Maddy wrote:
For the longest time, I've been scratching my head about the fact that "green" building regulations continue to mandate airtight living spaces coupled with more and more elaborate ventilation systems designed to overcome the problem of. . . you guessed it. . . airtight living spaces. Can anyone explain the logic of this to me? Why on earth would you insulate every wall and caulk every crevice if you're going to turn around and punch a four-inch hole in every wall to let air in? Why not return to the elegant, time-tested solution of living with a few drafty windows?
I agree with you 100, 1000 percent on the seeming inelegance of it. But there is a method to the madness, even if it is a sort of madness.
This will be long, because green building and construction is my current kick, and I am very opinionated on the subject.
The old construction style was to build leaky, with no regard for airtightness, and with little to no insulation either. These buildings were therefore more inexpensive to build, required no fancy mechanical systems for fresh air, and they were generally robust against moisture damage due to the air and heat moving through the building assemblies that dried out anything that got wet. It also helped that these old buildings were often built with thicker, harder, old-growth lumber that did not rot as quickly. And it further helped that the wall coverings were lime plaster, which has inherent antimicrobial effects due to its alkalinity.
These old buildings worked. But they were uncomfortable without near-constant space conditioning, which made them energy pigs that saddled the owners with very high utility bills. And despite this, there were usually still rooms that were never comfortable.
This green movement is all about reducing these utility bills and making the space more comfortable. But there's an order of operations you need to follow to make the process work:
First, control water entry.
Then, add mechanical ventilation with heat and moisture recovery.
Then, control air entry.
Then, control heat entry/loss.
Each builds on the other. If you insulate before air sealing, you may create a mold problem because exterior components that were previously being warmed by indoor heat are now cold, so they don't dry out and become condensation surfaced for humid interior air. If you air seal before stopping water entry, the same thing could happen--a building element that was getting wet may now have limited drying power. And if you air seal before adding ventilation, you'll poison the occupants due to the pollutants in the indoor air, particularly if there's a gas range, unvented gas heater, or non-sealed-combustion appliances. People could die. And of course if you add ventilation without heat or moisture recovery, you're completely eliminating the savings all the air sealing work you did, so you need heat and possible moisture recovery, which means adding an electromechanical gizmo.
A lot of this is necessary regardless of green building demands, because we now build with incredibly flimsy materials due to greater environmental consciousness (e.g. don't wanna chop down old-growth forests anymore) and the escalating cost of labor. Dimensional lumber is thinner, weaker, and younger than it used to be. Walls and floors are sheathed with OSB, not lumber. Walls are covered with paper-covered gypsum, not lime plaster. These materials are defective by design in my book. They are full of nasty chemicals, warp and rot and mold if they get wet, etc.
So the current mantra is therefore to scrupulously control everything to make sure there's no water in the first place, and no air can blow through it, and so on. With such flimsy materials, you
have to become an expert in this and control everything.
I don't like it, because it requires every builder to be a building scientist, and that's simply not likely because building science is an intellectual pursuit and building is a physical pursuit. The personalities of people attracted to these endeavors rarely overlap. So you get ignorant builders building mold and rot machines because they don't understand the science, and inspectors themselves are often no better, since many of them are former builders. And there's never going to be a way to totally shut off these risks. What about a burst water pipe? In an old house, you shut off the supply, evacuate the standing water, and let it dry. In a new house,
everything is ruined. The drywall irreversibly turns to mush. The lumber and OSB in the walls and floor weakens and grows mold everywhere. The high humidity causes mold to grow on the chipboard cores of cheap kitchen cabinets and IKEA furniture. It's a disaster. This happened to a home next door to mine a year ago and the devastation was
unbelievable.
Personally, I think this gordian knot can be cut by building with simple and durable components that are not vulnerable to water damage, like concrete blocks or bricks. Once you build a masonry unit wall, it's naturally airtight in the first place. And it won't be bothered if it gets a bit wet. So no matter what its current state is, you can safely install insulation boards on the outside.
Hopefully I haven't bored people to tears, but this is my current kick and I could go on forever if there's interest!
I'll let you know next time I come across one of those.
It is good for the planet you know.