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Natural Ventilation.

Natural Ventilation.

Natural Ventilation.

(OP)
Hi,

I'm currently at design stage of 130,000 sq ft office in Ireland. The architect and M/E consultant are pushing to naturally ventilate the building. What they are proposing sounds great in theory but I have read that there can be a lot of problems once built; humidity noise leakage etc. I am just wondering if anyone has any experience with how these buildings work practically and if there was any difference in performance from what was promised and what you ended up with. Thanks.
 

RE: Natural Ventilation.

I saw a underground 48" RCP run for 115' at 5% grade with the high end inserted into the basement mechanical and air handling room of a five story building. Four each 48" square vents at the roof/wall junction on each side of the building provided good ventilation, (air change each 10 minutes), with NO need to run the fans!

RE: Natural Ventilation.

You are really in the wrong forum for this query, but to answer you, I would refer you to esmagazine.

Natural ventilation is probably an additional feature to the normal HVAC mechanical building systems as some of these articles suggest. You can't have just natural ventilation. Otherwise, you are going to have problems controlling the moisture and heating, air changes, and indoor air quality.

http://www.esmagazine.com/Articles/Cover_Story/9b60392ebcda8010VgnVCM100000f932a8c0____

http://www.esmagazine.com/CDA/Archives/BNP_GUID_9-5-2006_A_10000000000000078737

http://www.esmagazine.com/CDA/Articles/Feature_Article/BNP_GUID_9-5-2006_A_10000000000000228519

http://www.esmagazine.com/Articles/Cover_Story/808904d6afe9e010VgnVCM100000f932a8c0____

An addendum that revises requirements for the use of natural ventilation for the American Society of Heating, Refrigerating and Air-Conditioning Engineers' (ASHRAE) ventilation standard has been approved for publication.

RE: Natural Ventilation.


.

Can you give more detail about what is being proposed?

.

 

tsgrue: site engineering, stormwater
management, landscape design, ecosystem
rehabilitation, mathematical simulation
http://hhwq.blogspot.com

RE: Natural Ventilation.

(OP)
Fresh air is drawn into the building through external louvres. There is a large atrium in the building which works as a passive stack. This looks after fresh air requirements. When the internal temperature is too high windows are either manually opened by the occupier or mechanically by sensors. There is no HVAC system at all. There is no humitity control either. It is been pushed hugely in Europe as the sustainable green option. I was just wondering if anyone has any experience working on or in such a building. Thanks

RE: Natural Ventilation.

It is difficult to believe that you have a building with no HVAC system. I doubt that they are finished with the design.

What about the heat for the building? Ireland is a cold damp country and modern buildings have heating systems.

The last reference listed above is a building in Cambridge and is not that far away from Ireland. The Cambridge building also has an atrium and natural ventilation from windows. But the Cambridge building also has a complete HVAC system and has a Platinum LEED rating from the USGBC.

"Steam provided by the power plant next door is also used for the four heat exchangers, which supply hot water to the fancoil and AHUs. Two small heat exchangers are used to produce domestic hot water.

The building uses four-pipe fancoil units with limited duct distribution serving interior zones, conference rooms, and perimeter zones. Separate fancoils are used for perimeters and the interior. A grand total of 560 fancoil units serve the Genzyme Center, and these units are automatically shut off when windows or doors are opened for natural ventilation.

Two 100% outside makeup air units located on the roof distribute ventilation air down through the building via two shafts, then a horizontal distribution is located at each floor to supply the ventilation air to the fancoil units. The two AHUs are 20,000 cfm each and can either be run in a pure heating or cooling mode to meet a temperature setpoint. They can also run in a humidity control mode, where the air is sub-cooled to remove the humidity and then reheated to the temperature setpoint. Heat wheels are located in each of the air handlers to recover energy from the exhaust air stream.

CO2 sensors are located throughout the building on a number of different floors, and if any of those sensors register above 1,000 ppm, the air handlers are signaled to bring in additional fresh air. "The supply air fan is on a variable-speed drive, and normally it's controlled to meet a static pressure setpoint in the air distribution ductwork. If CO2 levels are high, it will speed up to provide more fresh air, to try and bring them down," said Lou Capozzi, supervisor of facilities engineering at the Genzyme Center.

A large atrium space is located in the middle of the building, and radiant heating and trench heaters provide warmth for the atrium floor area in the winter. Trench heaters are a European product that are located in the floor and have a small fan that provides forced convection. "The trench heaters are for comfort as well as to keep the condensation off the glass," said McGough.

Given the size of the ground floor and its architecture, which includes water features, stairs, bathrooms, etc., it was not possible to obtain adequate capacity from the radiant floor heating system. The perimeter trench heaters supplement the radiant system, while providing the added benefit of blanketing the glass windows with heat."

RE: Natural Ventilation.


.

Passive ventilation and earth-air heat exchangers are excellent options for high performance building implementations in many locations. These are usually coupled with energy recovery units and dehumidification of some type (passive dessicant or active mechanical). Based on your information, it may be that the architect and mechanical engineer have been exposed to these concepts, but may not have a full understanding of the technologies. There are several excellent references out there for you on the subject matter. Since you are in Europe (almost anyway), I suggest you undertake some W3 searches for 'PassivHaus' if you are not already familar with this 'standard' (www.passivhaus.org.uk). You might also try W3 searches for 'natural ventilation' and 'passive ventilation'. My suggestion is to ask the architect and mechanical engineer for their information sources and then go from there.

.

 

tsgrue: site engineering, stormwater
management, landscape design, ecosystem
rehabilitation, mathematical simulation
http://hhwq.blogspot.com

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