Ooooh that smell
Have you ever wondered why the air in hospitals smells so stale? Me either - until I was sitting in a WiFi-less waiting room and had nothing else to do. It didn’t take much, however, to notice the floors were laminate, the walls were covered in layers of latex paint and the furnishing was melamine and plastic. I might as well have been inside a Ziploc bag!
In a hospital, this makes perfect sense since the highest priority is to not absorb germs and to be completely sterilized.
In your home, though, fresh and natural air can have a huge impact on quality of life. But to understand how materials can improve a room’s ability to “breathe”, we first have to take a look at the materials themselves and their properties.
Floor Anatomy
Foundation or Slab: The structure of the building.
Common materials: concrete
Joists: A lateral wooden frame system that sits on the foundation. Sometimes with landfill in between.
Common materials: beams of lumber, engineered wood
Subfloor: Rigid panels that attach to joists and form an even surface.
Common materials: plywood
Underlayment: A flat and continuous layer. Made of different materials depending on the desired properties such as sound deadening or moisture resistance.
Common materials: plywood, moisture-barrier, sound insulation foam, cement board
Surface: The finished surface that you walk on.
Common materials: vinyl laminate, engineered wood, hardwood, ceramic, stone, carpet
So which of these materials are allowed to “breathe” and which are sealed? I’ve underlined the air tight materials: moisture barrier membrane underlayments and vinyl laminate surfaces. Steer clear of those and your home should smell as fresh as a breezy strawberry field right? Probably not. Let’s keep thinking…
Walls
Gypsum Board: Hydrated calcium sulphate core wrapped in paper, otherwise known as “drywall”.
Skim Coat: Gypsum-based compound used for creating a very smooth surface.
Primer: Oil or latex-based layer that seals and acts as a moisture barrier for the absorbent gypsum-based substrates beneath it. It increases the durability of the paint layer by binding it to the drywall.
Paint: Oil or latex-based finished surface that you see and touch.
Here we can see a number of air-stopping layers.
Analysis
We can easily replace the few sealing materials in the floor with non-sealing ones. A moisture-barrier underlayment is usually only necessary for laminate flooring so opt for a solid or engineered wood floor and you’re set for both. Plus, it’s just better in every way other than cost.
The walls are a bit tougher. Even if we replaced the oil or latex primer/paints with something lime-based and natural, there’s still the issue of the paper backing on the drywall. Arguments could be made that paper is fibrous and so it allows some air admission but I’m not sold…
on any of this, actually. Because while each of these materials may technically be porous, I can’t imagine any air getting through over a foot of concrete, landfill, plywood, foam and wood. At least not nearly enough to make any noticeable difference.
So what could it be?
Without any proof or responsible research, my next guess is it may be due to the breakdown and off-gassing of the materials. In which case, it’s only the surface coat that has the biggest impact on this topic. Perhaps what we’re smelling in a hospital vs. an 18th century French chateau is plastic and latex breaking down instead of wood and stone.
Well, after all that we still don’t have any answers, but we did learn a lot about what’s behind and inside our floors and walls and got thinking about their properties and how they’re relevant to our experience. That’s why this is an exploration and not an explanation!
Check back in for the inevitable exploration into off-gassing. To be continued…
-MM