Help keeping second story cool

[Lee Schierer]

You need to check the air flow out of each register upstairs with a flow meter and compare that air flow to the down stairs registers. They should be the same. Also check the air temperature at all registers. Most likely you have significant air leaks in the duct work leading to the upstairs. You may also not have sufficient air returns on the second floor. A good HVAC company can help with this and yes you might need to open some walls to get to the duct work. If your duct work is running up outside walls or through the attic space most likely they are not well insulated and you are losing cooling in the uninsulated ducts. At $400 per month, it won't take long to recoup the investment to have a professional look at your system even if you have to open up some walls. On the Holmes Inspection series on TV they often encounter this type of problem and 9 times out of 10 it is poor duct work design and air leaks that are robbing the system of efficiency. Return air paths are not usually well done by contractors, they assume that drywall on studs and open cavities in walls will allow proper air flow back to the unit in the basement. Look inside your ducts to see what size the real opening back to the unit is. Your return air ducts on the second floor must be equal or slightly larger than the total square inches of the delivery ducts. The pro can also check to see if your compressor is working at optimum efficiency as well. You should have R40-50 in your attic. A hot 2nd floor ceiling indicates that the insulation isn't working.

When we upgraded our system a few years ago to add A/C we got a DC powered fan motor so it is variable speed. On the advice of the installer we run the fan on low 24/7 and it balances out the house temp due to sun loading. When the unit is actually cooling it jumps up one speed and then goes back to low once the temp is reached. The year we started the system we turned it on July 5 and ran it 24/7 until early October. We used exactly the same KW that summer as we had the previous year running fans and a dehumidifier. Our house is 2200 sq ft on one story and we pay about $110 per month for electricity (no gas, wood or oil bills either).

[Angie Orfanedes]

All good advice. After you have done the upgraded insulation and checked your ductwork, you should consider adding a zone control damper and zone control board run from a second thermostat upstairs. That way you can have your upstairs calling for all the air (or heating) when it is bedtime. Since I presume you are a diy kind of guy, you should be able to do this for about $275 in parts.

Angie

[Brian Ashton]

I've had it with this house. We live in a two story house with walkout basement. This is the second summer in the house and I'm tired of getting a $400 electric bill. It wouldn't be so bad if the upstairs was cooler than 80 degrees when I go to bed at night. There's only one forced air system for the whole house and I've got all the registers in the basement closed and still can't get decent cooling upstairs. There's plenty of blown in insulation in the attic so I'm looking for what else I can do. Below are a couple of my thoughts. Let me know what would be the most effective at reducing our energy consumption and improving the comfort on the second floor.

• Reflective rolls against the underside of the roof.
  Powered attic ventilation fan.

Input is much appreciated.

Thanks,
Wes

I've been living in Queensland for about 7 years now and one things for sure… it's the land of no insulation and steel or clay tile roofs… You want to talk about heat in the summer, attics can easily reach 45 degrees C, on a cloudy day. The cheapest alternative is to get as much air flow as possible into the attic. The more roof and soffit vents you have the more air flow you'll get. This has had good results on my house. The downside in your neck of the woods is cold winters where you don't want that air flow in the attic. Here winter mean you put on sox which is no big deal. Whereas you guys get real cold temps and air flow will cause your heating bill to go through the roof, so to speak. The more expensive is to insulate the roof and the ceiling. The roof insulation will inhibit the solar heat radiating into and heating the space in the attic and all the surrounding materials. And the ceiling insulation will stop most of any latent heat from radiating through the ceiling. The best is a combination of the two where by you can have controllable vents.

[Brian Elfert]

As far as zoning after the fact do most two story houses have a single trunk line to second floor? I thought a lot of two story houses don't necessarily have just one trunk line for second floor? I had zoning installed in my two story house when it was built in 2001 for about $700 additional. I have a separate trunk line for the second floor for the zoning. My house is built with floor trusses instead of joists so running the duct work was easy for the HVAC guys. I like my zoning as it is common even in Minnesota for the second story to be hot in the summer and too warm in the winter.

I've heard that in Pheonix hardly anyone has two story houses due to the heat. The second floor just gets too warm.

A crazy idea might be to just move the thermostat upstairs so the upstairs controls the house temp, but it get too cold on the first floor.

[Greg Portland]

How open is the upper floor to the lower level? If it is not sealed off then the cold air is going to flow right down the stairs (and the hot air is going to flow right up). In other words, closing off the downstairs vents are not going to help you and in fact will make the problem worse.

Assuming the duct work is properly designed and installed, running the air handler fan on 'low' will ensure that the air gets mixed effectively between the floors. Modern air handlers are extremely efficient so running it on low is pennies a day. My 2 floors are open to each other and running the fan keeps the temperature difference @ about 2-3 degrees (plus it keeps the air cleaner).

Now, how certain are you that your duct work is designed and sealed properly? How old is the home and what is the sq.ft.? I'd have a HVAC pro come out and inspect the home (at a minimum get someone who is NATE certified). They should be able to pinpoint your problem (insulation, air leaks, duct/system design, equipment, etc., etc.).

Finally, an old or poorly sized cooling system (low SEER, old air handler) is going to burn a lot of power compared with the modern efficient systems. Of course, the upgrade cost will be high. If the duct work has major problems a (large) mini-split system with multiple indoor units might be a more economical solution.

[Myk Rian]

The downside in your neck of the woods is cold winters where you don't want that air flow in the attic..

Quite the opposite.
If the roof isn't insulated, then you still want all the air flow possible. That keeps the attic cold, and prevents ice dams on the roof edges, which can creep under the shingles and wreak havoc.
The more insulation on the attic floor, the better.

[Carroll Courtney]

One of the problems w/houses that only have one system is not enought tonnage(400-500sq ft per ton) or lack of airflow due to a dirty coil,dirty filter,to small of a return air or an open return air(sucking hot air into the return)or maybe a dirty condenser coil.These are common problems here in Tx and I'm sure other places.If your in a subdivision and the floor plan is the same,check with your neighbor who has the same floor plan or same sq.ft for a comparision----Carroll

[greg lindsey]

I had HD put in through one of their contractors 20" in insulation, spray radiant barrier and add 9 soffets (sp) for 1700.00 last summer, I have a pretty big attic. My electric bill has dropped by 75.00 a month, believe me. I know what its like having electric bills upwards of 600.00 a month. Besides new windows and sliding doors , that was one of the best investments in saving energy I have had. Example: Before they started I checked my attic temp , it was 123 within two hours of completing it was 103. Glad I wasn't up there doing it myself.

[Brian Elfert]

Rules of thumb should not be used when sizing air conditioners. If you bring in a good HVAC contractor they will do a Manual J calculation that sizes the proper unit for your home based on insulation, number of floors, and other factors.

[Pat Barry]

My opinion is that you are better off putting a window AC unit in upstairs. This is point of use and will be highly effective. Takes the load off the main unit and will net reduce your electric bill. Much easier than some of the other options.