House AC question

[hdridinas1]

So here is my problem. The down stairs is nice and comfortable, but the upstairs I am sweating. I have closed all the down stairs vents and made sure that all the upstairs ones are open. I have tried leaving all the up stairs doors open or having them closed, neither one makes a difference. So, what can I do to even out the temps. I only have one ceiling fan in the master bedroom, but will soon be putting fans in both my daughters rooms too. I have read about putting an electric exhaust fan in the attic and adding a second layer of insulation, how well do either one of these work and are they cost effective? I would like to find the most economical way to solve this.

 

[phbsales]

That's the nature of the beast with a 2 story home. The second floor will always be 5-7 degrees warmer than the first floor, which is usually where the thermostat is located. Adding insulation is always a good idea, but that will not solve your problem.

The solution to your problem is zoning the ductwork. This is going to involve major duct modifications, the installation of zone dampers, a zoning control system, and a second thermostat for the upper floor.

End result: If the first floor has satisfied its thermostat, but the second floor has not, the system will continue to run until the upper floor has come to the desired temperature setting.

 

[hdridinas1]

Well, I only plan to be in this house another 3 years so investing in major duct rework and all is out. Any other options that aren't gonna have me taking out a loan?

 

[Steves32]

So here is my problem. The down stairs is nice and comfortable, but the upstairs I am sweating. I have closed all the down stairs vents and made sure that all the upstairs ones are open. I have tried leaving all the up stairs doors open or having them closed, neither one makes a difference. So, what can I do to even out the temps. I only have one ceiling fan in the master bedroom, but will soon be putting fans in both my daughters rooms too. I have read about putting an electric exhaust fan in the attic and adding a second layer of insulation, how well do either one of these work and are they cost effective? I would like to find the most economical way to solve this.

HVAC contractor here-

2 story homes are difficult to heat or cool with a single system.

Closing vents downstairs will raise static pressure in ducts & slow down blower & shorten equipment life. Bad idea. Leave them all open.

Ceiling fans- good idea.

Closing doors- bad idea. Leave all doors open.

Installing powered attic fans- bad idea. Was a popular solution 20 years ago but what happens is it will pull the cool air rght out of the house & into the attic through every hole drilled for plumbing, electrical, etc. It can actually be dangerous if your furnace is installed in the same attic.

Adding insulation in attic is a good idea.

Upgrading windows to double pane- good idea.

Zoning- I wouldn't recommend a zone system for 2 zones- ever- especially on a 2 story. If only 1 zone is calling- you will be dumping 1/2 of the total CFM right back into the return. You have to dump it somewhere. Kills efficiency & rarely works well (with 2 large zones). Best zoning on a 2 story is with 2 separate systems- one for each floor. Also- zoning works best w/ multi zones & 2 stage systems.

Your fix? You can try these suggestions, may not help but certainly won't hurt.
Close all windows & drapes/shutters. If windows are not covered- do so.

Keep all vents open.

Keep all doors open to every room.

Install ceiling fans

Make sure filter is clean.

Insulate attic to a minimum R38



What will fix the problen is proper duct sizing- equipment sizing- multiple returns- or best, 2 separate systems for each floor.

 

[pipsters]

I had the same problem. I went from R25 in the attic (NC house) to about an R45. I have a 2000 sq ft "square" type home and estimated the attic was around 1200 sq ft. I bought the insulation (and blower came free) for around $400, and received 30% back as a tax credit, although that has expired, so for me around $280. I used the cellulose insulation, and it took my wife and I about 5 hours start to finish.

I can't say how glad I am I did it, made a HUGE difference in the heat upstairs over the summer. We also have 2 units, up and down, and the upstairs runs a LOT less now.

Also, consider tinting any upstairs windows that face west or south, this will reduce the heat gain. But the insulation is what made the biggest difference.

 

[wb2vsj]

From what you said I'm assuming you only have one AC unit? By any chance do you have two sets of stairs to get to your upstairs? ( If you have two sets, you can set up a fan on the downstairs to start a air flow going up one side and down the other.)

I'm also going to guess that the duct work for the rooms upstairs is in the attic getting pre-heated quite nicely by the hot attic? What is the temp coming out of the vents? Compare downstairs/upstairs.

You can try replacing the attic duct work with a higher R value or wrap it in a duct blanket to increase the R value

One of my daughters rooms was always boiling in the summer. She had the longest run of any of the upstairs rooms. I ran her a new duct from a closer distribution box and that helped a lot.

 

[JakeKohl]

HVAC contractor here-
...
Keep all doors open to every room.
...

I hear this often - what's the reasoning behind this recommendation?

 

[Steves32]

If doors are tight fitting (carpet at bottom) and a single return in the house- close door & room will pressurize. Airflow will diminish in those rooms that are closed off. You are putting air into the room- you need to get the air out too. All air need a path back to the return grille- wherever that is. If you have supplys & returns in every room- then it's ok to close the door.

 

[hdridinas1]

Well, I dont have ducts in the attic. My furnace/ac unit is in my laundry room. I have a heat pump/gas. Only thing in my attic is insulation, one layer, and some wiring. I have 2 returns, one downstairs and one upstairs. Both are at the ceiling, same size. they are in the same location on both floors, its hard to explain typing. I have the sun block/dark out curtains for my room, the kids have blinds that stay closed. We pretty much have all of the windows facing the street covered and closed all the time. The back of the house is shaded almost all the time. All of the windows are about 1 1/2 year old double panes, so no need to upgrade there. Someone said that a 5-7 difference is normal. I haven't checked, but I think that it feels way more different then that. I can be chilly downstairs and sweat up stairs.

Temp between air coming from vents feels the same, once again, have not measured. Yes only one unit. Doors are not tight fitting. One set of stairs.

 

[Mike007]

When you are upstairs you can try leaving the fan switch in the "on" position. When the system cycles off the fan will continue to bring cooler air up stairs.

The problem you describe is usually due to not enough return air being taken from the upstairs. The formula Ive always used with great success is designing the return duct to take 75% return air from the top of a wall or ceiling upstairs and 25% from low near the floor downstairs. In a perfect world there would be a return in every room but the bathrooms and kitchen.

 

[JimL]

HVAC contractor here-

2 story homes are difficult to heat or cool with a single system.

Closing vents downstairs will raise static pressure in ducts & slow down blower & shorten equipment life. Bad idea. Leave them all open.

Ceiling fans- good idea.

Closing doors- bad idea. Leave all doors open.

Installing powered attic fans- bad idea. Was a popular solution 20 years ago but what happens is it will pull the cool air rght out of the house & into the attic through every hole drilled for plumbing, electrical, etc. It can actually be dangerous if your furnace is installed in the same attic.

Adding insulation in attic is a good idea.

Upgrading windows to double pane- good idea.

Zoning- I wouldn't recommend a zone system for 2 zones- ever- especially on a 2 story. If only 1 zone is calling- you will be dumping 1/2 of the total CFM right back into the return. You have to dump it somewhere. Kills efficiency & rarely works well (with 2 large zones). Best zoning on a 2 story is with 2 separate systems- one for each floor. Also- zoning works best w/ multi zones & 2 stage systems.

Your fix? You can try these suggestions, may not help but certainly won't hurt.
Close all windows & drapes/shutters. If windows are not covered- do so.

Keep all vents open.

Keep all doors open to every room.

Install ceiling fans

Make sure filter is clean.

Insulate attic to a minimum R38



What will fix the problen is proper duct sizing- equipment sizing- multiple returns- or best, 2 separate systems for each floor.

Dumping half into the return? Most variable speed motors will make up for a lack of duct work to a certain extent. Almost all 2 stories we do get zoned with one furnace. Size each zone to handle 100% capacity and they work fine.