Why a Furniture Store Cares About Your Basement Air
We've been delivering furniture, mattresses and appliances around Southeast Michigan since 1994, and a surprising number of the problems we're called about have nothing to do with how something was built. A dresser drawer that suddenly sticks every August. A mattress that comes up from basement storage smelling musty. A wool rug rolled up in the corner of a finished basement that's grown spots on the back. A leather sofa that cracks after its first winter next to a forced-air register. Most of those come down to the air in the house: too wet in summer, too dry in winter.
Michigan is hard on homes this way. Our summers are humid, a lot of our houses have basements that sit below the water table for part of the year, and our heating season dries indoor air out for five months. A dehumidifier and, for many households, an air purifier are two of the cheapest ways to protect everything else you own. They are also two of the most confusing appliances to shop for, because the ratings changed a few years ago and the marketing hasn't caught up. This guide walks through how to size both, what the labels actually mean, and how to store furniture in a basement without ruining it.
What Humidity Should Your Home Be?
Relative humidity (RH) is how much water vapor the air holds compared to the most it could hold at that temperature. The U.S. Environmental Protection Agency recommends keeping indoor relative humidity below 60 percent, and ideally between about 30 and 50 percent, to discourage mold growth. Dust mites, which are one of the most common indoor allergy triggers, also do poorly when humidity stays under about 50 percent.
| Relative Humidity | What Happens | What to Do |
|---|---|---|
| Under 30% | Dry skin, static, wood furniture and floors shrink and can crack; leather dries out | Typical in a heated Michigan house in January. Turn off dehumidifiers upstairs; consider a humidifier. |
| 30%–50% | The comfortable, furniture-friendly range | Target this. Set a dehumidifier to about 45–50%. |
| 50%–60% | Acceptable, but dust mites thrive and drawers may start to swell | Run a dehumidifier during humid stretches. |
| Over 60% | Musty smells, mildew on fabrics and the backs of rugs, mold risk on drywall and stored items | Dehumidify, and look for the source of the water. |
Wood is the reason we care so much. Solid wood takes on and gives off moisture with the seasons, swelling in humid air and shrinking in dry air. A little movement is normal and well-built furniture allows for it. Big swings are what split tabletops, loosen chair joints and make drawers bind. Keeping the house in a steady range is better for furniture than any polish. Our furniture care guide covers the seasonal side of wood care in more detail.
Measure Before You Buy: The $15 Tool
Before you spend a few hundred dollars on a dehumidifier, spend fifteen on a digital hygrometer, a small thermometer-and-humidity display. Put one in the basement and one on the main floor and watch them for a week. You'll learn more than any sales pitch can tell you:
- A basement that reads 65–75% in July needs a dehumidifier. That's very common in Michigan.
- A main floor at 55% with the air conditioning running usually doesn't. Central air removes moisture as it cools, and a separate unit upstairs is often wasted money.
- A house at 25% in February needs the opposite: humidity added, not removed.
Cheap hygrometers can be off by a few points. If two of them disagree, believe the trend more than the exact number. The built-in humidity readout on a dehumidifier is also only a rough guide, because it measures the air right at the machine. A separate hygrometer across the room tells you what the room is actually doing.
What Size Dehumidifier Do You Need?
Dehumidifiers are sold by pints: how many pints of water the unit can pull out of the air in 24 hours under a standard test. That sounds simple. It stopped being simple in 2019.
The 2019 Rating Change
The U.S. Department of Energy changed the dehumidifier test procedure, effective for models sold from 2019 on. The old test ran at 80°F and 60% relative humidity, which is warmer than most basements. The new test runs at 65°F and 60% relative humidity, much closer to real basement conditions. Cooler air gives up its moisture less easily, so the same machine earns a lower pint number under the new test.
The result is that the machine that used to be sold as a "70-pint" dehumidifier is now typically sold as a "50-pint," and the old "50-pint" class is now typically a "35-pint." Nothing got weaker; the label changed. This catches a lot of people replacing an old unit. If your trusty 70-pint machine from 2015 finally dies, the equivalent today is generally a 50-pint model, not a new 70-pint whole-house unit.
| Old Label (Pre-2019 Test) | Typical New Label (2019+ Test) | Common Use |
|---|---|---|
| 30 pint | About 20–22 pint | Bedrooms, closets, small damp rooms |
| 50 pint | About 35 pint | Small or moderately damp basements |
| 70 pint | About 50 pint | Most Michigan basements |
These are typical equivalences, not exact conversions. Compare models using the same standard. Some listings still mention the old number in the fine print, which is fine as long as you know which one you're reading.
Sizing by Space and Dampness
The amount of water you need to remove depends far more on how damp the space is than on its square footage. Use this as a starting point. It reflects typical manufacturer and industry sizing guidance, translated to the current pint ratings:
| Condition | Up to 1,000 sq ft | 1,000–1,500 sq ft | 1,500–2,500 sq ft |
|---|---|---|---|
| Moderately damp Musty in humid weather only | 20–22 pint | 35 pint | 35–50 pint |
| Very damp Always smells musty; damp spots on walls or floor | 35 pint | 50 pint | 50 pint |
| Wet Walls sweat; condensation on pipes; seepage after rain | 50 pint | 50 pint | 50 pint or whole-house |
| Standing water | Fix the water problem first. No portable dehumidifier can keep up with active leaks. | ||
When in doubt, size up. A larger unit running on a humidistat reaches the target and shuts off; an undersized unit runs nonstop, wears out sooner, and never quite gets there. In our experience a 50-pint unit is the right choice for the large majority of full Michigan basements, and the price difference between a 35 and a 50 is usually small.
Dehumidifier Features That Matter
Drainage: Bucket, Hose or Pump
This is the most important practical decision, and the one people regret most.
- Bucket only. In a damp basement in August, a 50-pint unit can fill its bucket once or twice a day. The machine shuts off when the bucket is full, so a weekend away means two days of no dehumidifying. Buckets are fine for a bedroom unit and a poor plan for a basement.
- Gravity hose. Most units have a hose connection. Run a garden hose or the supplied tube to a floor drain. The drain must be lower than the outlet on the unit, and the hose can't kink or rise along the way. Setting the unit on a sturdy stand or a couple of concrete blocks helps.
- Built-in condensate pump. A pump pushes water up and away: into a laundry sink, a washer standpipe, or out a basement window. Pump models cost more and add a part that can fail, but for a basement without a convenient floor drain they're worth it. Check the rated lift height (often around 15 feet) and the hose length. If your laundry is in the basement, our washer and dryer guide covers standpipe heights and drainage too.
Low-Temperature Operation and Auto-Defrost
Standard compressor dehumidifiers work by blowing air over cold coils. When the room itself is cool, those coils can drop below freezing and ice over. In April and May, when Michigan basements often sit in the high 50s and low 60s, that's a real issue. Look for auto-defrost, which pauses the compressor to melt ice, and a stated low operating temperature (many good units are rated down to around 41°F). For an unheated crawl space or garage that's colder still, a desiccant dehumidifier, which uses an absorbent wheel instead of cold coils, handles low temperatures better but uses more electricity.
Other Features Worth Paying For
- Adjustable humidistat with a real number setting (for example, 45%) rather than just "low, medium, high."
- Auto-restart after a power outage. Without it, a summer storm can leave the machine off for days without you knowing.
- A washable air filter that's easy to reach. A clogged filter cuts performance and makes the coils work harder.
- ENERGY STAR certification. Certified dehumidifiers remove the same water with less electricity, and since this appliance may run for months a year, that adds up.
- Casters and a sturdy handle if you'll move it. A full 50-pint unit with water in the bucket weighs more than most people expect.
- Noise. Many units run in the low-to-mid 50s in decibels, about the level of a refrigerator plus a fan. That's fine in an unfinished basement and noticeable in a finished family room or near a bedroom. Look for a stated dB rating and a low fan speed.
Where to Put a Dehumidifier
- Central, with room to breathe. Keep at least 12 inches of open space around the intake and exhaust, more if the manufacturer says so. Jammed into a corner behind boxes, it mostly dries the boxes.
- Near the damp source, but not in standing water. If one wall or corner is the problem, set it within a reasonable distance of that area.
- Close the basement windows while it runs. Running a dehumidifier with windows open in July is trying to dry the outdoors.
- On a level surface, so the bucket's float switch works correctly.
- Plugged directly into a wall outlet, not an extension cord. Most manufacturers say this explicitly.
What Does It Cost to Run?
Here's rough math, with the assumptions spelled out so you can redo it with your own numbers. A 50-pint unit commonly draws somewhere in the range of 450 to 700 watts when the compressor is running. Say 600 watts. In a damp basement in midsummer, set to 50%, the compressor might run around 12 hours a day. That's 7.2 kilowatt-hours a day. At an electricity rate of about 20 cents per kilowatt-hour, roughly what many Michigan households pay all-in, that's about $1.45 a day, or around $40 to $45 in a heavy month.
In spring and fall it runs far less, and in winter it may barely run at all. The number on your bill depends on your rate, the unit's efficiency and how wet your basement is. Two ways to cut it: buy ENERGY STAR, and set the humidistat to 50% rather than 35%. Going below about 45% in a basement costs a lot more electricity for very little extra protection.
A Michigan Year in Your Basement
| Season | What's Going On | What to Do |
|---|---|---|
| Spring (March–May) | Snowmelt and spring rain saturate the soil; seepage and sump activity peak; basements are still cool | Check the sump pump, clean gutters, extend downspouts. Start the dehumidifier; watch for icing on cool days. |
| Summer (June–August) | Warm, humid outdoor air meets cool foundation walls and condenses | Peak dehumidifier season. Keep windows closed and empty or drain continuously. |
| Fall (September–November) | Humidity drops as nights cool; heating starts | Lower the run time. Clean the filter and coils before storage or winter. |
| Winter (December–February) | Furnace air is dry; upstairs often falls to 20–30% | Turn off upstairs dehumidifiers. Leave the basement unit on its humidistat; it will rarely run. Consider a humidifier for wood furniture and floors upstairs. |
Air Purifiers: What They Can and Can't Do
A dehumidifier removes water. An air purifier (also called an air cleaner) removes particles: dust, pollen, pet dander, smoke and some mold spores. They solve different problems, and many homes benefit from both.
The honest answer to "do air purifiers help allergies?" is yes, partly. A properly sized purifier with a true HEPA filter does reduce the airborne particles in a room, and many people with seasonal allergies or pets notice the difference, especially in the bedroom. But the EPA is clear that air cleaners work best alongside controlling the source and ventilating, not instead of them. Heavier allergens like dust mite droppings and much pet dander settle onto floors, bedding and upholstery quickly, where a purifier can't reach them. That's why washing bedding weekly in hot water and vacuuming with a sealed HEPA vacuum matter just as much. Our vacuum guide explains what "sealed system" means and why it matters for allergies.
Most people get the biggest benefit from one purifier in the bedroom, because that's where you spend eight hours with your face a few feet from the air.
How to Size an Air Purifier: CADR and the Two-Thirds Rule
The number to look for is CADR, the Clean Air Delivery Rate, measured in cubic feet per minute. It comes from a test standard run by the Association of Home Appliance Manufacturers (AHAM), and units that have been independently tested carry the AHAM Verifide seal. You'll usually see three CADR numbers: for smoke, dust and pollen. Smoke particles are the smallest and hardest to catch, so the smoke number is the most conservative one to size with.
AHAM's long-standing rule of thumb is simple: the smoke CADR should be at least two-thirds of the room's floor area in square feet, assuming a standard 8-foot ceiling.
| Room Size | Example | Minimum Smoke CADR |
|---|---|---|
| 100 sq ft | Small bedroom, home office | About 67 |
| 150 sq ft | Average bedroom | 100 |
| 250 sq ft | Primary bedroom | About 167 |
| 350 sq ft | Living room | About 233 |
| 500 sq ft | Open living/dining area | About 333 |
For ceilings higher than 8 feet, scale up: a 12-foot vaulted ceiling holds 50% more air, so add about half again to the CADR. For allergies or wildfire smoke days, size up one step anyway, because the purifier will spend most of its time on a quieter, lower fan setting than the one the CADR was measured on.
True HEPA, "HEPA-Type," Carbon and Ozone
True HEPA vs. HEPA-Type
In the United States, True HEPA (high-efficiency particulate air) refers to a filter that captures at least 99.97% of particles at 0.3 microns, the size that's hardest for filters to catch. Larger and smaller particles are captured even more efficiently. Words like "HEPA-type," "HEPA-like," or "99% HEPA" are marketing terms that aren't held to that standard. Some of these filters are decent; some are not much better than a furnace filter. If the listing doesn't say True HEPA or give a specific efficiency at 0.3 microns, assume it isn't.
Activated Carbon for Odors
HEPA filters catch particles but not gases or odors. For cooking smells, pet odors or that basement mustiness, you need activated carbon. The thin, carbon-dusted pre-filter on many budget purifiers does very little; a filter with a meaningful amount of granular carbon does much more. If odors are your main problem, compare the carbon filter's weight or thickness, not just the presence of the word "carbon."
Avoid Ozone
Some devices sold as air purifiers produce ozone on purpose ("ozone generators"), and some ionizers and electronic cleaners produce it as a byproduct. Ozone is a lung irritant, and the EPA warns against using ozone generators in occupied spaces. A useful signal: California requires air cleaners sold there to be certified by the California Air Resources Board (CARB) for low ozone emissions. A CARB-certified unit is a reasonable sign the manufacturer has tested for ozone, even if you live in Michigan. If a purifier has an ionizer you can switch off, our advice is to switch it off.
Filter Costs and Noise: The Long-Term Price
The purifier is a one-time purchase. The filters are a subscription. Before you buy, look up the replacement filter price and the recommended interval:
- HEPA filters typically last 6 to 12 months in normal use and commonly cost $20 to $80 or more. Homes with pets, smokers or wildfire smoke go through them faster.
- Carbon filters often need replacing more often than HEPA, because carbon saturates with odors.
- Washable pre-filters catch hair and lint and protect the expensive filter. Vacuum or rinse them every few weeks.
- Check filter availability. An obscure brand with a hard-to-find filter can turn a bargain purifier into a paperweight.
Over five years, a $120 purifier with $60 filters every six months costs more than a $250 purifier with $35 annual filters. Do that math before you buy.
Noise decides whether you'll actually run it. A purifier on its top setting can be loud enough to talk over; on its lowest setting a good one is a quiet hum, often in the 20s to low 30s of decibels. For the bedroom, look for a stated dB rating on the low setting, a sleep mode, and a way to dim or turn off the display lights. This is exactly why we suggest sizing up: a bigger unit on low cleans as well as a small one on high, and much more quietly.
How to Store Furniture, Mattresses and Rugs in a Basement
The basement is where a lot of furniture goes between homes, between kids, or after an upgrade. We've seen what comes back up. Here's how to keep it in good shape:
- Get it off the concrete. Concrete floors wick moisture even when they look dry. Set furniture, boxes and rolled rugs on pallets, plastic shelving or wood blocks a few inches up, which also protects against a minor flood or a sump failure.
- Keep it off the exterior walls. Foundation walls are the coldest, dampest surfaces in the basement. Leave a few inches of air space behind anything stored against them.
- Don't seal upholstery in plastic for long-term storage. Shrink-wrap and plastic sheeting trap any moisture inside and can lead to mildew. Use breathable cotton furniture covers or old sheets instead. Plastic is fine for a short move, not a season in the basement.
- Mattresses need to breathe too. If a mattress must go in the basement, use a breathable storage bag, keep it off the floor, and store it the way the manufacturer recommends (many say flat, some allow on its side for short periods). Don't stack heavy boxes on it. Our mattress guide explains how different constructions handle moisture and storage.
- Roll rugs, don't fold them. Roll them pile side in, wrap them in breathable fabric or paper, and store them off the floor. Wool rugs in particular can mildew on the back if they sit on damp concrete. More rug care is in our area rug guide.
- Wood furniture: clean and dry it before storing, leave drawers and doors slightly open so air moves, and don't store it right next to the furnace or water heater, where it can dry out and crack.
- Leather should be conditioned before storage and covered with breathable fabric, never plastic.
- Stored refrigerators and freezers should be clean, dry and propped open, or they'll grow mold inside. Our kitchen appliance guide has more on appliance care.
- Run the dehumidifier all summer if you store anything you care about down there. That one habit prevents most of what we see.
When It's More Than Humidity
A musty smell is a warning sign, and a dehumidifier will often clear it up within a few weeks. Visible mold growth is different. The EPA's guidance is that if a moldy area is larger than about 10 square feet, you should consult its mold cleanup guidance and consider a professional. Small areas on hard surfaces can usually be cleaned with detergent and water and dried thoroughly, but upholstered furniture and mattresses with mold growth inside are usually not worth saving. And mold always means moisture: clean it without fixing the moisture source and it comes back. If anyone in the house has asthma, a weakened immune system, or symptoms that seem connected to the basement, talk to a doctor. That's a health question, not an appliance one.
Budget and What You Get
These are rough street-price ranges at the time of writing. Dehumidifiers go on sale heavily in spring and early summer, and purifiers often during allergy season and holiday sales. Our best time to buy guide covers the calendar.
| Product | Typical Price | What to Expect |
|---|---|---|
| 20–22 pint dehumidifier | $150–$230 | Bedrooms, closets, small damp rooms. Usually bucket and gravity hose only. |
| 35 pint dehumidifier | $180–$270 | Smaller or only moderately damp basements. |
| 50 pint dehumidifier | $220–$330 | The right size for most Michigan basements. |
| 50 pint with built-in pump | $260–$400 | Worth it when there's no floor drain near where the unit sits. |
| Whole-house dehumidifier | $1,200–$2,500+ installed | Ducted into the HVAC system; for large or very wet homes. |
| Small-room purifier | $80–$150 | Up to about 150 sq ft. Check filter cost. |
| Bedroom / living room purifier | $150–$350 | The sweet spot. True HEPA, AHAM Verifide, quiet low setting. |
| Large-room purifier | $300–$700+ | Open floor plans, heavy allergies, significant carbon filtration. |
Common Mistakes
- Comparing old and new pint ratings directly. An old 70-pint and a new 50-pint are typically the same class of machine.
- Relying on the bucket in a damp basement and going away for the weekend.
- Draining uphill. A gravity hose only works downhill.
- Setting the humidistat to 35% and paying for it all summer.
- Running it with the windows open.
- Never cleaning the filter on the dehumidifier or the pre-filter on the purifier.
- Buying a "HEPA-type" purifier for allergies.
- Trusting coverage claims instead of the CADR.
- Using an ozone generator in a room people live in.
- Wrapping stored furniture in plastic and leaving it on bare concrete.
- Treating the symptom while gutters overflow against the foundation.
Frequently Asked Questions
What size dehumidifier do I need for my basement?
For most full Michigan basements, a 50-pint dehumidifier under the current Department of Energy rating is the right choice. A small or only moderately damp basement under about 1,000 square feet can manage with a 35-pint unit, and a bedroom or closet with a 20 to 22 pint unit. How damp the space is matters more than its square footage, so size up if the walls sweat or the space always smells musty.
What humidity should a basement be?
The EPA recommends keeping indoor relative humidity below 60 percent, and ideally between about 30 and 50 percent. For a basement, setting a dehumidifier to around 45 to 50 percent protects stored furniture, rugs and mattresses without wasting electricity. Check with a separate digital hygrometer rather than relying only on the dehumidifier's own readout.
Should I run a dehumidifier in the winter in Michigan?
Usually not upstairs. Heated Michigan homes often drop to 20 to 30 percent humidity in winter, which is already too dry. A basement dehumidifier can stay on its humidistat set to about 50 percent; it will simply run very little. If the main floor is very dry, a humidifier helps protect wood furniture and floors.
Is a new 50-pint dehumidifier the same as an old 70-pint?
Typically, yes. In 2019 the Department of Energy changed the test conditions from 80 degrees Fahrenheit to 65 degrees at 60 percent relative humidity. The cooler test produces lower pint ratings, so machines once sold as 70-pint are now generally sold as 50-pint, and old 50-pint models as roughly 35-pint. The machines did not get weaker; the label changed.
What size air purifier do I need for my room?
Use the smoke CADR, or Clean Air Delivery Rate. The AHAM rule of thumb is that the smoke CADR should be at least two-thirds of the room's floor area in square feet, assuming an 8-foot ceiling. A 150 square foot bedroom needs a smoke CADR of at least 100, and a 300 square foot living room at least 200. Size up for higher ceilings, allergies, or so the unit can run quietly on a lower setting.
What is the difference between HEPA and True HEPA?
In the United States, True HEPA means the filter captures at least 99.97 percent of particles at 0.3 microns, the size that is hardest to catch. Terms like HEPA-type, HEPA-like or 99 percent HEPA are marketing language that is not held to that standard. For allergies, choose a True HEPA filter, ideally in a unit with an AHAM Verifide CADR.
Do air purifiers help with allergies?
They help, but they are only part of the answer. A properly sized True HEPA purifier reduces airborne dust, pollen, pet dander and smoke, and many allergy sufferers notice a difference, especially with one in the bedroom. Heavier allergens such as dust mite droppings settle onto bedding and floors, so washing bedding in hot water, vacuuming with a sealed HEPA vacuum and controlling humidity matter just as much. Ask your doctor about allergy treatment.
Six examples to compare
If you want a starting point, these are six product types that fit the advice above. Use the checks in this guide on any listing; the retailer's page has the current price, ratings and reviews.
Confirm the rating uses the 2019+ test, the pump lift height reaches your sink or window, and it has auto-defrost and auto-restart.
Check the smoke CADR is at least two-thirds of your room's square footage, and look up the replacement filter price first.
Buy two: one for the basement and one for the main floor. Watch the trend for a week before choosing a dehumidifier.
Pick by CADR and room square footage, not by the box photo. For living rooms, aim well above the room size rating.
Filter cost is the real running cost. Check the replacement price before you buy the purifier itself.
Michigan basements often need a hose drain. Auto-restart keeps it running after a power blip.
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