Fresh Air Return Duct Insulation is Dripping Wet

ChrisJ

Rich_49 said:

Crissie said:

The outdoor damper you showed us is an exhaust.  

The cover of it might look like an exhaust, but it is an intake. It pulls air in when the HVAC is running. Here is a link to the product. https://www.honeywellhome.com/us/en/products/air/ventilation/fresh-air-ventilation-system-with-truezone-damper-y8150a1017-u/

Crissie , I think you misunderstand what is being said . Nobody is questioning the parts that make up the Honetwell kit . The termination that has been used is in fact an exhaust termination most usually used for a gas dryer . It may have been used as an outdoor termination by someone but that does not make it so , those louvers open outward , not inward , ever . You would have been better suited with a hooded , open ended termination with stainless steel screen as a bug shield . No doubt in my mind that the damper system works , there is however a doubt whether the intended airflow can be pulled through the SLITS in that louver .

If they rigged it to hold the doors open, wouldn't such a small vent also encourage rain, snow etc to be sucked in?


@Crissie Do you feel air blowing out of that vent or being sucked in?

mattmia2

ChrisJ said:

If they rigged it to hold the doors open, wouldn't such a small vent also encourage rain, snow etc to be sucked in?

Rodents would be more of a problem.

Crissie

Rich_49 said:

Crissie said:

The outdoor damper you showed us is an exhaust.  

The cover of it might look like an exhaust, but it is an intake. It pulls air in when the HVAC is running. Here is a link to the product. https://www.honeywellhome.com/us/en/products/air/ventilation/fresh-air-ventilation-system-with-truezone-damper-y8150a1017-u/

Crissie , I think you misunderstand what is being said . Nobody is questioning the parts that make up the Honetwell kit . The termination that has been used is in fact an exhaust termination most usually used for a gas dryer . It may have been used as an outdoor termination by someone but that does not make it so , those louvers open outward , not inward , ever . You would have been better suited with a hooded , open ended termination with stainless steel screen as a bug shield . No doubt in my mind that the damper system works , there is however a doubt whether the intended airflow can be pulled through the SLITS in that louver .

it is what the HVAC company who installed it put in and the slots are always open, they don't get pushed up like the dryer vents. They don't move. I like the idea of a screen over it. I think the problem is I am bringing humid air into my HVAC and that is causing condensation.

Rich_49

The reason they are cut or added into the return side is so that the humid air being introduced passes over the coil before entering the house . That is where latent load is addressed in every properly designed system , latent ( moisture ) condensing on the coil .

Jamie Hall

Can we all get back to @Crissie 's original question? She is concerned, as I understand it, about the insulation -- which is fiberglass -- surrounding a duct which is bringing nice cold air in from outside and is hooked up -- correctly -- to the return of her forced air system.

The insulation is drenched because the air coming in from outside is cold and the humidity in the interior air is condensing on it. No mystery.

The solution -- the only solution -- to the immediate concern is to use closed cell insulation solidly attached to that duct of sufficient thickness to keep the occupied area surface above the dewpoint. Most likely two to four inches of the stuff.

Now there seem to be a number of other concerns on this system -- most of which sound valid -- but that is the situation for the initial concern.

Now as to some of the other concerns... they really boil down to needing a pretty thorough revisiting of her heating and air conditioning system.

Rich_49

Jamie Hall said:

Can we all get back to @Crissie 's original question? She is concerned, as I understand it, about the insulation -- which is fiberglass -- surrounding a duct which is bringing nice cold air in from outside and is hooked up -- correctly -- to the return of her forced air system.

The insulation is drenched because the air coming in from outside is cold and the humidity in the interior air is condensing on it. No mystery.

The solution -- the only solution -- to the immediate concern is to use closed cell insulation solidly attached to that duct of sufficient thickness to keep the occupied area surface above the dewpoint. Most likely two to four inches of the stuff.

Now there seem to be a number of other concerns on this system -- most of which sound valid -- but that is the situation for the initial concern.

Now as to some of the other concerns... they really boil down to needing a pretty thorough revisiting of her heating and air conditioning system.

With all due respect Jamie , it is all related . That duct may in fact end up being removed and addressing the situation in other than a " HOUSE AS A SYSTEM " approach does not SOLVE a problem as much as possibly hiding it .

This vent is actually where most , a majority of the latent load is entering the house . If it is not addressed and the incoming air is not dropping the moisture at the coil which it reaches before entering the house , have we solved anything . Just to be fair , Crissie has about a half dozen discussion threads going on about this home . main concern being it made her ill

Jamie Hall

Um... @Rich_49 ... the problem is the insulation on the outside of the pipe. In cold weather. Your comment above would be quite valid if it were on the inside of the pipe when the air conditioner is operating, and I'd agree with you. But... it's not. And it's not where the moisture in the house in the winter is coming from.

ChrisJ

Jamie Hall said:

Um... @Rich_49 ... the problem is the insulation on the outside of the pipe. In cold weather. Your comment above would be quite valid if it were on the inside of the pipe when the air conditioner is operating, and I'd agree with you. But... it's not. And it's not where the moisture in the house in the winter is coming from.

If that's sucking rain water in and then it's leaking into the insulation it sure would be a big part of the problem.

For now my eyes are 100% on that tiny "intake"

What is normally used to pull fresh air into a building?  My understanding was it needed to be large to keep velocity very low and of course filtered to keep bugs and dirt out 

Rich_49

Jamie Hall said:

Um... @Rich_49 ... the problem is the insulation on the outside of the pipe. In cold weather. Your comment above would be quite valid if it were on the inside of the pipe when the air conditioner is operating, and I'd agree with you. But... it's not. And it's not where the moisture in the house in the winter is coming from.

Jamie , the problem is the moisture in the house that is getting the insulation wet . Without dealing with that issue the problem will remain , I mean the moisture problem . The insulation will not be wet but that moisture will still be inside the thermal envelope and on our OP .
Could you please elaborate on what 'IT " on the inside of the pipe means , If WHAT were inside the pipe ? The insulation , that's just dumb

mattmia2

This is the reason the switched to foam insulation on refrigerators. With fiberglass if you had the tiniest leak in the outer cabinet the normal moisture in the household air would condense on the cold outer surface of the inner cabinet and ruin the insulation value of the insulation.

Jamie Hall

Ok. Th "it" refers to the visible moisture saturating the insulation. Sorry I wasn't clear on that. That moisture, as you correctly note, is being condensed in the insulation and comes from the moisture in the air inside the house. When the pipe itself is cold, at some point in the thickness of the insulation the dewpoint of the air in the house is reached, and at that point the moisture will condense.

If the air being drawn in through that pipe is at 0 F, the relative humidity in the house proper will have to be reduced to 24% at 70 F to avoid condensation on the pipe. This is probably not practical -- nor is it particularly desirable.

If it is desired to continue to draw fresh air in through that pipe, then it must be insulated with closed cell foam tightly bonded to the pipe of sufficient thickness to ensure that the surface of the insulation facing the occupied space is at a temperature above the dewpoint of the air in that space (coincidentally, if the interior RH is 50% and the temperature is 70, the dewpoint is also 50 F -- it doesn't always work out that way!)

ChrisJ

mattmia2 said:

This is the reason the switched to foam insulation on refrigerators. With fiberglass if you had the tiniest leak in the outer cabinet the normal moisture in the household air would condense on the cold outer surface of the inner cabinet and ruin the insulation value of the insulation.

As long as the insulation is open to the inside of the cabinet the refrigerator will dehumidify anything that gets in 

My cardboard insulation stays nice and dry even at 88 years old.

Jamie Hall

ChrisJ said:

As long as the insulation is open to the inside of the cabinet the refrigerator will dehumidify anything that gets in 

My cardboard insulation stays nice and dry even at 88 years old.

It may not be as efficient -- but it's surprising (shouldn't be) how often the old boys had things pretty well figured out.

Crissie

"This vent is actually where most , a majority of the latent load is entering the house . If it is not addressed and the incoming air is not dropping the moisture at the coil which it reaches before entering the house , have we solved anything . Just to be fair , Crissie has about a half dozen discussion threads going on about this home . main concern being it made her ill"

Just to clarify. I initially posted because of variations in boiler BTU sizing, then I posted specific questions about sizing, ventilation and this return vent air. My House doesn't make me sick. I am Only ill when the HVAC system runs. Notice I did not post anything with the topic of. 'Help, my house is making me ill.' It is because I know my HVAC system is making me ill and i am replacing it. And .. it started making me ill 4 weeks after this return vent was put in. So for 4 yrs here I lived here and had no issues. I put this fresh air vent in and bam, it started. IMO, this brought humidity into my leaky, dirty 40+ yr old HVAC system and started microbial growth. If I replace it with an HRV / Dehumidifier, I want to make sure it doesn't happen again. This is my reason for picking the brains of all you experts.
This podcast described the issue, it is product oriented but touches exactly on what I am dealing with at about 33 minutes into it. Thanks!! https://youtu.be/4ebBHQyC-JU

mattmia2

Perhaps it is bringing in something from outside that you are allergic to.

Crissie

mattmia2 said:

Perhaps it is bringing in something from outside that you are allergic to.

I don't have any allergies. Work in my yard for hours and do not have any issues. Love fresh air. No congestion or nasal issues at all.

Solid_Fuel_Man

May I ask, why then did you have this outside air intake installed? If all was well before? 

Crissie

Solid_Fuel_Man said:

May I ask, why then did you have this outside air intake installed? If all was well before? 

I needed fresh air in the home. I would leave a window cracked most of the year (still do). It was stuffy, I love fresh air and it is required by code for homes that are tight. All this being said, my HVAC did not make me ill before I had this put in. When they put it in, the reinstalled the furnace to put it on a box. Said it was necessary. Company who did it was acquired by another and the guy I worked with is no longer there.

The high temp here today was 53 degrees. Never had to turn my furnace on.

Jamie Hall

I'm sorry, @Crissie , but I confuse really easily.

Where, exactly, does this problem child pipe empty out? Into the return from the house to the furnace? Or is it actually an outside air intake for the burner, and not connected to the house ventilation system at all?

And -- what else was changed when this duct was installed? I'm thinking that there may have been some other change at the same time? Why was the furnace put on a box?

Perhaps the best thing to do now is to not worry about the dripping insulation. Rather, may I ask you to turn off the little fan or whatever is in that duct and close the intake connection securely? And run it that way for a few days to see how you feel?

Yes, I know that a fresh air intake is required if the house is too tight, for very good reasons, and that will have to be revisited.

But for the moment I would like to go back as much as possible to the state of the system before this duct was installed and see what happens.

I'm a little concerned that the duct may have been installed to provide combustion air, but not done properly.

Crissie

Jamie Hall said:

I'm sorry, @Crissie , but I confuse really easily.

Where, exactly, does this problem child pipe empty out? Into the return from the house to the furnace?
@Jamie Hall This 6 inch duct runs directly into the main return air duct for the furnace. It is bringing fresh air into the HVAC system. It is not at all related to the fresh air for combustion, those (intake and exhaust) are piped through PVC is a completely different location.
The company said the furnace was not installed correctly, it should have ben on a box. The furnace was starved for return air, 4 return ducts in the upper level were not pulling anything. The company also increased the size of the main return duct running into the furnace, it was very small on one a 90 degree angle right by the furnace.
I since tore out the drywall to expose the ducts and found that someone had disconnected the main return duct for the upstairs bedrooms. They left huge holes that were sucking insulation and debris into the system. Somehow, they connected a supply to those upstairs return ducts, they give off a tiny amount of supply air. This entire system is a dangerous mess.
The only other thing I can think of is if they cracked the heat exchanger when they reinstalled it. I recall seeing the guy grab it by the exchanger. I had it checked, no one can tell me for certain. No gases being detected.
Currently I have it off. If it is above 50 degrees I don't need it. I am short at least 4 ducts on the return side, that is why I was still using that fresh air return.
hope this helps to clarify.

Jamie Hall

I'm sorry @Crissie . On looking over all of this, it seems to me that that drippy duct is a relatively minor distraction in a real catastrophe of a heating system -- if it can even be called that.

Clearly there is a lot of work which needs to be done to get it working even remotely correctly, and it would seem that whoever you have had working on it is not really qualified to do the work.

What needs to happen is that someone needs to come in and first, verify that the furnace is working correctly and has not been damaged. Second, they will need to review all the ductwork and make sure it is of adequate size and connected properly (someone connected a supply to the returns? Say what? Insane!). Then they should install -- correctly -- a heat recovery ventilator to provide adequate air changes for the house.

Essentially go back to square one with the system and rebuild it the way it should have been done when the house was built and it was originally installed. Some disasters can be fixed with a patch here and a fiddle there, but from what you have written I have to say that this is not one of them.

Now having said all that... I honestly don't know what to suggest until you can fine a competent outfit to come and do the work.

Crissie

@Jamie Hall That is what I have been in the process of doing for the past 10 weeks, even longer. I am replacing the entire system. The company who did the fresh air intake install was a large HVAC outfit in my area. Neither of us were aware of the return duct issues. The prior owner did the return / supply duct tampering. All of that said, this fresh air duct is wet, I have licensed contractors tell me they are often / typically wet and I wanted to get some input from this group on that, specifically because I don't want to install an HRV/ ERV and have the same problem. Thx.

Jamie Hall

I truly think that we have discussed that fresh air supply duct almost to death. Without closed cell insulation tightly applied to it, yes it will be wet. Your contractors are absolutely correct on that.

ChrisJ

Jamie Hall said:

I truly think that we have discussed that fresh air supply duct almost to death. Without closed cell insulation tightly applied to it, yes it will be wet. Your contractors are absolutely correct on that.

I suppose my biggest issue with this is I have R8 insulation on my A/C ductwork in my attic which hits 130F in the summer. The plastic vapor barrier isn't perfect, it's far from it, but I did my best.

Over all, the ductwork is fairly good at not being a water factory. On average I'd say the temperature difference is about 85 degrees on hot days and the duct work is a solid 30 degrees below the dew point.

I would expect a dew point of no higher than 45F in the winter, otherwise you'll have big issues with windows etc especially if it's actually cold out (0F or lower).

I see no problem with R8 fiberglass and a half way decent vapor barrier on a duct like that. Even if it's below zero, the small amount of condensate which may form should escape through the same holes in the vapor barrier the next day when things warm up.

Jamie Hall

Fiberglas probably will help a lot, @ChrisJ and @Crissie , if it's carefully applied and taped. I'd still rather see closed cell foam...

It's all about dewpoint.