
so I am seeing the HVAC as flipped on its current head: vent/humid is
the core system, heating cooling a modular add in/on. 

In terms of the blob (I like this analogy), my thinking is this: 
slaving any total system to a single input variable (CO, CO2, RH, T)
will yield behavior that over/under ventilates...unless one of the
parameters can be argued as the anchor for the rest.  Perhaps CO2 is a
proxy for vapor load, for example.  Nevertheless, an algorithm that can
effectively model trending behavior - anticipate the loading profiles of
CO2, CO, RH, etc. may be able to "steer the ship" in increments,
avoiding swings. 
Barring that motherboard nightmare, perhaps decoupled systems (and the
different cfm requirements) would be another way to deploy current
technology and get this steering.

Ventilation occurs via an ERV separately ducted and CO2 sensors
controlled (open circuit).  Humidity control operates via RH sensors and
the heating/cooling system ductwork (I did read the B-S.com piece on the
problems with integrated DH; I wonder if they have been resolved by the
equipment manufacturers).  Heating and cooling operates via thermostat
and the same ductwork (closed circuit).  If the ventilation system
creates a load for the other systems, it gets noticed via their
sensors.  Challenge and response...but what happens when the bedroom
doors are closed?  It seems part of the design challenge here, perhaps
the greatest issue overall, is the compartment problem.

Thinking about combined ductwork for a second, a damper on an ERV
intake/output can control the cfm input to a central duct system, but we
have found the call on the air handler to fight the static load for
distribution drives up kWh draw by 9-10%.  It just isn't a great answer
for new design.  Retrofit, perhaps there is no other choice.

This and the compartment problem tend to focus my attention on
distributed H/C with central DH/venting.  The sensors would have to be
located in bedrooms and other compartmented, long residency time
spaces.  But what then about over-venting unoccupied space (the guest
bedroom, for example)?  Here again, the compartment problem...solved in
commercial spaces I suppose with CO2 sensor-coupled dampers and VAV
systems...

Brian


















 

On 12/15/10 4:25 PM, jfstraube wrote:
> Get such an integrated sensor is easy.  Controlling a system is the hard part.  Some systems cant be controlled, for example, systems with no independent ventilation system (many houses, most commercial multi-zone VAV systems) or no independent humidity control (essentially all houses and most commercial buildings).  And CO is not a control function is an alarm function, like a smoke detector is.
> I dont quite see the little benefit to having sensor that monitors temp, RH, CO2, CO as one integrated blob. I see many disadvantages. 
> Brian, did you have an idea of why this is good and what it might control?
>
>
> John
>
>
>
> On 2010-12-15, at 2:56 PM, John O'Brien wrote:
>
>> On Mon, Dec 13, 2010 at 4:21 PM, Brian Uher <brian at amicusgreen.com> wrote:
>>> Does anyone know of an integrated sensor system - temp., humidity, CO2, CO,
>>> etc. - that interpolates and controls the system - that works?
>>> Remote coupling to web?
>>>
>> An Arduino could probably do it. You'd have to build it though.
>>
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> John Straube
> www.BuildingScience.com
>
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>
>