Dryer Won't Dry Clothes- Broken Dryer, or Airtight Home? (feat. Scott True)

Blown-in insulation between rafters requires a vapor diffusion port at the ridge to function properly and avoid moisture-related issues, making this a critical detail in non-foam insulation strategies.

“I tried bats blown in this particular house had blown in insulation in between the rafters and by the way I did use the The Vapor diffusion port at the ridge I'm just throwing out that out there because there may be some people that that know that this strategy can be an issue unless you're including that vaporative Fusion”

In homes built on slopes with complex geometry including unconditioned stairwells that extend through the attic, electrical penetrations in the ceiling above unconditioned spaces become critical air leakage points that are easy to miss, whereas similar penetrations in normal ceiling cavities are less consequential.

“went up into the attic and with the geometry and Scotch geometries are like very interesting they're very like simple and straightforward in one respect but also kind of like there's a fancy element of what he's doing and so there are ceiling change Heights and there's things like stairs that lead to garages that are sunken we're building on a slope um and so the garage is is almost like a half basement in a way it's it's got the the concrete like retaining walls um so that garage is is one complete level down and that stairwell is not conditioned as part of the garage space but it goes all the way up and so there's a portion in the Attic where um all of the air sealing on on the ceiling of the house doesn't matter that much because my main air barrier is at the roof um but in this one particular spot it does matter because that portion of the ceiling right below it is that stairwell which is unconditioned so that does matter and so any electrical penetrations in that wall then it lights things like that are now a much bigger issue”

At an airtightness level of 1 ACH50, a home is tight enough that depressurization from undersized makeup air creates measurable performance problems (dryer failure, moisture intrusion), whereas in looser homes the accidental air leakage pathways prevent such problems from manifesting.

“and so after a week of magically the dryer works now when you open the window in the laundry room and you run the dryer like perfect perfect close every time then Scott is like you know I thought they were separate uh problems and actually it's the same problem and I think that that is such a powerful thing not just to hear from someone that I work with all the time that like it gives me I literally I have Goosebumps right now but also to have you go through that and learn it the hard way for yourself I remember those like aha moments in my own work and just being like Oh my God like I now just you drank the Kool-Aid and so you being able to use testing on an actual case that you you have to find a resolution for and being able to do something where you don't have to replace the dryer like you just saved a thousand dollars that's awesome um so I think that those kinds of things where you're solving multiple problems in the home by using Diagnostics to pinpoint the one cause that's that's doing all these different symptoms is amazing”

Scott transitioned from building tight homes 'without even trying' to intentionally designing for airtightness after crossing a threshold where ERV (energy recovery ventilation) systems became necessary for maintaining indoor air quality in very tight homes.

“by the way if you're thinking of building super airtight there's this line that that Scott is describing Crossing where you have to use ervs right you can't use that So eventually I crossed over that threshold where um you know I was building tight homes without even trying and and it was just a matter of just refining my methods and just having a you know a good a good strategy and Method and uh keeping things simple but thorough”

When a homeowner uses a kitchen exhaust hood regularly and it exceeds the makeup air capacity, the home becomes depressurized, which manifests as multiple simultaneous problems including dryer malfunction, moisture intrusion, and AC condensation.

“so this six inch makeup air damper was not big enough we and you can easily do the calculation once you have blur order test which we just ran and we have the uh size of the kitchen exhaust hood and we asked the homeowner because she happened to be there do you actually use that and she said yes dutifully every single time I cook which is like yay we want that but when she's doing that it's actually depressurizing the house because that six inch isn't big enough”

A moisture intrusion problem at exterior doors (sliding and French doors) that appears to be a flashing failure may actually indicate a different root cause such as air depressurization within the home.

“this was a homeowner that called to report some weird things going on um and this was a wild built house but um the homeowner reported some moisture coming in at the bottom of two exterior doors sledding doors right uh one was sliding and one was a French door and um so the four was getting wet and and so people that I work with their their first assumption was oh must be something wrong with the flashing and I'm like no well I mean anything's possible but I'm thinking no because I flashed those doors myself I do that work myself when I build and I know it's done well there's got to be something else going on”

The blower door test is primarily used to establish pressure imbalances within a home to enable zonal pressure testing and diagnostics, rather than primarily to measure the CFM50 (air leakage rate) in this diagnostic context.

“so we got the blower door obviously the blower door is where you start because if you're going to try and test air leakage you need something to initiate the air leakage and measure the air leakage so we do a bloated test it's tight we weren't using the blur to find the cfm50 we're using the blur to establish pressure imbalances within the home so that then we could do things like zonal pressure testing”

A six-inch makeup air damper for a kitchen exhaust hood is a standard default size that distributors typically provide without analysis, but in airtight homes this size is often undersized relative to the actual hood CFM requirement and the home's airtightness.

“so that is only for the range hood and then over here um they have this damper that goes outside it's just bringing in fresh air bringing it into the return and Scott show me the elbow right there it looks like it's a little kinked at the elbow it is and I will just say um you're probably going to get to this but this house was built uh before we started using Erv so it was several years ago it was that transition because prior to that I was I was trying not to build so tight because I told him to and by the way if you're thinking of building super airtight there's this line that that Scott is describing Crossing where you have to use ervs right you can't use that So eventually I crossed over that threshold where um you know I was building tight homes without even trying and and it was just a matter of just refining my methods”

Condensation dripping from AC grills on sidewalls in vaulted rooms is a diagnostic indicator of air leakage problems rather than a defect in the AC system itself.

“and then the other thing was in one room I've got the the AC grills on a sidewall because it's a vaulted room and the condensation is dripping down so this was kind of a mystery we had to solve”

A pressure pan placed over an HVAC grill boot can quantify the air leakage contribution from that specific penetration, helping builders understand the relative significance of different leakage sources.

“I i don't have one that I bought but I have one that you instructed me to make okay”

Anyone can learn to perform advanced building diagnostics with coaching and live guidance, even if they haven't recently used testing equipment, making diagnostic capability more accessible to builders.

“I love doing that kind of a consult where we actually do testing live so if you have a blower door that you haven't used in three months and you're like just nervous to do it let's spend an hour together while you're at your clients place and I can kind of like direct you to do some more advanced stuff because I think like anyone can do what Scott has done to just like dig in a little bit and start solving problems in a much more affordable way for you”

When a homeowner opens a window in the laundry room while running a dryer in an airtight home, the dryer begins to function normally because the opened window provides makeup air that relieves the depressurization.

“and so we did the experiment where she would run the dryer and leave an open uh window open so that makeup air can passively come in um by the way this house was really tight that's why this matters you're not going to see this in a house that's loose”

The diagnostic case required upgrading the makeup air damper from a 6-inch to a 10-inch size, air sealing additional leakage points (especially around the bathroom fan in the attic ceiling above the unconditioned stairwell), repositioning the existing supply duct, adding a second supply, and repairing floor damage.

“so you guys understand what we ended up doing um we we did replace that makeup air damper with a bigger one it was a we turned it into a 10 inch um we air sealed there there was one other spot that was not air sealed it was that for some reason that general area of the house had some um issues there I don't know I guess it was that day where people were skipping but um and uh but so we had that ceiling area that we talked about but also what's up into the left what's arcing up and to the left that ends in that really bright spot that's the bathroom fan can we can we go check that out sure it looks like there's air leakage into that it does higher cavity there yeah because that whole cavity is glowing it was loose and um so we sealed that up we repositioned that existing Supply closer to the problem area but then added another Supply we fixed our flooring because the flooring got damaged so we fixed that got it all pretty again”

Infrared imaging revealed bright glowing areas around the bathroom fan cavity in the attic, indicating air leakage concentrated in that zone.

“but also what's up into the left what's arcing up and to the left that ends in that really bright spot that's the bathroom fan can we can we go check that out sure it looks like there's air leakage into that it does higher cavity there yeah because that whole cavity is glowing”

Attic spaces show a pressure reading of approximately 10 pascals relative to outside while other zones like bedrooms show zero, indicating that air leakage is concentrated in the attic despite generally good air sealing elsewhere in the home.

“okay it means there's a 10 connection to outside in the Attic it should be a zero like all the bedrooms but it just means because there's no spray foam you did a great job air sealing this house but there's still some air leakage and it looks like a fair amount of it is in that attic”