[Greenbuilding] Stale Air

[jfstraube]

Hi John.  
I hope you mean CO2. CO levels of 1500 ppm would kill students in about 2 hours :)

ASHRAE Standard 62 requires 10 cfm/student +0.12 cfm/sf, which works out to about 15 cfm per student 25 students in a 1000 sf classroom which works out to around 1100 ppm CO2.   Many jurisdictions ventilate even more, like 20 cfm
Ventilating only for people, not buildings, at 10 cfm/person gets just below the 1500 ppm CO2 number that you report the UK requires.

Ventilation is a seperate function from air conditioning, and mechanical AC is easy to avoid in most parts of the UK and Canada.  Natural ventilation to meet the requirements are very difficult, because the forces driving ventilation (wind and stack effect) are highly variable.  To be safe, designers just massively over ventilate to ensure that in non-windy hours of modest outdoor temperature enough ventilation occurs.  As a consequence naturally ventilated buildings usually consume significantly more energy for heating than well-designed mechanically ventilated buildings.

John


On 2010-12-16, at 10:00 AM, John Bone wrote:

> Hi,
> Over here in the UK we require (state and non-state) Schools to ventilate classrooms to keep the CO levels below 1500 ppm to keep pupils alert and healthy. The English and Welsh and Scotish Buildoing Regualtions enforce this on all new buildings. The Victorians over 100 years ago felt that high ventilation rates were essential in schools and other public buildings.
> 
> The UK's building Regualtions have on the other hand recently required ever tighter buildings in terms of cnstructional "air-leakage" but also required good and controllable ventilation systems. Usually passive i.e. non-mechanical, the Uk has even drafted a ban on the use of only mechanical air-conditioning for new buildings. The EU (European Union) has also issued european laws on minimum efficientcy for mech ventilation.
> 
> http://www.silentshadow.org/
> 
> John Bone, MBEng, BSc Hons, ICIOB
> Buidling Compliance Consultant
> 
> On Wed, 15 Dec 2010 21:25:03 -0000, jfstraube <jfstraube at gmail.com> 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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John Straube
www.BuildingScience.com