Choosing the right insulation product for your project can have a large impact on your building’s energy efficiency, comfort and indoor air quality. By investing in your building with a quality insulation package you are taking the first step in producing an environment that is more comfortable, more healthy and will save money in energy costs for years to come.
HEAT LOSS
Heat moves through a building by three methods:
Conduction:
It’s cold outside. We want it warm inside…or vice versa. The heat that flows through the walls of a building is called conduction and is a function of the type of material and type of insulation the wall contains. R-value measures the resistance to heat flow through a material. Metal and concrete transfer heat easily, hence their R-value is very low. Foams and other fibrous insulation materials create dead air pockets and thus produce a barrier for heat to transfer and thus have a higher R-value.
Convection:
Air currents in a building produced by leaks in windows, doors or walls produce convective currents that strip the building’s energy as they move through it. The Department of Energy states that 40% of heat gain/loss in a building is due to air leakage caused by convection. Good air-sealing using proper insulation techniques and caulking is essential to maximizing a building’s performance. Ventilation is good, but we want to control where it occurs.
Radiant Energy:
The heat or “energy” you feel emanating from a south-facing brick wall after the sun has gone down is radiant energy. Heat also moves as electromagnetic waves and can be reflected by a mirror much the same as visible light. This is infra-red radiation and its presence allows us to take “pictures” of heat loss with a thermal camera.
FACTORS TO CONSIDER WHEN LOOKING AT INSULATION OPTIONS
Insulation is rated by R-value and thus addresses the conductive heat loss component of a building; however, it should also factor in the convection, or air movement, in a building. Insulation such as standard fiberglass or tri-polymer foam are not effective in stopping the movement of air through the framing members of buildings.
In addition, a building’s framing members can act as a thermal bridge that siphon energy from a building. A thermal camera can detect every framing member that connects the inside to the outside and produces energy loss. A builder can greatly reduce this heat transfer by installing proper air spaces and/or insulation product around these framing members and thereby isolating them from their sources of heat gain or loss. This is called decoupling.
Moisture permeability is also a key consideration for insulation materials in a building envelope. How does the material react to water intrusion, moisture laden air, and changes in temperature? Does the material allow moist air to collect in the wall or ceiling assembly? Does moist air have a tendency to condense and turn to water thereby creating mold, mildew or other problems?
Insulation materials can also be sound mufflers, particularly in tandem with decoupling the framing members. Noise between rooms and from outside can be reduced or eliminated with insulation. Spray foam insulation is one of the most effective methods to deaden sound transmission.
HOW TO GET THE BEST BUILDING ENVELOPE
Energy-efficient buildings are achieved through a combination of excellent air-sealing and proper installation of R-value insulation materials. Cellulose and acrylic-based fiberglass can be effective in tandem with an excellent caulking package; however, polyurethane spray foam can address both issues with one product. There are different types of polyurethane spray foams for different applications.
For truly superior performance it is recommended that an energy audit be conducted to identify sources of heat gain/loss. Once identified, the caulking of framing components followed by installing spray foam insulation offers the best building envelope. Because it is an adhesive, spray foam sticks to and encapsulates framing members. It also can be sprayed into open rafters and other hard-to-reach areas and will not succumb to gravity. By bringing attic areas into the conditioned envelope with spray foam, a builder can also install ducts into this space for easier HVAC retrofits. Spray foam is flexible and forgiving of water intrusion.
INSULATION PRODUCTS
Open-cell Spray Foam
Open-cell spray foam is one of the best all-purpose insulation materials. It is a lightweight, semi-rigid polyurethane foam insulation product that has roughly the consistency of a nerf ball or a seat cushion. It’s open-cell structure will allow liquid water to pass through without absorption but resists the flow of air and water vapor. It’s main advantage is that is provides an excellent air barrier, sticks to places other insulations cannot and has excellent sound attenuation properties.
Closed-cell Spray Foam
Closed-cell spray foam is a heavier, more rigid polyurethane foam insulation that provides a higher R-value than open-cell products. It provides a complete air and moisture barrier and is typically best for exterior applications where moisture may be an issue. We do not recommend this type of insulation for use with wood framing members as it is inflexible and may separate from wood that is moving and will not allow moisture intrusion in wood framing to be detected before significant damage occurs.
Open-cell Pour Fill
For wall retrofit situations we use an open-cell spray foam that is specifically designed to rise slowly and fill empty balloon frame walls. This material is by far the best material for filling walls. The drawback is that the work requires skilled installers and complete access to the wall areas being insulated.
Cellulose
Cellulose insulation is a fiberous material that is made from shredded newspaper, borates, and glue. The material can be a good solution to insulate a large ceiling area economically. With enough depth cellulose does provide a pretty good air barrier, but it is still a fiberous material that is subject to settling or shifting. It can also be mixed with water and applied vertically in stud cavities.
Fiberglass
Fiberglass is a fiberous material made of woven strands of glass. This material is used widely and has made a significant contribution to energy efficiency, mainly because it is very inexpensive and better than nothing…or at least somewhat better. We believe there is enough fiberglass in the world and thus, do not offer this product.
Cementous Foams
There are several types of “shaving cream” type foams that are used for wall injection and block fill. These foams are great because they are relatively inexpensive and you can push them relatively well in an existing cavity. You have to be careful when installing this product because the material is water based and is prone to shrinkage or collapse as it dries. We don’t currently offer this type of insulation but we have partners in the industry that can do this type of work.
Mineral Wool
Mineral wool is made from woven gypsum fibers. It is a good insulator and an excellent fire retarder.
Cotton Bats
There are several brands of recycled denim bats on the market that are a good substitute for fiberglass. They are neat because they use recycled cloth as an input and they have very good sound attenuation properties. They contain the same borate materials as cellulose to improve fire properties and inhibit mold growth. We like this material, but prefer foam that can provide better air sealing properties.
Structurally Insulated Panels
Structurally Insulated Panels or SIPS, are made of a sandwich of plywood and polystyrene foam. This is an excellent approach for new construction since it provides a great air barrier and thermal barrier. The key with SIPS is to make sure that the seams are well constructed so they don’t shift.
Insulated Concrete Forms
Insulated Concrete Forms or ICF is a very solid way to build a foundation wall or an entire exterior wall. It is made with a sandwich of polystyrene with concrete poured on the inside. This provides and excellent mass wall with great insulating and structural properties. Unfortunately you don’t the benefit of the thermal mass on the inside because of the polystyrene sandwich.
