HVAC/Ventilation question

RobMcBee

RobMcBee

Slow n easy when you're not gettin greasy....
Joined
Jan 12, 2009
Location
Fort Mill / Indian Land SC
After having our crawl space done our house is a little stuffy from lack of air movement. I'm wanting to put a fresh air intake on the return side of our air handler. Unfortunately I have to bring it out the same opening as my exhaust vent. The exhaust pipe is a 2" pvc so it wouldn't be hard to separate the two by adding more pipe.


What is the minimum distance needed between the two so I'm not sucking in CO?


Is there anything else that I need to be aware of?



Also air intake will be pre filter

Thanks
 
What's the relative humidity in the house right now?

Intakes need to be 10ft away from exhausts by code.

My guess is your house isn't suffering from high CO2, but instead from high humidity. Unless your house has been built in the last few years and has been tested for conformance with a green building standard, it's probably plenty leaky enough that you don't need outside air. This time of year, we usually (and have over the last few weeks) lowered the setpoint on the A/C so that it runs more frequently during the day. That takes care of the humidity issue, and the house is comfortable again.
 
RH stays around 45-50% in the summer. Unless it's raining then it gets up as high as 55. The crawl space solved a lot of that. It was very high, 70-80%.

The air just seems really stale. We open our windows occasionally , but I had read about adding an intake to just add a little more.
 
Did you get the crawlspace encapsulated?

Whole house ventilation fans are getting common now, they're like a oversized inline bathroom fan that is reliable enough to run 24 hours a day. Often a makeup air intake is added if the house is too airtight.

Any way you slice it, you're going to be throwing away conditioned air to the outside world through air exchange, so theres an energy loss there, but it's worth it if you need better indoor air quality.
 
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Fabrik8 said:
Did you get the crawlspace encapsulated?

Whole house ventilation fans are getting common now, they're like a oversized inline bathroom fan that is reliable enough to run 24 hours a day. Often a makeup air intake is added if the house is too airtight.

Any way you slice it, you're going to be throwing away conditioned air to the outside world through air exchange, so theres an energy loss there, but it's worth it if you need better indoor air quality.
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Yes, we did it a year or so ago. I looked into the air exchange units that are supposed to transfer the energy to the new air coming in. Too expensive for what they are IMO. The way I'm wanting to do it can be done for less than 100$. Using a baffle to regulate the incoming air to less than 10% of the volume. I'm thinking of doing it like pictured below. I'm thinking the wasted energy would be minimal but the overall air quality would be great.....

IMG_1622.JPG
 
To the OP:

Is your crawlspace closed or vented? From reading above I thought it was closed, but that image is of a vented crawlspace.

If it is closed, is there an exhaust fan installed for the crawlspace as outlined in R409 of the NC code?

If the crawlspace Walls are air sealed correctly outlined in the same section of the code, and you have an exhaust fan, the crawlspace should be under negative pressure.

The makeup air entering the first floor of the house should be adequate enough that you don't need a fresh air intake for the Hvac,

Unless you have a practically brand new house with all new weatherstripping and built uber tight.

Has anyone looked for excessive mold or dirt in your duct system or air handler?

My .02, you are doing everything possible to conserve energy and condition the inside of your home and limit the loss through good Windows, good insulation, and a closed crawlspace,

Then to put a fresh air intake on the Hvac seems like a waste of energy, especially when considering the high cost of an energy recovery device.

I would be more concerned with what aspect of your indoor air Qualtiy needs improvement. Ex: too much mold, too much humidity, too little humidity, too much dust, odors etc.
 
Start with the simple stuff. Pop the doors off of the ah or package unit and check for dirty coils and residual water in the pans. Good chance the ductwork is dirty too. For a reputable duct cleaning company to come in and do a full system cleaning won't be cheap but it will help greatly. The company I work for (Carolina Conditions) charges more for a cleaning but we're very thorough. Pull/disassemble/clean blower motor and fan assembly, coils, antimicrobial and of course NADCA mechanical cleaning method.
If you do call Advantaclean for a duct cleaning, insist that Kelvin gets dispatched to it. He trained me in duct cleaning years ago and has traveled the US doing huge projects like I have. Knows his shit.
 
Mac5005 said:
To the OP:

Is your crawlspace closed or vented? From reading above I thought it was closed, but that image is of a vented crawlspace.

If it is closed, is there an exhaust fan installed for the crawlspace as outlined in R409 of the NC code?

If the crawlspace Walls are air sealed correctly outlined in the same section of the code, and you have an exhaust fan, the crawlspace should be under negative pressure.

The makeup air entering the first floor of the house should be adequate enough that you don't need a fresh air intake for the Hvac,

Unless you have a practically brand new house with all new weatherstripping and built uber tight.

Has anyone looked for excessive mold or dirt in your duct system or air handler?

My .02, you are doing everything possible to conserve energy and condition the inside of your home and limit the loss through good Windows, good insulation, and a closed crawlspace,

Then to put a fresh air intake on the Hvac seems like a waste of energy, especially when considering the high cost of an energy recovery device.

I would be more concerned with what aspect of your indoor air Qualtiy needs improvement. Ex: too much mold, too much humidity, too little humidity, too much dust, odors etc.
Click to expand...


It is encapsulated or closed, no fan but we are in SC. I wasn't told we needed one. It's not a new home but I have replaced most of th weather stripping throughout.

XJsavage said:
Start with the simple stuff. Pop the doors off of the ah or package unit and check for dirty coils and residual water in the pans. Good chance the ductwork is dirty too. For a reputable duct cleaning company to come in and do a full system cleaning won't be cheap but it will help greatly. The company I work for (Carolina Conditions) charges more for a cleaning but we're very thorough. Pull/disassemble/clean blower motor and fan assembly, coils, antimicrobial and of course NADCA mechanical cleaning method.
If you do call Advantaclean for a duct cleaning, insist that Kelvin gets dispatched to it. He trained me in duct cleaning years ago and has traveled the US doing huge projects like I have. Knows his shit.
Click to expand...

Can flex ducts be cleaned? I had always heard it can do more damage than good.
 
RobMcBee said:
The air just seems really stale.
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Sounds like you have moisture SOMEwhere in the system.

I can't add anything more to what's already been said. Some great advice/knowledge in here already.

Check the coil/unit first. Then I'd look at the ductwork. If it's sweating in that enclosed crawlspace, that may lead you to the problem.
 
What mechanical means are in place to remove moisture from the crawlspace?

Can you post more details about specifically what has been done, and what currently is in use?

What I know currently.

Your iaq is poor and you have a crawlspace "encapsulation". Which I take that to be a ground vapor barrier that extends up and onto the walls and piers/pillars of the crawlspace with all joints overlapped, fastened, and sealed?

Are the crawlspace walls completely air sealed with insulation board and sealant? This should also include sealing any porch openings and or duct/wire/plumbing penetrations in the exterior wall.

You mentioned exhaust air, I take it the air handler is in the crawlspace and it is a gas furnace that the combustion air & exhaust has been plumbed to the exterior?

Is there a dehumidifier in the crawlspace?

Is there a supply air duct to crawlspace?

Is there a house air duct/damper to crawlspace?


Just trying to get a complete idea of that all you have and what's going on.
 
Yes. 150-175 constant psi, flexible rods and a forward/reverse head and most agitator heads will clean it well without damage.
I'll dig up some before and after pics of recent jobs. It's quite amazing.
 
In my experience a floor system will usually get 10x dirtier than one in the ceiling. Gravity sends all sorts of dirt, debris, liquids and everything else down inside the secondary lines and over the years, this buildup of stuff will collect moisture and grow mold. I've been on plenty of jobs where the homeowner will call us because of a musty smell and as a last resort get a duct cleaning. More often than not, that's the source, either moldy buildup of trash in the secondary lines or an air handler with a clogged drain, dirty coil, dirty fan or microbial growth on the inner lining. All of which is addressed and remedied by a good duct cleaning processional. Never a 100% guarantee, but never a waste of money.

This is a documentation photo I took of a 5 ton split system plenum box. For a system with fresh air return, this is typical for 10 years of buildup. This was in a doctor's office.
IMG_20160916_184144153.jpg

IMG_20160916_220717860.jpg

This type of duct lining is common in both commercial and residential systems and SUCKS to clean. Results are typical.

A lady in Sumter bought a house about 15 years old and had us come do a duct cleaning. Shes a clean freak and was tired of dusting 5 times a day lol. This was a floor system and had all kinds of mold growing in it. Anything organic is a food source for mold, and there was everything from paper dolls to cookie crumbs in it. On this one I used a 5k cfm gas powered negative air machine and shown in pic is a reverse head being used as I pull the heavy debris (what the negative machine had not already made airborn) from inside the trunkline back towards me and the negative machine.
IMG_20160816_144750317.jpg
 
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Yeah..... my ducts probably haven't ever been cleaned and I should look into it. The current system was installed in 2012 (I think) but not sure if they replaced all the ducts. I know some were replaced.

I don't have a media filter in the system. It has an electronic air filter that is supposed to be way better than a media filter. CleanEffects™

@Mac5005 Ill answer these the best I can....

What mechanical means are in place to remove moisture from the crawlspace?
RH dropped after having encapsulation done so we didn't add another dehumidifier. Figured the AC unit was doing it just fine.

Can you post more details about specifically what has been done, and what currently is in use?
Your iaq is poor and you have a crawlspace "encapsulation". Which I take that to be a ground vapor barrier that extends up and onto the walls and piers/pillars of the crawlspace with all joints overlapped, fastened, and sealed?
Yes it is a total encapsulation with 3" foamboard on the walls thick fiber reinforced liner and all penetrations sealed.

You mentioned exhaust air, I take it the air handler is in the crawlspace and it is a gas furnace that the combustion air & exhaust has been plumbed to the exterior? Yes

Is there a dehumidifier in the crawlspace? No

Is there a supply air duct to crawlspace? No

Is there a house air duct/damper to crawlspace? No
 
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XJsavage said:
In my experience a floor system will usually get 10x dirtier than one in the ceiling. Gravity sends all sorts of dirt, debris, liquids and everything else down inside the secondary lines and over the years, this buildup of stuff will collect moisture and grow mold. I've been on plenty of jobs where the homeowner will call us because of a musty smell and as a last resort get a duct cleaning. More often than not, that's the source, either moldy buildup of trash in the secondary lines or an air handler with a clogged drain, dirty coil, dirty fan or microbial growth on the inner lining. All of which is addressed and remedied by a good duct cleaning processional. Never a 100% guarantee, but never a waste of money.

This is a documentation photo I took of a 10 ton split system plenum box. For a supply with fresh air return, this is typical for 10 years of buildup. This was in a doctor's office.
View attachment 230223
View attachment 230224
This type of duct lining is common in both commercial and residential systems and SUCKS to clean. Results are typical.

A lady in Sumter bought a house about 15 years old and had us come do a duct cleaning. Shes a clean freak and was tired of dusting 5 times a day lol. This was a floor system and had all kinds of mold growing in it. Anything organic is a food source for mold, and there was everything from paper dolls to cookie crumbs in it. On this one I used a 5k cfm gas powered negative air machine and shown in pic is a reverse head being used as I pull the heavy debris (what the negative machine had not already made airborn) from inside the trunkline back towards me and the negative machine.
View attachment 230225
Click to expand...

i need my old ducts cleaned,.. any recommendation in raleigh area?
 
Where is your air filter located? don't draw unfiltered air in to your unit. almost no residential units are using outside air. I would have a pm done on your unit to ensure its operating correctly.
 
ok, think I found the source of my problem. Seems I have a small leak in the supply line going to my garage. Water was going underneath the liner where the line penetrated it. The ground seems pretty soft there so god only knows how much water got under there. The humidity never really changed inside the house but the air in the crawl space is stale smelling and I guess it's coming into the house... I'd still like to bring in some more fresh air and I'm gonna have my ducts cleaned
 
RobMcBee said:
ok, think I found the source of my problem. Seems I have a small leak in the supply line going to my garage. Water was going underneath the liner where the line penetrated it. The ground seems pretty soft there so god only knows how much water got under there. The humidity never really changed inside the house but the air in the crawl space is stale smelling and I guess it's coming into the house... I'd still like to bring in some more fresh air and I'm gonna have my ducts cleaned
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Do you not have a dehumidifier in the crawlspace now...?
 
it's weird, it's not your typical moldy mildew smell. I'm guessing that's why I was thinking that it was a fresh air issue. It' just a stale smelling air....



@XJsavage, is Kelvin at Advantaclean Charlotte or Rock Hill? They did our remediation when we had our crawl space done.
 
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Ductz of the Triangle is a great bet. I haven't personally met the owner but my manager has. Ductz is a national franchise that's very strict on cleaning techniques. They stick to the code, so to speak. The HVAC company I work for owns the Ductz Midlands SC franchise.
Home |
 
XJsavage said:
Ductz of the Triangle is a great bet. I haven't personally met the owner but my manager has. Ductz is a national franchise that's very strict on cleaning techniques. They stick to the code, so to speak. The HVAC company I work for owns the Ductz Midlands SC franchise.
Home |
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Mad thanks from over here also. Just purchased a renovation project in Durham and this is on the list of things to do...
 
RobMcBee said:
it's weird, it's not your typical moldy mildew smell. I'm guessing that's why I was thinking that it was a fresh air issue. It' just a stale smelling air....



@XJsavage, is Kelvin at Advantaclean Charlotte or Rock Hill? They did our remediation when we had our crawl space done.
Click to expand...

Kelvin in at the Huntersville Nc corporate office.
 
XJsavage said:
Ductz of the Triangle is a great bet. I haven't personally met the owner but my manager has. Ductz is a national franchise that's very strict on cleaning techniques. They stick to the code, so to speak. The HVAC company I work for owns the Ductz Midlands SC franchise.
Home |
Click to expand...

bad news they closed down..
 
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