Winter Utility Guide for Tiny Houses, Part 3: Insulation, Condensation, Humidity, Mold, and Wood Stoves

Are you ready for a tiny house but unsure of how or if they can withstand our New England winters? The following guide will familiarize you with all the challenges and choices you will face as you plan and build your perfect tiny house with special considerations for our harsh northern climate.

There are three major considerations: utilities, water, and warmth. This is part three of a three-part series on winter utilities, maintenance, and upkeep.

Part 1: Maintenance, Propane, and Electricity
Part 2: Fresh Water Access, Gray Water Disposal, and Blackwater Disposal
Part 3: Insulation, Humidity, Condensation, Mold, and Wood Stoves

Tl;dr? Building your dream tiny house is possible with the right building techniques, materials, budget, and appliances and of course, the right attitude!

People often ask me if tiny houses can withstand our New England winters and the answer is: Yes! We have clients in Maine and Vermont who report that they stay cozy and warm in their tiny houses throughout the winter. As long as your house is built well with the proper materials and the proper heating system, your tiny house will be a wonderful little pocket of warmth even in the darkest of winter nights - and your small heating bills may be another ray of sunshine!

The number one most important piece of advice I can give you about tiny houses in the winter is to not skimp on important investments like insulation, new double pane windows, mold and humidity abatement measures, and water resistant building materials where possible. Building your home using state of the art techniques and materials will ensure that your home is as efficient as it can possibly be, which is great for the environment, your wallet, and your tiny house investment.

Here’s what you need to know about prepping your house to stand up to cold temperatures:

Insulation

For New England climates, it is highly recommended to build your tiny home out of new materials with adequate insulation and that your house is not able to retain moisture which can lead to mold growth.

Tiny House Crafters uses the ZIP sheathing system for the exterior sheathing on the roof and walls, sealed with ZIP tape. The ZIP system has an integrated vapor and water barrier so there is no need to apply traditional house wrap. Between the siding and the ZIP we use a perforated rain screen which provides space and drainage for any moisture that gets stuck behind the siding. This allows the materials to dry out as fast as possible.

We highly recommend closed-cell spray foam as insulation. Not only does it have an R-value of around 5-6 per inch, but it also seals all air gaps and does not allow for moisture retention. It acts as a vapor barrier so there is no need for any interior membrane between the insulation and the interior cladding. There is controversy around spray foam insulation for its dangerous off-gassing of aldehydes and volatile organic compounds (VOCs). It’s true that installing spray foam releases fumes unsavory for our health and the atmosphere and some sensitive individuals do report issues from living in a spray foamed house because of possible latent off-gassing even after the foam has cured. This may be a good enough reason for not using spray foam and should be considered before applying. However, spray foam is the top tier for insulation in the industry and works extremely well in tiny houses. We have clients with spray foam insulation that are able to use their heating devices at low settings throughout winters in Vermont and Maine.

In comparison, extruded fiberglass, mineral wool, or other fibrous insulation has the ability to soak up and hold onto moisture like a sponge. If the insulation is unable to dry out - because of constant humidity, missing or inappropriately applied vapor barrier, or otherwise - then the wet insulation material will lead to mold growth. Not having to worry about your insulation absorbing moisture from condensation is another added bonus of spray foam.

Need spray foam work done in New England? We love working with Vermont local, VFI, Inc. Give them a call for your spray foam and energy consultations.

Humidity, Condensation, and Mold

I sometimes like to joke that the first thing you should consider when designing your tiny house is the venting! But joking aside, while venting may seem like a boring part of the process, proper ventilation and humidity control is no laughing matter. Tiny houses can be extremely susceptible to mold, especially in our wet summers and cold winter climate in New England. In the summer, we combat moisture infiltrating from the outside in and in the winter we worry about moisture getting from the inside out. Venting is extremely important and serious business.

It’s simple to mitigate rain and snow melt from penetrating your tiny home by making sure your roof is tightly sealed and there is adequate drainage between the exterior siding and exterior sheathing (use a rainscreen to ensure this). Parking your house on high ground and in a sunny location away from trees are also great ways to keep your house dry and happy.

In the summer, open windows, a ceiling fan, and a consistent temperature gradient inside and out allow us to vent and circulate air without even realizing it. In the winter, when we shut the windows and batten down the hatches, we face a different kind of moisture problem. Inside the house, we are running our propane heater at the same time as we are taking a hot shower; we are enjoying a lively conversation and a hot bowl of soup with our friends while our dogs sleep in the loft; we are coming in from a romp in the snow with a heap of wet, soggy gear. What do all these activities have in common? Moisture! Yes, even propane combustion devices create moisture, just like we do when we breathe.

Imagine your tiny house in your typical winter snowscape: there is snow up to the doorstep and a warm glow coming from the windows. Unlike in traditional houses, tiny houses do not have attics to act as buffers between the warm inside and cold outside. The comfortable interior of your house is separated by mere inches from the often below zero temps outside! And when the humid air rises up and meets the cold metal roof, for example, it cools rapidly and releases its moisture, creating condensation inside the house. The condensation can seep into your insulation (if you aren’t using spray foam) and soft framing members. Consistently wet building materials are breeding grounds for mold, which may not be noticed until it’s too late. Moldy building materials are a health hazard and can undermine structural qualities of your home and cause permanent damage in less than a year.  

By their own nature, tiny houses in New England should be tightly sealed and insulated. This ensures that the home can be heated efficiently. But it also causes problems because it becomes a sealed envelope that prevents the house and it’s materials from breathing properly. “Breathing?” you might ask. Yes! Houses need to breathe just like humans do and it’s important to both parties to have a house that breathes well. The house breaths by swapping stale air with fresh air and allowing materials to dry out, but sealing up your house with super-efficient spray foam will hinder the process… but you need the spray foam to stay warm and minimize air gaps! What to do?

Vent! Each appliance that uses propane combustion should have its own vent. At the minimum, that should include the propane oven, water heater, and heater. These are vented for safety concerns and because propane combustion also produces water vapor as a byproduct.

Installing an Energy Recovery Ventilator (ERV) Unit in your tiny house is highly recommended and nearly mandatory in New England climates. An ERV freshens the humid interior air that rises to the top of the tiny house by absorbing the heat from the air into its ceramic core on its way out and then blowing fresh air back into the house that is heated by the ceramic core so there is close to no thermal loss. Install your ERV in the highest point of your house so it can properly cycle humid air for fresh air.

Truthfully, there is nothing we can do that will totally eliminate possible condensation and mold in tiny houses in New England, which is why it’s great to be aware and vigilant of these issues from the start. Help your house out by setting it up to be as dry as possible by parking it in a sunny location and properly venting it during the winter. If you notice excess condensation forming in your tiny house, it’s important to remediate the issue before it becomes a larger problem.

Wood Heat

Right about now, you may want to ask me if you can install a wood stove in your tiny house. It’s a very popular request and it makes a lot of sense, especially if you live in forested New England, in that you have local access to your resource and wood heat is very drying, which is great for our possibly damp houses, right? And of course, the answer is yes! Just make sure you have a big enough cushion for it in the budget and in your mindset, as it is a luxury and a risk.

You can have a wood stove in your tiny house, but there are a few reasons why you might not want one.

  1. Wood stoves make a tiny house harder to insure. You may want to check with your insurance provider before you commit to your design.

  2. Wood stoves need a lot of clearance, so they take up more of a footprint beyond the size of the unit. There will need to be a space for wood storage, inside and out, so be sure to design that in and make sure that it is permitted in your parking spot to have an additional footprint for wood storage.

  3. The wood stove cannot be your only source of heat. Small stoves will not stay lit for as long as large wood stoves and will lose heat shortly after the fire goes out, so you won’t be able to leave the house for long periods if you constantly need to be stoking the fire. You will need a backup source. Electrical will work, although it is susceptible to power outages which can be tricky if you are away from your home during a storm. Propane is also an option. However, if you have an adequate propane heat source, do you really need a wood stove as well? See Part 1 for more information about backup power.

  4. Wood stoves can be a safety hazard, especially if you have children or pets. If you are using a wood stove, your house will be very dry. This is great for the building materials, but also increases the risk of fire. Make sure you are using an appropriately sized stove for the space and that you are 100% confident with the placement of your wood stove and the materials surrounding it. Consider adding a second egress to your tiny house layout in case of emergencies. Clutter can encroach on the stove and make it unsafe. Storing books or fabric or other flammable materials near the stove is always a bad idea.

  5. New wood stoves are expensive, sometimes prohibitively so. Make sure you do your research so you know you are getting the right stove for your situation. It is possible to install a second-hand wood stove, but make sure you are using the right size stove and that it is in good condition. The perfect wood stove for you might be hard to find at the right price when you are ready to build your house, so I recommend you start looking soon to see what’s out there!

When consulting with clients, I often recommend away from installing a wood stove in their tiny home, but I know that a big part of the allure of the tiny house movement is to allow space to dream for these rustic inclinations. And while we all might love wood stoves, know that it won’t necessarily simplify your utility needs. However, it is not out of the question to have one if you are willing to contend with the above responsibilities. Going tiny is all about making sacrifices and room for the important things.

Hopefully, this guide has gotten you thinking about your winter tiny house needs. Make sure your house is safely heated by ensuring you have adequate backup power in case of emergencies. Understand that if you need to create off-grid systems for your tiny house, that you will need to be willing to be very hands-on in order to provide proper maintenance and monitoring. Don’t forget to plan for solid venting for mold and humidity abatement. Make sure you discuss how you will be using your tiny house in the winter with your tiny house designer or builder.

It’s up to you to make sure your house is ready to survive our harsh winters. There are lots and lots of resources and tiny house experiences on the internet that deal with winterizing and off-grid system, so do your research to figure out what system will work best for you and your chosen climate.

Stay warm and dry out there, friends!

Ready for more on winter utilities, check out Part 1 (Maintenance, Propane, and Electricity) and Part 2 (Fresh Water, Gray Water, and Blackwater)!

Contact me if you have further questions or concerns about winter utilities.