Re: Dedicated Outdoor Air Systems: Rx for Sick Buildings

[Guest guest]

This article implies that a system bringing in fresh air will solve all

the problems. This is a gross oversimplification. Referrring to their

starting topic, the 1976 Philadelphia American Legion convention which gave

rise to the term Legionaire's disease: the legionella bacteria was growing

prolifically in the warm water of the cooling tower on the roof of the

building. It was sucked into the fresh air intakes of the building HVAC

system from the mist off these towers. It did not originate in the HVAC

system.

While bringing in fresh air is a good idea, HVAC design, placement,

operation, and maintenance require more care than simply choosing this one

supplier.

12. Dedicated Outdoor Air Systems: Rx for Sick Buildings

Posted by: " Christ " antares41_41@... antares4141

Date: Tue Aug 14, 2007 1:29 pm ((PDT))

http://www.ehponline.org/members/2003/111-13/innovations.html

Dedicated Outdoor Air Systems: Rx for Sick Buildings

- Full (PDF)

- Related EHP Articles

- PubMed:Related Articles

- PubMed:Citation

- Cited in PMC

- Purchase This Issue

It's been 27 years since bacteria spread by a hotel air-conditioning

system sickened 221 people and killed 34 at an American Legion

convention in Philadelphia, sounding a wake-up call to the American

public about the link between indoor air quality and human health.

Since then, there has not been another U.S. incident involving

multiple deaths from bad indoor air, yet concerns persist that

conventional heating, ventilation, and air-conditioning (HVAC) systems

are making people sick. Fortunately, the growing acceptance of a new

HVAC design known as a dedicated outdoor air system (DOAS) promises to

improve indoor air quality and comfort while lowering operating costs.

Most conventional HVAC systems circulate conditioned air through a

duct system to different parts of the building. Conventional HVAC

systems are designed to control both room temperature (the " sensible

load " ) and humidity (the " latent load " ) while providing sufficient

fresh air to dilute pollutants generated by building occupants and

equipment. Different amounts of outside air must be added to the

recirculating air and supplied to different parts of the building,

depending upon the number of occupants in each space.

In contrast, a DOAS allows the building designer to decouple the

latent and sensible loads, using separate systems to control

temperature, ventilation, and dehumidification. A DOAS provides the

exact amount of dehumidified ventilation air required in each part of

a building. And it can be used in conjunction with cooling systems

that discourage the growth of mold and microbes.

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[Guest guest]

Gil,

Excellent points. Also, this DOAS approach is basically " the solution

to pollution is dilution. " Which will work as long as polluted air is

being diluted by non-polluted air. Where does one find consistent

sources of non-polluted outside air?

ASHRAE, which long has taken the position that dilution via

ventilation was the correct approach, is shifting that to first

removing pollution from the outside air and better ways to handle the

indoor pollution. No small task.

Carl Grimes

Healthy Habitats LLC

-----

>

> This article implies that a system bringing in fresh air will solve all

> the problems. This is a gross oversimplification. Referrring to their

> starting topic, the 1976 Philadelphia American Legion convention which gave

> rise to the term Legionaire's disease: the legionella bacteria was growing

> prolifically in the warm water of the cooling tower on the roof of the

> building. It was sucked into the fresh air intakes of the building HVAC

> system from the mist off these towers. It did not originate in the HVAC

> system.

> While bringing in fresh air is a good idea, HVAC design, placement,

> operation, and maintenance require more care than simply choosing this one

> supplier.

>

>

> 12. Dedicated Outdoor Air Systems: Rx for Sick Buildings

> Posted by: " Christ " antares41_41@... antares4141

> Date: Tue Aug 14, 2007 1:29 pm ((PDT))

>

>

> http://www.ehponline.org/members/2003/111-13/innovations.html

>

> Dedicated Outdoor Air Systems: Rx for Sick Buildings

>

> - Full (PDF)

> - Related EHP Articles

> - PubMed:Related Articles

> - PubMed:Citation

> - Cited in PMC

> - Purchase This Issue

>

> It's been 27 years since bacteria spread by a hotel air-conditioning

> system sickened 221 people and killed 34 at an American Legion

> convention in Philadelphia, sounding a wake-up call to the American

> public about the link between indoor air quality and human health.

> Since then, there has not been another U.S. incident involving

> multiple deaths from bad indoor air, yet concerns persist that

> conventional heating, ventilation, and air-conditioning (HVAC) systems

> are making people sick. Fortunately, the growing acceptance of a new

> HVAC design known as a dedicated outdoor air system (DOAS) promises to

> improve indoor air quality and comfort while lowering operating costs.

>

> Most conventional HVAC systems circulate conditioned air through a

> duct system to different parts of the building. Conventional HVAC

> systems are designed to control both room temperature (the " sensible

> load " ) and humidity (the " latent load " ) while providing sufficient

> fresh air to dilute pollutants generated by building occupants and

> equipment. Different amounts of outside air must be added to the

> recirculating air and supplied to different parts of the building,

> depending upon the number of occupants in each space.

>

> In contrast, a DOAS allows the building designer to decouple the

> latent and sensible loads, using separate systems to control

> temperature, ventilation, and dehumidification. A DOAS provides the

> exact amount of dehumidified ventilation air required in each part of

> a building. And it can be used in conjunction with cooling systems

> that discourage the growth of mold and microbes.

>

> _________________________________________________________________

> Booking a flight? Know when to buy with airfare predictions on MSN Travel.

> http://travel.msn.com/Articles/aboutfarecast.aspx & ocid=T001MSN25A07001

>

>

>

> FAIR USE NOTICE:

>

>

>

[Guest guest]

I have to agree with this also. I put fresh air intakes into my

house and *at first* we all felt really great, 2004. I thought

everything was solved by that but every year house culture kits

showed more and more mold, even in winter. Finally I realized that

I was dragging in a tremendous amount of mold in fresh air intake,

particularly in summer when mold counts are extremely high here, as

well as humidity which I had to add additional dehumidifiers to

overcome. Finally I closed off fresh air intakes in summer. Even

so, I discovered that outside air was STILL getting into house,

coming into attic in summer and coming down into house through the

tops of interior walls, which were not sealed at top like newer

buildings, dragging summer humidity and mold through the insulation

and into house...so also carrying dangerous insulation fiber

particles incidentally. I have now capped off wall tops that are

exposed to attic air so the outside air cannot get down into them,

or at least very little can, but I now have to test these wall

cavities to make sure this humid, moldy air that has been coming in

since 2001 (when I *vented attic for first time*- it was unvented

attic when originally built 1924)...(air) from outside didn't creat

a problem inside the walls. I'm still enthused about having a fresh

air intake system but it needs some work to make it help and not

hurt the indoor environment.

>

>

> This article implies that a system bringing in fresh air will

solve all

> the problems.