Dehumidifying Energy-Recovery Ventilator (ERV)
OR
Dehumidifying (Supply-Air Only) Ventilator
This article is about Dehumidifying Mechanical Ventilators for HVAC Systems. There are 2 major types. Energy Recover Ventilators That Also Dehumidify In Summer AND Humidify In Winter. After that we discuss mechanical ventilators that supply fresh, dehumidified air (though they don’t exhaust air) we discuss why the latter may make a great add on to homes build since 1990. This information is not limited to DFW, it’s much the same for any newer home built anywhere in the U.S. since 1990.
Al’s Plumbing, Heating & A/C in Plano, Texas provides maintenance & repairs for all brands of Central A/C, Gas & Electric Furnace, and Heat Pumps. Additionally, we sell and install new HVAC Systems from American Standard (same company as Trane), Ameristar (same company as American Standard) and Coleman HVAC (same company as York HVAC).
Al’s also provides full service plumbing maintenance, repairs and replacements for every plumbing component in your home. Al’s sells and installs Rheem Professional Series gas & electric water heaters, and tankless water heaters. Al’s Plumbing, Heating & A/C is near your home in Plano, Allen, and Frisco. We service all homes in southern Collin and Denton Counties with no additional travel charge.
Call Al’s today to discuss any concerns or problems you have with your HVAC System or Plumbing. We will arrange an appointment at your convenience and offer 24/7 Emergency Service.
DFW’s Summer Climate Is Humid, Sub-Tropical
Image Source: Pixabay.com
- DFW’s hot season runs from early June to mid September.
- DFW’s summer climate is best described as Humid Subtropical. This is defined as hot & humid summers, with heat & humidity coming to DFW from Mexico and the Gulf Of Mexico.
- May is the most humid month of the year. The Average Relative Humidity in DFW during May = 70%.
- During May, the average Dew Point in DFW = 61 degrees.
DFW’s Winter Climate Is Inter-Continental
Image Source: Pixabay.com
Image Source: Pixabay.com
- DFW’s cool season runs from late November to late Februrary.
- DFW’s winter is best described as Inter-Continental. This is defined as cold-air masses come southward from Canada and warm-air masses come northward from Mexico & the Gulf Of Mexico. This is why DFW’s winter temperatures are so up & down.
- March is the least humid month of the year. Average Relative Humidity in DFW during March = 64%
- During March, the average Dew Point in DFW = 42 degrees.
- When cold-air masses arrive from Canada, the humidity becomes quite low. The January Dew Point in Ottowa, Canada = 8 degrees. That is desert-dry air.
What Indoor Humidity Level Is Best?
Shown: Humidity Gauge
Image Source: Pixabay.com
According to the Environmental Protection Agency (EPA), Indoor Humidity Levels ideally should be 30-50%. So the average outdoor relative humidity in DFW is higher than what Indoor Air Humidity should be all year long (except during brief periods when cold air-masses come from Canada).
- In DFW, Indoor dehumidification is needed.
- During brief periods, indoor humidification is needed when cold air masses arrive from Canada.
Is My Home’s Humidity Similar Or Higher Than Outdoors?
Image Source: ShutterStock
Why Newer Homes Need Mechanical Ventilation
Click Here To See A 4 Minute Video Explaining Mechanical Ventilation: Why Newer Homes Need Mechanical Ventilation
Image Source: Pixabay.com
- Newer homes can’t exchange enough indoor air with outside air through air leaks in the home (they are built too air-tight).
- If the home was left to ventilate itself, the Indoor Air would become toxic & very humid.
- To ensure acceptable Indoor Air Quality, air must be forced into and / or out of the home.
The Most Common Types Of Mechanical Ventilation Systems
Exhaust-Only Ventilator Fan In Bathroom
Image Souce: ShutterStock
- Exhaust-Only Mechanical Ventilation. Small, continuously running exhaust fans (usually in bathrooms) exhaust stale air & the humidity created. This creates a modest negative pressure that pulls in fresh air into the house either through cracks and air-intake ports. In some cases “make-up air” inlets were built when the home was constructed. Mechanical Exhaust-Only Ventilation is quite common due to its low cost.
- This type of mechanical ventilation is often identified by the presence of 2 exhaust vents in the master bathroom, or one that can’t be shut off. With 2, the owner can turn one on & off. The other one runs all the time.
- The vent that cannot be turned on & off is a mechanical, exhaust-only ventilator. It is placed in the master bathroom because it is the bathroom used in homes w/o children. It is there to remove excess humidity from the home — from the room that will always generate the most humidity. It also ensures the house intakes enough outdoor air to ensure Indoor Air Quality. It is forcing air to leak into the home. Some homes have fresh-air ports, other homes bring air into the home through air-leaks.
- Below Is A Paraphrased Description Of This Type Ventilation System By A Home Builder:
In an exhaust-ventilation system, a fan is used to remove air from the building, creating a slight negative pressure within the building. Typically, a standard bathroom fan is upgraded to one designed for continuous operation at its low speed. It also includes a manual control that allows the fan to run at high speed when desired. Makeup air enters the building either through air leaks OR through one or more passive air vents.
- The down side of exhaust-only ventilation is that the air it’s bringing into the home is the same temperature & humidity level as outdoors. Also, if the air comes through air leaks, some of it travels through exterior walls with insulation that becomes laden with dust over the years. The air coming through exterior walls is fresh, but not clean.
- Supply-Only Mechanical Ventilation. A fan brings in fresh air, forcing stale air out of the home through cracks or intentional air-leakage ports. The fresh air supply can be delivered to 1 location, or connected to the HVAC System that disperses the air. A supply-only ventilation system creates a modest positive pressure.
- This ventilation system is better than exhaust-only ventilation because it beings fresh air into the home directly from outdoors. This avoids outside air being brought through building materials (such as insulation full of dust).
- Below Is A Paraphrased Description Of This Type Ventilation System Used By A Home Builder:
In a supply-ventilation system, a fan is used to blow air into the building. This creates a positive pressure within the building, forcing air to leave the building either through air leaks or through one or more passive vents. The incoming air is controlled, filtered, heated, or cooled before it is dispersed into the home.
Shown: An Energy Recovery Ventilator (ERV)
Click On Image To: See Product, View Details, or Purchase From Amazon.com
- Balanced Ventilation. Superior ventilation is provided through a balanced system. In these systems, separate fans drive air into & out of the house. This system is connected to the HVAC System.
- Balanced Ventilation With Energy Recovery. This system removes the cooling or heating within the air it’s exhausting and uses that thermal-energy to cool or heat incoming air.
- Below Is A Paraphrased Description Of This Type Ventilation System Used By A Home Builder:
In addressing energy efficiency, there are options for recovering heat, coolness, & moisture from exhaust air and use it to condition incoming air. Incoming & outgoing ventilation air is brought into thermal contact by a device that transfers thermal-energy & humidity. In cold weather, the outgoing exhaust air pre-heats incoming outside air. In hot weather, the outgoing exhaust air pre-cools incoming outside air.
Two blowers may be used to drive the air streams, providing balanced ventilation to the home. An Energy-Recovery Ventilator transfers both the moisture & heat / coolness between the incoming & outgoing air. Humidity control is usually accomplished with a rotating wheel with the capacity to absorb & release moisture.
** SOURCE: https://www.buildinggreen.com/blog/6-ways-ventilate-your-home-and-which-best
How The Amount Of Required Ventilation Is Determined
Most states (including Texas) base their Building Codes on the International Residential Code (IRC) The 2018 International Residential Code (IRC) requires ventilation based on the formula below.
1% (of home’s entire indoor air) divided by the square footage of home + (7.5 Cubic Feet Per Minute (cfm) per occupant)
Using This Model — To Ensure Acceptable Indoor Air Quality (IAQ):
- A 2,000 SF home with 8 foot ceilings has 16,000 cubic feet of air inside. 16,000 X 1% = 160 cubic feet air must exchanged with outdoor air each minute.
- Using the formula, a 2,000 square foot home with 4 occupants must exchange 11,400 cubic feet of air per Hour (190 cfm X 60 minutes).
- 75% (3/4) of its interior air must exchange with outdoor air each Hour.
** SOURCE: https://www.energyvanguard.com/blog/update-residential-ventilation-debate
Homes Built (around 1990 & later) Have Mechanical Ventilation.
Some Homes Have An Energy-Recovery Ventilator.
- Exhaust-Only System
- Supply-Only System
- A System that both exhausts & supplies air.
Click Here To See An Energy-Recovery Ventilator: Diagram Of Energy-Recovery Ventilator
Image Source: Pixabay.com
Many ERV’s Have Little Ability To Reduce The Humidity Of Incoming Air
- The upper left corner (of the diagram you see with link above): “Warm Fresh Air From Outside” coming into the ERV.
- The ERV use air conditioned air it is exhausting to cool incoming air.
- In the lower right of the diagram you see: “Fresh Air To Inside (the home) Pre Cooled”.
- The ERV may remove a little of the humidity from incoming air.
- The ERV uses the heated air it is exhausting to warm incoming air.
- The ERV may add a little humidity to incoming air.
Click Here To See A Diagram Of What An HVAC System With ERV Looks Like: HVAC System With ERV
Click Here To See A Photo Of An ERV Installed In An Attic: ERV Installed In Attic
There Are ERV’s Available That Transfer Both Heat & Humidity
Click Here To See A Diagram Of An ERV System Installed: Diagram of ERV System Installed
RenewAir In Madison Wisconsin Makes ERV’s
With A Dehumidfying “Enthalpy Core”.
Click Below To See RenewAir’s ERV That Removes Humidity (in summer) & Add Humidity (in winter) To The Incoming Air **
RenewAire ERV With Enthalpy-Core
Adding A Duhumidifying Supply-Only Mechanical Ventilator
If your home was built with exhaust-only mechanical ventilation, you can improve Indoor Air Quality and reduce indoor humidity level by adding a Dehumidifying Supply-Only Mechanical Ventilator.
With this addition, the two systems will work together to provide fresh, dehumidified air to your home. These two systems have no ability to capture thermal-energy (cool or warm) from the air being exhausted from the home. The only way to do that is with an Energy Recovery Ventilator, or the upgraded ERV that also dehumidifies.
One Dehumidifying Supply-Only Ventilator Is Made By AprilAire. The Model 8191 & 8192 Ventilators with Dehumidification supply dehumidified outdoor air into today’s energy-efficient homes. They can be adjusted to the ideal amount of ventilation needed plus the humidity limit of the incoming air.
NOTE: There are likely other brands of Dehumidifying Supply-One Ventilators. Al’s does not endorse any brand only because we don’t have complete knowledge of all Ventilators available
Click Below To See AprilAire’s 8181 & 8192 Dehumidifying Supply-Only Ventilators:
Aprilaire 8191 & 8192 Dehumidifying Supply-Only Ventilators
These ventilators are connected to an outdoor-air intake and to the return-air side of the HVAC System. While the furnace is running, fresh air will be added to the recirculating air. This ventilator runs as needed. It runs as needed whether the HVAC System is running or not. When the HVAC System is off, you may feel small amounts of air coming from the ducts (which is normal).
The ventilators have High-Temperature Limits that can be set to prevent bringing in outdoor air during the hottest period of the day. The unit compensates for the ventilation time missed (during the heat of the day) by bringing in additional outdoor air during cooler periods of the day. This also ensures that ventilation occurs not less than 1 hour out of 4 hours.
Can’t I Simply Use The Air Conditioning To Dehumidify?
Image Source: ShutterStock
Yes, but running the A/C more, in order to remove more humidity, can cause the house to become too cool and notably increases cooling bills. And, there are times when the a/c is not needed, so outdoor air coming into the house is too humid and there is no way to reduce its humidity.
- If your home is equipped with a Mechanical Ventilation System that also reduces humidity, dehumidified air enters your home. There is nothing you need to do.
- Ventilation-Only Systems are common in new homes. The remove / exhaust enough air from the home to ensure acceptable Indoor Air Quality. They also remove heat in winter, a/c in summer and the air they bring into the home is the same temperature & humidity level as outside.
- If your home has a Ventilation-Only System (it only exhausts air) — you can add a device that provides dehumidified incoming fresh air. With it, outdoor air won’t be drawn through air leaks or open doors / windows.
Al’s Plumbing, Heating & A/C in Plano, Texas provides maintenance & repairs for all brands of Central A/C, Gas & Electric Furnace, and Heat Pumps. Additionally, we sell and install new HVAC Systems from American Standard (same company as Trane), Ameristar (same company as American Standard) and Coleman HVAC (same company as York HVAC).
Al’s also provides full service plumbing maintenance, repairs and replacements for every plumbing component in your home. Al’s sells and installs Rheem Professional Series gas & electric water heaters, and tankless water heaters. Al’s Plumbing, Heating & A/C is near your home in McKinney, Allen, Frisco & Plano. We service all homes in southern Collin and Denton Counties with no additional travel charge.
Call Al’s today to discuss any concerns or problems you have with your HVAC System or Plumbing. We will arrange an appointment at your convenience and offer 24/7 Emergency Service.