Passive Ventilation

[graybeach]

We are currently replacing the roof and siding on an existing building in the northeast US. The building is 25 feet wide by 55 feet long by 85 feet tall and houses some infrequently used mechanical equipment. Basically the building consists of a heavy steel frame, the equipment, and the siding. It is hollow with no separate floors. The building is unheated and uninsulated, but people do occasionally work inside. The new siding will consist of metal composite panels. There are no interior walls.

The existing siding has louvers at the bottom, and circular vents on the roof. There haven't been any issues with excess condensation, mold or poor air quality in the past. However, our installer is recommending against having either the louvers or the roof vents. He says they encourage leaks and are not needed because enough air will find its way in and out through the joints in the siding when the wind blows. The joints are equipped with rubber dams that channel out the water but could let air in.

Installing the louvers and vents will not be overly difficult, and I am prepared to tell the installer to just install them. But before I so - is there any merit to what he is saying?

 

[hoodguy]

What if the wind isn't blowing and it's a really hot day? You will cook in there. I guess I don't see his point about encouraging leaks either. I don't know much about this siding though.

 

[trashcanman]

No I don't see any merit. How much HVAC design has he done?

 

[graybeach]

Thank you very much for the responses. He has not done any HVAC design that I know of. Not only that, the siding system has never been installed on this exact type of building.

It is really a no brainer to just put back the ventilation system that was there, and I have directed the contractor to install the vents and louvers. But I offered to allow him to experiment by temporarily blocking the vents and louvers on a hot day. I will report back if he does this.

 

[willard3]

The simple response for your contractor is to point out that hot air rises.....have him think about that.

 

[Ron]

His comment about incidental ventilation through the panel joints is a crock. Won't and shouldn't happen.

Louvers and vents can be installed without leaks, if done properly.

Also, it would seem that since you are replacing all the roofing and siding that you have to comply with current code requirements, including energy efficiency...is that not the case and why not?

 

[graybeach]

Ron,
The energy efficiency codes do not apply to this building because the it is not heated or air conditioned. Our building permit stipulates that we meet the governing building code, but that does not really spell out ventilation requirements. I figure that we can't go wrong just putting back what was there. The area of the existing roof vents appears to be based on the 1/300 rule for unheated attic ventilation. This and the responses to my post are very helpful because the contractor's attitude is that he is humoring an overly conservative engineer, and our management probably agrees with him. I am getting my vents and louvers though. Yay!

 

[Waramanga]

I am not sure where your job is but in Australia the fact that you are not heating or cooling the place does not get you off the building fabric efficiency hook in most circumstances. Most building classes here are assumed to have active heating or cooling at some time in their life even if they are not installed initially.