Ducts in the Attic
I have been in my home for just over 7 years. Home is a 1972 ranch style with a basement and garage, I think its one of those ModuKraft home or something. It was originally built with electric baseboard heat and a whole house fan. I do not use the fan and I heat the basement with the electric baseboards. I have done a decent amount of work to keep the energy bills lower. However as time goes on the upgrades will be getting more expensive. I currently have a 3 ton Nordyne HP (10 seer?) that was installed in 2000 or 2001. Ductwork is in the attic and some of the flex is rated R4, some R2. I have mastic sealed most of the flex and pulled it tight while cutting off the extra. I have foamed the central crack in the house from the attic side and foamed around the easy to access penetrations but there are more left. The attic has a ridge vent and 2 gable vents but it looks like I have NO soffit vents and also in the attic it looks like my soffits are sealed with black plastic. Was this normal?
The basement is water tight and very comfortable during the summer. It is fed by 1 8? inch flex duct from the attic that is ran through my coat closet in the living room. During the winter it can get as cold at 58 degrees down there while the upstairs is 68-70. I have started putting in joist insulation with rigid foam board and spray foaming around that. The basement is finished but I dont think there is any insulation behind the drywall. It looks like its just 2x3s or something and plastic again the concrete wall. I dont think I have any mold problems. Humidity is always below 45% except in the swing seasons and I do run a dehumidifier if needed.
The questions I have is should I just get the ductwork redone and put everything in conditioned space as the flex would should/need to be replaced in the attic? I thoght about burying my ducts in cellulose but IDK if that is a good idea. I live in Roanoke Va so climate can be humid at times.
Should I bury my ducts and put a minisplit in the basement for heat?
Should I add soffit vents?
If I bring everything down to conditioned space will the basement be too cold in the summer and would it still be too cold during the winter? How could that be balanced out easily?
I have no clue which path to take as we only plan to be in the house for 10 more years or so. (Maybe Im too caught up on ROI) HVAC costs are so high that I’m unsure I will ever get back my money on efficiency.
A bit more info..
Windows are original AFAIK, I have caulked some closed and insulated the others
Doors could be better but they are decent enough for right now and I dont think that will make a major difference.
Attic needs more insulation but I’ve been holding off until I get more direction on duct work.
average summer electric usage is ~1850kw. last bill costs $211.64 and I used 1816 kWh.
I plan on getting a hybrid water heater as some point.
2 adults and 2 kids live at home
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Replies
Is moving the duct work and equipment to the basement off the table?
If you get 50% more efficient equipment and get the leaky ducts out of the attic the potential savings seems unbelievable.
Walta
No, not at all but it seems every HVAC contractor is against it. It also seems expensive?
I would move the ductwork. There's a good chance your contractors are against it "because [we] always put it in the attic". That's not a good reason though -- attic HVAC installs are problematic.
Regarding savings, get a quote to do the work, see if you think it's worthwhile. There WILL be some savings in cooling costs, but it's unlikely to be massive. Maybe $50/month, maybe more, it depends on the system, how much you run it, etc. etc etc... If you save $300/year, but the project costs $6,000, you won't recover your investment for 20 years, so keep that in mind.
Bill
I can't even get an equipment change out for less than $6,000.
Then sealing an burying the ducts may be your best option in terms of cost effectiveness. Another potential option, although more difficult and more expensive, would be to bring the attic space inside the building envelope, which would require insulating the rafters/roof area instead of the attic floor. Bringing the attic "inside" would be the preferred option.
Bill
I have thought about that and the quote was for $5400 or so and that was just for open cell foam a few inches thick. I think it would have been R-22.
Also something else to factor in.. My unit in the attic is a 3 ton. They may have to change ductwork to accomidate the reduced air flow for a 2 ton? When I had my energy audit done they said the upstairs was a 1.87 tons. Also would a 2 stage unit be worth it? They also recommened a 9k BTU minisplit for the basement. If I went that route I would just get the minisplit on 70 or 72 and leave it 24/7/
If you have issues with humidity, then the two stage unit will probably help. If it stays hot enough often enough that the air conditioner runs long cycles most of the time, then it should dehumidify no problem. If you tend to have a lot of "warm but not too hot" days that are still humid, then the larger A/C probably won't run long enough cycles to do a good job dehumidifying. The two stage unit will run only one stage on those days, which means it will do a better job with dehumidification. In my own home, I have two 3 ton units, and I set things up so that one does most of the work. This results in longer cycles, which helps a lot with dehumidification -- we're always pretty humid here.
I wouldn't necassarily think "if I have a minisplit, I'll try to only run that". You want to run whichever helps keep your house the most comfy. Humidity levels might be a big concern, which could change how you configure your system. A small A/C running long cycles is the best way to do that. If you don't have issues with humidity, then it doesn't matter as much how you run your system. A large unit running short cycles or a small unit running long cyles, assuming similar performance specs for each, will use similar amounts of energy so there isn't much cost savings either way.
BTW, I would recommend closed cell spray foam for an attic insulating project like you may be doing. Closed cell spray foam is less risky here.
Bill
I would consider doing an energy audit to get a better understanding of how the house is performing. If the house is leaky, you could do some air sealing. If the attic insulation is subpar, you could add air permeable insulation or foam the sheathing and move the thermal boundary.
After you've gotten the house tighter, you could order a Manual J and talk to the engineer about options for meeting the project heating and cooling loads. FWIW your electrical usage doesn't sound extreme, but maybe the house is a lot less comfortable than it could be.
I keep the house at 73 and the humidity is around around 36% all the time. At night when we're sleeping I have to keep it around 70. During the winter I keep it around around 68/70 with no setbacks due to electric strip heat as the back up.
I had an energy audit and it was very thoroughly done I think. ACH50 is 8.38, ACHn is 0.39. That was done 3 years ago. I have done more sealing since then.
As this thread's title doesn't differentiate between types of ducts, I would like to ask:
What's the consensus on placing ERV/HRV ducting in/through unconditioned attic spaces?
I would put it in my garage and run the duct through the ceiling of the basement. I would like to get an ERV as my CO2 levels are sometimes up around 200oppm. It would also recover some costs associated with having fresh air indoors.
Although my question would seem to match up with the subject title I realize that it is likely to become a distraction to the OP's intended question. I've started a new threa: https://www.greenbuildingadvisor.com/question/erv-hrv-ducs-in-un-conditioned-attic
Sorry for messing this thread up.
BIll.. I was talking about the minisplit just keeping the basement warm as I spend my nights down there as my entertainment area and I do some work on my PC down there also. I was thinking that during the winter, especially on cold nights, I would run the minisplit and the heat would offset some of the electric strip usage of the unit that runs upstairs. IDK what my balance point is but with a 2 ton replacing my 3 ton I assume my balance point would move a bit. Im also under the assumption that conventional HP systems are still inefficient on cold nights unless you get one with a high HSPF. My thoughts on the minisplit are to save money by not running the electric baseboard heat in the winter while Im in the basement.
As for upstairs I do not really have humidity problems but I do have comfort problems as air blowing on us as we sit on the couches. I also just want the most efficient setup I can get while having a healthy home. I also don't want to spend a ton of money without some payback. If we were going to live in this house for the rest of our lives then I would be doing solar panels and the whole 9 yards. At the same time I don't want to be uncomfortable or be worried about how much my electric bill is gonna cost me. I have already lost several thousands this summer on AC repairs and a lightning strike.