{“title”:”Research Note #23: What Dry Construction Gave Up”,”content”:”
It was the autumn of 2019. I was restoring one of my properties — eighteen years old at that point — and when I peeled back the wallpaper, I found a uniform pale-brown stain spread across the entire back surface. That was the moment I started looking at gypsum board seriously, and suspiciously, for the first time.
Dry construction is fast. There is no need for a plasterer to apply finish coats and then wait days for them to cure, the way wet construction requires. Attach gypsum board to the framing, apply wallpaper on top, and a room is finished in a matter of days. Construction timelines shorten. Labor costs compress. When dry construction took over job sites from the 1970s onward, I think the reason was purely economic logic.
Let me digress briefly here. When I was a student, my grandfather’s house had earthen plaster walls. Every summer when I visited, the air directly in front of those walls felt noticeably cooler — and there was no air conditioning. I understood only much later that the walls were absorbing humidity and releasing it through evaporative cooling. Those walls breathed. Dry construction stopped that breathing, in the name of efficiency.
Except that is not quite right. And this is where things get complicated.
Gypsum board is actually a porous material. Its countless internal pores absorb moisture and release it again. Product specifications describe it as having excellent moisture absorption and release performance — and the numbers support that claim. I had assumed, early on, that dry construction had simply stopped the wall from breathing. But gypsum board itself does breathe moisture. That is part of why indoor humidity in newer apartments still stabilizes reasonably well through seasonal transitions.
The problem was not there.
Gypsum board does not absorb only moisture. It absorbs odors too. Tobacco smoke, cooking fumes, pet-related compounds, volatile organic substances from human occupation — those same porous channels that take in water vapor take in all of these as well, one after another. And then they release them. When temperature rises, the release accelerates. In one measurement I did in a vacated room last February, surface temperatures on the south-facing wall reached 38°C on a sunny afternoon. The room smelled noticeably worse in those hours than it had in the morning.
Moisture absorption and odor accumulation come from exactly the same physical structure. The strength and the defect cannot be separated. This is what I have been calling the gypsum board paradox.
Replace the wallpaper but leave the board in place, and the odor stays. Deodorizing sprays only react with what is already being released from the surface — they are always chasing the problem, not addressing its source. Surface-applied photocatalytic coatings work at the surface layer and do not reach what has accumulated deep inside the board. None of the standard approaches has a way to extract what has already been absorbed into the interior of gypsum board.
I still cannot tell whether the industry is unaware of this paradox, or whether it is aware and has simply chosen not to focus there.
What I am confident about is this: what dry construction gave up in exchange for speed was not only the breathing wall. It also gave up the wall that does not accumulate odors — and that second loss has gone almost completely unexamined.
“,”excerpt”:”In autumn 2019, peeling back wallpaper in an 18-year-old property, I found uniform pale-brown staining across the entire back surface. That moment made me look at gypsum board differently. Dry construction brought speed and lower labor costs — but gypsum board’s porous structure, the same feature that gives it its well-documented moisture regulation performance, absorbs odors and VOCs just as readily. The two behaviors cannot be separated. Replace the wallpaper, the odor stays. Surface treatments cannot reach what has accumulated inside. This structural paradox has been sitting in plain sight for decades. I am not sure the industry has named it yet.”,”tags”:[“dry construction”,”gypsum board”,”moisture absorption”,”odor accumulation”,”structural paradox”,”VOC”,”building materials”,”porous materials”]}