@ Teej
What are some of the more common misinterpretations? Ideally it would be good to have both so I can collect my own data and be sure of the interpretations but budget wise I really only want to do one. I'm confident I could rig my own blower door aswell. The company I'm considering hiring will be looking to sell work to minimize heat loss after the inspection.
@ Pman
I'm definitely wishing I had one of those homes atm.
Its sort of a long list, but, some areas are more common/normal leak points, and, there can be water damage that can fool people into thinking its air infiltration and visa versa if focusing on hot/cold areas.
The most important thing to consider starts with the outdoor conditions relative to the indoor conditions at the time of your testing.
For example: If its hotter outside, infiltrating air will be warmer...but, the longer the pathway, the cooler it will become as it exchanges heat with its passageway materials, etc.
Studs, etc, will essentially act as breaks in the insulation, so, in the winter for example, will appear colder than the insulation to either side.
Insulation is supposed to be installed with the vapor barrier flaps or "ears" overlapping the studs or joists, etc...but many installers are lazy/uninformed and simply tuck the ears into the stud bays, etc.
Batting typically has breaks at seams...so if they are stuffing a section of batting in, and don't seat it to the next section well and tape the seam, there will be a break in the barrier at that seam, etc.
Corners and headers and places where the framing lumber is doubled or tripled, etc, have no space to put the batting, so, that area/junction will be more similar to the outside temp, and, tend to not have a continuous vapor barrier.
Some places have reversed vapor barriers, where the contractor applied a rule of thumb that should have had an exception. For example, the vapor barrier should face the direction the vapor is coming from.
Many contractors interpret this to mean facing the occupied side, if they are from the north, where the humidity, etc, tends to be from the occupants.
Some, from the South where it is more humid outside, put the barrier facing outside, not on the occupied side.
Some buildings are built by crews who might be from any combination of states...and who put in the barriers the same way they always did...w/o thinking about why.
Some buildings are built by those who stopped insulating at points that they felt an inspector was unlikely to check. For example, the crawlspace has insulation visible from the hatch, as far as a flashlight can hit from there, but, beyond that and around the corner is bare, etc.
Some places had renovations that covered an existing vapor barrier with a another set of materials that acted as a second barrier, resulting in a doubled barrier which traps moisture, etc.
Moist air is LIGHTER than dry air, so it rises. So, attic insulation tends to have the barrier facing down. If you add a second layer of insulation, it should not also have a barrier, to avoid that trap.
Many windows are designed to accept a certain amount of rain, etc, in, but to drain it back out. That often involves an air passage, and plugging that can cause the window water to drain back into the wall, etc. Some windows are not flashed in or insulated properly, and the air gap/flashings are a problem that needs to be fixed. (You need to know what you are looking at to know which response is appropriate)
And so forth.
