Tiny House Roof Insulation – All You Need to Know

Proper insulation is critical for a tiny home, but figuring out the best way to insulate it can be challenging.

The best insulation for one tiny house isn’t necessarily the best for another, as necessities vary with different builds and lifestyles.

You want materials that will keep your house’s internal climate stable without taking up too much of your tiny space, all while ensuring your installation lasts; and what material fits best for your life really depends on the climate where your tiny house resides. 

We’re here to help you with all your tiny house roof insulation questions.

This article covers the best insulation materials for tiny house roofs, how you can install your own insulation and what the expected costs will be. Let’s go.

Are tiny house roofs well insulated?

Tiny homes have the capacity to be well insulated, it all depends on the R-value of the materials you use and the type of job you do during installation.

R-value is the rating system that’s used to grade insulation products.

The r-value is a way to measure the efficacy of the tiny house roof materials in preventing heat flow and the material’s thermal resistance. The higher the number, the more insulated your home will be.

You can determine a material’s r-value by dividing the thickness of the insulation material by its thermal conductivity.

For example, a classic tiny house roof insulation material such as polyurethane foam is usually around an R-value of 3.4 per inch whereas fiberglass typically has an R-value of 2.5 per inch.

While this means that polyurethane is better at preventing heat flow than fiberglass, a lower r-value shouldn’t always keep you away from selecting those materials.

You can stack them to create a heat flow barrier which is sometimes stronger and less expensive than relying on one layer of thicker material alone. 

What is the best insulator for a tiny house roof?

While the debate about what the best insulator for a tiny house is has been ongoing, the material favored by most tiny home experts is fiberglass.

That being said, it’s important to take into consideration the following factors when choosing your tiny house roof insulation materials:

Climate – how thick your insulation should be is heavily dependent on the climate. For instance, if your tiny house is in a cold, wet climate, you may want to opt for something thicker than the industry-favored fiberglass, like rock wool. If you opt to put your tiny house on wheels, think about the different environments and climates your house will be in, less may be more in this case. 

Allergens – many tiny house roof insulation materials can elicit allergies, it’s important to be aware of any allergies you may have and any allergies the material may expose before installation. 

Cost – the cost of insulation can get hefty, depending on the material and your experience level. It can also affect the thickness of your tiny house roof. The chemicals used on insulation materials are hazardous, for example, direct exposure to fiberglass can result in skin rashes and eye irritation. You’ll need to take into account the cost of protective gear for you and whoever is helping to install your insulation or an installation team. 

Different types of tiny house roof insulation

Fiberglass

As we said about, fiberglass is favored amongst tiny house builders.

Fiberglass is made by heating a combination of sand and glass at an extremely high temperature. The mixture turns into small, scratch balls similar in texture to cotton balls.

Fiberglass is very easy to use due to how lightweight of material and inexpensive it is.

However, fiberglass is more prone to mold, so most would agree if you decide on fiberglass you should install a vapor barrier.

This insulation can easily irritate the eyes and skins so it’s extremely important to wear protective gear during installation and ensure none of the insulation is exposed in your tiny home. 

Rock Wool

Great for cold climates, rock wool is a material composed of natural basalt rocks.

The basalt rocks are heated at high temperatures and create fibers when melted down that are perfect for insulation.

This material is environmentally sustainable, flame-retardant, and does not attract rodents and/or insects.

However, it is heavy and any exposure to water will ruin this insulation.

This material is also irritating towards eyes and skins, so protective gear is necessary for handling it. 

Spray Foam

The most commonly used spray foam is polyurethane spray foam, which is a high-density closed-cell foam that seals tight the walls and roof.

With an R-value of R-20, this insulation will keep your tiny house safe from the elements, but the installation of this foam requires expertise and extra caution due to the chemical makeup of the material.

Overall it can be quite pricey. 

How do you insulate a tiny house roof?

Installing the insulation on your roof correctly is arguably one of the most important parts of keeping your tiny house warm, as the roof is a major location for heat loss.

Because of this, codes will typically require an insulation thickness R-30 for tiny house roofs.

While proper insulation is of the utmost importance for a safe and comfortable living environment, with the right tools and instructions nearly anyone can learn to insulate a tiny house properly.

It’s also important to allow for tiny house roof ventilation at the same time as insulation.

Below is a list of materials and tools needed, as well as a step-by-step guide on how to insulate your tiny house roof using fiberglass. 

Equipment

Recommended Tools/Equipment: 

• Safety Goggles and/or dust mask
• Utility Gloves 
• Long-sleeved shirt
• Utility Knife 
• Screwdriver 
• Straightedge yardstick
• Tape measure 
• Stapling gun and extra staples
• Caulk Gun 

Step 1: Prepare the Insulation

Fiberglass insulation comes in large rolls, known as batts.

Determine the length and width needed for your roof framing by measuring the roof’s cavity structures.

Cut the insulation a few millimeters larger than your measurement.

Be sure to be wearing proper eye and skin protection as stated previously, fiberglass is known to be irritating. 

Step 2: Install Soffit Baffles

One of the most common mistakes people make when installing their own tiny house roof insulation is accidentally covering their ventilation systems.

By installing soffit baffles you’ll be able to keep the soffit vents open and allow proper airflow underneath your insulation. 

Step 3: Lay Out Insulation 

• Cavities – Beginning laying the batts along with your roofing, starting from the outside of your attic/roof space to the center. Staple your insulation slats into the roof cavities and cut any excess insulation off with your utility knife. 
• Electrical wires and lighting – There’s a chance your tiny house will have electrical wires of recessed lighting fixtures to work around while insulating the roof. For lighting, keep insulation at least 1inch/25mm away from the lighting fixture or recessed lighting post. For wires, it’s best to never bash or press down harshly on wires, make sure the insulation is resting upon the wires not adding any extra pressure. Fiberglass isn’t combustible on its own, but exposure to faulty electrical wires or an extra hot light feature could encourage a fire. 
• Tight corners and obstacles – If you run into any pipes, tight corners, or cross-bares, simply cut a notch in the fiberglass and keep going. Don’t compress or squeeze the fiberglass to fit into spaces, as it loses its insulation value the more your press into it. 

Step 4: Vapor Barrier

The vapor barrier is plastic material that is laid against your tiny house roof insulation, either before or after depending on the climate you’re in.

In a warmer climate, it’s suggested you install the vapor barrier prior to installing your insulation, so that your vapor barrier is on the outside between your roofing material and the insulation.

If you live in a colder climate it’s best to install the vapor barrier at the end of your insulation installation, so that it lays between the fiberglass and your ceiling materials.

This is because, in colder climates, there’s much more heating going on inside the tiny house, which means the moisture build-up is going to be coming from the inside of the house more so than outside; and vice versa for warmer climates.

If you have questions about what would be best for your climate, reach out to an insulation specialist.

How much does it cost to insulate a tiny house roof?

While costs vary, the average cost to insulate a tiny house roof is around $200.

This is based on a full DIY estimate, assuming you use basic materials such as fiberglass. If you were to go for a material such as spray foam or rock wool, which has higher prices per square foot, it would increase your tiny house roof insulation costs.

Hiring a professional labor team would tack on another $150 to $250. You’ll also have to consider if you’ll include a vapor barrier or not, if you do these can range from $180 to $210. 

Summary

A DIY insulation project may be considered cheap in comparison to what you’ll spend on other aspects of building your tiny house, but it’s definitely a time investment.

The best choice of material for a tiny house really depends only on your lifestyle. You need to make sure to install the material properly and securely to ensure your interior stays safe and sound through whatever climate your tiny house resides in.

Once you’ve nailed that down, you can look into the r-value that fits best for your lifestyle, and go from there.