under a house

What is the Best Way to Insulate Under a House?

When it comes to maintaining a comfortable and energy-efficient home, proper insulation is key. However, insulating the space beneath your house is often overlooked. In this guide, we’ll explore the best methods for insulating under a house to keep it cozy in winter, cool in summer, and energy-efficient year-round.

Understanding the Importance of Underfloor Insulation

Before delving into the different insulation options, let’s first understand why insulating the space beneath your house is crucial. Without adequate insulation, heat can escape through the floor during colder months, leading to increased energy bills and discomfort. Similarly, in warmer weather, uninsulated floors can allow heat to penetrate upwards, making your home feel uncomfortably hot. Proper underfloor insulation helps maintain a consistent indoor temperature, reduces energy consumption, and improves overall comfort.

Types of Underfloor Insulation

Fiberglass Insulation

Fiberglass insulation is one of the most common options for underfloor insulation. It consists of tiny glass fibers and is available in batts or rolls. Fiberglass insulation is relatively easy to install and provides excellent thermal resistance.

Foam Board Insulation

Foam board insulation, also known as rigid foam insulation, offers high thermal resistance and moisture resistance. It comes in various thicknesses and can be installed directly onto the underside of the floor joists.

Spray Foam Insulation

Spray foam insulation is a versatile option that expands upon application, filling gaps and creating a seamless barrier against heat transfer. While more expensive than other types of insulation, spray foam provides superior thermal performance.

Reflective Foil Insulation

Reflective foil insulation, also called radiant barrier insulation, reflects heat away from the underside of the house, helping to keep the interior cooler in hot weather. It is typically installed foil-side down, directly under the floor joists.

Factors to Consider Before Insulating Under a House

Before proceeding with underfloor insulation, consider the following factors to ensure optimal results:

  • Climate: Choose insulation materials and methods that are appropriate for your climate zone.
  • Moisture Control: Address any moisture issues, such as leaks or condensation, before installing insulation to prevent mold and mildew growth.
  • Access: Evaluate the accessibility of the underfloor area and choose insulation options that are suitable for the space available.
  • Budget: Consider your budget constraints and weigh the upfront cost of insulation against long-term energy savings.

DIY vs. Professional Installation

Professional Installation

Deciding whether to tackle underfloor insulation as a DIY project or hire professionals depends on various factors, including your skill level, available time, and budget. While DIY installation can save money, professional installers have the expertise and equipment to ensure proper insulation and minimize the risk of errors.

Frequently Asked Questions (FAQs)

What are the signs that my house needs underfloor insulation?

If you notice uneven temperatures throughout your home, drafts near the floor, or rising energy bills, it may be time to consider underfloor insulation.

How long does underfloor insulation last?

With proper installation and maintenance, underfloor insulation can last for decades. However, factors such as moisture damage or pest infestation may require replacement sooner.

Can I install underfloor insulation myself?

While DIY installation is possible, it’s essential to follow manufacturer instructions carefully and take necessary safety precautions. If in doubt, consult with a professional.

Is underfloor insulation environmentally friendly?

Many insulation materials are now available with eco-friendly options, such as recycled content or natural fibers. Researching sustainable insulation choices can minimize environmental impact.

Will underfloor insulation reduce noise transmission?

Yes, underfloor insulation can help reduce noise transmission between floors, creating a quieter and more comfortable living environment.


Insulating the space beneath your house is a smart investment that offers numerous benefits, including improved energy efficiency, enhanced comfort, and reduced environmental impact. By understanding the various insulation options and factors to consider, you can make informed decisions to create a more comfortable and energy-efficient home.

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