MINNESOTA GREEN AFFORDABLE HOUSING GUIDE

Promoting Sustainable, Healthy, Durable & Energy Efficient Housing

Components: Insulation

Materials

Fact Sheet»

Description

Whether it takes the form of batt, loose fill, sprayed-in foam, or rigid foam, insulation is an essential part of any housing. Insulation slows the transfer of heat (energy) from warmer areas to colder areas. It can also serve to reduce noise. Insulation effectiveness is typically measured in R-value. A higher R-value for insulation is better. A well-constructed insulation system will help reduce air infiltration and heat transfer and help control moisture. All of these factors need to come together to produce a comfortable and healthy living environment. The following analysis examines the relative economic, energy, and environmental impacts of the following insulation types: fiberglass batt, blown and loose fill cellulose, blown fiberglass, foamed-in-place polyisocyanurate or polyicynene, extruded polystyrene, expanded polystyrene, and rigid polyisocyanurate.

Recommendations

Loose fill, blown and batt insulation is more cost effective in walls and attics than rigid board insulation. Foamed-in-place insulation should be used when budget permits, its high R-value combined with excellent air sealing increase the overall performance of the assembly. Look for insulation materials that have stable R-values over time.

Extruded polystyrene (XPS) insulation with CFC or HCFC's as blowing agents should not be used. Rigid insulation alternatives include: wood fiberboard, (some made entirely from recycled cellulose), expanded polystyrene (EPS), fiberglass board, or cellular glass board.

Citations
Sustainable Design Resource Guide, AIA Colorado www.aiacolorado.org/SDRG

Insulation Alternatives

alternatives cost/sq. ft./R (materials & labor) energy (R- value per inch) IAQ expected product life (years) life cycle thinking practice
fiberglass batt .03 3.2 typical 15 standard standard
cellulose blown and loose fill .02 3.7 good 15 good standard
fiberglass blown .04 2.2 good 15 standard standard
foamed-in-place polyisocyanurate or polyicynene not available 3.6-5.0 better 15-30 better requires trained installer
rigid perimeter: extruded 0.14 5.0 typical 10-15 standard standard
rigid perimeter: expanded 0.13 3.85 typical 15 good standard
rigid perimeter: polyisocyanurate 0.09 7.2 typical 15-30 better standard

Criteria Summaries

Cost: Loose fill, blown and batt insulation materials have a low cost per R-value and rigid board materials. Higher first costs associated with increased insulation thickness of any type may be recouped over the life cycle of the building through reduced heating and cooling costs. Premium costs associated with insulation with higher R-values per inch not only reduce operating costs but also use less material.

Energy: Rigid insulations typically have a higher R-value per inch than batt or blown insulations.

IAQ: If left undisturbed in wall cavities and attic spaces insulation poses no threat to human health. Respiratory masks should be worn when handling fiberglass and mineral wool batts, since they may potentially release fibers into the air during handling.

Expected Product Life: The R-value of most insulation materials decreases with aging. Polyisocyanurate and polyicynene have the longest expected life with the greatest R-value stability. Loss of R-value can be attributed to several different factors. Batt insulation can slump in cavities, or become damaged by moisture. These effects can be limited by proper construction and detailing. Rigid insulation can shrink and or dry over time, while loose fill insulation can settle, decreasing its effectiveness.

Life Cycle Thinking:

  • Energy consumption (non-renewable, fossil fuel energy): The manufacturing process for fiberglass and mineral wool batts is energy intensive although less than for rigid products. Where recycled content is higher, energy impacts related to manufacture are further reduced. Rigid insulations have high embodied energy from extraction through production, though they offer higher R-value per inch thickness, and require less material overall.
  • Pollutants generated in production: Extruded polystyrenes still use HCFC's, while expanded and some polyisocyanurates use alternative agents.
  • Potential for off-gassing: Not an issue when insulation is not exposed to the interior.
  • Durability of the product: Prolonged contact with moisture can cause the paper backing on batt insulation to deteriorate, and also mat down batt and blown insulation, reducing the effective R-value of the material.
  • Potential for future recycling: Blown insulation suffers from settlement, but can be recovered easily for reuse. Certain expanded polystyrene rigid insulation products use recycled content in their products (or at least reused waste products).

Practice: With the exception of sprayed-in-place insulations, which require training and professional installers, all insulation types are considered common practice.

Environmental Context

A large share of the energy used for heating and cooling in Minnesota (75%) comes from burning coal, which has serious negative environmental impacts such as greenhouse gas emissions and air pollution. Reducing the amount of fuel to heat and cool also reduces environmental damage and costs. Insulation effectiveness is usually measured in R-value (thermal resistance) - the higher the R-value, the better the insulation value. Other considerations include the amount of recycled content, the ability to reuse or recycle the insulation, the ability to meet code requirements (in Minnesota amendments to the Uniform Building Code and the residential building code), and off-gassing of the products in place. Batt and blown insulation materials will generally have lower embodied energy than rigid insulation materials.

The Guide

Scale

Neighborhood

Yard

House

Assemblies

Components

List All Design Strategies

List All Analysis & Recommendations

Case Studies

Resources