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Insulation comes in a variety of forms. Loose fill is blown onto attic rafter spaces and wall cavities. Rigid foam boards are usually put between the interior wall and the house’s siding, and foam is sprayed into wall cavities and used to seal air leaks. Blanket rolls and batts are used in attics and unfinished walls and cavities. Properly installed, both loose fill and rolls and batts are effective at reducing heat loss from conduction and air infiltration.
To narrow the field of possible materials for your project, begin with your climate. The Department of Energy's website shows estimates of the total R-value (a rating of a material’s resistance to heat flow) that parts of your home should have based on your climate. RMI's Home Energy Brief #1 also gives a good introduction to how insulation and heat flow work. The table below will help you further narrow your decision.
For a list of insulation products approved by GreenHomeGuide’s subject editors, see our Insulation Product Directory.
| Material | Application Tips | Pros | Cons |
| Cellulose | Available as loose fill. Appropriate for small to large remodels in areas with very low to no moisture. Good for wall cavities or attic floors and ceilings. Wall cavities need small holes to spray through. | * Requires up to 30 times less energy to make than fiberglass and mineral wool * At least 75% post-consumer recycled content * No significant effect on indoor air quality |
* Absorbs moisture * May consume paper pulp usable for higher-grade applications |
| Cotton | Available as batt and loose fill. Appropriate for small to large remodels in areas with very low to no moisture. Good for wall cavities or attic floors and ceilings. Batts require open walls. | * Renewable, plant-based material * At least 70% post-industrial recycled content * No significant effect on indoor air quality |
* Cotton farming requires large volumes of water and pesticides * Absorbs moisture |
| Fiberglass | Available as board, batt, and loose fill. Appropriate for small to large remodels in areas with very low to no moisture. Good for wall cavities or attic floors and ceilings. Batts and boards require open walls. Boards can be used in interior basement spaces. | * Made of abundant materials * Up to 40% recycled content |
* Releases eye, throat and skin irritants * Energy-intensive manufacture * May contain formaldehyde |
| Polyisocyanurate | Available in board form. Appropriate for larger projects or new construction in areas with low to no moisture. Best for interior basement walls, beneath siding, and attic ceilings. |
* No hydrochlorofluorocarbons (HCFCs) * Typically no indoor air quality effects |
* Not recyclable * Absorbs moisture * Made from petrochemicals |
| Polystyrene–Expanded (EPS) | Available in board form. Appropriate for larger projects or new construction in areas with low to no moisture. Best for interior basement walls, beneath siding, and attic ceilings; can be used below grade if coated with foil or plastic. |
* No HCFCs * Recyclable * Typically no indoor air quality effects |
* Made from petrochemicals * Not very moisture resistant |
| Polystyrene–Extruded (XPS) | Available in board form. Appropriate for larger projects or new construction in areas with moderate to no moisture. Best for interior basement walls, beneath siding, attic ceilings or below grade. | * More moisture resistant than EPS * Typically no indoor air quality effects * Recyclable |
* Uses HCFCs * Made from petrochemicals |
| Spray Polyurethane Foam (SPF) | Appropriate for small to large remodels in areas with moderate moisture. Good for wall cavities and attics. Sprayed through small holes in walls. | * No HCFCs * Prevents air leakage * Doesn’t settle * No indoor air quality effects * Low density SPF can use up to 33% soy oil |
* Not recyclable * Most SPF products are made primarily from petrochemicals |
| Mineral Wool | Available as batt and loose fill. Appropriate for small to large remodels in areas with moderate to no moisture. Good for wall cavities and attics. Batts require open walls. Can be used below grade if made for that purpose. | * No additional flame retardants necessary * Abundant materials * Moisture resistant * Up to 80% recycled content |
* Energy-intensive manufacture * Releases some eye, throat and skin irritants |
On January 31, 2007, Charles Hamilton wrote:
Hi,
Are you aware that fibreglass also contains lead. In research carried out here by myself in a univeristy study, I was advised by computer recyclers that lead from CRTs is being sold to fibreglass manufacturers. Whilst inert in the fibreglass, it may create a serious problem in the process of the break down of the fibreglass in the future.
Cheers
Charles
On February 14, 2007, Oliver Hayden wrote:
Two things are missing here:
1 - what do these levels of moisture mean, specifically. What are “moderate” moisture levels? Is it average humidity alone that matters, or a combination of temperature and humidity?
2 - Along those lines, it looks like there’s not really very freindly options availalbe for wetter climates at this time… Any ideas? Natural sealants that could be used or combined with the more natural products to reduce mold or fungus likelihood?
On May 14, 2007, Anna Hackman wrote:
Oliver-
There is closed cell versus open celled SPF. A technical bulletin in http://www.fomo.com/resources/technical-bulletins/opencellvsclosed.aspx does a nice job summing up the differences. Closed cell is good for moisture. I have an open celled in my basement and 1st and 2nd floor. (Icynene) and I love it. My basement does not have any humidity. SPFs are pricey but worth it. My heating bills are so much lower because of the foam. I have heard and may not be true that the closed cell off gasses alot at the beginning. Make sure you find that out before you use. Has anyone else heard this???
Also John Manville makes a product geared to high moisture situations and is Formaldehyde free. (MR® Faced Batts) Since I do not know where you live, I do not know why there is so much moisture. Is this moisture in your basement?
Also you could use the cotton with a vapor barrier on one side or the other depending on your climate. Take a look at http://www.eere.energy.gov/consumer/your_home/insulation_airsealing/index.cfm/mytopic=11810 for a good discussion of vapor barriers. Hope this helps. anna hackman http://www.green-talk.com
On October 20, 2007, Mike Schmidt wrote:
Air Krete Foamsulation is ignored in this article. Non expanding, non shrinking foam can be injected into existing wall without peril to plaster or drywall. 100% fireproof, bug, rodent and mold proof. Take a look. I think you will be amazed.
On November 15, 2007, Oliver wrote:
I live in Oregon - so it’s wet and cool here about 8-9 months a year. Many homes in newer developments are ranches with just a crawlspace, but in older neighborhoods in Portland and other towns there are full basement houses, which often have moisture issues, either from improper drainage from downspouts or just bad site drainage. Many basements i’ve seen must not have any moisture barrier because you get moisture buildup on the floor in low-air circulation areas that behaves like it’s being drawn in thru the concrete.
On February 25, 2008, Ron Scicluna wrote:
I am interested in using 3/4” thick EPS sheets against a poured basement wall. Each sheet will sit in a space between the cement wall and the stud wall (where fiberglass insul will be placed). Are you aware of health studies discussing the movement of plasticizers from EPS (or even XPS) foam boards into the living space? Otherwise, what do you base your own “safe rating” on?
You suggest that EPS foam absorbs moisture and is therefore not recommended below grade. How do I reconcile that with the following quote downloaded from an EPS website? e.g. apart from opinions or hype, are there studies that back up either point of view? I’m on the verge of closing up a wall so your quick feedback will be most helpful.
“EPS has been used successfully for many years in areas where moisture is a concern, specifically below grade. Fungi, bacteria and rot do not affect EPS. The performance properties will not deteriorate when exposed to moisture and/or water. EPS will breath, allowing the diffusion of moisture. EPS insulation is available in a variety of densities to suit project needs. ASTM C578 provides performance properties on expanded polystyrene foam insulation.”
Thanks in advance for your help with this and for your very well designed website. Ron Scicluna
On April 12, 2008, Barbara Smith wrote:
I was definitely considering using Air-Krete, but I heard somewhere that it doesn’t adhere properly to walls. Does anyone know if this is true or not, or under what conditions this may or may not be true?
On April 15, 2008, Mike Schmidt wrote:
Air Krete is cement based foam bubbles. Air Krete requires a 4 sided chamber to fill. Air Krete has no adhesion qualities. What Air Krete does have is a 100% clean bill of health. No VOC’s, no air born fibers, no harmful chemicals, etc. Mr. Green Jeans himself, Al Gore, used air krete to insulate his home in October of 2007. See my website http://www.schmidtexteriors.com or go to http://www.airkrete.com
Want to share your experience? Post a comment here.
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