One fantastic way to create an air-tight barrier between the living space and a vented attic was featured in Fine Homebuilding magazine. The builder put ZIP sheathing on top of the attic floor joists and taped all the seams. He sealed the outer edges of the panels to the top plates of the exterior wall. All the attic insulation was on top of the sheathing layer leaving the attic floor cavities empty and available for can lights, ductwork, plumbing pipes and electrical wiring (which is fine since these attic floor cavities are within the conditioned space). The few penetrations from the conditioned space through the attic floor system (like vent pipes, etc) are completely air sealed. Then you just place your roof trusses on top of the attic "floor" and you've completely isolated the vented attic from the conditioned interior space.
Good points addressing the added labor/planning costs that might not be apparant. Ive heard the same claim about latex paint on drywall being the most cost effective vapor barrier
I have seen in a hotel where a bed was placed next to the PTAC where the air was forced into the corner of the room. When renovating, it was found that the back side of the sheetrock was covered in mold. As you know air coming off a coil is typically 100% saturated. I would be very careful on placement of a PTAC or mini split.
I live in Texas where it’s hot and humid 90% of the year. I have been debating about doing a DIY energy retrofit of my house. It’s a 2 story production house so no frills. My ideas focused primarily on the second floor since that’s where the bedrooms are and where we feel it most, especially in the summers. First idea was to remove the drywall from the exterior walls only from the inside and re-insulate with a better high performance batt insulation. Then add a layer of 1/2 foam board over the studs before adding a new layer of 1/2 drywall. Had no plans to do an air tight install, just wanted to increase the capacity of the exterior walls. This method would be most affordable due to the diy abilities. Second option would be removing all the siding on the exterior and obviously the cardboard sheathing since that’s what we have on the exterior of the framing and adding the new insulation to the cavities then foam board sheathing over that before replacing the siding material with the original hardie or new. Obviously this approach is much more costlier than the first but would be the best solution. Thoughts or suggestions???
Great question, the second option that you described is what you should do. Rigid foam is a vapor retarder and you really want to make sure that the vapor retarder is located on the exterior in these hot humid climates, as installing it on the interior side of the studs will trap moisture in the cavity (we see a lot of mold in these situations). You have to ensure that the wall cavity can dry to the interior since vapor drive is predominantly from the outside inwards. Check out this video I made a couple months ago about remodeling homes in hot humid climates: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-1TuRK3CI7jc.htmlfeature=shared
I work on log built buildings where you can almost see the outside from inside, air barrier is a real challenge and where previous contractors or owners have attempted to seal up wall assemblies, I’m repeatedly finding mold, rot and decay. Because log construction is niche compared to standard building methods, I’m making up my own rules and could use the knowledge and science of Mr. Asiri. I watch every video and bought his PDF book. Should I invest in the Cad library ? A picture is so valuable these days.
Thanks for your support, the CAD library has some good details but they aren't applicable to log homes. As you probably know, log homes use a lot of gaskets, backer rod, and sealant to seal in between each individual log, and quite frankly there are a lot of ways to accomplish a continuous air barrier. You may want to consider something like Aerobarrier, in which they pressurize the home and aerosolize a water-based acrylic sealant to fill in every little nook and cranny.
Awesome content. Building a house in humid coastal Canada. What would be your best recommendation for interior vapor retarder? Using plywood with blue skin and 2-in hard foam insulation on exterior. 2x 6 wall
What about Aeroseal for a new build? You do not need well trained workers to seal drywall if you can seal everything in a controlled fashion at the end. Sure you need to educate the owner but other than that that this is a pretty efficient way to go
Sharif, I truly appreciate your content and agree with you on almost everything in all of your videos. You waste no time and cover a lot of details and information. Always well worth the watch. Thanks for sharing... 😁👍⭐⭐⭐⭐⭐
I really like the double wall or wall with a smart barrier and at least 1.5” furring under drywall. At least it gives a fighting chance at maintaining integrity of the wall. RR Building takes this approach with his post frame structures.
I've specified it before and it's actually quite a common strategy in places like Germany, Austria, and Switzerland. Taping the joints is key. It's not my favorite approach though.
It's a good thing, we don't want humid air to accumulate and get trapped in the cavity otherwise we get condensation and mold issues. Let it dry out, either to the interior or to the exterior. This is a "flow through" assembly approach.
@@ASIRIDesigns But then all winter it is letting vapour into the wall and then it can't dry out in the summer unless you keep the humidity really low which most people don't do. They try to run the A/C as little as possible.
Is there ANY way to make your house more efficient without causing problems? The tighter you make it, it seems the worse it is for air quality and issues later with mold. Better to have a leaky house air wise that may cost a little more to heat/cool than have all these mold/rot issues because something happened later to compromise the structure. We live in Illinois where you can have cold winters AND hot humid summers. How do you build for that?
I wonder about this as well. I've watched hundreds of hours of content about high-performance house building and it always requires fancy air exchange/makeup equipment. I have to wonder when these designs break even, financially speaking. If a leaky home costs me another hundred dollars a year to heat and cool, then does it make sense to spend tens of thousands of dollars on so-called high-performance building techniques? After all, we have houses built a hundred years ago that are still in excellent condition. Is all this building science not a bit overrated?
I'm very interested in this, too, in the context of remodel. I'm in Ottawa, Canada. It was 25 degrees and 100% humidity *overnight* last night, and we have days in the winder than can go to -38 with windchill. I remodel builder grade houses into much nicer ones. 6 Mil poly is ubiquitous here, and when we go changing where air and moisture barriers are in the assemblies, even the inspectors want an engineering report before anything remotely unconventional happens. Even if it's in one of the prescriptive code sections.
Illinois has a good variety of temperatures. In summer, the exterior side of the wall dries by the sun, in the winter you dry the interior by heating and ventilating. The mold is a problem for climates which either don't have a great variety of temperatures, or when it's summer or winter all year round. In all other climates you just calculate the Dew point and put thick enough insulation on the appropriate side.
@@jboyd85 Easy: you have a winter climate. 25 degrees summer is nothing compared to -38. Put insulation on the exterior. You'll have plenty of winter days to dry out the moisture driven into walls in summer.
I just looked at a situation on a building that is about 10 years old where there is obvious issues at the bottom of the window jambs, and I'm almost certain that the drywall air barrier method is to blame for this.
