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How Much Insulation Do I Need? Your NEPA Homeowner’s Guide

Insulation is a valuable product that can help you achieve better energy efficiency and comfort in your home.

While some insulation is usually better than none, you can achieve better results by understanding how much insulation you need for each job.

This step-by-step guide will help you calculate how much insulation you need based on your climate, the age of your home, and the materials you can afford. 

Step 1: Calculate How Much Insulation You Already Have

First, determine what type of insulation already exists in your home and evaluate its current state. Most homes with insulation over fifteen years old have fiberglass batts. 

Based on fiberglass’s longevity, batts can last anywhere from 80 to 100 years. Look at the quality of the material to see if it has been subject to mold, degradation, or shredding due to rodents. 

If you determine that your existing insulation is good enough to keep, you can simply add more insulation to reduce costs. 

Since most fiberglass batts have an R-value of 3.2 per inch, measure the batts’ thickness and multiply it by this value to determine their overall R-value.  

Research Recommended R-Values for Your Climate

Next, subtract the existing R-value of your current insulation from the recommended values listed by EnergyStar

R-value is a simple measurement of a material’s ability to resist heat flow. The higher the R-value, the better the insulating material. 

Based on Pennsylvania’s climate zone, you’ll want to install insulation with an R-value of 49 in your attic if you have existing insulation or 60 if there is no insulation.

Determine Which Areas Require Insulation and How Much

To accurately estimate your insulation costs, you’ll need to examine every area of your home, from the attic to floors, walls, basement, and crawl space. 

Based on the values from EnergyStar, you’ll want to insulate the following areas of your home with the corresponding R-values:


R-60 (Uninsulated)/R-49 (Previously Insulated)


R-5 to R-10 (Sheathing)



Basement/Crawl Space

R-15 (Sheathing) to R-19 (Batts)

Choose Which Materials You Require and Their Thickness

As we previously alluded to, R-value is both a measure of an insulating material’s heat resistance, as well as its thickness.

Based on the R-value per inch of an insulation material, you must reinforce your insulation with additional material to reach your intended R-value. In simpler terms, if you buy R-30 fiberglass rolls to insulate your attic, you’ll want to install a second roll on top of the first to reach the intended R-value of 60 for an attic. 

The most common types of insulation and their R-values include:

    • Closed-Cell Spray Foam (R-6 to 7 per inch): Closed-cell spray foam is considered the best insulation material for attics and walls because it offers the best heat resistance per inch. However, spray foam requires a professional to install because it requires special equipment.  
    • Open-Cell Spray Foam (R-3.9 per inch): Like closed-cell foam, open-cell foam offers superior heat resistance, though it’s generally a lighter material. Open-cell foam is considered a great sealant, helping insulate hard-to-reach areas of the home, including rim joists and crawl spaces. 
    • Cellulose (R-3.1 to 3.8 per inch): Blown-in cellulose is an environmentally friendly option for insulating wall cavities and hard-to-reach places. 
    • Fiberglass Batts (R-2.9 to 3.8 per inch): Fiberglass batts are an economical option that can be purchased in bags or rolls. Most rolls come in options for everything from R-9 to R-49 rolls. 
    • Blown-In Fiberglass (R-2.2 to 2.9 per inch): This loose-fill material is less efficient than other insulating materials but offers a flexible and economical option for people trying to insulate existing homes. 

Consider factors such as cost, ease of installation, and compatibility with your home’s structure when choosing insulation materials and thickness.

Additional Considerations

Several factors can influence your home’s insulation needs beyond R-Values and material types:

  • Age of Home: Older homes may have insufficient insulation or outdated materials that require upgrading to meet modern energy efficiency standards. Likewise, installing materials, such as spray foam, may require additional venting based on your home’s architectural design. 
  • Attached Garage: If your home has an attached garage, ensure that it is adequately insulated to prevent heat loss or infiltration into adjacent living spaces. We have a guide on insulating your garage to help you understand what’s required. 
  • Air Sealing: Proper air sealing is essential for maximizing insulation effectiveness and preventing drafts and energy loss. Seal gaps around windows, doors, and other penetrations before adding insulation.
  • Professional vs. DIY Installation: While DIY insulation installation is possible, hiring a professional ensures proper installation and compliance with building codes. Consider your skill level, time availability, and budget when deciding whether to DIY or hire a contractor.

Determining how much insulation your home needs requires careful consideration of factors such as existing insulation levels, recommended R-Values, material types, and additional considerations like age and air sealing. By following the steps outlined in this guide and consulting with insulation experts, you can ensure that your home remains comfortable, energy-efficient, and environmentally friendly for years to come.

Frequently Asked Questions: How Much Insulation Do I Need?

How do I know if my home needs more insulation?

Signs of inadequate insulation include fluctuating temperatures, high energy bills, drafts, and uneven heating or cooling throughout the home. Conducting a home energy audit can help identify insulation deficiencies.

What is the difference between R-value and insulation thickness?

R-Value measures the insulation’s thermal resistance, while thickness refers to the depth or thickness of the insulation material. Increasing thickness typically increases R-Value, but different materials have varying thermal properties.

Can I install insulation over existing insulation?

In most cases, yes. However, ensure that the old insulation is in good condition and compatible with the new insulation material. Adding insulation on top can improve thermal performance and energy efficiency.

Is it possible to over-insulate my home?

While adding insulation can improve energy efficiency, there is a point of diminishing returns where additional insulation may not provide significant benefits. Consult with an insulation professional to determine the optimal insulation levels for your home.