Upstairs always hot (Howe: home, inspection, square footage)

[EcoDeb]

We have one 5 ton unit with 4 zones for 4500 sq ft, upstairs and downstairs are cooling at the temps we have set. Our home is Passive Solar and Insulated out the ying yang with vapor barrier and very tight! We designed based on load calculations. Sounds like you may have a poorly designed system. There may be duct leaks as and little insulation too, get these taken care of and possible an analysis of the systems design. Your utility company may provide this service for FREE, we have Co-Serv (Co-op) and they'll do an energy audit at no charge. You may want to check into an efficient ductless split unit to help, as well as ceiling fans to circulate. Hope it gets resolved.

[tcualum]

What sort of windows do you have? They can make a big difference.

[TheOverdog]

Your A/C is relatively large for the room square footage - I'd check your attic insulation as long as your house isn't from approximately 1980 or earlier and your windows aren't in terrible condition, should be able to cool your upstairs below 78F. You should have about 16+ inches in your attic. I'd also check to make sure your A/C is coming out cool. You don't say how long it is running, so if it runs for hours at a time, then you have a problem.

[DfwNoMad]

Originally Posted by escanlan

There are many variables, including how you operate the systems, that can result in this condition. If you feel you have significant issues now, in this Summer heat, is a very good time to perform a full energy audit on the home. Not one of these free audits where they come in and just look around and give suggestions. I am talking about a full audit with blower door test, duct blaster test, thermal imaging, etc.


The cooling capacity of an air conditioning unit is not a very good gauge of its capability all by itself. This too has many variables associated with determining if it is sufficient. Newer homes are much better insulated, better sealed, and have other features that actually allow units with lower cooling capacity than what are seen on older homes of the same size.



How old is the home?


No on the attic fans and you could wind up causing more issues with them under your current roof configuration. By installing fans you can cause a "Short Circuit" condition of the air flow where the fans actually draw air in from the ridge vents (never should be allowed) and exhaust through the fans. When this occurs it typically causes air and moisture lower in the attic to be trapped there and not properly exhaust. The people at Air Vent Inc. (actually located here in Dallas) have some very good materials and videos discussing proper attic ventilation and the problems that can be caused. Their resource WEB page is located here Resources - Air Vent, Inc. .


Just out of curiosity you stated you had "installed returns in all the rooms upstars". Did you actually install returns to the HVAC system or just jump ducts from the rooms to the common area? If it was actual vents to the HVAC system did the HVAC people, or you, repair any disrupted attic insulation?

The house was built in 1997. I have lived there for 4 years. We braved the first 2 summers with a really old A/C unit that barely worked and so we just assumed that was why the upstairs was not cooling right.

We replaced both the upstairs and the downstairs unit 2 years back and it did improve quite a bit but as I said it's not where I want it to be...78 degrees upstairs when it's 100 outside is not that great.

We had a A/C company come in and inspect the house and they said returns in each room would help because the upstairs had only one return in the hallway. So now the upstairs unit has 4 returns and I'm not seeing much of a difference in performance. The A/C company is supposed to come back and take another look but I'm wondering if we went down the wrong path with the returns and if it's something else. The returns all go back to the big box upstairs (not sure what it's called...plenum I think).

[DfwNoMad]

Originally Posted by TheOverdog

Your A/C is relatively large for the room square footage - I'd check your attic insulation as long as your house isn't from approximately 1980 or earlier and your windows aren't in terrible condition, should be able to cool your upstairs below 78F. You should have about 16+ inches in your attic. I'd also check to make sure your A/C is coming out cool. You don't say how long it is running, so if it runs for hours at a time, then you have a problem.

The A/C is coming out cool. I bought one of those IR guns from a home imporvement store and measured the temperature difference between the supply vent and the return and I'm seeing 12-14 degrees. We also had a A/C service done a couple months back so I know it's not a coolant being low problem.

[DfwNoMad]

We have double plan windows but the home inspection when we bought the house revealed a few of those panes had broken seals in them. Sure I could replace them for a thousand or so but would they make that much of a difference? Id hate to waste more money chasing the wrong problem if I can help it.

[DfwNoMad]

Originally Posted by Soccernerd

What do you have your HVAC zones set to?

I have the upstairs set to 74 and the downstairs also set to 74. The downstairs cools to 74 and stops while the upstairs runs all day till sundown and never goes below 78 (when it's 100 outside). The most ive been able to get between upsirs indoor temprature and outside temperature is 21, sometimes 22 degrees (i.e. when it's 100 outside the upstairs stays at 78-79).

[EDS_]

Originally Posted by DfwNoMad

I have the upstairs set to 74 and the downstairs also set to 74. The downstairs cools to 74 and stops while the upstairs runs all day till sundown and never goes below 78 (when it's 100 outside). The most ive been able to get between upsirs indoor temprature and outside temperature is 21, sometimes 22 degrees (i.e. when it's 100 outside the upstairs stays at 78-79).

Given what I think I know about your set up it sure sounds like the upstairs AC isn't performing well. It could be anything from a dirty outside unit (covered in dust, leaves, shrubs etc.) to a dirty fan to leaking ductwork to low coolant and several other things including an insulation issue as noted above.

Are you straight up sure the corresponding filter is clean?

[DfwNoMad]

Originally Posted by EDS_

Given what I think I know about your set up it sure sounds like the upstairs AC isn't performing well. It could be anything from a dirty outside unit (covered in dust, leaves, shrubs etc.) to a dirty fan to leaking ductwork to low coolant and several other things including an insulation issue as noted above.

Are you straight up sure the corresponding filter is clean?

All 4 filters in the returns are new so yes, I'm sure. Also, as I mentioned the unit was recently serviced and they cleaned everything. I also inspected the unit outside a few days ago and it's clean.

As far as insulation goes, the attic has insulation but I have no idea how much. If I had to guess, I'd say 12 inches. I've heard here that it should be 16. Will 4 inches make that much of a difference?

Also, does insulation ever go bad or shrink? Why would I need new insulation, if the house already came with it when built?

[ea0337]

Originally Posted by DfwNoMad

The A/C is coming out cool. I bought one of those IR guns from a home imporvement store and measured the temperature difference between the supply vent and the return and I'm seeing 12-14 degrees. We also had a A/C service done a couple months back so I know it's not a coolant being low problem.

If the house doesn't cool down below 78 even late after sundown, that certainly sounds fishy.

If you have that IR gun, check which areas upstairs show up hot on the IR images. That may provide some clues on whether insulation is a probable cause.

Also, check for leaks around window frames. If you have a leak of some sort, you'll be able to feel it just by running your hand around the edge of the window frame. And IMO, replacing window panes won't resolve the issue.

You may also want to check the area around the attic door. Sometimes leaks around them can be an issue, although nothing so severe. Hope this helps troubleshoot.