Basement freezing, upstairs broiling

We've got a 18 yo 3-story house with a the right size a/c for our home. During the summer, the basement is freezing (55 F) and the upstairs is too hot (80+ F) Even when we shut off all the vents in the basement & 1st floor and open them wide upstairs. It would be really great if the whole house could remain about the same temp.
Any suggestions on what the problem could be and how to fix it?
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How do you know it's the right size???

Have someone come out and check the system out. Sounds like you either have the WRONG size for your house or you have a problem with airflow (meaning your ductwork isn't sized properly or your air handler is an insufficient size).
Ask your friends or neighbors who they would use.
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I have the same problem, 1 close basement vents 2 open return in basement 3 insulate basement ducts 4 run duhimidifier in basement to 50% RH 5 add secondary gas heat in basement
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If you open the return in the basement be sure to use a dehumidifier. One possible problem with opening the return in the basement is that you will suck warm moist air from upstairs (or outside) and it could increase the RH in the basement and maybe cause mold.
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*no spam* wrote:

Think: "Heat Rises" and go from there.
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*no spam* wrote:

Was the A/C isstalled when the home was built, or added later? In either case, do you know if you have enough return ducts on the first floor and upstairs?? If the A/C can't pull hot air back from the upper floors, the effectiveness of just dumping cooled air into them is less than perfect.
Roof / Attic / venting / Insulation??? - Traditional peak roof or flat? Assuming not flat, any ridge venting or other means of letting heat get out of the attic?, any insulation up there to isolate your living area?
Finally, "right size A/C for your home" - sez who? Have you had a competent contractor do the calculations, or are you basing it on (not trying to be a wiseguy, but) "well, uncle Joe's house is the same size as this, and he has a ___ ton unit..."?
BTW, not that I totally believe it, but I've read on here that trying to close off registers to force air to other locations can damage your equipment. I have my doubts, but maybe it's something you should consider in your situation, as it sounds like you're doing lots of it.
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I watched a "repair show" and they dealt with this very problem. What they noticed in that they lost about 350-400 cfm of air on the way upstairs. They tested the main trunk and found no tape at the seams, etc. They taped all the seams in the main trunk and all the take offs and they recovered quite a bit. They then focussed on the way the ducts went up to the third floor. They noticed a lot of flexible pipe which is one of the worst for restricting air flow. They removed them, reran rigid ducting and recovered almost all of the lost cfm. They also insulated the main trunk.
It was a lot of work but necessary to solve the problem. It was neat the way they showed all the lost air: they used a mister blowing into the bottom of the furnace and it really poured out of the trunk.
Good luck

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We had precisely the same problem in a previous house. Closing the downstairs registers helped. But what really fixed it was an attic fan. I also opened the hatch from the top floor to the attic about an inch. It probably wasn't the most economical way of doing it because it sucked cool air out of the house. But in so doing it created an upward circulation that evened out temperatures on the three floors. I always suspected we had the wrong size unit.

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within range of 50 to 65 degrees winter and summer. Occasionall add heat if we are working down there in mid winter So few really hot days here AC not needed. We do carefully ventilate the attic at all times of the year to avoid heat and humidity/mould rot etc. problems. We do dehumidify one section of basement to protect some electronics and tools from dampness due to condensation of warm upstairs air that gets inadvertenly into basement, but have to be careful that dehumidifyer is set to cycle on/off so it doesn't freeze up its coils! So my question would be why is the OPs upstairs so hot? Attic ventilation? Upstairs not well insulated? AC unit too small? AC not properly installed? Controls in wrong location ................. ?
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I've struggled with this problem since moving into our 40 year old home 3 years ago.
Here is what I've learned through trial-and-error:
1. Seal the attic to prevent air infiltration from the upper floor into the attic. This will prevent the loss of conditioned air into the attic space.
2. Make sure the attic has lots of ventilation - soffit vents, channels in the rafter spaces where rafter meets header, ridge vent or passive vents high-up in the roof. Make sure that all of the vents, etc, are unobstructed. Good passive ventilation will help to reduce the heat in your attic space. A cooler attic will mean that your upper storey ceiling will act less as a giant radiant heater!
3. Install an electric powered attic exhaust fan that is thermostatically controlled, and set it for about 100 degrees.
These three steps made a huge difference in our house in terms of keeping the upper storey cooler without the a/c working so hard.
The advice in earlier posts is great about closing vents in basement and 1st floor and opening them upstairs. Just be careful--if the airflow becomes too restricted the pipe going from the outside condensor to the furnace may ice up. It that happens, change the air filter first. If it continues to ice up with a new filter, then you've restricted the airflow too much.
I have used a small portable box fan laying on top of the upstairs floor vents to help boost airflow. You can also buy special booster fans or in-line fans to do the same task. It helps a bit.
The second part of the problem is the basement overcooling. This is caused by three factors:
1. Cool air sinks. Try closing the basement door, if you can. I tried that, but my dog doesn't like it.
2. Regular HVAC vents do not fully restrict airflow. If you're lucky, your system may have individual shutoff valves for each register. Find them and close the valves for the basement vents. If you can't find a valve, they stuff a plastic bag full of crumpled paper and shove it into the ductwork until the airflow is entirely restricted (remember to take it out come winter when the furnace kicks in). I would also close off any return air ducts in the basement--you want the hot air returned, not the freezing cold air from your basement.
3. HVAC ducts often leak both air and temperature. Sealing all of the ductwork carefully will ensure better airflow in the HVAC system (cooler air upstairs) and less conditioned air leaking into the basement. Insulating any exposed ductwork will also prevent the radiant heating/ cooling effect. Before I sealed and insulated my ductwork in the utility room in the basement, I would be able to close the door, and within 15 minutes the adjoining basement family room would be 5 degrees warmer.
Working through these steps have helped me....good luck.
Mr Fixit eh
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I've struggled with this problem since moving into our 40 year old home 3 years ago.
Here is what I've learned through trial-and-error:
1. Seal the attic to prevent air infiltration from the upper floor into the attic. This will prevent the loss of conditioned air into the attic space.
2. Make sure the attic has lots of ventilation - soffit vents, channels in the rafter spaces where rafter meets header, ridge vent or passive vents high-up in the roof. Make sure that all of the vents, etc, are unobstructed. Good passive ventilation will help to reduce the heat in your attic space. A cooler attic will mean that your upper storey ceiling will act less as a giant radiant heater!
3. Install an electric powered attic exhaust fan that is thermostatically controlled, and set it for about 100 degrees.
These three steps made a huge difference in our house in terms of keeping the upper storey cooler without the a/c working so hard.
The advice in earlier posts is great about closing vents in basement and 1st floor and opening them upstairs. Just be careful--if the airflow becomes too restricted the pipe going from the outside condensor to the furnace may ice up. It that happens, change the air filter first. If it continues to ice up with a new filter, then you've restricted the airflow too much.
I have used a small portable box fan laying on top of the upstairs floor vents to help boost airflow. You can also buy special booster fans or in-line fans to do the same task. It helps a bit.
The second part of the problem is the basement overcooling. This is caused by three factors:
1. Cool air sinks. Try closing the basement door, if you can. I tried that, but my dog doesn't like it.
2. Regular HVAC vents do not fully restrict airflow. If you're lucky, your system may have individual shutoff valves for each register. Find them and close the valves for the basement vents. If you can't find a valve, they stuff a plastic bag full of crumpled paper and shove it into the ductwork until the airflow is entirely restricted (remember to take it out come winter when the furnace kicks in). I would also close off any return air ducts in the basement--you want the hot air returned, not the freezing cold air from your basement.
3. HVAC ducts often leak both air and temperature. Sealing all of the ductwork carefully will ensure better airflow in the HVAC system (cooler air upstairs) and less conditioned air leaking into the basement. Insulating any exposed ductwork will also prevent the radiant heating/ cooling effect. Before I sealed and insulated my ductwork in the utility room in the basement, I would be able to close the door, and within 15 minutes the adjoining basement family room would be 5 degrees warmer.
Working through these steps have helped me....good luck.
Mr Fixit eh
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Others have noted that leaking vents or pipe joints in the basement can overcool that area. A somewhat similar experience of mine ------
We designed and built an office building for a sister organization. Basement was too cold to work in. Designer had failed to specify insulation on exposed ductwork in the basement. The exposed duct metal was enough it chill the basement without any open vents or other air leakage. Insulation fixed it.
SJF
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