healthy house institute

4 Free HHI Books:

Creating a Healthy Household, The Healthy House Answer Book, Healthy Home Building, The Healthy House 4th Edition
Your email will only be used as described in our Privacy Policy

Follow us on Twitter



Proud Supporter of:



HHI-Pedia Entry


By HHI Staff

A material that inhibits the flow of heat. See also insulation. More below...


entry continues below ↓

We do not strictly control Google ad content. If you believe any Google ad is inappropriate, please email us directly here.


Above definition Copyright © The Home Ventilating Institute. Some content originally appeared in John Bower's book, Understanding Ventilation, published in 1995 by The Healthy House Institute.


More info from HHI:


Insulation in the walls, floors and attic is something like a blanket on a bed – the thicker it is, the warmer you’ll stay during the cold months while keeping heating costs down. The same principle works in reverse during summer, as insulation keeps heat out, reducing the air conditioner’s burden.

For this reason, all forms of insulation can be thought of as “green.” Reducing the need for gas, heating oil, electricity, or wood to keep a home comfortable at times of temperature extremes, means less carbon dioxide and other pollutants in the atmosphere – and a lighter burden on your energy budget. Even better, it keeps on saving energy and money, because insulation doesn’t wear out over time under normal conditions.

In addition to energy and environmental benefits, better insulation can mean better health. A well insulated and sealed home may have a higher relative humidity in winter than one without such improvements. A relative humidity between 30 percent and 50 percent is sufficient for most people to avoid sinus problems and vulnerability to illness from constant exposure to a dry environment, while being dry enough to prevent growth of mold in the home. In dry climates, this also may reduce or eliminate the need for artificial humidification, resulting in even greater energy savings.

Many existing homes were built with what’s now considered to be inadequate insulation, and may lack it entirely. Insulation wasn’t required as part of home construction until the mid-1960s.

Even in newer homes with better insulation, sloppy installation can still mean cold walls and drafts in unexpected places. That’s because most forms of insulation are not designed to block air infiltration around corners and gaps. In addition to better insulation, products like spray foam and caulk may be installed both indoors and outdoors to block drafts through gaps in the wall.

Indoors, components such as plumping pipes and electrical wiring installed through walls, subfloors and ceilings allow cold and warm air to enter or escape. Cold (or hot) air also enters the home from outside through gaps at corners, edges and between trim and siding, and around service entrances such as water pipes, gas mains, electrical wires and telecommunications cables.

The surest way to determine insulation and sealing needs is to hire an energy auditor, a contractor who uses specialized tools to find hidden air leaks in walls, ceilings and ducts. The auditor will analyze the test results and furnish a report with recommendations for better energy efficiency. The service costs about $300 in most major markets. Many private home inspectors also perform energy audits, as do some electrical and natural-gas utility companies.

Armed with this information, you’ll know what to ask for when considering contractors to beef up your insulation effectively while avoiding the expensive “extras” your home doesn’t really need.

A discussion of the pros and cons of the most common forms of insulation follows in the table below. Comprehensive information may also be found at the U.S. government’s ENERGY STAR Home Sealing page.



 Insulation material
Insulation type
Cellulose  Loose fill
Inexpensive. Can be more effective than fiber glass. Insulation formed by combining recycled newspaper and other paper products with fire retardant chemicals. Best suited for attics and flat ceilings.Compression over time reduces effectiveness somewhat. Requires power equipment for application. Must be applied evenly for best results. Flammable at sufficiently high temperatures. Loses effectiveness when moist and can be a source of mold contamination if allowed to remain damp. Correct moisture or water problems before installing cellulose to prevent mold. Handy homeowners can rent application equipment to add attic insulation. Wear a respiratory mask during application. Hire a contractor to add cellulose to closed walls or ceilings. 
Fiber glass  BattWidely used in homes. Moderately priced and fairly easy to install. Fire and mold resistant. Manufacturers using increasing amounts of recycled materials in new products. Can be used in walls, floors, attics, basements and cathedral ceilings.Must be installed neatly and consistently for best results. Microscopic fibers can lodge in lungs or irritate skin during installation. Persistent dampness reduces insulation effectiveness, and can be a source of mold growth.  A respiratory mask, plus skin and eye protection, are required when installing fiber glass products. Correct persistent water or moisture problems before installing to prevent potential mold growth.
 Fiber glass
 Loose fill
Applied using method similar to cellulose installation. Inexpensive. Best suited for attics and flat ceilings.
Compression over time reduces effectiveness somewhat. Power equipment required for application. Must be installed evenly for best results. Microscopic fibers can lodge in lungs or irritate skin during application. Requires separate vapor barrier (plastic sheeting) in some situations. Persistent dampness reduces insulation effectiveness.A particulate mask, plus skin and eye protection, are required when installing fiber glass products. Handy homeowners can rent application equipment and add attic insulation. Hire a contractor to add loose-fill fiber glass to walls or closed ceilings. Correct persistent water or moisture problems before installing to prevent possible mold growth.
Expanding foam Spray on
Nearly waterproof if applied correctly. Closed-cell structure eliminates need for vapor barrier against moisture. Excellent for blocking air infiltration through large gaps around plumbing, electrical or HVAC openings through walls, ceilings and soffits.
Expensive. Some products rely on propellant gases harmful to ozone layer, though makers are phasing in use of more benign propellants.Handy homeowners can use spray-can foam products to block air infiltration. Wear skin and eye protection; liquid foam is extremely sticky and difficult to remove. Installation of foam insulation between open stud cavities requires specialized knowledge and equipment best used by professionals. 
Rigid foam  PanelRigid boards have high R-value per inch. Easy to cut panels to desired size. Forms good vapor/moisture barrier. Makers are beginning to use reclaimed materials during manufacture.Fairly expensive. Edges must be sealed with either caulk or foam to block air infiltration completely.
Well suited for concrete basement walls and rim joist above foundation sill. Do-it-yourself installation is simple and non-hazardous.
 Rock wool
 BattInstallation and suitability similar to that of fiber glass batts. Reclaimed rock or slag used in manufacture. Highly resistant to fire and mold contamination. Excellent sound-deadening capability.Not as widely available as cellulose, fiber glass or foam products. Wear respiratory mask, gloves, skin and eye protection while installing to prevent irritation. Use a sharp knife while trimming batts to minimize airborne fibers.
Rock wool Loose fill Highly resistant to mold contamination. Best suited for attics and flat ceilings. Excellent sound-deadening capability.Compression over time reduces effectiveness somewhat. Installation requires specialized know-how and equipment.Installation is best left to professionals.




HHI Error Correction Policy

HHI is committed to accuracy of content and correcting information that is incomplete or inaccurate. With our broad scope of coverage of healthful indoor environments, and desire to rapidly publish info to benefit the community, mistakes are inevitable. HHI has established an error correction policy to welcome corrections or enhancements to our information. Please help us improve the quality of our content by contacting with corrections or suggestions for improvement. Each contact will receive a respectful reply.

The Healthy House Institute (HHI), a for-profit educational LLC, provides the information on as a free service to the public. The intent is to disseminate accurate, verified and science-based information on creating healthy home environments.


While an effort is made to ensure the quality of the content and credibility of sources listed on this site, HHI provides no warranty - expressed or implied - and assumes no legal liability for the accuracy, completeness, or usefulness of any information, product or process disclosed on or in conjunction with the site. The views and opinions of the authors or originators expressed herein do not necessarily state or reflect those of HHI: its principals, executives, Board members, advisors or affiliates.

Insulation:  Created on October 9th, 2009.  Last Modified on December 25th, 2009


References listed above credit sources The Healthy House Institute consulted for background or additional information.

All HHI-PediaTM content is © 2005-2018 The Healthy House InstituteTM.

Except for third-party Copyrighted© material, you may freely use, excerpt or cite this material provided the Healthy House Institute receives credit and the Web address is plainly listed with all uses, excerpts or citations.


We do not strictly control Google ad content. If you believe any Google ad is inappropriate, please email us directly here.



Information provided by The Healthy House Institute is designed to support, not to replace the relationship between patient/physician or other qualified healthcare provider.

Education Partners



Popular Topics: Air Cleaners & Air Purifiers | Allergies & Asthma | Energy Efficiency & Energy Savings | Healthy Homes | Green Building
Green Cleaning | Green Homes | Green Living | Green Remodeling | Indoor Air Quality | Water Filters | Water Quality

© 2006-2018 The Healthy House Institute, LLC.


About The Healthy House Institute | Contact HHI | HHI News & Media | Linking Resources | Advertising Info | Privacy Policy | Legal Disclaimer


HHI Info