Question from Murray
Hi Debra.
Can pesticide vapor move across/through drywall between units in a conjoined block of units? How? (I guess obviously via cracks, pipes, etc.?). However, what about moving across the porous gypsum component of the drywall product? Everything I’ve found strongly suggests that this can occur.
This opens up a big can of worms re poisoning from insecticide “bombs” and repeated domestic pesticide sprayings, does it not? I’d like to use your answer in a major Essay I’m writing as we speak, if that’s OK?
Kind regards, Murray Thompson
Debra’s Answer
This is a question I can’t give an absolute answer for because all buildings are different.
Yes, if there were cracks, pipes, electric outlets, etc that had a direct connection between the two units, pesticides and other toxics could certainly find their way from unit to unit. However, I’m not sure what the likelihood is of those spaces being there between units. I would think that buildings would be constructed to be individually sealed.
That said, I believe that buildings can have air exchange between units through the ventilation system. But again, may or may not. This needs to be checked on an individual basis.
Now, as to your question about pesticides or other volatile chemicals can get through drywall, the answer appears to be no.
On the GreenBuildingAdvisor.com website it says:
What have you seen that suggests there can be air movement through drywall? Yes, it is porous in that water can move through it so theoretically air could move through it too, but as indicated above, it is considered an air barrier in building circles.
You;re absolutely right. The greatest risk of pesticide exposure in a multi-family housing unit is through natural and mechanical ventilation shared areas like hallways, and cracks in the building envelope (not all of which are visible).
When someone uses their bathroom or kitchen fan or opens their door or window, contaminants hitch a ride on the resulting air current.
When they walk through a shared hallway, they leave pesticide residue in their footsteps.
When units are not carefully air sealed (around electrical outlet amd switches, pipes, baseboards, windows, doors, attic spaces and in basements) and those air seals are not rigorously maintained, air from adjacent units enters and bring contaminants with it.
Practically speaking, when an adjacent unit a multi-family housing structure is treated with pesticides, you will also experience some exposure. If you can detect cooking odours, smoking, etc. from the adjacent unit, your exposure will be greater.
k2
The only potential problem I can see would be if you ran an air filter without opening any windows. It might suck odors, etc., in from other units, through electrical outlets, etc.
The article Debra quoted from GreenBuilding Advisors is a great article but it is being misinterpreted here. First the question you are asking is about vapor diffusiion through materials. Vapor can move through what seems to be solid materials to us mortals. The rate of diffusion or ability to move through a material is rated in perms (how permeable it is) Drywall is very permeable at 50 perms for a 0.375 inch thickness of board. The second problem is air tightness. Drywall is an air barrier if it is continuous with all seam taped and connections to other building materials sealed appropriately. In 99.9% of all construction old and new this is not happening. Our buildings across the country are very “leaky”, meaning their air barriers are not intact. So, yes in multi-family buildings both vapor and air move fairly unrestricted between units. Residential Energy by Krigger and Dorsi available from Saturn Resource Management has a materials permeance appendix as well as sections on vapor diffusion / permeance and air barriers in buildings.
I lived in a 20-unit apartment building. Cigarette smoke and fumes from painting came into our apartment through the return air heating vent and the gas fireplace from other apartments. If there is the slightest crack in any pipe or vent, the odor creeps in through these openings. I solved the problem by placing large trash bags over the openings with duct tape (including the fireplace) and this solved the problem. I also had to secure the plastic bags to cover the front door with tape, since on the day when the maintenance crew came and slopped around with their mops full of toxic chemicals, the smell drifted into the apartment. It is a good idea to close heating vents, if odors are a problem.
I know that many, many new homebuilders in the south (N. Carolina included) include the Traexx (?) system in all their homes (tubes-in-the-wall) pesticide program. The pesticide mist literally comes out of holes in the tubes, and in theory, kills the bugs if they hide in the walls. This always seemed very toxic to me; living in your home, with consistent spray coming out of tubes within your own walls. (the technicians visit each month, and spray from a truck hose, into an opening with a locked cover, on the outside wall of your home. Debra – thoughts on this?
COMMENT FROM DEBRA:
What will they think of next?!?!?!?
Pesticides are NOT necessary to control pests. I wouldn’t live in a house with this system. The pesticides will get into the living space anywhere there is a possibility.