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The Difference Between Cold And Hot Roof Insulation

Posted on July 24, 2023

Estimated Reading Time : 5 Min.

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Cold Vs. Hot Roof Insulation

Insulating your roof is crucial for maintaining a comfortable and energy-efficient home. It helps regulate temperature, reduces energy loss, and prevents condensation issues. While there are different methods used to apply roof insulation, one common question that arises is: can you insulate a roof from inside your attic? In this comprehensive guide, we will explore the options, benefits, and considerations of insulating the roof from the inside.

Understanding Roof Insulation: The Cold Roof vs. Hot Roof Debate

Roof vs. Hot Roof Debate

Before delving into the specifics of insulating a roof from the inside, it’s essential to understand the difference between the two main approaches to roof insulation: cold roof and hot roof systems.

The Cold Roof Method

The cold roof method involves installing insulation inside the roof beneath the roof deck and the structural framing, creating a layer of insulation in the attic space. Otherwise known as inside insulation, this approach was widely used in the past but is now considered outdated. Insulating the roof from the inside with the cold roof system can lead to condensation issues within the rafters, which can damage the roof structure and reduce the effectiveness of the insulation.

The Hot Roof System

The hot roof system, also known as external insulation, is the recommended approach for insulating roofs. With this method, rigid insulation is installed on top of the rafters, below the roof deck. This effectively prevents condensation issues and provides superior insulation performance. Hot roof insulation materials are also the preferred choice for long-term insulation solutions.

Reasons Why Hot Roof Insulation Is Recommended

While some homeowners may still consider insulating the roof using the cold roof method, there are several compelling reasons why insulating via the hot roof system is the preferred option.

1. Enhanced Thermal Performance

Insulating the roof with a hot roof insulation system offers superior thermal performance. Placing the insulation layer on top of the roof’s framework effectively prevents heat transfer, keeping your home cooler in the summer and warmer in the winter.

2. Minimized Condensation Risks

Insulating the roof using the hot roof system eliminates the risk of condensation issues that can occur with the cold roof method. By placing the insulation layer on top of the framing, you create a barrier that prevents moisture from reaching these structural elements, reducing the chances of rot, mold, and other moisture-related problems.

3. Preservation of Interior Space

Hot roof insulation allows you to maximize the interior space of your home. With the hot roof system, less insulation takes up the physical space of your attic, which means you can utilize all the available space in your attic without compromising on insulation performance.

Materials for Hot Roof Insulation

Before jumping into your insulation project, it’s essential to be familiar with the materials commonly used for roof insulation. These materials are often used for other applications, such as attic or wall insulation.

1. Spray Foam Roof Insulation

Spray Foam Roof Insulation

Spray foam insulation is a popular choice for roof insulation due to its excellent properties and ability to create an airtight seal. It expands to fill gaps and cracks, providing superior thermal insulation and preventing air leakage.

2. Rigid Foam Roof Insulation

Rigid Foam Roof Insulation

Rigid foam insulation boards, such as expanded polystyrene (EPS) or extruded polystyrene (XPS), are commonly used for roof insulation. Both offer high R-values, moisture resistance, and durability.

3. Fiberglass Insulation

Fiberglass Insulation

Fiberglass insulation is another option for roof insulation, although it is more commonly used in attics. It consists of fine glass fibers and is available in batts or loose-fill form. Fiberglass insulation is an affordable option and offers good thermal performance.

4. Reflective Insulation

Reflective insulation, also known as radiant barrier insulation, is often used in combination with other insulation materials. It reflects heat radiation, reducing the transfer of radiant heat into the home.

The Step-by-Step Process of Installing Hot Roof Insulation 

While insulating roofs through the cold roof system is not recommended, some homeowners may still choose it for many reasons, including budget considerations. Instead of opting for the less efficient insulation style, homeowners can save additional money by installing insulation as a DIY project. The steps to install hot roof insulation are as follows:

1. Assess the Existing Roof Structure: Before starting the insulation process, inspect the roof structure for any signs of damage or structural issues. It is crucial to address any problems before proceeding with insulation.

2. Choose the Insulation Material: Select the appropriate insulation material based on your specific requirements and budget. Consider factors such as insulation thickness, R-value, moisture resistance, and ease of installation.

3. Prepare the Roof: Repair any damaged areas before proceeding with the insulation. Check for issues with the roof deck and foundation, and repair them as needed. 

4. Install A Vapor Barrier: Install a vapor barrier or membrane over the roof deck to prevent moisture from penetrating through it and getting into the insulation. This helps maintain the effectiveness of the insulation and prevents condensation issues.

5. Place/Spray the Insulation Material: Install the chosen insulation, ensuring a snug fit and covering the entire surface area. Follow the manufacturer’s guidelines for proper installation techniques.

6. Seal Gaps and Missed Spots: Seal gaps or joints in the insulation material to ensure a continuous and airtight barrier. This helps maximize insulation performance and prevents air leakage.

7. Allow Curing Time: Let the spray foam insulation or any chosen material cure as per the manufacturer’s instructions. This usually takes a few hours to a day.

8. Regular Maintenance: Regularly inspect the roof and insulation for any signs of damage or moisture. Address any issues promptly to maintain the effectiveness and longevity of the insulation.

9. Consider Professional Assistance: It is highly recommended to seek professional assistance when installing the insulation on your roof. Experienced contractors can ensure proper installation, address any structural concerns, and provide expert advice.


While it is technically possible to insulate the roof with the cold roof method, it is not the recommended method due to potential condensation issues and reduced insulation effectiveness, as mentioned above. Insulating the roof with a hot roof insulation system offers superior performance, minimized condensation risks, and preservation of the interior space. No matter which method you choose, it is important to carefully assess the roofing structure, choose appropriate insulation materials, and follow proper installation techniques. However, it is always advisable to consult with professionals to ensure the best insulation solution for your specific needs.

Remember, proper roof insulation is essential for maintaining a comfortable and energy-efficient home. Whether you opt for insulating from the inside or outside, prioritize insulation to enjoy the benefits of improved thermal performance and reduced energy costs.

Seek Professional Assistance When Insulating Your Roof

If you are considering installing insulation, whether it’s with the hot or cold method, consider seeking professional assistance. It may be your first time insulating a roof, so there are chances you may leave gaps during the DIY process. However, with professional assistance, you can be sure the project is done right. With our team of expert roofers at BRH Enterprises, your home will be energy-efficient in no time. Contact our experienced team to inspect your roof and initiate the process as soon as you’re ready. Call us today at (920) 249-4228 and speak with one of our specialists to get your roof insulation questions answered.

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