Ductwork with R8 insulation better for attic?

[545GAlady]

We still are not satisfied with all the issues related to HVAC that's going on in the house. The companies seem unwilling to help.

We have noticed that when our upstairs A/C runs in the Summer, the air coming out of the registers is not very cold. whenever the temperature is below 80 outside, the airflow seems a bit colder. During our annual tune-up, the tech checked charges and everything was proper. The system is a Goodman SSX14 2-ton air conditioner with a Goodman CAPF3636A6 indoor coil that was installed a year ago. The furnace is a Lennox SL280v, and it was installed back in July. Airfow was lowered by the tech to 825 cfm (825 cfm for the first 7 minutes then speed increases) and that didn't help solve the issue. I'm now thinking it's the ductwork that's wrong since it has R6 insulation. None of the companies ever mentioned anything about the ductwork. Is this issue typical with attic systems?? Should the ductwork be replaced? Thanks.

[TwincamDave]

How hot is the attic getting, could be heat intrusion. May need an attic exhaust fan, how old is the home?

[second opinion]

Is either the unit or return in the attic?

[2old2rock]

Check the temp coming out of the air handler, then check the temp coming out of the farthest vent.

[545GAlady]

How hot is the attic getting, could be heat intrusion. May need an attic exhaust fan, how old is the home?

I will need to check temperature up there. We already have a solar-powered attic fan which has really brought down the attic temperature.

The house was built in 2001-2002.

[545GAlady]

Is either the unit or return in the attic?

The furnace is located in the attic. Thanks for asking.

[545GAlady]

Check the temp coming out of the air handler, then check the temp coming out of the farthest vent.

Thanks for the reply. I checked supply temp last summer and it was reading 68*F and I forgot what the return temp was. Last weekend I checked it again and it read 58*F on the supply side and 72*F on the return side. Of course it was cooler outside when I checked temps last weekend. It was maybe in the 80's when I checked last summer.

[motoguy128]

R8 may help, but I would suspect that air leaks are the biggest problem. Repalcing the ductwork (flex?) would kill 2 birds with one stone. You get better insulation, if installed properly and pulled tight your static pressure will drop and you'll get more airflow/capacity.

You could also seal the attic and spray foam the roof deck, but that's a expensive alternative and has it's advantages and disadvantages.

[second opinion]

Do you have any other diagnostic information from the technician as far as temperatures and pressures? You should be closer to a 20 degree split if system was running correctly with 50% relative humidity.

[jtrammel]

You most likely have duct leakage causing the symptoms. A home energy audit would find the problem areas.

[545GAlady]

The ducts were sealed back when the furnace was installed. I was hoping that will solve the issue, but it did not. Our first floor systems always blows out ice cubes, but not the upstairs system. We do plan to have an energy audit done.

[545GAlady]

Do you have any other diagnostic information from the technician as far as temperatures and pressures? You should be closer to a 20 degree split if system was running correctly with 50% relative humidity.

As of now, I don't think I have any other diagnostic info from the technician. He never told me the actual pressures.

[545GAlady]

R8 may help, but I would suspect that air leaks are the biggest problem. Repalcing the ductwork (flex?) would kill 2 birds with one stone. You get better insulation, if installed properly and pulled tight your static pressure will drop and you'll get more airflow/capacity.

You could also seal the attic and spray foam the roof deck, but that's a expensive alternative and has it's advantages and disadvantages.

That will be nice, but we currently don't have the money for more insulation.

[ga-hvac-tech]

I see you are in GA, not sure where (and have not read your previous threads).

If you are interested in a different set of eyes looking for issues with your system(s) (for a fee), look in my profile (click on my screen name) and send me an Email.

[jtrammel]

If they didn't test the duct leakage before and after how do you know if they sealed it.

[mark beiser]

Airfow was lowered by the tech to 825 cfm (825 cfm for the first 7 minutes then speed increases) and that didn't help solve the issue.

Other issues aside, for a 2 ton system around 800 CFM should be the maximum airflow setting that the blower ramps up to.

[jimj]

We already have a solar-powered attic fan which has really brought down the attic temperature.
.

Not a good idea, Your cooling your attic at the expense of cooling and comfort in your home!

[545GAlady]

Not a good idea, Your cooling your attic at the expense of cooling and comfort in your home!

Well what I mean is the attic is still very hot in the summer time but the attic helped lower temperatures a few degrees cooler. We have a large attic, and it's always hot during the warmer months.

[545GAlady]

If they didn't test the duct leakage before and after how do you know if they sealed it.

The contractor who was here last summer to quote us on the new furnace tested duct leakage and there was quite a bit and the ducts were never sealed. After the new furnace was installed, the installers sealed all of the ductwork.

[545GAlady]

Other issues aside, for a 2 ton system around 800 CFM should be the maximum airflow setting that the blower ramps up to.

The tech who was here for the A/C tune-up said he didn't want to lower airflow too much as it can affect the performance of the whole system.