Determining dehumidifier requirements on drying jobs can be complicated enough but I would like to talk about one aspect of the puzzle I think is over looked. For years we have taken the total cubic footage of an area to be dried and used that to calculate how many dehumidifiers you need for a particular situation. You also need to take into account things like number of people using the space while drying, temperature of the area, and the amount of porous material within the area that is affected. This is all well and good and most drying contractors can calculate this pretty efficiently and quickly. However, do we ever account for the fact that the return air plenum is inside our area to be dried?
Say we have a 2500 square foot house with 10 foot ceilings and about a 1000 square foot of the house affected by a fresh water leak. We put up containment on the 1000 square feet area and determine that we need 250 pints of dehumidification to properly dry the 10,000 c.f. However it ends up taking you 5 days to dry the area when it should have taken you 3. Then you realize the air conditioner return plenum for the entire house is in the containment area. So every time the air conditioner kicks on it takes some of your dry air and puts it throughout the entire house. Do you need to account for this in some way? Are adjusters going to understand and approve any extra equipment or extra steps to account for the loss in dry air?
Here’s two ways you could handle it. First, figure your dehumidifier requirements on the entire house. Still put up containment but put all your dehumidifiers inside the contained area.
Second only use the required dehumidifiers for the contained area and rig up some kind of ducting from the return air plenum to the containment barrier and pull unaffected air into the return so you don’t loose your contained drying chamber.
So how do you handle it? Have you even ever thought about it?