Moisture Control in Park Model Tiny Homes
How to keep your home dry, comfortable, and mold-free in any climate
Moisture control is one of the most overlooked parts of tiny home ownership, and one of the most important. Park Model RV Tiny Homes are smaller, tighter spaces, so humidity from showers, cooking, and everyday life can build up quickly. If you do not manage it, you can end up with window condensation, musty smells, and in worst cases, mold.
The good news: moisture control is totally manageable, especially when the home is built right from the start.
Our standard builds use R11 walls and floors and R21 ceilings, which helps with comfort and energy efficiency. But moisture control is not just insulation. It is also ventilation, airflow, and how the home is used day to day.
Below is a simple breakdown of what works best by climate, plus the universal checklist every tiny home owner should follow.
The moisture basics in tiny homes
Moisture comes from three places:
Daily life: Showers, cooking, breathing, wet clothes, pets, and even houseplants.
Outdoor air: Some climates bring in humidity constantly if windows are open or the home has air leaks.
Bulk water: Rain, plumbing leaks, poor drainage, and water intrusion are the fastest way to create serious problems.
If you only remember one thing, remember this: a smaller home needs intentional ventilation.
Moisture control must-haves for every climate
1. Use your bathroom fan every single shower
Run it during the shower and 20 to 30 minutes after. If you want to make life easier, use a fan timer or a humidity-sensing fan.
2. Vent cooking moisture
Boiling water, simmering, and using the stove adds a surprising amount of moisture to the air. Use a vent hood if you have one. If not, use the bath fan and crack a window a bit while cooking.
3. Keep air moving
A tiny home can have dead zones where air gets stale and damp, like behind a bed, inside closets, or under a loft mattress. A small fan on low can prevent a lot of issues.
Quick tips:
Keep furniture slightly off exterior walls
Open closet doors occasionally to air them out
Use a breathable pad under loft mattresses if you live in a damp area
4. Monitor humidity
A simple hygrometer is cheap and removes the guesswork. A solid target range is:
40 to 50% indoor humidity most of the year
In cold winter weather, lower is usually fine
If you are consistently above 55 to 60%, make a change.
5. Avoid ventless gas heaters
Any unvented propane heater adds moisture into the air. If you heat with gas, vented systems are the safer move for moisture and indoor air quality.
Moisture control tips by Pacific Northwest climate
The Pacific Northwest is not one climate. Moisture control looks very different in Portland than it does in the Cascades or on the coast. Below is how we think about it when designing and advising Park Model RV Tiny Homes in this region.
Portland and the I-5 corridor
(Mild temperatures, long wet seasons, limited AC use)
This is the most common setup for NW Tiny Homes customers.
Main risk: Persistent dampness during fall, winter, and spring. Not extreme cold, not extreme heat, just long stretches of cool, wet air that can make a home feel clammy if moisture is not managed.
What works best in Portland-style climates
Consistent bathroom and kitchen ventilation
Run the bath fan during showers and at least 20 to 30 minutes after. Do the same when cooking. This matters more here than anywhere else.Light, steady heat in winter
Keeping the home a stable, comfortable temperature helps prevent condensation on windows and exterior walls. Big temperature swings create moisture issues.Dehumidifier support during rainy stretches
In Portland, a dehumidifier is not always running, but it is extremely useful from October through April, especially during weeks of nonstop rain.Air movement in hidden spaces
Closets, corners, behind beds, and under loft mattresses are common trouble spots. A small fan or occasional airing-out goes a long way.ERV over HRV
For Portland and similar areas, an ERV generally makes more sense. It provides fresh air without over-drying the space or making the home feel cold and drafty.
This climate is all about balance. You are not fighting extreme conditions, you are fighting slow moisture buildup over time.
Mountain and high-elevation Pacific Northwest
(Cascades, eastern mountain towns, cold winters, snow)
Main risk: Condensation during cold weather when indoor humidity meets cold surfaces, especially windows and metal components.
What works best in mountain climates
Strong, consistent ventilation habits
Use bath fans religiously. Moisture from showers builds up fast in cold weather.Stable interior temperature
Avoid letting the home swing between cold nights and warm days. Cold swings lead to condensation.Air sealing matters more here
You want moisture leaving through fans, not leaking into walls or ceilings.Window management
If you see condensation, window upgrades or seasonal interior window film can make a noticeable difference.Humidity awareness
Mountain climates can actually get very dry. If indoor humidity drops below 25 to 30 percent and feels uncomfortable, a small humidifier can help. Just do not overdo it in freezing conditions.
Mountain moisture control is about preventing condensation, not fighting mold year-round.
Coastal and marine Pacific Northwest
(Coast, coastal foothills, fog, salt air, constant moisture)
Main risk: Constant damp air combined with mild temperatures. Homes can feel clammy even when it is not cold, and mold can develop if moisture lingers.
What works best on the coast
A dehumidifier is often essential
Unlike Portland, many coastal homes benefit from running a dehumidifier regularly, sometimes year-round.Consistent ventilation habits
Bathrooms and kitchens need active ventilation, even when it feels cool outside.Airflow everywhere
Behind furniture, inside closets, under beds. Coastal air likes to sit still and cause problems.Plan for travel and downtime
If the home is closed up while you are away, have a moisture plan. That usually means a dehumidifier with a drain line or someone checking it.ERV preferred
Marine climates benefit from ERVs because they reduce the clammy feeling while still providing fresh air.
On the coast, moisture control is not about one big system. It is about consistency and not letting dampness settle in.
A quick Pacific Northwest takeaway
If your Park Model Tiny Home is in the Pacific Northwest:
Vent moisture at the source
Keep indoor temperatures stable
Use a dehumidifier when rain does not let up
Keep air moving in small, hidden spaces
Favor ERV-style ventilation for comfort and balance
Most moisture problems here are slow and quiet, not dramatic. If you stay ahead of them, they never turn into real issues.
Simple moisture control checklist
If you want the short version, do this:
Run bath fan during showers and 20 to 30 minutes after
Vent cooking moisture
Keep indoor humidity around 40 to 50%
Use a dehumidifier if you are frequently above 55 to 60%
Keep furniture slightly away from exterior walls
Air out closets and hidden corners
Fix leaks fast and do not ignore musty smells
Want the full deep-dive guide?
Download the full, detailed breakdown, including ventilation system options, vapor barrier logic, ERV vs HRV, material choices, and premium upgrades by climate
