DFW’s Summer Climate Is Humid, Sub-Tropical

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• 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 

• 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.

• 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.

• 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)

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• 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

Homes Built (around 1990 & later) Have Mechanical Ventilation.

Some Homes Have An Energy-Recovery Ventilator.

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Many ERV’s Have Little Ability To Reduce The Humidity Of Incoming Air

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

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).