New construction home - HVAC in attic?!

@4BYTOY @toyodajeff @Extra Hard Taco @OZ-T

What are your thoughts on the placement of the thermostat? It is on the 3rd floor of the townhome. I feel as if the tstat should be on the 2nd floor. The listing agent says the HVAC guys said "this is not adviseable". Why? I don't see what difference it would make, other than the fact that the living room would be the control center. There are no doors separating air flow from the bottom all the way to the top floor so naturally all of the cold air will settle to the bottom floor and the hot air to the top floor.

 

Every two story Ive been in had a thermostat on every level. Not sure about homes with a 3rd story. One thermostat controlling the temp on multiple levels doesnt sound right to me.

What state is the house located in and whats your square footage?

 

TN. 1550sqft

 

@ThunderOne I had to step back and take another look at your situation and questions from another perspective. My situation is different than yours and may not even be relevant. For background, I am located in Colorado on the east side of the Rocky Mountains. Our climate is dry with an average of 16" or rain a year, so we have low humidity. Our temperature can swing from -20 degrees to +105 degrees in a year; so a swing of 125 degrees from winter extreme to summer extreme. With our climate, as a general rule we would not think of having any of our Heating or W/H units located outside of a "conditioned" environment. So I don't think your quest for a conditioned environment for your heating equipment is out of line.

Your question about thermostat placement is good. In our part of the country, thermostats are located on the first floor of 2 story homes (remember we have basements). Looking at your floorplan, I don't think there is an ideal placement. I do think the second floor is the best option, remember thermostats are usually located away from stairwells, outside walls, kitchens, etc.. (areas that can be "artificially" heated by solar gain, cooking, drafts, etc.) You might also investigate the use of two thermostats.

@OZ-T had a great solution for you as far as design of the conditioned space. I would talk to your builder and see what the upcharge is for building a "conditioned" space in your attic. You may find that the charge is too high and the pay back time is not worth the cost. On the other hand, you may find that the builder can not honor your request. This is usually the case when some type of production builder (whether national or local) is constructing the unit. Their hands are often tied by set of "allowable options". I would also give your local building inspector a call and discuss you concerns and questions.

Remember, I am looking at the situation from afar and HVAC is not my strong suit in the building trades. Good Luck and keep us posted!

4BYTOY

 

I've completely forgotten everything I've learned in my solar/building science classes in college. The location of the thermostat, I can't imagine why it'd be up there, but my best guess is that the designer assumes heat goes up, when you're trying to go to bed and it's hot or warm that you'd just want to go out the door and make the adjustments right then and there.

As to your HVAC question, again, i've forgotten most everything from my building science classes, but BSC has some great articles and insights as to the design of your roof as well as what you've read.

https://www.buildingscience.com/documents/insights/bsi-088-venting-vapor

https://www.buildingscience.com/documents/insights/bsi-077-cool-hand-luke-meets-attics

 

Here's where I was thinking. Interior wall, no window sun heat, away from supply vents, kitchen, bathroom, washer and dryer.

 

Have you thought zoning each floor?

One Thermostat with room sensors?

https://store.nest.com/product/nest-temperature-sensor/T5000SF

When we built our TH I put in the base infrastructure for a duel fuel system with thermostat wire to each floor for damper controls...

 

I did read many things about this, but I think it would installing a "non-standard" HVAC system, no? It may be difficult to negotiate in this sort of a request.

I did receive word today that if they cannot install the thermostat on the second floor, they would use a Nest instead so I could use my phone to adjust. I'll take that as a win-win..

 

Sounds like you know about where to put the thermostat to me. Alot of the houses we did had a thermostat and a/c unit dedicated to each floor.
I dont think townhouses normally had multiple units but we dont have many town houses around here. We also didnt do much residential new construction. It was either residential swap outs or commercial new construction. It's been about 6 years since I worked there so they weren't building many houses then anyways.
You might just want to make sure that you have the thermostat around a return duct. Not sure if it would matter though as long as it on a interior wall and not next to a window or something.

We also did a few houses where they wanted to zoning. Dont remember it much except that it was pretty complicated and costly. It might be worth it though if it helps your energy cost.

You might also consider putting in a mini split unit in the basement, living room level, or whatever floor doesnt have the thermostat. They were pretty simple and cost effective way to condition a smaller space like a living room or converted garage.

If they try to charge you more than about $250 for that nest thermostat I'd just pass on it. They are $215 on Amazon and it's pretty simple to install a new thermostat. If you can change the oil on your truck or swap the radio you can do a thermostat.

 

The third floor will probably also be the hottest and it might get hot af up there before the a/c kicks on. But if your 3rd floor is built like a bonus room in the attic then it would be really easy to move the thermostats to the 3rd floor after that fact. Just poke a hole in the drywall and run the tstate cable through that.

 

I build houses in South Texas. The AC is usually in the attic with a fresh air return vent pulling in air from outside. Your attic needs to be vented to allow for the contraction and expansion of air in your attic. The PVC pipes you took pictures of are for your plumbing. The darker boxes are for attic ventilation. Yeah its inefficient to have your AC ducts running through the hottest part of your house, but then again nobody likes to hear the AC turn on whenever its centered in a closet in your house.

 

They said they wouldn't charge extra for the Nest.

 

The PVC pipes sticking out from the roof..? For plumbing??

We already figured out was for the furnace. Can you tell if there is a fresh air return on the roof? I just see PVC and the attic vent boxes

 

The downside of it being up there is the other floors would be cold AF. So I think the middle would just be more balanced. Who knows though

 

I think if that T-Stat is on the 1st floor th rest of the house is going to starve for cool or heated air.....

 

It'll be on the middle floor (at least that's where i want it, currently they want to put it at the top floor at the stairs on the wall by the HVAC handler. There's 3 floors. See post 86

 

It's a 1550 square foot three level townhome, so each level is just over 500 square feet, I can kinda understand the concept of having one thermostat based off of that.

 

Not following you , can you elaborate

 

Correct. One flue pipe for exhaust of combustion gases, one air intake for combustion air.

In the five years or so that I was installing and repairing residential HVAC, I can only remember finding one here in our area that had an outside air intake into the return air side of the air handler, that would then pull fresh air into the living space. We were doing replacement units and repairs though, not new construction.

Here the only people making their attic part of the building "envelope" are those that are very heavily into lowering their carbon footprint. Those folks also realize that there has to be a certain amount of air coming into the house to keep it from going into negative pressure whenever an exhaust fan or clothes dryer is running. I was able to take a class on that subject where we were able to take pressure readings from all the different rooms and watch what happens when switching on a fan, the dryer, etc. The takeaway from that was that most newer houses that are sealed up tight will go into negative pressure often. Curiously, I still haven't seen one of these tightly built houses have a fresh air intake linked to the HVAC system. What many of these building efficiency "green" types end up doing to solve the negative pressure issue is to put in a pet door (seriously).

 

Honestly, it sounds like you don’t know that much about the proper setup of an HVAC system for the area and type home you are building. Instead of asking random strangers, ask the people who do it for a living. Have them explain why they do it the way they do. Talk to several companies and go with the professionals you have the best feeling with.