Hvac and insulation guys I need some advice

[Bennylava]

Well the Texas summer heat has is here, and my house's AC just can't keep up. It runs all day long, and doesn't actually cool the house to 74 degrees. It can only cool it to about 76 degrees in the afternoon. Cearly I have some kind of problem, and I think it's air escaping the house. I've tried to fix this before by having that attic foil stuff installed. Then I had some company do 12" of the blown in insulation. I think the attic is taken care of.

I wanted to ask where the air typically escapes from a normal brick house with slab foundation. Is it the front and back door?

If so, which seals would you recommend? Is there a superior seal available, or should I just go with whatever Lowes has?

Thank you

 

[WisJim]

A blower door test would tell you where leaks are for sure. Air leaking into the house is probably the problem. Did you have the attic sealed (between the attic and the conditioned space in the house) before the blown-in insulation? And what is "attic foil stuff"?

 

[Bennylava]

A blower door test would tell you where leaks are for sure. Air leaking into the house is probably the problem. Did you have the attic sealed (between the attic and the conditioned space in the house) before the blown-in insulation? And what is "attic foil stuff"?

We did not have the attic sealed. Did not know that was a thing.


The attic foil is something that you staple to the underside of the roof. We did notice a drop in our electric bill after putting it in. Went from $350 in the summer down to $250 in the following years.

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[462867aa]

How are the ducts? I replaced my flex ducts with hard duct. Made a world of difference in ac performance

 

[MovingAlong]

You didn't mention how old your current system is. A good cleaning of outdoor coils, indoor coils, blower and ducts can help ease the airflow.

But at the end of the day, what worked for me was a new variable speed system designed to run 23 out of 24 hrs a day. Keeps the thermal cycling (warm/cool/warm/cool/etc) of the walls/floors/furniture/etc.. to a minimum and eliminated hot spots in the house because there is always cool air moving. Most of the time the system idled around 30-40% but would kick up higher as needed. Changed my life...

Oh, and it also cut my electric bill in half!

 

[Bennylava]

How are the ducts? I replaced my flex ducts with hard duct. Made a world of difference in ac performance

I'm not really sure about their overall condition, and they may be the original ducts from 1983 when the house was built. They are the soft type.

The whole hvac system was replaced in 2014. The heat runs on gas.

I've always dreamed of a house that is very well insulated with minimal need for the AC to run.

 

[fitter30]

Call our elextric company the might offwr a energy audit tat includes a blower door test like other have stated at a very reasonable price.

 

[drmarkr]

I presume you've put in a new filter and cleaned the coils?? If not, do that before proceeding. Then grab a pyrometer and see what your delta is on intake and discharge vents in the house. Should be 15-20 degrees. Less than 15 suggests duct leak, or inadequate coolant levels in your system. Do you have the ability to measure coolant levels, or know someone who can do so for you?

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[Dumber than lumber]

How are the ducts? I replaced my flex ducts with hard duct. Made a world of difference in ac performance

I think the ducts (hard ducts) in the 43 year old house (from which we recently moved out) deteriorated a little more each year. This is based on how the electric increased just a little more each subsequent year.
Some people will say that the ductwork should be replaced after 20 years. Who knows? Nothing lasts forever.
I wonder what the payback period on AC ductwork would be.

 

[Bennylava]

I think the ducts (hard ducts) in the 43 year old house (from which we recently moved out) deteriorated a little more each year. This is based on how the electric increased just a little more each subsequent year.
Some people will say that the ductwork should be replaced after 20 years. Who knows? Nothing lasts forever.
I wonder what the payback period on AC ductwork would be.

Wonder how much it would cost to replace old soft ducts with new hard ones. Guess that depends on the size of the house, mine is 2400 sq ft.

 

[danski0224]

Well the Texas summer heat has is here, and my house's AC just can't keep up. It runs all day long, and doesn't actually cool the house to 74 degrees. It can only cool it to about 76 degrees in the afternoon. Cearly I have some kind of problem, and I think it's air escaping the house. I've tried to fix this before by having that attic foil stuff installed. Then I had some company do 12" of the blown in insulation. I think the attic is taken care of.

I wanted to ask where the air typically escapes from a normal brick house with slab foundation. Is it the front and back door?

A blower door test will help show where the building envelope issues are. It isn't just doors and windows.

If the ductwork is in the attic, then that is a huge problem.

Duct sealing wasn't really required by code until the adoption of the 2012 International Energy Code, at least in my area. Unsealed ductwork will have a minimum of 20% leakage to the outdoors/attic. This can also be tested.

Then there is the issue of undersized ductwork, especially flex ductwork, restricting airflow. Sealing undersized ductwork will not help.

Making the attic conditioned space by insulating the roof is another approach. Duct insulation, depending on how old it is, can be as little as R4.2- so it is *almost* useless if it is installed correctly. Flex duct that is R10 is available, but I have never seen it in person. The most common in my area is R6, even though R8 is also readily available. None are a match to a 140º attic though. Actually properly insulating ductwork in an attic is challenging.

If you have a powered attic fan, turn it off. Make sure that the attic is ventilated properly if it is not going to be foamed.

 

[danski0224]

Wonder how much it would cost to replace old soft ducts with new hard ones.

More than what 99.98% of the people on this board will pay.

I can say that residential attic HVAC work, using mostly metal, will take 3-4x as long as an equivalent system in a basement.

Then it has to be sealed and insulated. The brush on mastic has to dry.

I've been told to do some pretty substandard work at prior employers.

The only way to do it "fast" is to use flex duct, with all of the drawbacks that come with using it in a typical installation.

 

[danski0224]

I think the ducts (hard ducts) in the 43 year old house (from which we recently moved out) deteriorated a little more each year.

Those ducts were not sealed.

This is based on how the electric increased just a little more each subsequent year.

I would assume that the electric rate went up.

Some people will say that the ductwork should be replaced after 20 years.

Metal ductwork does not "deteriorate" unless it is smashed or rusts- neither will happen naturally to the metal if it is installed properly.

Who knows? Nothing lasts forever.

Nope.

I wonder what the payback period on AC ductwork would be.

Would be quite difficult to come up with an actual number. If it is done right, the comfort improvements would be noticed immediately.

 

[Dumber than lumber]

I would assume that the electric rate went up.

Go ahead and assume. But I was speaking of actual kilowatts consumption.

 

[Dumber than lumber]

Metal ductwork does not "deteriorate" unless it is smashed or rusts- neither will happen naturally to the metal if it is installed properly.

Who ever said I had metal ductwork? In fact, the ducts were made out of that insulated ductboard and mastic.

But thanks for trying to help with the situation.

 

[bob smith1]

Well the Texas summer heat has is here, and my house's AC just can't keep up. It runs all day long, and doesn't actually cool the house to 74 degrees. It can only cool it to about 76 degrees in the afternoon. Cearly I have some kind of problem, and I think it's air escaping the house. I've tried to fix this before by having that attic foil stuff installed. Then I had some company do 12" of the blown in insulation. I think the attic is taken care of.

I wanted to ask where the air typically escapes from a normal brick house with slab foundation. Is it the front and back door?

If so, which seals would you recommend? Is there a superior seal available, or should I just go with whatever Lowes has?

Thank you

Next to no information here to know if you have a house problem, an HVAC sizing problem, or HVAC performance problem. Why don't you start by explaining the year and build type of your home. Also what roof and color. Then a pic of the label on your condenser.

I find that most residential HVAC techs are lazy hacks. Getting a real evaluation, including duct pressures would go a LONG way!

 

[shoot summ]

Next to no information here to know if you have a house problem, an HVAC sizing problem, or HVAC performance problem. Why don't you start by explaining the year and build type of your home. Also what roof and color. Then a pic of the label on your condenser.

I find that most residential HVAC techs are lazy hacks. Getting a real evaluation, including duct pressures would go a LONG way!

Exactly, chasing an air leak without fully understanding what they have. He did mention 2400 sq ft, but no mention of unit size, and is that a single story? Properly sized units will make a lot of the small issues seem less significant, windows will not resolve an improperly sized system.

 

[drmarkr]

All this back and forth about ductwork....and you haven't even assessed your AC unit? Or have you done that, and just don't want to post about it?

I'll try one more time. What is your delta on air temps???

 

[bob smith1]

I presume you've put in a new filter and cleaned the coils?? If not, do that before proceeding. Then grab a pyrometer and see what your delta is on intake and discharge vents in the house. Should be 15-20 degrees. Less than 15 suggests duct leak, or inadequate coolant levels in your system. Do you have the ability to measure coolant levels, or know someone who can do so for you?

Couldn't resist......

 

[drmarkr]

Couldn't resist......

ok....refrigerant.....guilty as charged.

 

[bob smith1]

ok....refrigerant.....guilty as charged.

Ha, no "cold juice", or my personal fav, "reefer".

 

[danski0224]

I find that most residential HVAC techs are lazy hacks.

Not limited in any way, shape or form to residential HVAC.

 

[danski0224]

In fact, the ducts were made out of that insulated ductboard and mastic.

Yummy stuff right there.

I don't see much ductboard in may area. What I have seen, lacked any duct sealant where the collars were attached for the flex duct. That's besides the wrong type of collar being used, and that they were too small.

 

[Bennylava]

I presume you've put in a new filter and cleaned the coils?? If not, do that before proceeding. Then grab a pyrometer and see what your delta is on intake and discharge vents in the house. Should be 15-20 degrees. Less than 15 suggests duct leak, or inadequate coolant levels in your system. Do you have the ability to measure coolant levels, or know someone who can do so for you?

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Well it stopped working altogether, and the local AC tech replaced the capacitor, and now it's working again. Don't know if that would be a contributor to running most of the time though.

The delta is 13 degrees between the main sucker and the vent that's furthest away from it. The intake near the blower motor is 73 degrees, the far vent is 60 degrees. The house is brick with a single story, typical architectural shingle roof. I've been good about changing the 20x25x5 air filter on time. I use Merv 8. The system is 14 years old.

I will try to get some pics up later of the stickers on the unit. I'll see about cleaning both sets of coils.

 

[bob smith1]

I think you will need to get a pro eval. There is just too much of a competence gap.

 

[Bennylava]

I think you will need to get a pro eval. There is just too much of a competence gap.

I did exactly what he said, it's not at all difficult to measure the difference between the intake and the vents.

The rest is me answering the other questions from the thread. You maybe misunderstanding...

 

[drmarkr]

Well it stopped working altogether, and the local AC tech replaced the capacitor, and now it's working again. Don't know if that would be a contributor to running most of the time though.

The delta is 13 degrees between the main sucker and the vent that's furthest away from it. The intake near the blower motor is 73 degrees, the far vent is 60 degrees. The house is brick with a single story, typical architectural shingle roof. I've been good about changing the 20x25x5 air filter on time. I use Merv 8. The system is 14 years old.

I will try to get some pics up later of the stickers on the unit. I'll see about cleaning both sets of coils.

You could get the most accurate return/-intake temps taking the filter out and measuring it right there. Also measure at the closest register rather than the furthest. You're trying to assess the AC unit itself and you don't want the confounding factors of all the potential ductwork problems.

The Delta at those two points I described should be 15 to 25. Do you know if the AC tech that came out and replaced the capacitor measured the refrigerant levels??

 

[bob smith1]

You could get the most accurate return/-intake temps taking the filter out and measuring it right there. Also measure at the closest register rather than the furthest. You're trying to assess the AC unit itself and you don't want the confounding factors of all the potential ductwork problems.

The Delta at those two points I described should be 15 to 25. Do you know if the AC tech that came out and replaced the capacitor measured the refrigerant levels??

I have to strongly disagree. Opening anything changes the flow dynamics and gives a false read. Drill hole in sheet metal and insert probe. Little plug or Al tape when done. I do it every single system. Measurements about 4-6ft away from A coil on supply, and 3ft from AH for return.

BUT, what he has shown already is concerning. Which is that either it's not running right, or he has supply outside the conditioned space, thus getting heat soaked on the trip. Like ducts in the attic.....

 

[drmarkr]

I have to strongly disagree. Opening anything changes the flow dynamics and gives a false read. Drill hole in sheet metal and insert probe. Little plug or Al tape when done. I do it every single system. Measurements about 4-6ft away from A coil on supply, and 3ft from AH for return.

BUT, what he has shown already is concerning. Which is that either it's not running right, or he has supply outside the conditioned space, thus getting heat soaked on the trip. Like ducts in the attic.....

Man, I defer to your expertise on accurate measurements! But....I hold to my original point that he hasn't yet confirmed that the unit IS running right, and has to do that before chasing potential duct issues. That would be the proper diagnostic order, no??

 

[bob smith1]

Man, I defer to your expertise on accurate measurements! But....I hold to my original point that he hasn't yet confirmed that the unit IS running right, and has to do that before chasing potential duct issues. That would be the proper diagnostic order, no??

It can be SO many things, and I can tell he doesn't understand any of it, so I really think a pro is needed.

You cannot assess a system as "running right" without ALL the pressures, SH/SC, temps, and knowing both coils are clean! Otherwise this is just chasing a moving rope. Just knowing the temp split over the a coil tells you about NOTHING! Why? I can go block all your vents, drop the CFM to about nothing, and your dT will go to about 25*, and someone would say, "awesome, it's running great". NOPE.

We don't even know the system, is it fixed orifice or TXV, what are system parameters. There are about 12 different values that determine the state of health. This one needs pro eval.

 

[bob smith1]

This is absolute gold!!! Seriously, this world is so screwed. Remember when people be driving off cliffs because the Garmin said to? Yeah, it's like that.

 

[dcg9381]

If so, which seals would you recommend? Is there a superior seal available, or should I just go with whatever Lowes has?

There is good advice here.
The way they build homes in Texas is easy:
Stupid, cheap, and as fast as possible.

AC performance is generally measured by differential in intake and exhaust temps.

How old is your system?
Leak test will tell you if you have a doors/windows problem, but the "overall" problem (in TX) is that they shove a giant air handler into a poorly conditioned black-colored roof with no decking insulation and expect it to perform in 130+ degrees of attic heat. Dumbest thing ever.


Reflective barriers, and foam insulation can change things, but you have to have the right design and right contractors to change it.

 

[danski0224]

black-colored roof

From what I have read, there is very little actual temperature difference in an attic under an asphalt shingle roof of other colors besides black.

 

[karoc]

When I was in trade, I always stuck my head inside return air to check for leaks. More so in subdivision where they built cookery cutter homes. I find big opening where return was pulling heat from attics