Help on ERV Solution for Basement

tilhasbb · Sep 22, 2023

Hello Everyone,

I'm trying to solve 2 issues with 1 solution.
My Radon levels are at the low end but if the house stays closed with no windows open (winter) it does start to go up. I had a team come in and said just open a window once a week for 1hr but the real issue is my house is under a pretty big negative pressure because I have a kitchen exhaust range and 6 bathroom fans with no make up air system. They said from experience if I add a makeup air solution or ERV I'd be good.

My basement as normal basement is humid and has a "musty smell" the temperature is always hovering between 68-73 all year round so the HVAC isn't on enough to remove humidity. So I had installed a dedicated humidifier in the mechanical room which reduced the humidity from 65% to 50% in mechanical room and 60% to 55% in conditioned area.

2 Questions.
1) Do I need TWO ERV systems or can I use one?
2) Which system would you recommend?
Clean Comfort, Fantech, Panasonic, Broan, etc.

BNME8EZ · Sep 22, 2023

ERVs are a nice product but not sure if it will help all of your problems.

Most ERVs are designed for equal flow so X-cfm in X-cfm out X being dependent on the brand and model. It will exchange your air but it will not eliminate the negative pressure in the house unless it can be balanced to overcome all the equipment that creates the negative pressure in the house. With all the items listed that may take a commercial unit rather than a normal residential one.

Having said that if the ERV can be positioned to where the exhaust from the bathroom exhausts can be routed through the ERV so it actually replaces the exhaust fan then you only have to deal with the kitchen hood which if big enough may be done with a fresh air intake on the hood.

May not be ideal but it's one way of improvement. Ideally you would want a slight pressurization of the house, just enough so it is not neutral or negative.

teddy bear · Sep 22, 2023

Your basement space and house may be better served by using make-up air ventilation only. You have many exhaust device that cause negative pressure and will suck in more soil gases. There are dehumidifiers that have Merv 13 air filters that have fans that will bring in exact amounts of fresh air, mix the fresh air with house air, filter the air and and duct the air to basement or multi areas. This best done on a steady trickle bases. This arrangement will dehumidify when ever the indoor %RH is above the desired levels.

Might you have one of these ductable dehumidifiers. There will be a big benefit in keeping the entire home <50%RH and with fresh air.

The whole house dehumidifiers that are designed to do this are the Santa Fe Ultra, Broan, Trane,etc.- with the fresh air option. The benefit from the ERV is minimal
compared to the benefit.

Keep us posted.

Regards Teddy Bear

tilhasbb · Sep 22, 2023

****! One part I forgot to mention which is important.
The house has a basement, first floor and 2nd floor. 3 independent HVAC systems, that's why I didn't look into the whole home humidifier as I'd need 3! 2nd and 1st floor are always around the happy 50% mark. It's the basement that has high humidity.

I was hoping to have an ERV that can create positive pressure and bring in fresh air. I know when I open 1 window in the basement there is no more negative pressure even if I turn on all the exhaust fans and kitchen range to max speed. So I don't think I need much positive airflow for it to eventually balance out.

Also exchanging the air in the basement would reduce the radon levels even lower as an added benefit and reduce the stale air smell and bring in fresh air.

pecmsg · Sep 22, 2023

Install a whole house dehumidifier with outside air hookup.

teddy bear · Sep 22, 2023

ERVs are balance flow. A home with adequate fresh air change will be damp evenings and rainy days when the a/c does not run enough. Most IAQ experts are recommending a fresh air change in 3-5 hours when occupied to purge indoor pollutants and renew oxygen. If you live in a green grass climate with moisture from the fresh air change and occupants requires 2-4 pints of dehumidification per hour during +60^F dew points evenings and rainy days. This will provide IAQ and comfort. These were lessons learned from COVID.

Keep us posted.

Regards Teddy Bear

tilhasbb · Sep 22, 2023

Thank you everyone.
I'm going to call up to get a quotes.

Any recommendation on ERVs? ECM Motor for low power usage and one with bypass feature and dual fans for positive pressure?

pecmsg · Sep 23, 2023

tilhasbb said:
Thank you everyone.
I'm going to call up to get a quotes.

Any recommendation on ERVs? ECM Motor for low power usage and one with bypass feature and dual fans for positive pressure?

How that work?

tilhasbb · Sep 23, 2023

pecmsg said:
How that work?

What this guy did => https://www.youtube.com/watch?v=uui5IzYHb8w

I'm reading about the different Ventilating Dehumidifiers and they can get some fresh air mixed with the stale air to dehumidify but they are not exhausting the stale air.
I need a combo ERV and Dehumidifier.

teddy bear · Sep 23, 2023

Even a foam house has many imperfections that allow air to leak in or out. Most will leak .1-.2 of an air change per hour in a 7 mph wind (considered an average winter wind) and stack effect. This is what keeps occupants of naturally ventilated home barely alive. In calm winds and no stack effect, natural infiltration declines to near zero and are not healthy spaces with accumulated pollutants and low oxygen.

A 2,000 sq.ft. home with 9' ceilings is 18,000 ft^3 of air volume. On a average winter day, these homes will leak 30-60 cfm of fresh air into and out of the inside space. During mild seasons with calm winds, fresh air change declines in response to the natural pressures.

Adding an ERV to these homes increases the air change rate of the home to the natural infiltration rate plus the mechanical balance air flow in/out of the ERV.

Adding a ventilating dehumidifier with make-up air effects in the air change rate of the same house by a lesser amount because the stale air must exfiltrate the home via the natural air leaks in home. The exfiltrating stale air slows or stops infiltration of fresh air depending on the size of the air leaks.

ASHRAE and AM. Medical Assn. suggest a fresh air change in 3-5 hours. An 2,000 sq.ft. home with a fresh change in 4 hours would be 75 cfm of fresh when occupied. Using 75 cfm of make-up Merv 13 filtered fresh air stop all of the unfiltered infiltrating fresh except when indoor exhaust devices (kitchen hood and clothes operated.

During colder winter conditions many home get enough infiltrating fresh air to not require mechanical fresh air. Monitoring the CO2 levels in the home will determine when the home is occupied and infiltrating fresh air is inadequate to purge indoor pollutants and need to renew oxygen.

For most homes, filtered make-up air is the most practical via a ventilating whole house dehumidifier like the Santa Fe Ultra, Broan, Trane, etc..

In defense of the ERV, it is certainly better than no mechanical fresh air ventilation. You will certianly need a whole house to maintain 50%RH during evenings and rainy days to remove the moisture that passes through the unit and moisture from the occupants. We test market a combo ERV and dehumidifier unit for the residential market. There was not enough payback to justify the investment.

Keep us posted.

Regards Teddy Bear

tilhasbb · Sep 24, 2023

teddy bear said:
Even a foam house has many imperfections that allow air to leak in or out. Most will leak .1-.2 of an air change per hour in a 7 mph wind (considered an average winter wind) and stack effect. This is what keeps occupants of naturally ventilated home barely alive. In calm winds and no stack effect, natural infiltration declines to near zero and are not healthy spaces with accumulated pollutants and low oxygen.

A 2,000 sq.ft. home with 9' ceilings is 18,000 ft^3 of air volume. On a average winter day, these homes will leak 30-60 cfm of fresh air into and out of the inside space. During mild seasons with calm winds, fresh air change declines in response to the natural pressures.

Adding an ERV to these homes increases the air change rate of the home to the natural infiltration rate plus the mechanical balance air flow in/out of the ERV.

Adding a ventilating dehumidifier with make-up air effects in the air change rate of the same house by a lesser amount because the stale air must exfiltrate the home via the natural air leaks in home. The exfiltrating stale air slows or stops infiltration of fresh air depending on the size of the air leaks.

ASHRAE and AM. Medical Assn. suggest a fresh air change in 3-5 hours. An 2,000 sq.ft. home with a fresh change in 4 hours would be 75 cfm of fresh when occupied. Using 75 cfm of make-up Merv 13 filtered fresh air stop all of the unfiltered infiltrating fresh except when indoor exhaust devices (kitchen hood and clothes operated.

During colder winter conditions many home get enough infiltrating fresh air to not require mechanical fresh air. Monitoring the CO2 levels in the home will determine when the home is occupied and infiltrating fresh air is inadequate to purge indoor pollutants and need to renew oxygen.

For most homes, filtered make-up air is the most practical via a ventilating whole house dehumidifier like the Santa Fe Ultra, Broan, Trane, etc..

In defense of the ERV, it is certainly better than no mechanical fresh air ventilation. You will certianly need a whole house to maintain 50%RH during evenings and rainy days to remove the moisture that passes through the unit and moisture from the occupants. We test market a combo ERV and dehumidifier unit for the residential market. There was not enough payback to justify the investment.

Keep us posted.

Regards Teddy Bear

Thank you for the detailed explanation.
My situation might be a little different, my 2nd and 1st floor humidity level is always around 50%. It is my basement that is 55-65%. It is always more humid in the basement than outside (except when it's raining) !!!
I'm worried if I install a whole home dehumidifier rule my 2nd and 1st floor will have humidity levels drop below 50%.
Also the ducting for each floor is completely separate and there is no way to link them up. I can potentially link up 1st and 2nd floor as both units are in the attic but the basement is in the mechanical room and there is no open chase. I know because I was trying to run another dedicated outlet last year.

So, back to your recommendation.
I have two "easy" options.
1) ERV for basement
2) Dehumidifier with fresh air inlet.

Note: The basement is enclosed by concrete and only 1 side has windows. So the natural infiltration is significantly reduced compared to 1st and 2nd floor.

1) ERV
Cons and Pros.
Pros = I can take air out of the mechanical room (unconditioned) and basement (conditioned) and add fresh air.
Pro 2 = It might increase the temperature of the basement in summer which will allow the Air Condition to run longer and dehumidify.
Con1 = Potentially I can increase the humidity in summer months but most ERVs have a humidity sensor that turns the ERV off if outdoor humidity is higher than a certain limit.
Con2 = More duct work needed

2) Dehumidifier with fresh air.
Pro = Much more efficient at Reduce humidity
Pro 2 = Will bring in fresh air
Cons = Any positive pressure in basement will have a hard time to escape and might choke the system as it won't be able to pull as much fresh air because of the higher pressure difference
Con2 = Won't exhaust that much stale are and might open windows (back to square 1)

pecmsg · Sep 24, 2023

Basements require a separate system from the main system due to being below grade. Different heat load loss.
Here a small heat pump and dehumidifier works perfectly.

teddy bear · Sep 24, 2023

tilhasbb said:
Thank you for the detailed explanation.
My situation might be a little different, my 2nd and 1st floor humidity level is always around 50%. It is my basement that is 55-65%. It is always more humid in the basement than outside (except when it's raining) !!!

Your main floor is not getting much fresh air because it is always around 50%RH evenings and rainy days. If the upper home was getting significant fresh air during evenings and rainy days, the space would be more humid after 2-3 air changes during the evening and 6 times on a rainy day when the a/c is not running. 50%RH without fresh air change to purge indoor pollutants and renew oxygen is not ideal. You need fresh air to the main floor and supplemental dehumidification to remove the moisture in the need fresh air to maintain 50%RH. The exhaust on the main floors will continue to cause negative pressure in the home. This is another reason to use make-up fresh air ventilation for the kitchen hood/bath fans and clothes drier.

I'm worried if I install a whole home dehumidifier rule my 2nd and 1st floor will have humidity levels drop below 50%.
Also the ducting for each floor is completely separate and there is no way to link them up. I can potentially link up 1st and 2nd floor as both units are in the attic but the basement is in the mechanical room and there is no open chase. I know because I was trying to run another dedicated outlet last year.

I suggest that you get your basement fixed to maintain 50%RH with enough fresh air for the entire home coming in through the dehumidifier.
I would connect the dehumidifier return to a floor grill in the open part of main floor and outdoor air. This would blend fresh air with the main floor air, MERV filter both, dehumidify if needed and supply to the basement furnace for distribution. The door under cut and leakage between floors will allow the extra air from the dehumidifier to circulate back to the main floor. The home is pressurized by the fresh air and migrates up through the home, exiting upper exterior of the home.
This will warm your basement during the summer while dehumidifying the basement. Also, basements like this will provide a 1 ton of free cooling as the air as it is circulated from the main floor through the basement and back up though the entire home. More benefit, the basement will become part of the main floor with steady air recirculation of the main floor air. On more benefit, during winter ventilation, the fresh air will be blended with the main floor air, filtered by the dehu Merv 13 air filter and returned to the main floor via to the basement.

So, back to your recommendation.
I have two "easy" options.
1) ERV for basement
2) Dehumidifier with fresh air inlet.

Note: The basement is enclosed by concrete and only 1 side has windows. So the natural infiltration is significantly reduced compared to 1st and 2nd floor.

1) ERV
Cons and Pros.
Pros = I can take air out of the mechanical room (unconditioned) and basement (conditioned) and add fresh air.

Where is the utility room getting the air from?
Pro 2 = It might increase the temperature of the basement in summer which will allow the Air Condition to run longer and dehumidify.

Your a/c is not going run enough with heat load from the ERV to remove significant moisture??

Con1 = Potentially I can increase the humidity in summer months but most ERVs have a humidity sensor that turns the ERV off if outdoor humidity is higher than a certain limit.

This when you really need fresh air ventilation. Its usually humid outside. Not a good strategy for indoor air quality issues.

Con2 = More duct work needed

2) Dehumidifier with fresh air.
Pro = Much more efficient at Reduce humidity
Pro 2 = Will bring in fresh air
Cons = Any positive pressure in basement will have a hard time to escape and might choke the system as it won't be able to pull as much fresh air because of the higher pressure difference

We do not know the air tightness of the basement to rest of the house. The door undercut can be enlarged. A vent could be put in the door or floor.
Con2 = Won't exhaust that much stale are and might open windows (back to square 1)

That basement is the tightest interior space you have.
You could start with your strategy if you want and change if needed. Or start with mine, and change if needed. We have done the basement recirculation many times without identified failures that we know of???

Keep us posted on what you do and how it works either way, its how we all learn.

Regards Teddy Bear

tilhasbb · Sep 25, 2023

Thank you Teddy Bear!

To answer your question > Where is the utility room getting the air from?
It's not! It's DEAD air inside.... I just enclosed the mechanical/utility room in a yellow box. 3/4 of the walls are concrete and the walls facing the condition space is almost air tight to conditioned space. The assembly from conditioned to mechanical room is Drywall on Vapor Barrier, R13 insulation, Vapor Barrier in a 2x4 stud. The door in a solid door (4hr fire rated) and has gaskets on all 4 sides making a seal.
I've put my phone playing music inside the room and closed the door.. it's sound proof. So I'm pretty sure it's air tight inside there and the smell is stale. I had to put a dedicated dehumidifier (Frigidaire 70) to keep that room at 50%.

So part of the ERV's advantage is I can suck air out of that mechanical room and replace it with fresh air. Have 4 exhausts, 2 in closets (conditioned) and 2 on each side of the mechanical room. Then two fresh air inlets one in the mechanical room and other into the HVAC unit.

tilhasbb · Sep 25, 2023

This picture is more clear to show Unconditioned (Yellow) vs the rest Conditioned

~400sqft (unconditioned) & 650sqft conditioned. Total 1050sqft
Ceiling height 9ft

teddy bear · Sep 25, 2023

tilhasbb said:
Thank you Teddy Bear!

To answer your question > Where is the utility room getting the air from?
It's not! It's DEAD air inside.... I just enclosed the mechanical/utility room in a yellow box. 3/4 of the walls are concrete and the walls facing the condition space is almost air tight to conditioned space. The assembly from conditioned to mechanical room is Drywall on Vapor Barrier, R13 insulation, Vapor Barrier in a 2x4 stud. The door in a solid door (4hr fire rated) and has gaskets on all 4 sides making a seal.
I've put my phone playing music inside the room and closed the door.. it's sound proof. So I'm pretty sure it's air tight inside there and the smell is stale. I had to put a dedicated dehumidifier (Frigidaire 70) to keep that room at 50%.

So part of the ERV's advantage is I can suck air out of that mechanical room and replace it with fresh air. Have 4 exhausts, 2 in closets (conditioned) and 2 on each side of the mechanical room. Then two fresh air inlets one in the mechanical room and other into the HVAC unit.

The concept is that you need a fresh air change throughout your home 3-5 hours when the home is occupied with a steady flow to purge indoor pollutants and renew oxyen. When the wind blows and it is cold outside, the stack effect and +10 mph winds, your home gets this level of ventilation naturally. When winds are calm and stack effect declines, your natural infiltration declines to near zero. Fresh air change is from opening doors, operation of the cloths drier, kitchen hood, and bath fans.

How does sucking air from your utility room and supplying fresh air to the utility room supply a steady flow of filtered fresh air through the home? Also you realize that ventilating your utility room with an ERV will make the room humid like the outside after about 3-4 air changes. ERVs do partially reduce moisture partially, if you exhaust 50%RH air. After one air change, the indoor %RH rises. The moisture transfer decreases to about half. The next air change has the reduction effect again. You need supplemental dehumidification to maintain 50%RH in the space to get the initial effect.

Your a/c will maintain 50%RH during days while there significant sensible loads by removing 2-9 lbs. per hour. Evenings and rainy days you, you need 2-6 lbs. per hour of supplemental dehumidification to maintain 50%RH through out the home. How does the utility room concept do this?

Reducing the negative pressure in this home is important to reduce sucking in soil gas which contains radon. Hope there are no open combustion devices in the home. Using a make-up air ventilation will reduce the negative pressure in the basement.

Keep us posted.

Regards Teddy Bear

tilhasbb · Sep 28, 2023

Sooo, I had an HVAC company come to look at options.

They said if I decide to do a Dehumidifier with Fresh Air for the basement. That would solve the negative pressure since it will equalize and dehumidify the basement. The issue is the utility room won't be connected to that since it's not in the conditioned space. They said you'd need an ERV in the utility room since the room above is my office and the if I do have a Radon issue (They don't have equipment to measure) it will go UP into my office which I'm there 8hrs a day... they said your only other options are Spray Foam the ceiling or make the utility room a conditioned space by adding a vapor barrier and link up your HVAC system to this side... They looked and said well my HVAC is oversized its 1.5TON and the conditioned space is only 650sqft. Soo linking to unconditioned space will bring it up to 1050sqft which would make it balanced...

ehhhh the costs are just going up up up up.

They referred me to a general contractor to get pricing on making the utility room conditioned...

Hmmmmmmmmmmmmmmmmmm

teddy bear · Sep 28, 2023

tilhasbb said:
Sooo, I had an HVAC company come to look at options.

They said if I decide to do a Dehumidifier with Fresh Air for the basement. That would solve the negative pressure since it will equalize and dehumidify the basement. The issue is the utility room won't be connected to that since it's not in the conditioned space. They said you'd need an ERV in the utility room since the room above is my office and the if I do have a Radon issue (They don't have equipment to measure) it will go UP into my office which I'm there 8hrs a day... they said your only other options are Spray Foam the ceiling or make the utility room a conditioned space by adding a vapor barrier and link up your HVAC system to this side... They looked and said well my HVAC is oversized its 1.5TON and the conditioned space is only 650sqft. Soo linking to unconditioned space will bring it up to 1050sqft which would make it balanced...

ehhhh the costs are just going up up up up.

They referred me to a general contractor to get pricing on making the utility room conditioned...

Hmmmmmmmmmmmmmmmmmm

A couple more suggestions.
Using a whole house dehumidifier with a 6" dampered make-up fresh air duct and a a 10" dampered return from the main floor connected to the dehumidifier return, through a Merv 13 air. The dehumidifier supply is connected to the basement a/c supply duct. In addition a 6" duct with a balancing damper from the dehumidifier supply to the utility room. The damper in the 6" supply from the dehumidifier provides enough air to provide a slight positive pressure and humidity control in the utility room. The dehumidifier fan would operate 24/7 to control the radon in the utility room. A dehumidistat would be located in the finished basement and on the main floor to maintain 50% RH.
The dampered 6" dehumidifier supply can be adjusted to get enough fresh/house air to reduce radon and avoid high humidity in the utility area. The most of the dehumidifier supply will circulate the basement and then migrate through the floor and door undercut back to main floor. z

In case the radon is not controlled by this, suggest a radon fan be connected through the utility floor to maintain a strong negative pressure under the basement slab.

All of the suggestions used must be followed by radon and CO2 testing for to confirm the level of radon and fresh air change in the home. Most suggest a fresh air change in 3-5 hours to purge indoor pollutants and renew oxygen. Check local codes for acceptable radon levels.

YOur thoughts. Keep us posted on what you do and how it works.

Regards Teddy Bear

teddy bear · Sep 28, 2023

tilhasbb said:
Sooo, I had an HVAC company come to look at options.

They said if I decide to do a Dehumidifier with Fresh Air for the basement. That would solve the negative pressure since it will equalize and dehumidify the basement. The issue is the utility room won't be connected to that since it's not in the conditioned space. They said you'd need an ERV in the utility room since the room above is my office and the if I do have a Radon issue (They don't have equipment to measure) it will go UP into my office which I'm there 8hrs a day... they said your only other options are Spray Foam the ceiling or make the utility room a conditioned space by adding a vapor barrier and link up your HVAC system to this side... They looked and said well my HVAC is oversized its 1.5TON and the conditioned space is only 650sqft. Soo linking to unconditioned space will bring it up to 1050sqft which would make it balanced...

ehhhh the costs are just going up up up up.

They referred me to a general contractor to get pricing on making the utility room conditioned...

Hmmmmmmmmmmmmmmmmmm

A couple more suggestions.
Using a whole house dehumidifier with a 6" dampered make-up fresh air duct and a a 10" dampered return from the main floor connected to the dehumidifier return, through a Merv 13 air. The dehumidifier supply is connected to the basement a/c supply duct. In addition a 6" duct with a balancing damper from the dehumidifier supply to the utility room. The damper in the 6" supply from the dehumidifier provides enough air to provide a slight positive pressure and humidity control in the utility room. The dehumidifier fan would operate 24/7 to control the radon in the utility room. A dehumidistat would be located in the finished basement and on the main floor to maintain 50% RH.
The dampered 6" dehumidifier supply can be adjusted to get enough fresh/house air to reduce radon and avoid high humidity in the utility area. The most of the dehumidifier supply will circulate the basement and then migrate through the floor and door undercut back to main floor. z

In case the radon is not controlled by this, suggest a radon fan be connected through the utility floor to maintain a strong negative pressure under the basement slab.

All of the suggestions used must be followed by radon and CO2 testing for to confirm the level of radon and fresh air change in the home. Most suggest a fresh air change in 3-5 hours to purge indoor pollutants and renew oxygen. Check local codes for acceptable radon levels.

YOur thoughts. Keep us posted on what you do and how it works.

Regards Teddy Bear

tilhasbb · Sep 28, 2023

Thank you Teddy Bear.

So there is no way to connect main floor to basement. The main floor and 2nd floor ducting all go up to the attic. There is no chase or opening to go from main floor to basement.
With that in mind, what would be your recommendation?

Help on ERV Solution for Basement

tilhasbb

BNME8EZ

teddy bear

tilhasbb

pecmsg

teddy bear

tilhasbb

pecmsg

tilhasbb

teddy bear

tilhasbb

pecmsg

teddy bear

tilhasbb

tilhasbb

teddy bear

tilhasbb

teddy bear

teddy bear

tilhasbb

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