Vented vs. Ventless Attics - Cost vs Performance - surprising results

1. IBC code requires vented attics with the exception of a licensed PE Mechanical Engineer designing a non-vented system. 2. In Arizona, nearly every home in the state has a vented attic. 3. In cold climates, vented attics prevent damage to the roof from ice dams and condensation buildup under the roof waterproof membrane. 4. Ductwork run through a vented attic does lose more energy than a conditioned attic; however, there are many ways to insulate ducts that are installed in the attic. As a licensed GC and a Civil Engineer, one of the methods I use is to have the main ducts installed close to the top of the bottom truss chord. Then, I blow in 14 - 20 inches of cellulose insulation to cover the ductwork. Also, most ducts in AZ are flex ducts. R-8 insulated flex duct is cheap, and you can add a higher insulation factor if you choose. This works extremely well and shields the attic ductwork from the AZ heat in the summer. No, it's not as "energy efficient" as Matt's house, but it costs a fraction (probably 1/8) of what Matt's house energy system costs. This system also doesn't require any maintenance. 5. Matt's sealed house HVAC system requires SEVERAL expensive filters to be replaced every year. Several of them have to be replaced every three months. That would drive me crazy and it probably costs at least a thousand dollars or more a year just for filters. 6. Not only does Matt's HVAC system require an exorbitant amount of maintenance, but the upfront costs are obscene. Matt probably spent $40,000 just on filter systems to circulate air in his house, and that doesn't include his heating/cooling systems and main ductwork. I am guessing that Matt spent somewhere around $80,000 for the engineering and installation of his sealed house HVAC system. Matt will never recover that upfront cost by energy savings of his system. 7. Matt is incorrect when he states that ductwork in the attic accumulates mold. That would depend on a lot of different factors. In AZ, nearly every home has ductwork in the attic. Obviously, if installing ductwork in the attic caused mold to form in the HVAC ductwork, major homebuilders would not be putting ductwork in the attic. In Texas, where Matt is, often some areas have high humidity. In those situations, then precautions have to be taken to prevent condensation from forming in the ductwork, WHETHER YOU HAVE A VENTED ATTIC OR A SEALED ATTIC - BOTH REQUIRE MOISTURE PROTECTION. While I don't deal with high humidity, but I have seen builders install whole-house dehumidifiers to prevent condensation and moisture buildup in the house. Having ducts in the attic doesn't magically [POOF!] cause moisture condensation in the ducts. If moisture condenses in the ducts, there probably are moisture and high humidity issues throughout the house, and they are not limited to the ductwork. 8. Sealed, airtight walls CAUSE mold growth in their interstitial space (inside the walls) if water somehow gets into the walls. Granted, with the advent of ZIP board systems, water penetration is not a problem, provided they are installed correctly. But what happens if you have a sloppy, lazy, sheathing contractor or a contractor who isn't trained well with sealed wall systems? It happens all the time. Then the chances of water getting into your walls and roof spaces explode exponentially, and if you have used closed-cell foam insulation in the walls and attic, you are screwed! If you design your roof and wall systems to be able to drain and vent any water that may get by the sheathing, then a poorly skilled contractor has less of an impact on your waterproofing system. Plus, building walls that vent at the exterior provides an additional layer of protection against water infiltration. 9. Not only is Matt's HVAC system incredibly expensive to purchase, it is also incredibly expensive to repair if it breaks down. Matt is using very high-end, cutting-edge tech, and using that tech to heat, cool, and filter the air in your home comes with a very high price. HVAC repair parts are not readily available; they are expensive, they have to be specially ordered, and not every HVAC contractor can work on complex, engineered HVAC systems. ALL of these factors point to sky-high repair costs for Matt's HVAC system when it fails, because every HVAC system fails over time. When I replaced my house's split system HVAC system (it's heated by gas and cooled by an AC unit), I chose a relatively simple two-stage Trane system. I could have purchased Trane's cutting-edge variable AC systems, but my HVAC contractor, who has worked with me on several projects, warned me that repairing them was very expensive. I checked into the efficiency difference between the luxury variable stage AC systems. Trane's specifications state that their variable speed AC units are only around 5% more efficient than their two-stage systems. Why? It's really pretty simple. My house requires a 5-ton AC unit, but I don't need that full cooling capacity most of the year. Trane's two-stage unit gears down to the equivalent of a 3-ton unit when the exterior temperatures don't require all of the cooling capacity of the 5-ton unit. Because my house is very well insulated, the AC runs at its lowest stage (the 3-Ton stage) almost all the time. Even in the hottest summers, my unit runs at the low-energy first stage most of the time. Only very rarely does it kick into the second-stage, 5-ton cooling mode. The point is, cutting-edge HVAC tech isn't always the best choice because not only does it cost a LOT more than established HVAC systems, it also can be incredibly expensive to repair. ANY licensed HVAC contractor can work on my two-stage Trane unit and repair it. They are relatively simple to diagnose and repair. The parts are reasonably priced, and most Trane vendors have them in stock. Variable speed units from Lennox, Trane, and other manufacturers require highly trained techs to diagnose and fix them, and they also require special tools. And all of that cutting-edge tech MIGHT save you 5% or so in actual cooling costs. It's just not worth the headaches. I don't really care if Matt promotes sealed, airtight homes; there's nothing wrong with the design of his home, provided everything is installed correctly and engineered. However, sealed homes do require an engineer to design them, and engineers cost money. The vast majority of home buyers cannot afford to spend $40,000 on air filtering systems and $1000.00 a year just on air filters. Most home buyers are struggling to get into a home. What frustrates me is that Matt seems to be grossly ignorant about alternate systems that have been thoroughly proven to work are very energy efficient, and cost a fraction of what his HVAC system and insulation systems cost. If Matt is going to present himself as an expert, he should first do his homework. The vast majority of people who are building a home would be better served to install a well-sealed home with a ZIP system with redundant drainage and venting in the walls and roof, and a vented attic with R-60 cellulose insulation. Insulate your walls to around R-30. Seal the penetrations into the roof and walls just as Matt's guest shows in this video. Install a Trane Clean Effects (or similar) air filtration system. You can wash your filters with a hose every three months on a Trane air filter system, and it will do a great job purifying and cleaning your interior air. Install a standard AC unit or heat pump that is energy-efficient, reliable, and easy to repair. On a larger home install a couple of super-efficient mini-split heat pumps at key areas of your home (they are very cheap and reliable). Then, use the huge amount of money you save for this established construction design and install a 10 KW solar system. Done correctly, you will have NO energy costs for your home, few maintenance issues, and you will be able to use as much energy as you want without always being concerned about how much your electric bill will be. If your standard heat pump breaks down, you will easily be able to find an HVAC contractor who can fix it, and the parts won't cost you an arm and a leg. Most of the time, your mini split heat pumps will be able to heat and cool the house, and you will hardly use your main central heat pump unit. That will greatly extend its life and save you even more money. In high-humidity areas, install a whole-house dehumidifier system to get the moisture out of the house. This is the smart way to build a cost-efficient home.

I love how Matt always tells people he's going to link to them below but never does 😆. Keepin' all that link-fu to yourself!!

Have to say this is the first time I’ve heard this level of detailed discussion on how to do a vented attic properly where you design from the beginning (no load bearing interior walls, seal penetrations, run ducts under the air sealing drywall layer) for success. Would love to see more designs that showcase these techniques to do successful high level vented attics

Jake is very intelligent. He has the ability to simplify something that others would overcomplicate.

Thank you for setting the record straight for vented attics. I was surprised that sheetrock could be used as an effective air barrier on the ceiling. I would like to see a video detailing how to place walls under the ceiling penetrations.

Matt Risinger; Come to Norway. A lot of the stuff you talk about with ventilated fascades, attics, roofs, wind-proofing details etc we practice in our building codes. The same with well insulated walls, 2/8 framing etc. We also build according to very strict codes in general, also as it relates to frost and snow. Our building method is almost exclusively wood for small residential buildings.

Back when I was touring a bunch of model homes, the one thing that stood out to me is that every home that used spray foam insulation everywhere had almost no dust anywhere. Every other home with typical blown-in type insulation was quite dusty. That may be a big factor for those that suffer with allergies.

Once we get the initial construction figured out to build a good building, we need to talk about what will happen to that building over the next 10, 20 and 30 years, and how we can build it to be maintainable and even modifiable such that the performance does not degrade over time. Talking about recessed cans that require constructing a box in the attic and extending the envelope over that box is great, but what happens in 3 years when the homeowner wants to add or relocate a can? I love the idea of no load-bearing walls, making it easy to remove or move a wall, but even just adding an outlet or a switch requires running some wires, likely breaching the envelope. How hard is it going to be to seal it up again? How hard is it going to be to teach everyone doing all that kind of interior work what needs sealing and how to maintain the envelope? For insulation the blown in cellulose is easy, quick and so cheap. But blown in cellulose tends to settle and lose R-value over years and decades. The rockwool batts in the conditioned attic are good unless/until physically damaged. The iso on the roof deck is pretty good, but can soak up water if/when there is a roof problem. I think putting the envelope on the outside of the house makes the most sense, and in future work it is pretty easy to understand that a hole to outside needs sealing. I'm still not sure if that will result in as durable a building as one that breaths, but I sure like that a sealed building keeps the bugs out a lot better!

Recently moved to Japan, modern houses are built with a closed 2ft concrete foundation that is then insulated with closed cell foam. AC is installed under the floor and blows into the underfloor cavity, escaping through floor grills (no ducting). The inlet side is ducted from the peak, condensation is run outside through a drain. Walls and ceiling are sprayed closed cell foam, creating a continuous air barrier.

A+ wow! love this conversation i deleted all my attic HVAC ducts and central ac and went full mini splits heat pumps and few months ago CBS 1980s home built by commercial contractor built solid.! so 5 single heads run whole house in humid FL. next year planning to install small 4" ducted circulatory octopus to recirculate air around house thru all rooms with a 4" 20x20 near HEPA MERV 14+ media filter and UV light...electric bill already cut in half and house is so comfortable ...plus every room has insane power to move temp where ever i want within 5 minutes... need time to understand and design a fresh air intake and then air condition it because humidity in FL is rarely below 85pct need like a dehumidifier AC modular box to tap into ... awesome awesome conversation Thank You

14:40 excellent point about lower ceiling in the hallway. Modern homes are so scared of lower ceilings anywhere, and frequently lack intimate private spaces tricking us into thinking we need more space

I went with three ductless 30 SEER mini splits in my ICF house, NO crappy flex duct in an attic! 18 inches of cheap blown in pink fluffy in the ceiling R50. spray foam top plates and baffles, 360 bird block soffit vents and 72 feet of peak vents in low SRI standing seam metal roof over Sharkskin high temp membrane. The vision was build a yeti cooler under an easy up shade cover- house. Then add an ERV to breath it. 55 days of temps over 110 degrees in Phoenix last year, that's what I'm competing against!

One thing you didn't touch on is the added square footage of insulating the roof versus insulating the ceiling. Your R-value is per square foot and insulating the roof is adding 50% + more surface area depending on the pitch. For that reason alone, I'm with Steve, vent until it doesn't make sense to vent. Finding a way to run ducts inside the envelope as much as possible and minimizing the size of the unvented mechanical room would have been the more ideal solution.

So, I like that Jake Bruton gives his perspective on homes that have to deal with both the cold and heat of climate zones that aren't Texas. My home is in Climate Zone 5. What NONE of the home improvement folks, not even Mike Holmes way up in Canada (side note: he'd be a great guest) have really tackled is the most cost-effective way to improve the insulation of a 1960s-era production home. Specificaly, the worst type of homes for the upper midwest: split-level or raised ranches. Please tackle this topic. Now, this spring, we're finally getting our siding re-done to include house wrap and insulation on most of the outer walls (they recommended working with someone else to insulate from the inside for the cast concrete walls), soffit vents, and pretty much everything that's not covered by siding will be wrapped in aluminum. We're hoping the next home improvements will be windows and doors, and then a new roof. When we do the roof, of course I want the F Wave Synthetic Shingles that the Stud Pack guys used (https://www.youtube.com/watch?v=vIHZclO20ag), but also the correct exhaust fan venting for all the bathrooms and replace the attic fan with a ridge vent. The ultimate dream for the attic is to move the access from a bedroom closet hatch over to the hallway. We don't store anything in there, it's just for maintenance and it's got blown-in cellulose on the floor and no insulation on the gable walls.

Great video man. I love what Jake is talking about with a continuous layer of drywall on the ceiling before framing interior walls. I also love what was mentioned about the "airtight" recessed lighting fixtures. Couldn't agree more with that.

I'm doing a post frame house with a vented attic following Jake's guidelines. No load bearing walls, minimal penetrations, all HVAC inside, continuous ceiling drywall. 40x40' the basic shell is up and I just ordered the wall insulation.

I appreciate the honest and RESPECTFUL conversation. If only we could all do that.

We built in zone 6a last year and almost all homes around here have basements, where the HVAC handlers go. We used Zip-R12 sheathing over 2x4 studs with closed cell foam for R-30 walls one a one story home. We had 2" of closed cell sprayed on top of the ceiling drywall and over boxes built over can lights and bath fans. Then blown fiberglass to R-60 in attic. The attic space is vented as usual. This was the best air sealing and insulation method we could come up with. I wanted to use mineral wool between wall studs (money savings and better sound reduction) but my contractor said the closed cell SF would add shear strength to the 2x4's with 4" nails coming through the 2-1/2" thick ZIP-R. Our blower door tested 75% below passing threshold.

Matt, Jake, What a wonderful and fun video! 😎 I would love to see you guys, with Steve, do a much deep dive into the issues of the Vapor Diffusion port. What it is; the problem; the solution... I remember Doc Joe L. discuss this some time ago, but you guys have a much better production capability and could provide a valuable service here! Cheers, Eric

Matt, I'd consider what you have in your house a loft and not and attic. It is located above the structural bottom chords/ceiling joists (like a loft in a barn), but it fully part of the house. An attic I think of as more "dead space" between what is the house and the house's envelope and the roof system. In Post and Beam construction we do a lot of lofts then carry the thermal envelope/air barrier up the pitch and vent only the roof with a criss-cross lattice of 1x4's (not a style of construction that lends itself to vented attics).