Solution needed for poor upstairs airflow
Here's my situation:
I have a 100 year old, 2300 sq ft (roughly 1300 down 1000 up), two-story home with 10 foot ceilings on the first floor. Since we've lived here (about 2 years) the upstairs is relatively comfortable in the winter (due to heat rising) but is very warm in the summer.
The house has an older 90-percent efficient Trane furnace in the cellar, and has a single 8x14" duct supplying air to five registers upstairs.
There are two return airs in the entire house, both of which are in the floor on the first level (one below the thermostat, and the other about 15' away (albeit around a corner) near the stairs to the upstairs).
I have a location where I could install a 12"x12" chase (maybe bigger, though it's hard to tell exactly) from the cellar to the second floor.
I've had one HVAC company tell me I need to install an air-handler in my attic, and another suggest a zoned system. Money is tight, and this furnace will be failing soon. I can't afford a big change (the options the aforementioned HVAC companies gave were seemingly out of my budget), so I either need to find an inexpensive solution, or just learn to be content with a window air-conditioner in my second floor.
It seems like my options are:
A) A larger, or second, upstairs supply run
B) An upstairs return air
C) A more powerful furnace (though I've been told this one is rated for pretty good pressure)
D) Booster fan(s) in conjunction with one of the above
My question is, what is the best bang for my buck?
Adding a return would be what I would do first. Keep in mind cooling is the removal of heat, not the addition of cold air, so with that in mind, no matter how many supply vents you have, you need a return on that floor to remove all the heat that is rising up or trapped on the second floor.
A larger/more powerful furnace would only make the issue worse. Air goes the path of least resistance, so if the furnace is more powerful the path of least resistance is probably the downstairs of the house, meaning with more airflow all your going to do is get more cool air to the main floor which will cool the main floor faster and shut the system down faster, if anything, probably going with a smaller furnace with less airflow would help, but that is just a guess and I would need to see your house to verify.
The last option is that you could turn the "fan" setting on your thermostat to on during the summer so you can constantly cycle air from the upstairs to the downstairs to help keep the temperatures more consistant.
Where is your house located?
My home is in the midwest... hot and humid summers, cold and dry winters...
Originally Posted by SkyHeating
I had suspected the return air would be the best route, but all the HVAC people I had look at it seemed to disagree. I hate to say it, but I think they may have just been looking to get me to spend more.
No offense to Sky (King) heating, but a return air to the second floor will not help assuming the doors (on the 2nd floor) are always open and there is enough return air to the system now (of course).
Originally Posted by ThisOldFurnace
The 14x8 duct riser is good for (only) 600 cfm. I would have installed at least a 20x8 (900cfm) or equal. I like more air than not enough. I think this is a simple concept but contractors seem to have a problem with it. They'll put an 8 cylinder engine in their trucks to drive around town but not install enough ductwork to get the air where it needs to go.
Five supplies, depending on the sizes, may not be enough either. Not enough information at this to say.
Fair enough. I guess we'll see what the consensus is...
Originally Posted by George2
The only way to truly solve the problem is to install another unit for the upstairs, second best option is to install a zone system and return air upstairs, 3 rd option is to install a return and more supply runs up there and kill it with air, you could install a manual damper for the upstairs trunk to better regulate the amount of air going up there from season to season. Options from high price to low.
You suggest a new second floor system and (of course) a new first floor system will be in order, correct? The reason a new 1st floor system will be needed is because the existing 3ton (a guess) will be too large for the first floor (1,300 sq. ft.) alone?
Originally Posted by jtrammel
That would be a good idea if the old system is 20 years old and the home owner has money to burn.
I like your second idea about zoning after the ductwork correction. That would be my #2 suggestion. My #1 suggestion would be correct the ductwork (supply). This is the least expensive, will probably do the job, and if it needs improvement, he can add zoning and then it'll be perfect for the least amount of money.
He said it was an older furnace in his first post and mentioned going up in size on his existing furnace so I'm thinking he's already on track to buy a unit for the first floor. Those were my options from highest price to lowest price also best comfort to least comfort respectively IMO.
Originally Posted by George2
10-4. I don't have a problem at all with two systems But, for that size home, I personally would favor keeping the system in the basement (for noise reasons and servicability) with a properly sized 2nd fl. duct riser and properly sized second floor supplies. Install manual dampers (for now, zoning later if needed) and I think he would be in heaven.
Originally Posted by jtrammel
First thing I'd look at is the duct work that goes to the 5 registers upstairs. Does it go into the attic and the registers are in the ceiling? (This is how most of the old houses that got "moderized" to forced air systems with AC were done around here.) Make sure that duct work is very WELL insulated if it's in the attic. Not talking 1.5" fiberglass either, if the attic is insulated to R-38, then the duct work should be too. Most of the ones I worked on the rectangular duct was laying on the floor of the attic which makes it easy to insulate. Also make sure all joints in the ductwork in the attic are sealed so you're not paying to air condition the attic, this is also a good idea for the entire run and around the registers.
I agree with the least expensive way to get the summer conditions on the second floor as best as they can be for the $'s you sound able or willing to invest is to add a return on that level. Whatever you can get is going to help, but the more air you can pull off the ceiling on the 2nd floor the better. One option I've used in the past is the old chimney, with if you have a 90% furnace now is more than likely not being used. Not a cheap option to pull it but it does usually open up a big hole from the basement right to the attic.
Is this option perfect? No. But I'm not there and from where I'm sitting all I can do is give an opinion.
Use the biggest hammer you like, pounding a square peg into a round hole does not equal a proper fit.
2 separate systems is what will give the ultimate in comfort.
For the upstairs system it could be a straight A/C with electric heat strips to keep costs down. Heat doesn't run much over the winter since the heat will mostly be rising from downstairs. When the downstairs system is replaced you could go with a smaller system to save $$$. Do a calculation to see how long the payback time is for each type of systems, an 80% furnace may make more sense for your area.
A reasonable cost system COULD be like this, depending on load calculations:
Downstairs: 45,000BTU 80% furnace with 1.5 ton 13SEER A/C
Upstairs: 5KW electric heat with 1.5 ton 13 SEER A/C
Here's a few possible upgrades depending on your budget:
Go to 14 SEER unit for upstairs A/C
Go 14SEER for downstairs A/C
Get heat pump for upstairs instead of straight A/C.
Get 90%+ Furnace for downstairs instead of 80%.
Nope... registers are in the floors upstairs... they don't go to the attic. They simply dropped the ceilings in a couple of rooms downstairs.
Originally Posted by firecontrol
2,300 sq. ft. and two systems............really? Even if money was not an issue, I could never recommend that. Just me.
Originally Posted by 54regcab