HVACs in the House? Complex questions on home air related to spray foam insulation

[s0me0nesmind1]

Breakdown:

• 3 ACs in our Home – 1x 4t for upstairs. 1x 3.5t for downstairs. 1x 2t for master bedroom suite
  • Master bedroom is entirely dead, the evap. Coils are leaking so much that if we refill the freon it leaks straight back out
  • Upstairs isn’t coiling efficiently at all – and it never really has. Bedrooms on the opposite side of the house upstairs barely gets any cool air if any from their output vents. If we turn the thermostat to 75, it would run 20 hours+ in the day.
  • Downstairs unit seems to work “ok”
• Going into this, I felt like I wanted to go with Trane – because over the years of meeting many different HVACs to fix stuff – I would always ask for their favorite brand and this is generally what they would tell me. I’ve also heard some consistent issues with the likes of Lunnex – but I’m no expert here.
• My main thing for my replacement ACs is I just want the Toyota. ACs are generally rated for something to last 10-15 years, and I want something that lasts 20+ years when properly maintained.
• Mold Growth – Rampant problem In our area and lawsuits are going on. We’ve seen it in the attic on the duct-work and even seen it in the duct work at the output vents after taking off the output vents. Some people seem to attribute this to 2 things
  • New rule in home building that states part of the AC input air has to come from the outside. Our outside is HEAVY humidity air. Were right next to the gulf.
  • Wind from the bay also comes in through our attic via holes under the roof.
• Many In the neighborhood (including the home builder that is fixing these issues) think that the answer to this is seal off the attic entirely – and then condition the attic space with the rest of the home.

So going into this we had these for our plans and for getting quotes

1. Replace all the ACs + Ductwork to new models
2. Seal attic with spray-foam insulation
3. Replacement of furnaces with non-combustible since attic is sealed
4. Replace Gas tank water heaters with tankless non-combustible since attic is sealed
5. 5. Install dehumidifier in the attic for the whole-house

So Far I’ve gotten 2 quotes – and they aren’t turning out how I imagined:
Quote#1 came and said he doesn’t like the sealed attic route, and thinks it will create more problems from “changing the dew point” in the attic and says all the humidity will rise to the sealed attic. His general philosophy was generally it would create more problems than good – and even basically said if we went that route then he would prefer if we just went with someone else.
Roughly wants $30k to replace with SEER-16 Trane units and install a dehumidifier if I opt to NOT get the attic sealed.

Quote#2 came and basically said the problem was crap builder installation. He was measuring up all the inputs (return vent length x width) and comparing it with the output and generally found that our return air was roughly HALF of our output air on our 9.5 tons of total AC. He also showed parts where when the return air came back to the unit was much smaller than the vents that connected to the evaporator coil basic. Thus he was saying only “part” of the evaporator coils were being used. I can provide pics of this stuff if desired....
Quote#2 also believes that the stuff we are seeing in the attic isn’t mold, but rather mildew just based on bad installation, uneven input/output, etc… Roughly wants $26k to replace the ACs with 3x Armstrong / Lennox units, and also open more input space, fix the inefficiencies, etc... Also said he used to install Trane for 20+ years, but said they recently have started to go downhill with cutting corners in manufacturing.

So with all that said –

1. Do you recommend going with the sealed attic route with spray foam insulation? It seems nice on paper – cooling the attic – which also means all the HVAC duct-work doesn’t have to travel through 115+ degree weather with cooled air
2. Any agreeance on brand – Like I said, previous HVACs I’ve met recommended Trane, but if that isn’t needed then I’ll understand. I just want to make sure it’s something that can last 20 years.
3. Any truth to Quote #2 / Quote #1 and if 1 or none were generally better to go with? Should I avoid sealing the attic? Is it not worth it? Too expensive? Could cause further problems with humidity like Quote#1 said?
4. Any other general comments / recommendations? I will get at least 4 quotes before I proceed, so I will update this thread as I go…

 

[Greenman]

Start at the beginning.
How big is the house?
How old is the house?
What insulation exists now?
Single or double glazed windows?
Exterior wall construction.

Right off the bat, unless we're talking about a huge house, over 4k square feet, three systems is either world class stupid, or the designer totally screwed the pooch and never thought about HVAC until the place was farmed, and they ended up stuffing parts in where ever they could make them fit. Adding in the mold issues makes me think there was never a cohesive design.

All of the issues can be solved, but it has to be a designed system, not a conglomeration of parts and ideas. Right now, you have enough cooling capacity for a 6000 square foot house. Something is seriously fucked up.

 

[snoopy7548]

I agree with Greenman. Three condensers for a single home... your house is either massive or whoever designed the HVAC was smoking crack.

Sounds to me at a minimum you need to replace the evap coil for your "Master Bedroom" AC (the fact that the master bedroom needs a dedicated two ton AC is simply bonkers). If your upstairs isn't cooling well and the condenser is OK, you've either got poor ducting (not enough returns or airflow) or your attic insulation/air sealing is non-existent.

I'd hire a professional HVAC company to perform a manual-J and completely re-design the system; sounds like the builder didn't know their head from their ass.

 

[herm0016]

agree with both above.

go with whoever is going to actually redesign the system and will perform manual J calc.

 

[Greenman]

Along with that design should be installation standards and careful inspection. If the design is really good, and a bunch of halfwits install the flex duct, the system is still going to suck.

 

[herm0016]

you could go with something like the Mitsubishi heat pump that you could have the 3 inside updraft units, and one outside unit. you could use splits for the master or the section that the ducting is nearly useless also. Do not let yourself be hemmed into having the 3 updrafts like it is now, it's obv. never been designed properly.

 

[s0me0nesmind1]

Start at the beginning.
How big is the house?
How old is the house?
What insulation exists now?
Single or double glazed windows?
Exterior wall construction.

Right off the bat, unless we're talking about a huge house, over 4k square feet, three systems is either world class stupid, or the designer totally screwed the pooch and never thought about HVAC until the place was farmed, and they ended up stuffing parts in where ever they could make them fit. Adding in the mold issues makes me think there was never a cohesive design.

All of the issues can be solved, but it has to be a designed system, not a conglomeration of parts and ideas. Right now, you have enough cooling capacity for a 6000 square foot house. Something is seriously fucked up.

How big is your house: ~4300 sqft.... I think to be exact it's like 4270
How old is the house: 10 years.
What insulation exists now: Standard? Attic insulation. Whatever you think a 10 year old home would have is probably what we have
Double glazed windows
Exterior wall construction: Stucco I believe?

While the tonage overall seems high, upon HVACs coming and calculating when you account for "rounding up" for each area, it comes out to being semi-reasonable.

 

[s0me0nesmind1]

I agree with Greenman. Three condensers for a single home... your house is either massive or whoever designed the HVAC was smoking crack.

Sounds to me at a minimum you need to replace the evap coil for your "Master Bedroom" AC (the fact that the master bedroom needs a dedicated two ton AC is simply bonkers). If your upstairs isn't cooling well and the condenser is OK, you've either got poor ducting (not enough returns or airflow) or your attic insulation/air sealing is non-existent.

I'd hire a professional HVAC company to perform a manual-J and completely re-design the system; sounds like the builder didn't know their head from their ass.

That's sounding more like what Quote#2 is saying. His main points is that the builders did a piss-poor job of not making enough return airflow, so his quote is to install a couple more return vents.

Also theres no question at this point - I'm replacing the ACs entirely and not fixing them. What we currently have is junk and at the end of life as far as I'm cocnerned.

 

[Greenman]

How big is your house: ~4300 sqft.... I think to be exact it's like 4270
How old is the house: 10 years.
What insulation exists now: Standard? Attic insulation. Whatever you think a 10 year old home would have is probably what we have
Double glazed windows
Exterior wall construction: Stucco I believe?

While the tonage overall seems high, upon HVACs coming and calculating when you account for "rounding up" for each area, it comes out to being semi-reasonable.

Check out the attic insulation to be sure it's adequate. Converting the attic to conditioned space may or may not be of any benefit, no way to tell from two thousand miles away. If you leave it as unconditioned space, verify the ventilation. To much is way better than not enough. Require a manual J calculation for the new system, and spec out how the new ducts are installed. Flex duct should always be in reasonably straight runs, very well supported and stretched. Tight bends should be made with ridged elbows, and connections coated with air seal (NO DUCT TAPE). Require a HERS test on the completed system.
You're going to drop a pile of money on this system, it's foolish to skip any steps and end up with something that's only marginally better than what you have now.

I still think nine tons of cooling is insane. My hunch is that they're over sizing the system to cover for poor instillation, a very leaky house, or a crap design. Could be all three.

Note on duct tape: When used on HVAC systems it has a 100% failure rate. It's a temporary seal, good for a few years at best.

 

[snoopy7548]

New rule in home building that states part of the AC input air has to come from the outside. Our outside is HEAVY humidity air. Were right next to the gulf.

I've never heard of this. My home was built in 2012 and the central AC does not take air from the outside - that would counteract the secondary effect of central air which is humidity removal.

My condenser is located outside the home, which is extremely common in the Northeast, probably since we have basements where the furnace and ductwork are located. It would be much more work to have an outdoor condenser without a basement.

I think sealing off the attic and turning it into a conditioned space will create additional problems. The condenser pumps out heat as it cools your home, so you're now getting into a situation where you're cooling down a space (attic) that you're constantly dumping heat into.

If you're finding mold on your ductwork in the attic, it's because you've got conditioned air leaking from them. Conditioning the attic will resolve this, but it doesn't sound like the proper solution.

If it were my house, I would first have an energy audit done. I bet your attic has very little to no insulation, and air-sealing between it and the conditioned living area is non-existant. You also seem to have leaky air ducts, which is contributing to your lack of cooling/humidity control, and creating mold.

As Greenman said, your attic needs to have proper ventilation if it is unconditioned. Make sure the soffit vents aren't covered up with insulation. An energy audit will go through all of this; my electic company does them for free, and even covers a sizable portion of the costs for new insulation and air-sealing.

The rule of thumb is around 1 ton of AC per 600 sq. ft., but this changes according to lots of factors including your insulation. If you keep the same tonnage and increase your insulation, you may find that your AC will cool the house quickly but not remove humidity, which is why you need a manual J.

In short, start with an energy audit, get your insulation and air-sealing up to par, and go from there.

 

[Greenman]

I've never heard of this. My home was built in 2012 and the central AC does not take air from the outside - that would counteract the secondary effect of central air which is humidity removal.

My condenser is located outside the home, which is extremely common in the Northeast, probably since we have basements where the furnace and ductwork are located. It would be much more work to have an outdoor condenser without a basement.

Snipped out the part I want to address.
The outside air requirement depends on how tight the house is. Extremely tight construction requires outside air.
The AC condenser is always placed outside, everywhere.

 

[herm0016]

I've never heard of this. My home was built in 2012 and the central AC does not take air from the outside - that would counteract the secondary effect of central air which is humidity removal.

modern systems employ a vapor open energy recovery device (erv) it passes the incoming, fresh air through a vapor and heat exchanger that recovers the energy in the cool air and pulls water from the incoming air. Fresh air is essential to a healthy and functioning system in a house that is well sealed up.

My condenser is located outside the home, which is extremely common in the Northeast, probably since we have basements where the furnace and ductwork are located. It would be much more work to have an outdoor condenser without a basement.

nothing to do with a basement. condensers are always outside.

I think sealing off the attic and turning it into a conditioned space will create additional problems. The condenser pumps out heat as it cools your home, so you're now getting into a situation where you're cooling down a space (attic) that you're constantly dumping heat into.

the condenser is outside, the evaporator is inside. the air goes through the evap to cool it. the heat transferred to the fluid in the system and is dumped outside at the condenser.

also, know that if you put the condenser and the evap in the same space, it would heat the space every time. 1st law of thermodynamics.

 

[snoopy7548]

Damn... what was I thinking? Please disregard my stupidity!

 

[Greenman]

Damn... what was I thinking? Please disregard my stupidity!

But I was looking forward to ridiculing you! Having never been mistaken about anything in my entire life (or at least since this morning) I felt I had the right. I'm so disappointed.

 

[Micrornd]

I've never heard of this.

No, you're right.
There is nothing new about this "rule".
It has been around for quite a while, depending on where you live and also doesn't exist, depending where you live.
It's implementation (as well as ALL the specifics that are involved) are entirely up to the AHJ.
It is, however, a guideline that is adhered to by those that build overly "tight" houses (which can present it's own unique set of problems).
My guess would be that it's been around for 20+ years in Cali and still doesn't exist in Montana or Tennessee, as a code requirement.
Some believe in it strongly, others not so much, as it's actual benefits are NOT universal, but rather based on how it is implemented and also where (local climate conditions)

 

[s0me0nesmind1]

I think sealing off the attic and turning it into a conditioned space will create additional problems. The condenser pumps out heat as it cools your home, so you're now getting into a situation where you're cooling down a space (attic) that you're constantly dumping heat into.

If you're finding mold on your ductwork in the attic, it's because you've got conditioned air leaking from them. Conditioning the attic will resolve this, but it doesn't sound like the proper solution.

I don't think condensation in the attic is limited to just if the ducts are leaking? I'm fairly sure that none of our ducts are leaking.

If it were my house, I would first have an energy audit done. I bet your attic has very little to no insulation, and air-sealing between it and the conditioned living area is non-existant. You also seem to have leaky air ducts, which is contributing to your lack of cooling/humidity control, and creating mold.

As Greenman said, your attic needs to have proper ventilation if it is unconditioned. Make sure the soffit vents aren't covered up with insulation. An energy audit will go through all of this; my electic company does them for free, and even covers a sizable portion of the costs for new insulation and air-sealing.

The rule of thumb is around 1 ton of AC per 600 sq. ft., but this changes according to lots of factors including your insulation. If you keep the same tonnage and increase your insulation, you may find that your AC will cool the house quickly but not remove humidity, which is why you need a manual J.

In short, start with an energy audit, get your insulation and air-sealing up to par, and go from there.

I actually did get an energy audit - and he was one of the ones pushing for sealing off the attic-space.

Our attic definitely has your standard insulation - I don't know what the R value of that stuff is, but there is insulation.

As far as leaks in general, the energy audit came back with what we expected... an overall very tight house. Blower-door test revealed that any "leakage" is at ideal levels based on that measurement - so sealing off things in the house would offer basically zero additional results.



The other thing I'm having to consider is if we should get the newer (and much more expensive) variable speed units as well.

 

[Greenman]

I don't think condensation in the attic is limited to just if the ducts are leaking? I'm fairly sure that none of our ducts are leaking.





I actually did get an energy audit - and he was one of the ones pushing for sealing off the attic-space.

Our attic definitely has your standard insulation - I don't know what the R value of that stuff is, but there is insulation.

As far as leaks in general, the energy audit came back with what we expected... an overall very tight house. Blower-door test revealed that any "leakage" is at ideal levels based on that measurement - so sealing off things in the house would offer basically zero additional results.



The other thing I'm having to consider is if we should get the newer (and much more expensive) variable speed units as well.

Outside air intake makes sense under those conditions. You need some fresh air in the house, though it doesn't have to be drawn in through the AC. It can be as simple as a small fan drawing outside air through a 3" duct.
I just remolded a place that had an 8" duct connected to the return air plenum and run straight to the outside. This was a very old house that didn't require any outside air, it leaked plenty. I never could figure out why they did it.

 

[s0me0nesmind1]

Just got done with my latest quote with a different HVAC company. They seemed like the most well-informed I've seen thus far.

They wanted to run a manual J - but in order to be as accurate they wanted me to try and obtain building plans for my home. Called the city and they wouldn't release me that information... Greaaaaaaaaat, can't even get the building plans for me own fuckin' home.

Anyone else know of how to get that kind of information? They are wanting everything - besides just room measurements but also stuff like window measurements...

 

[skull]

Outside air intake makes sense under those conditions. You need some fresh air in the house, though it doesn't have to be drawn in through the AC. It can be as simple as a small fan drawing outside air through a 3" duct.
I just remolded a place that had an 8" duct connected to the return air plenum and run straight to the outside. This was a very old house that didn't require any outside air, it leaked plenty. I never could figure out why they did it.

Even with a leaky house its ideal to pull the outside air thru the hvac and condition it versus having it come in all over as drafts. With dryers, exhaust fans, and natural draft water heaters a lot of air gets sucked out of houses and needs made up, it can come in around your doors windows etc. or you can pull it into the furnace and condition it first.

 

[skull]

Just got done with my latest quote with a different HVAC company. They seemed like the most well-informed I've seen thus far.

They wanted to run a manual J - but in order to be as accurate they wanted me to try and obtain building plans for my home. Called the city and they wouldn't release me that information... Greaaaaaaaaat, can't even get the building plans for me own fuckin' home.

Anyone else know of how to get that kind of information? They are wanting everything - besides just room measurements but also stuff like window measurements...

You shoudl be able to get it from the county auditors keep trying. If not I always do my manual js by hand measuring every window, door and which side of the sun it faces along with exterior wall sq footage climbing in attics and measuring insulation depth. Insulation in walls can be tricky, on older houses I'll peak in around a outlet and if its there just call it r11. Newer house if the owner doesn't know if the outside walls are 2 x 4 or 2 x 6 theres always the option of putting a hole in the wall and finding out.

 

[Fanatical Meat]

I am no HVAC expert, I want to say we are extremely happy with our Bosch heat pump. Works great, cools good but slow like all heat pumps and is very easy on the electric. During summer our net electric usage is flat from before the heat pump (maybe a little higher this year because of work from home). Cooling wise the unit uses the electricity of two or three fans.
Its even pretty efficient at heating, we used about $600 more on electricity last winter but we only burned 30 to 40 gallons of oil. Plus we kept the house a constant 68-70 which is two degrees warmer than before.
Regarding mold in the ducts, our ducts are under sized. I know pricing is location dependent but the replacement cost was insane for apx 1200 square foot ranch. Replacement cost would never be recovered thru more Effie next heating/cooling.
Maybe a better idea is to have them regularly cleaned. I know there is some sealant mold preventer stuff that can be sprayed into them but again it is not cheap. Regular standard cleanings may be the proper solution.

 

[Greenman]

You shoudl be able to get it from the county auditors keep trying. If not I always do my manual js by hand measuring every window, door and which side of the sun it faces along with exterior wall sq footage climbing in attics and measuring insulation depth. Insulation in walls can be tricky, on older houses I'll peak in around a outlet and if its there just call it r11. Newer house if the owner doesn't know if the outside walls are 2 x 4 or 2 x 6 theres always the option of putting a hole in the wall and finding out.

Or measuring the width of a door jamb.