What is the best insulation for wood frame walls?
Insulation is one of the most important concerns in Quebec. Given the significant temperature variations brought on by the seasonal cycle, it is crucial that all buildings be equipped with adequate thermal insulation. Houses and other wood-frame buildings are no exception to this rule and must be properly insulated.
In this article, our prefabricated wood wall specialists present a short guide to wood frame wall insulation featuring several crucial pieces of information. Among other things, you’ll discover why walls should be insulated, two insulation techniques and which insulation materials are suitable for these types of exterior walls.
Why insulate exterior walls?
In areas with wildly fluctuating climates, proper insulation of a building’s exterior walls is the key to maintaining the appropriate temperature inside. It keeps rooms cool in the summer and warm in the winter.
In addition to improving comfort levels in all seasons, proper insulation also helps save energy. Less exposure to outdoor conditions often translates to savings in heating and cooling costs.
Quebec standards for exterior wall insulation
In addition to the various benefits it provides, exterior wall insulation for new structures is also required by the law. In fact, according to the Quebec Construction Code, an insulation value of R-24.5 is required for exterior walls.
The R-value is the heat resistance of a layer of material and is expressed in m2K/W or ft² °F h/BTU for those using the imperial system. The higher the R-value, the greater the heat transmission resistance and the more insulating the material.
Different techniques for insulating wood frame walls
Prefabricated wood frame walls have cavities (between the studs) that make insulating them much easier.
However, since each project is different, you should know that there are two options when it comes to insulating wood frame walls.
Thermal insulation of walls from the inside
In a house under construction where the exterior walls are not yet sealed with drywall, thermal insulation from the inside is the simplest technique to apply.
Wood frame walls are designed to be very easy to insulate from the inside. In fact, their load-bearing structure made up of studs spaced a few dozen centimetres apart accommodates a generous layer of insulation material without encroaching on the living space. In addition, many insulation manufacturers will cut the material to fit easily between the studs.
You can also add insulation in front of or behind the studs to further improve performance, without ending up with a wall that is too thick once it is closed up.
Thermal insulation of walls from the outside
Although thermal insulation of walls from the outside is not incompatible with wood frame structures, it usually only complements wall insulation from the inside. This is because this technique requires encroaching on the land area, whereas insulation from the inside makes the most of the available space.
That said, it is entirely possible to insulate walls from the outside and achieve good results. This option should be considered when it is not feasible to open the walls of a building to improve the insulation.
What type of insulation should I use for wood frame walls?
As mentioned above, wood frame walls used in many projects can be insulated with a variety of materials. But which insulation is best for this type of wall?
La réponse va dépendre de plusieurs facteurs, dont le budget disponible. Cependant, il est recommandé de baser son choix d’un isolant sur des caractéristiques telles que :
The answer will depend on several factors, including the available budget. However, we recommend that you base your choice of insulation on characteristics such as:
- Fire resistance
- Temperature maintenance (R-value)
- Noise reduction properties
- Water resistance
- Adaptability to architectural design and ease of installation
Naturally, the insulation materials that offer the best overall performance are the most frequently used. Here they are:
Wool insulation for wood frame walls
Usually sold in preformed batts that are easily inserted between the studs of wood frame walls, wool insulation slows the spread of heat, cold and noise in structures by trapping pockets of air.
Fiberglass wool insulation
Made of extremely fine glass fibers, fiberglass wool is marketed in various densities. It is commonly used for exterior wall insulation because of its R-value which can range from low to very high.
Mineral wool is formed by spinning or drawing molten mineral or rock materials such as slag and ceramic. Its fibers are positioned randomly in relation to each other. Its R-value is also variable and it is sometimes called “rock wool”.
Cellulose: an eco-friendly alternative for wall insulation
Cellulose insulation is an environmentally friendly, effective and non-toxic thermal solution worth considering. It is most often sprayed inside walls by professionals and reaches a density of around 3.5 pounds per cubic foot.
Cellulose is “green”. It is composed of post-consumer recycled newsprint, among other things. The fiber is chemically treated with non-toxic borate compounds to resist fire, insects and mold.
Rigid insulation panels for prefabricated walls
Rigid insulation panels can be used to insulate almost any part of your home, from the roof to the foundation. However, they are particularly effective for insulating prefabricated wall panels. They offer up to 2 times the thermal resistance of most other insulation materials of the same thickness. In addition, they reduce thermal conduction through structural elements, such as wood. The most common types of materials used in the manufacture of foam panels include polystyrene and polyurethane.
Spray polyurethane foam
In addition to being a thermal insulator with a very high R-value, spray polyurethane foam also acts as an air and vapor barrier when applied to the interior of a wood frame wall. It conforms perfectly to the shape of the wall and is moisture resistant.
However, this insulation technique is more expensive than wool insulation and loose-fill cellulose. Moreover, it is preferable that polyurethane foam be applied by qualified professionals for the best results.
Precautions to take when insulating wood frame walls
Exterior wall insulation is a job that needs to be taken very seriously, as it can be quite complex to correct any problems identified once the walls are closed in and covered with paint or siding.
Here are some things to watch out for at this stage.
Leave no space unused
Thermal bridges are one of the problems that can occur when insulation is not properly installed. They occur when an area of the wall is not filled with enough insulation.
It is important that the right amount of insulation material covers every surface of the exterior walls. It should also be anticipated that some materials may have a tendency to settle over time.
Follow the recommendations of the insulation manufacturers
Some insulation manufacturers provide specific guidelines for the use of their products. It is important to follow these guidelines to the letter to take full advantage of their insulating potential.
Watch out for moisture
Insulation and waterproofing work hand in hand. If an exterior wall is poorly sealed, the insulation materials inside could get wet and lose their effectiveness.
Vapor barriers must be installed where needed and doors and windows must be properly sealed to ensure that the money and energy invested in insulating a building is well worth it.
Insulation is included when you choose UsiHome wood frame walls
In conclusion, exterior wood frame wall insulation is a topic that can easily be expanded upon. We trust that we have convinced you of its importance and that you will feel better equipped if you are planning to improve the insulation of an existing building or a new project.
At UsiHome, we always include insulation in our wood frame walls to make life easier for building contractors. This can take different forms depending on your needs and preferences, but one thing is for sure, it guarantees the energy efficiency of our prefabricated walls.