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@TechConnectify The point of making an attic include d into the conditioned space isn’t to reduce the relatively minimal AC losses, it’s to deal with the condensation that results when an attic that reaches 150F and 80% humidity reaches an interior space conditioned to 75F or so. Your solution doesn’t address the fundamental problem we deal with in the South where we have night-time temperatures higher than desirable, high humidity, and no basements.

@TechConnectify What is fundamentally different between a wall and a roof? A wall can be shaded from the vast majority of solar thermal load simply by building overhangs. The roof cannot.

@TechConnectify So, instead of continuing the building scheme we’ve used since before there was A/C, it’s better to remove the pressure cooker that is an attic entirely. Is it cheap? No. But in new construction, the price differential is a handful of dollars per square foot and in my area, far superior than any other alternative.

@transcendentape I mean, if you want to remove the attic space, go ahead.

But understand that for homes around here, *NOTHING* goes in the attic. The attic has tons of vents at the eaves and the peaks to keep air flowing through it. Does it get beastly hot up there when the sun shines? Absolutely! But there's a layer of R-50 insulation above the ceiling to battle that intrusion.

And that beats the pants off of any insulated ductwork.

@TechConnectify I mean, go ahead. We live in entirely different climates with entirely different residential construction norms.

@transcendentape my central point is that I think people in different climates could learn a thing or two from us. Our summers can be just as bad as down South, if less consistently. Perhaps that's the only reason our attics don't get moldy, but I'm doubtful.

You pointed to duct losses as minimal, but the first estimate I found puts them at 25-40%. That's a lot of energy being wasted and money being spent to condition space you're not in.

We just... don't do that.

@transcendentape our M.O. has largely been to treat the attic as a space which is there to frame the roof and that's it.

It's functionally outside, so once the sun sets the conditions up there equalize with the outdoors quickly. And sometimes we even use a fan controlled by a thermostat to force some airflow! But that's relatively uncommon.

From my perspective, the reason we don't deal with mold is mostly that there's nothing up there colder than ambient temps.

@TechConnectify “It’s functionally outside”

This gets to the heart of the matter. I don’t think you appropriately appreciate how bad attics are in my climate.

Pre-A/C, homes were built with 10 or 12 foot ceilings and windows to allow cool air in the bottom and warm air out the top. When we got A/C and started insulating walls, we ran into all kinds of problems with mold. Walls can be protected by rooves, but there’s nothing to protect the roof.

@transcendentape Well, to be honest, I'm confused by what you mean by "bad attics." Can you elaborate?

But to circle back to the climates things, when you say "started insulating walls" - this is it right here. We've been doing that *forever* because we have to. And absolutely critical to that is a nice thick blanket of insulation above the ceiling. It doesn't really matter how hot the roof (or attic) gets when you have that barrier in-place.

@TechConnectify As a matter of fact we have not been doing that forever, at least in my climate. This is precisely the confident ignorance that I am upset with you about.

@transcendentape OK... let's rewind, here.

This whole discussion is about regional/climactic norms. It started with my challenging them, and you described what's done in your area as "the best approach"

Really, all I'm trying to do is challenge that, and offer up what's been normal here for a long time as an alternative. Perhaps, if someone ventured to try building a home down there just like we do up here, it would be much more comfortable and take less energy to cool.

But, perhaps not.

@TechConnectify You could test that hypothesis by observing what good homebuilders are building.

Matt Risinger is an Austin,TX homebuilder that deals extensively with these kind of questions, and he has a Youtube channel that covers a lot of the issues we’ve covered.

@transcendentape I'm familiar with those channels, and Risinger specifically! I largely like a lot of what they feature, but there's other things I totally don't.

For instance, I think tankless water heaters are extremely overrated and a barrier to home electrification. And I'm still perplexed by the attic thing - I need to log off soon but I want to repose my thoughts here on last time in a different way:

@transcendentape What does the air handler do? It produces the cool (or warm) air that you need, and it costs you money to use it. Therefore, that air has a raw dollar cost and you probably want to minimize waste.

This is the raw crux of my whole deal. It seems entirely self-evident to me that you should put the machine that costs money to use inside the space you want it to heat and cool. And, you should keep all components of that machine (i.e. ducts) in that space, too.

@TechConnectify I mean, yes. We are arguing the same point. The difference is that in the south, where nighttime temps are frequently above ideal and humidity is an issue, moving the structure of the A/C down to the liveable area doesn’t solve the problem. In fact, it makes it worse. The problem in the South is the existence of unconditioned attic spaces.

I’ve never walked outside to -20F temps.

I have seen a cloud below my ceiling due to dewpoint.

@TechConnectify What you might not be appreciating is the very different response water vapor has between-20f and 80f versus 150f and 80f

@transcendentape Oh no, I appreciate this but... again, in the summer this absolutely something we deal with. And to be honest, I feel like putting a cold thing in the attic is /way worse/ than not doing that.

In fact, why is keeping the AC entirely in the conditioned space worse? I need you to explain that because truly I'm not seeing it.

Our homes just flat out don't have ceiling penetrations into the attic other than an access hatch and electrical boxes. The attic, as I said, is outside.

@TechConnectify “Why is keeping the A/C entirely in the conditioned space worse?” Because in my climate, in conventionally built homes that aren’t built to the standards that we both are advocating for, those losses are necessary to ensure the attic doesn’t become a pressure cooker.

@transcendentape ehh... to be honest I still think there's something we're talking past each other on, here.

In my head, you can take any existing home where you are, get the HVAC out of the attic and run ducts below the ceiling, then patch up all the holes, add the sea of cellulose that's normal up here above the ceiling, and you'd be right where I want you to be.

No mixing at all of conditioned air with attic air, and sufficient ventilation prevents mold.

Am I missing something?

@TechConnectify No, you’re not missing anything except for the fact that very few people look at a 1200 square foot home and think, “How can I reduce the usable size?”

@transcendentape OK, if we're there then, this is all buttoned up.

To be clear, I'm not saying people should sacrifice floor space and get the air handler out of the attic. If they want to maximize both energy efficiency and usable space, I would probably push towards a mini-split setup.

But what I /am/ saying is... next time you build a home, add another 50 sq feet for the air handler closet. That's only been in my head 'til now, but that's where I've been from the start.

@TechConnectify Absolutely no arguments from me… except that if you’re building a new home in my climate, you should consider eliminating the attic as a non-conditioned space, regardless of where your HVAC is.

@transcendentape Agreed. I would, however, be curious to know whether there have been comparisons between a conventional attic with R-50 or maybe even R-75 insulation above the ceiling and a home where the attic has been eliminated or otherwise mildly conditioned.

But at this point, that's just academic!

@TechConnectify It’s not only academic, but entirely unrealistic. The only way you could ever find thise R values is if you paid someone to build your house for you.

I can wave a magic wand as well.

@TechConnectify You’re essentially requiring a second structure to be built around the structure simply to hold the insulation. What in the world do yo propose to use as a regular building material with R50?

@transcendentape Blown-in cellulose! That's pretty common and has an R-value around 3 per inch. Create a sea of it in the attic above the celling and once you're above the rafters you can easily be at R-36. Go to 18 inches and you're at R-54.

Code in Illinois is actually R-49 right now.

@TechConnectify You’re hung up on insulation, while I’m trying to tell you that the existence of the unconditioned attic is the problem. Do you think no one in the south has considered insulation?

As you tighten up the building envelope, which is a requirement for efficiency, you exacerbate humidity problems that were previously dealt with by expected losses. Your gut feeling is simply not at all appropriate in my climate.

@TechConnectify From the most basic level, observe where vapor membranes are applied in your climate versus where they are in my climate.

@TechConnectify Now, given the fact that if I am not actively venting my attic, then I can expect it to be at least 50F higher than my conditioned space for maybe five months out of the year. 24/7. That’s not equivalent to outside temperature. And blown in insulation doesn’t have the vapor barrier on the correct side.

There’s a reason different climates have different building norms.

@TechConnectify Actively vent the attic? Why? When nightime temps are above 85F for three months what does actively venting the attic prove? The problem for me, in my climate, is the attic.

@TechConnectify We used to deal with this problem by having twelve foot ceilings and double hung windows and leaky construction with no A/C. Now that we are striving towards efficiency, the attic is the problem, and there’s a good history of home construction to show that attic insulation alone isn’t the solution.

I understand you also have hot days. I’m not talking about hot days. I’m talking about the fact that the lows do not drop below desired temps for months on end.

@TechConnectify Putting the mechanicals in the attic is silly in my eye, but it saves a bit of space in new builds. Putting the ducting in the attic simply makes sense when compared to whatever it is you are advocating. If it is your argument that the ductwork should be in the conditioned space, I agree. There’s a clear advantage to bringing the attic into the conditioned space that exceeds the idiocy of having ductwork inside the living space in my climate.

@transcendentape I feel like you missed some replies in the order I sent them - you seemed surprised by R-49 being code, or at least I pieced that together when I floated R-50 ceiling insulation and you said nobody would do that (or similar).

Regardless, I will grant you that I don't know the fundamentals of combatting moisture well enough to speak intelligently on the subject. However, I still question which approach makes more sense:

@transcendentape Make the attic part of the conditioned envelope, or create a moisture barrier between it and the living space then leave all mechanicals out of it.

Assuming a vapor barrier could be added to the R-50 ceiling insulation that's code here now, then why bother conditioning the attic at all? That's really the crux of my bafflement, and the normality of putting mechanicals up there where you live may cause the less effective thing to be standard due to legacy factors.

@TechConnectify How do you add a vapor barrier above the ceiling in an attic with wooden trusses?

It was almost impossible until a few years ago with closed-cell foam insulation.

@transcendentape I mean, it seems pretty straightforward to me. Simply adding a floor up there to box-in the cellulose insulation ought to work as OSB itself is a vapor barrier. And lots of people do that anyway to make walking around in the attic (and using it for storage) more practical.

@TechConnectify If you think OSB is a vapor barrier, then it’s clear I’ve wasted my time and I’ll bow out until you do the very minimum to educate yourself.

@transcendentape It's listed as an impermeable vapor barrier here:
https://en.wikipedia.org/wiki/Vapor_barrier
And like... I don't see why it wouldn't be! You could use mastic to seal it against the joists if you want to be extra-careful.

But, I'm willing to be wrong.

@TechConnectify I’m not interested in arguing with you any longer. I’ve never seen your house, but I know for a fact that your attic is not sealed with OSB and I think if you gave it half a second to think about why it wouldn’t work, instead of posting a wikipedia article that shows a wall, you would be able to understand why.

You do you, I’m done. Contact home builders or do better google-fu.

@transcendentape I will gladly be done!

I'll just say this - you wanted to know how to prevent moisture from forming on the backside of the colder ceiling drywall. At least, I think that's what you were asking.

Doesn't seem like rocket surgery to me to add an air and vapor barrier above the foot of cellulose insulation on top.

I really think we're talking in circles because how we imagine attics to function is too different.

@TechConnectify Maybe I could have made it more obvious, but despite the fact that you clearly don’t have any fucking clue what you’re talking about, it’s easy to insulate a wall. If you insulate the roof deck, it’s almost the same. When you insulate the ceiling, fuck off with your vapor barrier with conventional home building.

@TechConnectify But of course you wouldn’t be expected to know why that’s a problem. You’ve just spent two fucking days arguing it isn’t while I’ve been trying to explain to you why it is. So please, do your homework. I’m done.

@transcendentape Alrighty, I can't help it - you said earlier that it was the act of adding air conditioning that led to mold problems. Is that correct?

It's not simply that the attic is /there/ it's that there is now a place being maintained colder than ambient temperatures near to it.

Now, as far I as can tell, homes here are built like highly-insulated boxes. That box than gets a roof plopped on top of it.

I truly don't know what you mean by "it's easier to insulate a wall"

@transcendentape Basically, we keep going back to the central contention here of "turn the attic into a conditioned space" vs. "keep the attic /separate/ from the conditioned space"

Air handling equipment up there is what's blurring that line, imo. And if for some reason your homes /aren't/ built like boxes first and then the roof is framed such that it sits atop that box, I won't be surprised but I can't imagine what that looks like.

@TechConnectify I absolutely do not agree that keeping a living environment at 75f versus 0f is the same as keeping 75f versus 100f. You seem to be claiming that it is. I’ve tried to make it clear that water vapor, not simply insulation is the difference. You needn’t take my word for it. Do the most basic of diligence.

@transcendentape And it seems to me that the immense effort we spend to keep heating from escaping /into/ the attic would do just as fine a job at keeping the heat up there from coming back in.

Undoubtedly the details of the vapor barrier would need to change! There's no disagreement there. But you seem to think it would be impossible to adapt the principles of Midwest home design to Southern climates and, well, I don't.

For real, though, let's just end this. It's been nice chatting

@TechConnectify In conventional new construction here, why in the world would I be concerned about heat escaping into an attic space that is almost guaranteed to be higher temp than desired for the majority of the year?

@TechConnectify If your argument is that ducting should be in the conditioned space… good news! I agree. Except instead of your proposal, I think it’s better to eliminate the major structural issue by including the attic into the conditioned space. It needn’t be 75f up there, but the air up there IS NOT outside air, so humidity isn’t a problem.

@TechConnectify I don’t know, but maybe you could look into how long it takes wood to shed moisture when it goes from say 80 RH to 30 RH, and, for example how much water does that represent when you’re talking about standard roof trusses?

@TechConnectify It’s these kind of questions that differentiate what builders in my climate are dealing with compared to builders in your climate.

@transcendentape I agree with you 100% that the techniques required to effectively isolate the living space from the attic would need to be different in your climate vs. mine. There is literally no disagreement.

I strongly question, though, whether bringing the attic into the envelope actually makes sense both in terms of immediate construction cost and ongoing energy needs.

@TechConnectify I am not at all advocating for what works here in stupid hot and humid environments to be rilled out in the north. What I am asking is that you consider why what works for you may not be the best choice here.

@transcendentape That, truly, was the crux of this whole thing to me.

I probably sounded like I thought you could just build homes like we do with zero modifications, and to be clear I don't think that's the case /at all/

@TechConnectify When A/C was introduced, we started becoming interested with buttoning up the envelope, which led to many new problems. Regular roof ventilation now introduced humidity, and there’s been many successive construction standards that have tried to juggle stopping airflow while allowing moisture flow. What I think is standard now is to prevent every bit of airflow and to deal with air quality separately

@TechConnectify Notably, and I can’t stress this enough… prior to A/C, no one in their right mind lived here. Those that did had ten or twelve foot ceilings and windows designed to open both at the bottom and the top in order to get decent airflow.

@TechConnectify Prior to A/C, attics weren’t an issue because the entire structure must have had airflow or else the occupants would die. There’s entire architecture built around this fact. Look at ‘shotgun’ houses for example.

@transcendentape That barrier for us is mainly thermal. You're right, we don't deal with hot and beastly conditions enough for moisture to be a concern thanks to cooling.

But the barrier is /everything/ and I feel like it could be adapted and perfected in your climate. You'd end up with a very modern structure sitting below a very old-school structure, and (if you ask me) the key to making that work is keeping modern systems and concepts out of the old-school part of the structure.

@TechConnectify It’s remarkable to me that you think you are arguing for keeping modern systems and concepts when in fact you are arguing for precisely the opposite in my case.

@TechConnectify Maybe you could do a YouTube video on how climate dictates roof structure?

@TechConnectify Absolutely nothing about what I’ve been advocating is ‘the norm’. It’s simply what I think evidence shows is the best approach in my climate. I’m extremely frustrated that wr continue to have this same sticking point.

@TechConnectify Stay away from the ice dams, I hear they’re killer in Phoenix.

@TechConnectify 2. That wasn’t a problem through the 80’s, as homes weren’t air tight enough to matter. This is where our concept of insulation and HVAC functionally diverges due to climate differences. You seem to be worried about heat loss through the ceiling. I want heat loss 3/4 of the year. My problem is humidity. The more efficient the building envelope becomes, the worse humidity becomes unless I am able to exclude ambient air from the structure. That’s easy for me to do in walls

@TechConnectify 3. But it’s very hard for me to do in the attic. Vapor barrier goes on the hot side, and my hot side is my attic for easily 9 months of the year. It is not feasible to install a vapor barrier above insulation in an attic unless you make the roof deck the insulation and vapor barrier and treat it the same as walls. This is, I think, the fundamental difference between building for my climate and building for yours.

@TechConnectify 4. Since the 80’s, we’ve had a problem with the more efficient the building envelope is, the more likely you are to have mold problems. It’s got nothing to do with the ducts, as that would be an easy fix… and including them in the living space would not eliminate the problem. The issue is that for all of at least 3 months and for the majority of 9 months, it is both hotter and more humid outside than is desired inside. Insulation deals with temp, but not the humidity