How to Mitigate Moisture Issues in a Tiny Home

All houses deal with temperature fluctuations throughout the day and each passing season as temperatures rise and fall. Tiny houses are no exception and although they are built like a house on a foundation and far more insulated than recreational vehicles or van/bus conversions, they still face their own challenges as the cold sets in for winter. 


Let’s begin from the bottom up. A tiny house on wheels (THOW) is the distinguishing factor from a little house on a foundation and needs to be addressed accordingly when the tiny house is built. This also goes for van or bus conversions since they all have a steel subfloor frame/chassis.

Often the floor of these tiny homes is the coldest part of the building, and a great deal of heat can be lost through the subfloor. It also means cold toes, which isn’t the most comfortable.

A tiny house that is secured to a trailer sits up off the ground and therefore cannot benefit from the thermal mass of the ground itself. The space under the trailer can range roughly from about 15”-24” inches depending on the style of trailer and can be higher if it’s lifted off the wheels and axles. This creates a cold exposed space under the home where the house connects to the steel beams of the trailer. Metal is a fantastic conductor of temperature and therefore moves that cold temperature right into the floor and up the walls of the tiny home.

Thermal bridging through trailer and subfloor

In the planning and building stage it’s important to address that temperature transfer (thermal bridging) through the subfloor by building the home up off the steel with wood and insulation. The steel wheel wells must also be insulated significantly as they project into the living space of the home. It can be challenging with tiny houses because they must adhere to height restrictions, so we do the best we can. Tiny houses without lofts can build this way more effectively because they aren’t significantly inconvenienced by eliminating interior headspace. 

Additionally, applying an insulative skirt around the tiny house trailer and up partially to cover where the walls meet the trailer can make a huge difference. This is because it keeps cold air and wind from entering the area below the tiny house, and helps to maintain a slightly warmer temperature underneath at all times. 

If the tiny home is in a cold climate and the potential for thermal bridging isn’t addressed in the design phase of the build, then slippers will be your favorite item of warmth. And, unfortunately your home may suffer from excessive condensation inside where humidity laden air is drawn to collect on cold surfaces. 

Non-insulated wheel wells

Windows and Doors 

Make sure that the seals on windows and doors are fully intact, which will insure that they don’t leak air and moisture into the home. This can be a main factor for condensation on the inside when it’s cold outside. Often these seals can be easy to replace before the temperature drops.

However, building an airtight house in the first place will reduce areas where air and moisture can come in and out without your permission. These places of air penetration are also non-filtered and can be bad for our health if it carries dust mites, mold spores, or other allergens with it. 


We cook, bathe, and breath inside a tiny space and a great deal of moisture is produced. When this moisture has nowhere to escape, it collects on the cold surfaces within the home. These are typically on the windows and doors, on the floor, or in cabinets and under built-in furniture where air flow and heat has trouble reaching. Once the moisture condenses, it will be absorbed by whatever will take it on. If it doesn’t have the opportunity to dry out then it will begin to grow mildew and mold. 

Yes, reducing interior levels of humidity is helpful but condensation at some level is basically inevitable in a tiny home and should not be a surprise as you see it creep throughout your house in your first winter. 

Addressing moisture management during the building stage is ideal, and installing a heat recovery ventilation unit can help to refresh and filter the air. Adding a dehumidifier preemptively can make a huge difference along with a humidity sensor that will keep you in the know of where your humidity levels are at.

Visible condensation from cold trailer beams right under subfloor

What to Do if I have Excessive Moisture Now? 

If you are currently experience severe moisture issues like the homes in the pictures below, then get a dehumidifier asap, address your ventilation and alter accordingly, create airflow in storage areas, skirt your home with something insulative like straw bales in a dry climate or wood/mineral wool boards, use loose bowls of silica around your house that will absorb moisture and can be dried out and reused, clean mold/mildew with warm soapy water and then add vinegar to prevent future growth.

Each winter I offer consulting to help combat these moisture issue in tiny houses all over. If you would like to set up a time to chat please reach out because there are ways to keep you and your home healthy throughout each passing year. 

Mildew in built-in storage

Written by Isabelle Nagel-Brice, founder of A Tiny Good Thing and a Sustainable Homes Professional

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7 thoughts on “How to Mitigate Moisture Issues in a Tiny Home

  1. Reply
    Susan Pabst
    October 15, 2021 at 1:23 pm

    I would like to know how all this applies to a tiny house in Florida weather. I am planning a tiny home at some point in the future and you seem to be the expert in ventillation and condensation, etc. I will be on a foundation. I really enjoy listening to you and all your expert and intricate knowledge!!

    • Reply
      October 18, 2021 at 3:29 pm

      Hi Susan,
      Thanks for the comment! I offer a free 15 minute consult and would love to discuss your project.
      Please schedule on here or send me an email at to schedule.

  2. Reply
    Jamie Cook
    January 14, 2022 at 7:56 pm

    I am building a tiny camper on a brand new trailer from Tractor supply! I was going to remove the pressure treated planks and replace with pressure treated ply, a sheet of foam board inside a 2×2 frame with another sheet of ply on top. Would I be better off building over the top of the plank floor that’s already there?

    • Reply
      January 14, 2022 at 8:48 pm

      Hi Jamie,
      Please email me at to discuss further. I also offer free 15 minute initial consults if you would like to chat about your project. It’s important to look at the build as a whole and incorporate building science (address thermal bridging, air tightness, insulation, ventilation etc.) and high performance materials throughout. The subfloor is key, but isn’t the only factor to consider.
      Thanks and looking forward to speaking,

  3. Reply
    December 21, 2022 at 9:15 pm

    Thank you SO much for this great article! After years of wanting a tiny house, I bought one from Escape Traveler last February. It is currently located in Vermont. Just this month, I found some condensation hidden along my closet floor, and under my couch. Areas that were not getting proper airflow. I am hoping the dehumidifier that I ordered will solve this issue, I immediately added a fan, and it’s been helping the under the couch issue. I’m so glad you wrote this article, I didn’t think of silica, great idea!

  4. Reply
    June 11, 2023 at 8:24 am

    Is it important to put polystyrene in ceiling and walls with other insulation too in a marine steel tiny house build to help stop condensation?

    • Reply
      August 7, 2023 at 10:34 pm

      Hi Sandie, no that would likely cause more issues… It could trap moisture and cause rusting out and an opportunity for mold growth.

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