Hi everyone. New to the forum here.

I have a 3 story home that has two furnaces. This summer I had a licensed Heating/AC specialist/thermographer scan the house. Found a few things, some of which were significant, but all have been repaired.

The problem during the summer was having the bottom floor (walk out basement) stay about 65 or cooler, and the upstairs working hard to maintain 76. He suggested closing off returns and registers specific to the heating/cooling cycle we were in. For example, during heating, he suggested closing off the return completely in the walk out basement (it's in the ceiling and was doing what he called short cycling) and then closing off most of the supplies on the main floor but leaving its supply open. This has helped tremendously, and hopefully will help any of you experiencing the same issue.

However, the upstairs is my "problem child." Just yesterday I had more insulation blown into the attic. It now has an effective R-38+. More than sufficient In my opinion. So I thought when I got home last night, I'd go upstairs and discover the rooms that had been cold, would now be normal. Not the case. As a sidenote however, I had left a bathroom exhaust vent on all day, and I'm sure that didn't help. Anyway, I set the thermostat on 71 last night on the way to bed. The hallway where the thermostat lives was 73. I have a 2 zone electronic thermometer, and it showed the master bedroom at 71, and one of the other bedrooms at 68.9. At one point late, I woke up to see the master bedroom temp at 73, and the other at 66! Now, the cooler bedroom had the door cracked and the curtains drawn. The only anomalies shown during the thermal scan showed some heat gain (remember I had this done in the summer) around the smoke detector. I have since sealed this. I have also sealed the outlets, and light switches, however they didn't show any heat gain during the scan. This temp. difference is the exact reason I had the thermal scan done, and the insulation added.

I'm at a loss here. I've done everything but one that the expert recommended. That one thing was to add a second cold air return in the ceiling upstairs. With the west facing cathedral ceilings, the expert said that the roofline acted as a big heat conductor. Also, fireplace heat, and rising supply from the downstairs unit, stratifies at the high point of the ceiling. He thought adding the second return would eliminate the stratification, and help more in the summer, but in the winter as well.

Any experts out there want to help me out? There are some other things I've done to eliminate air infiltration, but none of them showed as being problematic during the scan, so I haven't listed them in this already lengthy post.

Look forward to your responses.

Chris

Sounds like you have done much to try and solve the problem. Do not feel bad since builders usually spec the cheapest way to heat and cool, a house and the air distribution ducts are the first thing to be cheated on. This inturn causes major problems. Actually the different temps you have are not that bad considering other I have seen and heard about.

The added return sounds like a good idea and should work well for you. Unfortunately there is no way I can actually see your system from here so you will have to rely on the contractor to make a judgement call.

It makes me wonder if anyone has actually done a manual D on your duct system. That is a critical calculation method used by the real professional HVAC companys to insure equal and accurate air distribution and temperatures.

Just an update to pass along.

I ended up disconnecting a supply to a bedroom closet, and closing down vents to about 40% on all the vents on the trunk supplying the cold bedroom. Apparently that increased the volume enough. The bedroom is now staying within 1 degree of the master bedroom and hallway.

Thanks for the help. And feel free to ask about specifics of what I did.

Chris

NIce job, but the AC contractor should have done this. The cold air return is not in the ceiling, but rather near the floor.

Having cold and hot air returns that you can turn on/off depending on the season really helps.

If you have cathedral ceilings then a ceiling fan might help.

Make sure the temp difference is still within spec for the unit. That info should be posted on the label as temp rise. Just use a thermometer and take the air temp of the return air. Then take the temp of the discharge air while the furnace is running. The difference between the two will be the differential. You never want to run the unit to hot. Closing down the vents etc can drop the air flow across the furnace.

A bypass damper can be installed if necessary, so the furnace isn't adversely affected by closing off registers. Some, rare, furnaces don't need them,

NIce job, but the AC contractor should have done this. The cold air return is not in the ceiling, but rather near the floor.

Having cold and hot air returns that you can turn on/off depending on the season really helps.

If you have cathedral ceilings then a ceiling fan might help.

Yes, the contractor SHOULD have done this. But, everything in this house was done so quickly, and cheaply, that now I have to go back and figure out how to fix it.

There was a suggestion about adding a damper. And I think I will have to add one. Off my plenum box are two supply lines. One line supplies 3 ducts. The other one supplies 5. I've noticed since balancing, that one of the bedrooms is heating up too much, too quick. It just so happens to be on the trunk that supplies only the 3 ducts. Which tells me I could baffle that supply line, increase the volume to the other trunk, and not have to close vents as far to get volume to the bedroom in question.

I had a HVAC contractor come out this past weekend to take a look, and help me figure out what the problem was. Here's the breakdown of what I was told.

The furnace, which is located in the attic, is "backwards". The plenum box is on the right side of the furnace (looking from attic stairs). Unfortunately, 80% of the space that needs heated/cooled, is on the left side of the furnace. Which means the supply has to make a 180 degree turn to get to that side of the house.

If I were going to be in the house for another 10 years or so, I'd probably have the problem corrected, and everything done correctly. However, I think we'll be out of the house in the next 5 years. So, for now the baffle is the most cost efficient fix. And quite honestly, I think will basically achieve the same result as flipping the unit... you would still probably have to baffle for the other side after flipping anyway.

Thanks to everyone for the input and suggestions. I think with a small investment, and a little bit of time, I can fix this, and have a lot more comfort.

Good luck with it.

A "bypass damper" connects the return and supply at the furnace with a regulator of sorts (a weight), thus you can open and close registers at will. This is exacting what happens in a zoned system.

Without out it, the electricity bill to run the fan goes up and the motor has to work much harder.