Official Tennessee Thread

I've heard it's badass. They are regularly selling out shows

Papadosio was there earlier this year and I wish I wasn't a peasant so I could have gone

 

It's definitely worth seeing.

 

Suspension group buy!!

 

Do any of y'all know anything about house building/ building science?

I'm trying to figure out a way to tell the builder of the place I'm buying that they need to make the attic unvented and conditioned, because the air handler and ducting is up there. Right now, all of the roofs I'm seeing are vented and unconditioned, which is horribly inefficient when the attic inevitably gets to 140° in the summer and all the ductwork is up there. People have mentioned in articles that moisture could be an issue, but if the attic is properly sealed and the ceiling insulation is removed, the temp and humidity should be fine. A supply vent could be added to the attic just to be certain.


I'm wondering how to tell if the HVAC system pulls in fresh air. Because things I'm reading say that sealing the attic could cause air quality issues. A non issue if the HVAC pulls in fresh air, but I'm not sure how to tell. Here's some pictures if that helps.





And as you can see, the attic is totally vented. Stupid when the HVAC system is up there.

 

You want the attic vented like that, its setup correctly. If it's not you will have all kinds of mold and shit up there and your house will actually be even less efficient because science.

 

Not from what I've read, the mold shouldn't exist if the foam is closed cell and sealed properly. And if the attic is conditioned either by removing the batt insulation from above the ceiling or by adding a supply vent (or both), would keep the humidity in check.

The problem with the vented attic is mainly because the HVAC is in it, which is very inefficient. Just wondering how to tell how fresh air is supplied to the home

 

You need more insulation blown in there not less. Not to.mentiom your AC bill would be insane cooling that space which is now being soaked with solar heat, and if it ever ice or snows there you would have ice dams which will fuck up your roof and cause leaks. What you can do is install an attic fan on a humidistat to vent out the hot air.

Up here we have to ventilate the shit out of our eves and roofs because of the ice dams.

You ac system pulls in air from inside the house. Fresh air comes in from the natural leaks in the house which you need to maintain proper air quality.

 

I've read that too lol. Apparently for that situation in colder climates, a vapor barrier is required if sealing an attic. But not in the south. If the attic gets to 140° and the HVAC ductwork is trying to move 60° air... well that's a problem

 

https://youtu.be/7SpEjIuSQn8

https://youtu.be/wcj0sC91tYI

https://youtu.be/F7D4Q3mjgdQ

 

No vapor barriers in the attic up here, its plywood and roof.

I did all kinds of research on this after thinking the same thing you did seeing my ducts up there. Conclusion was I need more blown insulation and more attic/eve venting and possibly an attic fan. Since this isn't my forever house I said fuck that. I actually fucked around with the vents that fed the upstairs coming out of the HVAC unit and bought some better windows and now my upstairs is within 5* of downstairs. Before it was like 20* warmer.

 

Vapor barriers would be if there was spray foam on the roof deck. I feel like you and I are similar with trying to squeeze efficiency out of the HVAC systems haha. I just want to make sure I'm doing this right. Everything I've read says HVAC in the attic is dumb and the best way to deal with it is to seal up the attic and get it inside the "envelope"


I'm watching this right now
https://youtu.be/Vwos211XlXo

 

I just wanted my upstairs cool.

 

#1, good luck with trying to convince a builder to do something different from a YouTube video.

#2, duct work is insulated for that reason, and properly sealed shouldn't be an issue.

#3, air is moving through the duct work when cooling, so there isn't much time for heat soak.

#4, as mentioned previously, air intakes are in living spaces. Change your filter regularly.

#5, the cost involved in changing what already works would not likely be recouped over moderate efficiency gains.

#6 if you really want to do it that way, just put the unit in the spare bedroom. Guests would love it.

 

To add to dave... If you are building a house, putting the air intakes for the hvac unit as close to the ceiling as you can up stairs will help way more than messing around with the attic. What I learned talking to the HVAC engineer on my team is it's all about circulating air within the living space, 90% of what you interpret as "cool" is air moving around via the hvac system.

That's also weird they put the hvac unit in the attic down there, here it's in the basement or in a closet in the downstairs living space.

 

Funny you mention this but look at the purchase agreement.

I could easily bend this in my favor. Also, I went ahead and made a new thread on this topic. To make it short, ductwork generally has a low R value so it'll heat soak as soon as the AC stops running. There's a 40% increase in efficiency by moving HVAC into the building envelope. As for fresh air, it's needed for air quality I'm pretty sure. Just changing the filters only helps the air already in the house (which is what I'm trying to get clarification on at this point). There's more discussion here and just google "HVAC in attic" and see what pops up

https://www.tacomaworld.com/threads/new-construction-home-hvac-in-attic.606240/

 

Both of those are in the building envelope which are fine. The attic is what builders are doing now since living space is a premium but it's at the cost of efficiency if not done correctly.

 

Since you are learning from internet, verify search results against multiple search engines. G gets paid to hide things.

 

I have an ASHRAE HVAC design handbook. If i remember this evening, i'll skim through it. Been a long time since i designed a system or even really thought about it.

Heat soak on residential ducts is a minor inefficiency. Air leaks in ducts or equipment and improper insulation are big things to watch.

Most guys do a rule of thumb for sizing residential equipment. Not bad usually but I'd be surprised if they did a real thermal load analysis on your house. It gets pretty detailed to do the analysis right.

Seal your doors, windows, and any wall openings correctly. Don't pack insulation. You need it fluffy. Dont leave gaps in insulation. Light colored curtains/blinds esp on south facing walls. Use fans. Moving air makes a huge difference in "feel". Plant some fast growing trees to eventually cast shade on walls but dont put close to walls.

 

A huge difference maker for us was keeping the blinds closed while we are at work.

Seems like all the little things add up over time regarding home efficiency

 

This is what I've been worried about, new construction is thrown up so fast there will inevitably be duct leakage unless the building inspector is super thorough. Making the attic unvented and conditioning it would at least mitigate leakage and help with conditioning the attic space.

As far as sizing HVAC, I too have been wondering about this. The return filter is a single 20x30 for a 1550 sqft home. I'm guessing that's enough return air. I'm not sure about the system size itself but I am going to see if I can get a spec/build sheet. I was unable to find a label on the unit itself to help me determine anything about it.