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Mold Remediation & HVAC Changes

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#21 ·
SthnLdy said:
I’m confused on something else now. The diagram and instructions for the UltraAire dehumidifier state it needs a dedicated return.

The current HVAC system has one return register inside the house. All this time, I have been thinking based on the wording that a 2nd return register has to be installed inside the house for the dehumidifier. Is this correct, or do you install the dehumidifier in the existing inside return?

The diagram shows the register vent labeled “indoor air return.” It shows above that an HVAC return next to the air handler. Is the HVAC return a piece of equipment located in the attic?
Click to expand...
Best to have an independent return from the open part of the home to the dehumidifier. This assures good mixing of the dry air throughout the home via the a/c supply/dehu supply.
Most new a/c systems have and a return from each room that has a door. with a single return, you depend on the a/c supply to return to the a/c via the door undercut on each conditioned room if the door is closed.
Keep us posted.
Regards Teddy Bear
 
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Discussion starter · #22 ·
teddy bear said:
Best to have an independent return from the open part of the home to the dehumidifier. This assures good mixing of the dry air throughout the home via the a/c supply/dehu supply.
Most new a/c systems have and a return from each room that has a door. with a single return, you depend on the a/c supply to return to the a/c via the door undercut on each conditioned room if the door is closed.
Keep us posted.
Regards Teddy Bear
Click to expand...
The existing return is on the bottom of the wall in the hall. We are having it relocated to the ceiling. It is in an ideal location between the walls as you exit the living room to the short hall where the smaller bedrooms and guest bath are located..

We are having all hard pipe ducts installed. I understand they can be noisy. Also understand the dehumidifier can be even more noisy. Trying to figure out where else to locate the 2nd return for the dehumidifier.

How far away from the existing inside return register should the return register for the dehumidifier be?
 
#23 ·
How about using the old return space near the floor with the duct going to the dehumidifier. The dehu supply goes to the a/c supply duct down stream of the a/c cooling coil. Fresh air goes to the dehu return.
Make sense. The high return to the a/c favors warm air from the ceiling. Ok with me. Dehumidifier will use cooler air on the floor, also ok.
Fresh air will require a couple of balancing dampers to proportion fresh air verses house air.
Keep us posted.
Regards Teddy Bear
 
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Discussion starter · #24 ·
teddy bear said:
How about using the old return space near the floor with the duct going to the dehumidifier. The dehu supply goes to the a/c supply duct down stream of the a/c cooling coil. Fresh air goes to the dehu return.
Make sense. The high return to the a/c favors warm air from the ceiling. Ok with me. Dehumidifier will use cooler air on the floor, also ok.
Fresh air will require a couple of balancing dampers to proportion fresh air verses house air.
Keep us posted.
Regards Teddy Bear
Click to expand...
Good in theory, but I went back to the mold consultants remediation plan and guidance. The old return cavity will need to be abandoned and sealed at both ends. It can’t be adequately cleaned, so cross contamination would be an issue.

So, we’ll be putting the dedicated dehumidifier return register in the ceiling. How far away from the AC return register does it need to be?
 
Discussion starter · #25 ·
And . . . . Yes, another question!!!

Can you advise on the MERV rating for the filter. We are getting the Aprilaire mechanical filter and the UltraAire 98h dehumidifier and the fresh air intake. Outside environment is humid year round. I know the outside air has PM2 particulate matter in this area.

I am inclined to go with a MERV 13 filter for the Aprilaire. Would it be advisable to have a MERV 13 filter for the UltraAire as well or a MERV 11?

On the one hand, the dehumidifier filter will be directly filtering the fresh air intake, so it would make sense to use a 13 filter there also to filter particulate matter. However, I am very concerned about mold (which is the entire reason all this is being done). Fresh air will be humid and dirty. A 13 filter is going to slow the speed and force of air passage more than an 11 filter. Will that increase the risk of the filter getting moldy from the dampness and dirt on it?
 
#26 ·
The Ultra-Aire 98h has a merv 13 as the standard filter for fresh air and return air from the home.
The return air from the open part of the home should be located in space without a door that is closed. The dehu supply is best routed to the a/c supply after the a/c cooling coil.
The allows the dehu to operate with or without the a/c blower.
It is important for the a/c to be adjusted to provide dry air while cooling. Suggest a supply dew point 5^F lower than the desired room dew point. If you want 75^F, 50%RH, a 55^F dew point, the a/c supply air flow should be adjusted to to provide <50^F dew point air to the space will cooling during typical high cooling loads. The will keep the home dry during high sensible cooling loads without the dehu operating.
The dehumidifiier is needed during partial or no sensible cooling loads and high outdoor dew points.
Keep us posted on results.
https://www.ultra-aire.com/dehumidifiers/98h/

Regards and thanks for the support
Teddy Bear
 
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Discussion starter · #27 ·
I got a surprise yesterday. Found out the HVAC folks installed Reflectix bubble wrap as insulation around the new all metal ducts. I thought they were installing R-8 fiberglass insulation with the shiny outer surface.

I talked to the HVAC rep this morning and he told me he thought the bubble wrap would be better because he knew we had mold concerns and he had seen fiberglass insulation get moldy in places where it got torn.

I already knew about the controversy over Reflectix’ R-value claims and would have said no if he had talked to me about it beforehand.

I asked if the company had used this type insulation before, and he said a few times. They did NOT use spacers.

Can someone please tell me what effect this is going to have? The ducts are all metal, in an unconditioned attic in SE Georgia.

Will the Reflectix cause condensation INSIDE the ducts? OUTSIDE the ducts? Will this install cause mold or condensation? What will the energy/electric bill effects be, since it basically has an R-value of 1 installed without spacers?

Should I have them remove it and install normal R-8 fiberglass insulation with the silver colored outer surface? Will fiberglass insulation cause mold if it’s installed properly?
 
Discussion starter · #29 ·
Thx for the response. I’m checking into more. I did get the exact product. They put in the Big Bubble product # HVBB48075. Website says R-8 with spacers, R-6 loosely wrapped. I am checking with the contractor to see exactly how it was installed. He sent me a photo of the product label. It has instructions on the label for how to do the spacers.
 
Discussion starter · #30 ·
I have another question/comment that is related to mold on metal ducts.

I often see (and feel SEVERE health effects from) mold on the OUTSIDE of exposed metal ductwork handing from rafters inside commercial buildings. Some may say mold won’t grow on metal, but what I see and feel effects from is most definitely MOLD. Perhaps dust and dirt collect on the outside of the ducts, along with condensation, and the mold is growing on those particles

I have seen the same type mold on the outside of plastic water pipes.

Bottom line is I do not want mold on or in the ducts.

Will Reflectix carry this risk more so than regular fiberglass installed around the outside of the ducts.
 
Discussion starter · #32 ·
pecmsg said:
If the bubble wrap gets wet it doesn't affect the insulation value and will eventfully dry out unlike fiberglass.
Click to expand...
“Eventually” - that doesn’t sound too assuring.

Isn’t the whole point of insulation to prevent condensation from forming on surfaces of opposing temperatures?

What insulation would do the best job of that in this set-up?

Also, I had the UltraAire 98h dehumidifier installed with the ventilation duct. Are they supposed to be insulated the same as the AC ductwork?
 
#34 ·
SthnLdy said:
“Eventually” - that doesn’t sound too assuring.

Isn’t the whole point of insulation to prevent condensation from forming on surfaces of opposing temperatures?

What insulation would do the best job of that in this set-up?

Also, I had the UltraAire 98h dehumidifier installed with the ventilation duct. Are they supposed to be insulated the same as the AC ductwork?
Click to expand...
Insulating the dehu ducts like the a/c should be good. The dehu supply into the a/c supply will reduce the a/c supply duct temperature when the dehu operated.

I would operate the dehu fan 24/7, this will dry and warm the a/c duct to assist the drying.
Keep us posted.
Regards Teddy Bear
 
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Discussion starter · #35 ·
TeddyBear,

Would you operate the dehumidifier 24/7 if normal fiberglass insulation had been used instead of Reflectix?

I don’t want to have to do some workaround. This is a brand new system. It needs to be set up right from the beginning.
 
#36 ·
SthnLdy said:
TeddyBear,

Would you operate the dehumidifier 24/7 if normal fiberglass insulation had been used instead of Reflectix?

I don’t want to have to do some workaround. This is a brand new system. It needs to be set up right from the beginning.
Click to expand...
The dehu will not operate unless the %RH is above the set point. I was talking about the fan only which will mix warm air from the home with the cold air from the a/c or if the dehu is needed warm dry air which will warm the cold air in the a/c ducts..

Keep us posted.
Regards Teddy Bear
 
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