Your AC Is Working
Overtime — and Your
Floors Can Feel It.
Most Northern Virginia homeowners know winter dryness hurts hardwood floors. Far fewer know that summer AC does the same thing — quietly, from the other direction, while the heat index is 98° outside.
Here is the assumption most Northern Virginia homeowners carry into summer: the AC keeps the house cool, and outdoors is humid, so the floors are fine. It's a reasonable assumption. It is also, in a significant number of homes across Fairfax, Loudoun, Prince William, and Arlington Counties, wrong — and the floors are the thing that knows it first.
Air conditioning is a dehumidifier. That's not a side effect — it's a core function of how refrigerant-based cooling works. When your AC removes heat from the air, it also removes moisture. In a Northern Virginia home running AC nearly continuously from June through September, the system can pull indoor relative humidity down to 42–48% — territory that looks fine on a thermostat but is below the 45–55% range that hardwood floors prefer, and measurably below what the wood expects to experience in summer.
The result: summer floor behavior that looks like winter behavior. Slight gaps between planks. A bit more movement than expected. In some cases, an amplification of existing issues that homeowners assumed were seasonal winter problems already resolved. Floors and Beyond fields these calls every June, July, and August across all four counties. Here's the complete picture.
Why AC and Hardwood Floors Are in Tension
The hardwood floor in your home is hygroscopic — it absorbs and releases moisture continuously in response to the surrounding air. In a Northern Virginia summer without AC, the floor would absorb outdoor humidity and expand toward its summer dimension. With AC running continuously, the indoor air is meaningfully drier than the wood's seasonal expectation — and the floor contracts instead of expanding. The degree of contraction depends on how efficiently your specific system dehumidifies, how tight your home's envelope is, and how much outdoor air infiltrates between AC cycles.
The Counterintuitive Reality
"In a well-sealed Northern Virginia home with a high-efficiency HVAC system, summer can actually be harder on hardwood floors than a moderate winter — because the AC's dehumidification is consistent and continuous, while winter humidity varies with heating cycles. We see more AC-related floor questions in July than we see heating-related floor questions in January."
What to Look For — Signs Your AC Is Over-Drying Your Floors
Gaps that appear in June or July — when you'd expect the floor to be at or near its most expanded state — are a signal that indoor humidity is running below the floor's seasonal expectation. Not necessarily alarming, but worth monitoring with a hygrometer. If the gaps are wider than a credit card thickness, something is off.
Squeaking that develops or worsens in summer — when most homeowners expect floors to be at their quietest — often indicates planks contracting slightly under AC dehumidification and moving against each other or subfloor fasteners. If the squeaking appears in summer and goes away in fall when AC runs less, AC-related drying is the likely cause.
The sign that your humidity management is working: the floor feels and sounds the same in June, July, and August as it did in April and May. No new gaps, no new sounds, no visible changes. This is what active humidity monitoring — with a hygrometer and responsive thermostat management — produces.
The opposite problem — and worth distinguishing. If planks near exterior walls or near the perimeter of the room show edge-raised cupping, outdoor humidity is infiltrating from below or around the perimeter while the AC dries the center. This is a two-direction moisture conflict that Floors and Beyond should assess before it progresses.
Northern Virginia Home Types — How AC Affects Each One Differently
Ashburn, Brambleton, and One Loudoun homes built after 2010 typically have high-efficiency HVAC systems in well-sealed building envelopes. The combination produces the most aggressive indoor dehumidification of any home type in Northern Virginia. These systems can pull indoor RH to 40–44% during a Northern Virginia heat wave, well below the hardwood floor's comfort range. LVP handles this better than hardwood — but engineered hardwood in these homes is more susceptible than most homeowners realize. A whole-home humidistat connected to the HVAC system is the most effective solution here.
Fairfax County colonials built in the 1970s and 80s have less airtight building envelopes than new construction. Outdoor humidity infiltrates more readily — partially counteracting the AC's dehumidification effect and keeping indoor summer humidity closer to the floor's target range. The risk here is not AC over-drying but rather the combination of AC dehumidification with localized high-humidity zones (kitchen, bathrooms) creating uneven moisture distribution across the floor. Rooms farthest from AC supply registers are most susceptible.
Northern Virginia's townhome communities — South Riding, Cascades, Countryside, and Reston's established neighborhoods — combine small conditioned square footage with efficient systems and shared walls that affect thermal performance. A townhome AC system cooling 1,400 square feet runs fewer cycles to maintain temperature than the same system in a 2,800 square foot colonial, but each cycle dehumidifies the same volume of air — producing relatively drier indoor conditions per square foot. Townhome owners with hardwood floors should monitor RH in summer specifically, as these buildings are among the most susceptible to AC over-drying.
Arlington County's established neighborhoods have significant housing stock from the 1930s through 1960s — homes with aging or supplemental cooling systems that are less effective at dehumidification than modern HVAC. These homes often run warmer and more humid indoors in summer, keeping floors closer to their natural high-humidity summer state. The floor concern in these homes is more likely summer swelling and minor cupping than AC over-drying. Arlington homeowners with original hardwood and older cooling systems should monitor for summer cupping near exterior walls rather than for dryness-related gaps.
Prince William County's newer construction in Gainesville, Haymarket, and Bristow shares the high-efficiency HVAC characteristics of Loudoun County new builds. Manassas and Woodbridge's older stock is more comparable to Fairfax County's moderate risk profile. Prince William homeowners in newer subdivisions should treat their summer humidity management the same as Loudoun County: monitor with a hygrometer, target 45–55% RH, and consider a whole-home humidistat if the system is running the floor below target.
What to Do — The Summer Humidity Action Plan
You cannot manage summer humidity without measuring it. A digital hygrometer shows real-time indoor relative humidity. Place one in each room with hardwood floors. Check it morning and evening for a week and note where the readings land. If you're consistently below 40% RH in June, your AC is running the floor below its safe range. If you're consistently above 60% RH, the opposite problem is developing. Ten minutes of setup and one week of reading tells you everything.
The hardwood floor's year-round comfort range is 45–55% relative humidity. In summer, the AC typically needs to be managed to stay in this range — not just to maintain temperature. Most modern smart thermostats can display current humidity. If yours doesn't, add a separate hygrometer. If indoor summer RH is consistently below 45%, running the AC slightly less aggressively — raising the setpoint by 2–3 degrees during the hours you're not home — reduces dehumidification and brings humidity closer to target.
When summer AC brings indoor RH below 40% consistently, the floor is experiencing conditions comparable to a dry winter. A whole-home humidifier integrated with the HVAC system is the most effective solution — it adds moisture to the distributed air throughout the house. A standalone console humidifier works for individual rooms with hardwood floors. The goal is not tropical humidity — it is keeping the floor in its 45–55% target range while the AC manages temperature separately.
Northern Virginia's early summer mornings — 5 to 8 AM — are the most comfortable outdoor conditions of the day, with moderate temperatures and humidity that's lower than peak afternoon levels (though still 65–75% RH). Opening windows during these hours, before the heat builds and before the AC needs to run hard, allows natural humidity at a more moderate level to enter the home. This reduces the total dehumidification work the AC does during the day and can meaningfully raise average indoor RH toward the floor's target range.
Summer gaps that appear in June and don't close by late September, or cupping near exterior walls that develops in July, are not self-resolving conditions. These are symptoms of a humidity situation that has exceeded the floor's tolerance. Floors and Beyond assesses the specific conditions — measures the floor, evaluates the humidity history, determines whether the issue is AC over-drying or outdoor humidity infiltration — and recommends the specific correction. Assessing before the condition worsens is always less expensive than waiting.
Humidifier or Dehumidifier? The Summer Question
Summer humidity management for hardwood floors in Northern Virginia homes involves both problems — and the right device depends entirely on what your hygrometer reads.
✚ Add Humidity (Humidifier)
If your high-efficiency AC is pulling indoor summer humidity below 40%, a whole-home humidifier or console humidifier adds moisture back to the conditioned air. This is the less common summer scenario but is increasingly common in Loudoun and Prince William County's newer, tighter-envelope construction. The symptom: summer gaps in hardwood that look like winter gaps. The solution: active humidity addition during peak AC operation.
✗ Remove Humidity (Dehumidifier)
If outdoor humidity infiltrates faster than the AC removes it — common in older Arlington and Fairfax County homes with less airtight envelopes, or in basements where soil moisture adds to the load — indoor summer RH can exceed 60%. Above 60%, wood swells and cupping risk increases. A standalone dehumidifier in the most humid zones (basement, first floor near exterior doors) helps the AC manage the total moisture load and keeps floors in the safe range.
Not sure whether your AC is helping or hurting your floors this summer? Floors and Beyond offers free floor assessments across all four counties.
Book a Free AssessmentFrequently Asked Questions
My hardwood floors had winter gaps that closed in spring — but now new gaps are appearing in June. Is something wrong?
This is the AC over-drying pattern described in this guide. The floor cycled correctly through winter and spring — gaps opened, then closed as expected. Now the summer AC is creating a secondary drying event that the floor is responding to. The gap size matters: if they're similar in width to the winter gaps, you're likely dealing with AC dehumidification that's pulling the floor below its target range. Get a hygrometer reading and see where summer indoor RH is landing. If it's consistently below 42%, the AC is the cause and active humidity management is the solution.
We keep our home at 72°F all summer. Why would the floors be drying out?
Temperature and humidity are separate conditions. Maintaining 72°F tells you nothing about relative humidity — an air conditioning system can maintain 72°F while pulling indoor RH to 38% or maintaining it at 58%, depending on the system's efficiency, the outdoor conditions, and the home's envelope tightness. Temperature setpoint does not protect your floors. Humidity measurement does. This is precisely why a hygrometer is the most important tool a Northern Virginia hardwood floor owner can have — it measures the condition that actually affects the wood.
Is LVP immune to these AC humidity effects?
SPC LVP is significantly more tolerant of humidity variation than solid or engineered hardwood. The stone polymer composite core does not absorb moisture or expand and contract meaningfully in response to humidity changes. That said, LVP is not completely unaffected by extreme conditions — and the adhesive systems and subfloor materials beneath LVP can be affected by sustained low humidity. For practical purposes, LVP in a Northern Virginia home with aggressive AC will not show the gap or movement behavior that hardwood does. This is one of the primary functional advantages of LVP in new Loudoun County construction where high-efficiency HVAC is standard.
Should I turn up the AC thermostat to protect my floors in summer?
Raising the temperature setpoint reduces total AC runtime, which reduces total dehumidification. If your summer indoor RH is consistently below 42%, raising the setpoint by 2–3 degrees (from 72 to 74–75°F) during off-hours or overnight can meaningfully increase indoor humidity toward the floor's target range. This is a reasonable intermediate step before investing in a whole-home humidifier. The trade-off — slightly warmer indoor temperatures during low-occupancy hours — is modest compared to the benefit of keeping floors in their target humidity range through a full Northern Virginia summer.
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