How to replace insulation in walls

Adding Insulation on framed basement walls

Heat typically flows from warm areas to cool areas. In Florida, this means heat is flowing from a warm outdoors to an air-conditioned indoors. During winter days, heat flows from a warmer inside to cold outside. Insulation reduces the amount of heat that flows, decreasing cooling, and heating costs.

Insulation is generally rated in terms of its thermal resistance. This resistance, or insulation R-value, refers to the specific performance of insulation by measuring the resistance given to heat flowing through the insulation over time. Insulation material with greater resistance (higher R-value) to heat flow means that less heat will enter your home during summer and less heat leaves your home in the winter months when you are heating the interior space.

Slow heat flow means decreased cooling and heating costs. In addition, health and comfort factors are significantly impacted by how readily heat flows through a building and its exterior shell, called an envelope. Heat flows in three ways: convection, conduction, and radiation. Controlling heat, in one way, will not necessarily affect the other two.

Why Is It Important To Insulate The Attic?

Attic insulation is critical because significantly more heat per square foot travels through your ceiling than any other area in a house. The easiest and most cost-effective method to insulate your home is adding insulation in the attic. You can measure the thickness of the attic insulation with a ruler and multiply the number of inches by the insulation R-value of that particular insulation material to get an insulation rating. The Department of Energy’s Insulation Fact Sheet offers information on how to determine the R-value using this technique. Information provided in Table 1 may also be of assistance.

Table 1. Common Insulation R-Value Char (Per Inch of Thickness)

Fiber Insulations

Cellulose 3.0 – 3.7
Fiberglass 2.2 – 4.0
Mineral Wool 2.8 – 3.7
Cotton 3.0 – 3.7
Perlite 2.5 – 3.3

Foam Insulations

Polyisocyanurate 6.0 – 6.5
Extruded Polystyrene (XPS) 5.0
Expanded Polystyrene (EPS) 3.6 – 4.4
Open-Cell Low Density Polyurethane 3.6 – 3.8
Closed-Cell spray Polyurethane 5.8 – 6.8

If the rating is lower than R-19, you will definitely benefit by adding more insulation. If you’re uncertain about the type of insulation already existing in your home, take a sample to an insulation professional.

Typically, current best home building codes and practices indicate an R-30 to R-38 for attic insulation. The Florida Building Code recognizes two distinct “climate zones.” Climate Zone 1 entails the following south Florida counties: Monroe, Hendry, Lee, Broward, Collier, Miami-Dade, and Palm Beach, and require minimum R-30 attic insulation. All other Florida counties are categorized in Climate Zone 2 and need a minimum R-38. Certain conditions may pre-exist in the home, such as cathedral ceilings, limiting the ability to meet these R-values.

The efficiency of an insulated wall or ceiling also highly depends on how and where the insulation is installed. For instance, compressed insulation will not give its full rated R-value. Also, the overall insulation R-value of a wall or ceiling will be somewhat different from that of the insulation itself because some heat will flow around the insulation through the joists and studs in wood- or steel-framed construction (thermal bridging). With careful design, this challenge can be reduced.

The key to an efficient insulation system is quality insulation or proper products. A building should have a continuous insulation layer around the entire building envelope—with no gaps or compression. This is termed as your “thermal envelope.” Studies show that an inappropriately installed thermal envelope can decrease the overall performance by 30 percent or more.

What Types Of Insulation Materials Are Available?

One of the different insulation types

Attic insulation

Remember, the insulation R-value for materials depend on the type and thickness of the insulation. Fiberglass insulation is the most common type of insulation, produced from sand and recycled glass. Rock wool insulation is manufactured from natural rocks—basalt primarily—and formed under extremely high heat. Mineral wool is primarily made from recycled insulative materials from steel mill wastes. Cellulose is made from cotton, and recycled newspapers are often made from post-industrial recycled cloth like denim–both being treated with fire-retardant chemicals.

Polyisocyanurate (ISO board), expanded polystyrene (EPS or beadboard), extruded polystyrene (XPS or blue board), or other materials are usually found in rigid board form. These boards are lightweight and typically have an R-value of 4 to 7 per inch. Spray foams, such as urethanes and polyicynene, are also available with R-values from 3 to 6 per inch.

Some Insulation Installation Tips

  • Never compress insulation…it will reduce the insulating capacity.
  • Seal all openings and cracks along with the home’s ceiling, light fixtures, and top and sole plates with the appropriate product(s) before installing insulation.
  • Never cover your soffit or attic vents with insulation.
  • Access hatches and doors should be weather-stripped and re-insulated to a level equivalent to the insulation on the surrounding surfaces
  • Match your wall entire system type to the most compatible insulation.
  • Mark attic trusses with spray paint for proper insulation depth and uniformity.
  • Wear protective gear and clothing and always read and adhere by manufacturer’s labeled directions.
  • Unless specifically signified on recessed light fixtures, motors, bare stove pipes, or any other equipment, always install insulation clear and away from heat sources to reduce the potential risk of equipment failure or fire.
  • To reduce your home’s insulation degradation, offer easy access to all parts of the attic and fasten cables, wiring, and other systems above the insulation accessible by a service easement platform.

What Other Factors Should I Consider?

Properly insulating your home will not only help reduce your heating and cooling costs but also make your home feel more comfortable. However, adequate insulation must be combined with proper air sealing and moisture control measures to ensure optimal occupant comfort.

Life-cycle analysis, environmental impact, and human health issues associated with resource extraction, manufacture, use, and disposal of insulation are also important considerations. See the Environmental Building News (EBN) article in the resources section for a good overview.

Additionally, for companies and consumers with concerns about false advertising, improper installation, and other related insulation considerations, there is a Federal Trade Commission Rule designed to protect you (Title 16 – Commercial Practices, Part 460 – Labeling and Advertising of Home Insulation). There are heavy fines for companies that break this Rule.

Monetary incentives, rebate programs, and/or free or low-cost home energy audits are often available from the state or federal government as well as from many utility providers. When looking for upfront financial incentives related to renewable energy and efficiency, visit the Database of State Incentives for Renewables & Efficiency (DSIRE) website and enter your zip code. You can also search, by zip code, for special offers and rebates as related to ENERGY STAR certified insulation products.

Before building a new home or adding insulation to an existing home, do the research to help you make the best decision for your home, wallet, and the environment as lower utility costs will mean less need for power from your utility company and, therefore less use of our natural resources.

References and Resources