types of home insulation
heating, ventilation, insulation terms
installing home insulation
blown in wall insulation
attic & wall home insulation materials
home wall & attic thermal insulation
home weatherization
hvac - heating, cooling systems
home insulation overview
r-value of insulating materials
COMMONLY USED INSULATION MATERIALS
A selection of insulation materials can aid in building insulation. All of these are based on standard principles of thermal insulation. Materials used to reduce heat transfer by conduction, radiation or convection are employed in varying combinations to achieve the desired outcome (usually thermal comfort with low energy consumption).
Choice of insulative material
The choice and degree of insulation is based on a number of factors:
* Prevailing climate.
* Ease of installation
* Durability
* Cost
* Toxicity
* Sustainability
Usually a combination of materials are required to achieve an optimum solution for a building over a range of climatic conditions. There are also some products that combine different types of insulation in one product.
Systems used for insulation
Insulation can be installed in a number of forms:
Non-structural
* Batts (insulation) - e.g. fiberglass, mineral wool
* Blankets (insulation)
* Loose-fill (insulation) e.g. cellulose (may also be wet-sprayed), vermiculite
* Spray foams (insulation) e.g. synthetic polymers
* Reflective Insulation (insulation) e.g. foil-foam-foil
Structural
* Rigid Panels (insulation)
* Structured panels (insulation)
* Straw bale
Batt insulation is the most common at this time, though batts generally allow for more air transfer than other options. Options that seal the wall cavity completely may have some heat loss through studs and joists due to Heat bridging, though this is likely to be a lesser issue than air transfer.
Spray Polyurethane Foam (SPF) Insulation
SPF, a two component mixture comes together at the tip of a gun, and forms an expanding foam that is sprayed onto concrete slabs, into wall cavities of an unfinished wall, against the interior side of sheathing, or through holes drilled in sheathing or drywall into the wall cavity of a finished wall.
Advantages
* Blocks airflow.
* Serves as a vapor.
* Expands while curing.
* Increases structural stability.
* Cementitious foam is fireproof.
Rigid panels
Rigid panel insulation is made from fibrous materials (fiberglass, rock and slag wool) or from plastic foam. They are sometimes sold in sections designed to fit tightly in standard wall cavities. When sold this way, they are called "batts", and they come in different thicknesses to match the depth of wall cavities.
Where rigid panels are most often used:
* Against footings and exterior backfilled foundation walls.
* Against exterior exposed foundation.
* Against exterior walls between foundation and roof.
* Either under or on top of the roof sheathing.
* Inside unfinished interior walls.
* Where space is limited.
Structural insulated panels
Structural insulated panels (SIPs), also called stressed-skin walls, use the same concept as in foam-core external doors, but extend the concept to the entire house. They can be used for ceilings, floors, walls, and roofs. The panels usually consist of plywood, oriented strandboard, or drywall glued and sandwiched around a core consisting of expanded polystyrene, polyurethane, polyisocyanurate, compressed wheat straw, or epoxy. Epoxy is too expensive to use as an insulator on its own, but it has a high R-value (7 to 9), high strength, and good chemical and moisture resistance. SIPs come in various thicknesses. When building a house, they are glued together and secured with lumber. They provide the structural support, rather than the studs used in traditional framing.
Fiberglass batts and blankets
Batts are precut, whereas blankets are available in continuous rolls. Compressing the material reduces its effectiveness. Cutting it to accommodate electrical boxes and other obstructions allows air a free path to cross through the wall cavity. One can install batts in two layers across an unfinished attic floor, perpendicular to each other, for increased effectiveness at preventing heat bridging. Blankets can cover joists and studs as well as the space between them. Batts can be challenging and unpleasant to hang under floors between joists; straps, or staple cloth or wire mesh across joists, can hold it up.
Gaps between batts (bypasses) can become sites of air infiltration or condensation (both of which reduce the effectiveness of the insulation) and requires strict attention during the installation. By the same token careful weatherization and installation of vapour barriers is required to ensure that the batts perform optimally. Air infiltration can be also reduced by adding a layer of cellulose loose-fill on top of the material.
Straw bales
The use of highly-compressed straw bales as insulation, though uncommon, is gaining popularity in experimental building projects for the high R-value and low cost of a thick wall made of straw. When using straw bales for construction, the bales must be tightly-packed and allowed to dry out sufficiently. Any air gaps or moisture can drastically reduce the insulating effectiveness.
Asbestos
Asbestos once found common use as an insulation material in homes and buildings because it is fireproof, a good thermal and electrical insulator, and resistant to chemical attack and wear. It has been found that asbestos can cause cancer when in friable form (that is, when likely to release fibers into the air - when broken, jagged, shredded, or scuffed). Only some people exposed to asbestos develop cancer.
When found in the home, asbestos often resembles grayish-white corrugated cardboard coated with cloth or canvas, usually held in place around pipes and ducts with metal straps. Things that typically might contain asbestos:
* Boiler and furnace insulation.
* Heating duct wrapping.
* Pipe insulation ("lagging").
* Ducting and transite pipes within slabs.
* Acoustic ceilings.
* Textured materials.
* Resilient flooring.
* Blown-in insulation.
* Roofing materials and felts.
Fiberglass
Fiberglass is the most common residential insulating material, and is usually applied as batts of insulation, pressed between studs. Health and safety issues include potential cancer risk from exposure to glass fibers, formaldehyde off-gassing from the backing/resin, use of petrochemicals in the resin, and the environmental health aspects of the production process. Green building practices shun Fiberglass insulation.
The World Health Organization has declared fiber glass insulation as potentially carcinogenic. The product is still required to carry a cancer warning label in the USA.
Fiber glass is now the most thoroughly evaluated insulation material in the market.[citation needed] The fiber glass insulation industry is committed to ensuring that fiber glass products can be safely manufactured, installed and used. This industry has funded tens of millions of dollars of research at leading independent laboratories and universities in the United States and abroad. The weight of the scientific research shows no association between exposure to glass fibers and respiratory disease or cancer in humans.
Loose-fill cellulose
Cellulose is 100% natural and 75-85% of it is made from recycled newsprint. Health issues (if any) appear to be minor, and most concerns around the flame retardants and mold potential seem to be misrepresentations.
* Cellulose is classified by OSHA as a dust nuisance during installation, and the use of a dust mask is suggested.
* Cellulose is treated with a flame retardant and insect repellent, usually boric acid and sometimes borax to resist insects and rodents. Boric acid has a toxicity comparable to table salt.
* Mold has been seen as a potential concern. One thing that has not contributed to mold problems is the growing popularity of cellulose insulation among knowledgeable home owners who are interested in sustainable building practices and energy conservation. Mycology experts (mycology is the study of mold) are often quoted as saying: "Mold grows on cellulose." They are referring to cellulose the generic material that forms the cell walls of all plants, not to cellulose insulation. In fact, due to its favorable moisture control characteristics and other factors associated with the manufacturing process relatively few cases of significant mold growth on cellulose insulation have been reported. All the widely publicized incidents of serious mold contamination of insulation have involved fiber insulation materials other than cellulose."
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