How to choose the best insulation for the attic?

How to choose the best insulation for the attic?

Warning: This basic insulation guide does not replace the advice of a professional. Owners should obtain expert advice and consult their local building code before choosing the type of insulation and its level of quality. Insulator should be placed by professionals.

Should you isolate the inside of your roof? Insulating your home is a great way to increase your energy efficiency. Indeed, good quality insulation will reduce your heating and air conditioning costs. According to the United States Department of Energy, this economy can reach 10% to 50%, depending on various factors. However, insulation in the attic is not only used to reduce energy costs. Adequate insulation can also prevent deterioration of the roof by preventing the formation of condensation and ice dikes.

The building code in force in your locality may require a certain degree of insulation. That said, installing insulation beyond this requirement can only be beneficial for you and your roof. However, excessive insulation can warm your shingles to the point of affecting their lifespan. This is especially true if your roof is poorly ventilated. It is therefore crucial to balance the two essential needs of your roof: insulation and ventilation.

Almost all building codes and all manufacturers of asphalt shingles require the roof system to be well ventilated, regardless of the type of insulation. Certain types of insulation will affect not only the life of your roof, but also the manufacturer’s cover under the guarantee he offers you. Make sure you read and understand the warranty for your roof and its limitations on air circulation and roof insulation.

Find out what to know about insulating your attic and its impact on the performance of your roof.

Benefits of isolating your attic, for you and your roof

Here’s how the proper insulation of your attic can benefit your roof :

  • Prevents the formation of ice dikes. In the absence of insulation, the heat from your house escapes from the ceiling, towards the attic. This is why, during the winter, your shingles are warmer than the outside atmosphere and can melt the snow that covers them. Then, when the temperature drops, or when the melt water flows towards the cooler front, ice forms. This is called an ice dike. Ice dikes affect the performance of your roof and the lifespan of your shingles. They also increase the risk of roof leakage and can damage the gutters if they reach them. Adequate insulation is the best way to prevent damage from ice dikes. Make sure your attic is well ventilated and install a protector against ice and water on the roof, such as the StormShield® membrane.
  • Prevents interstitial condensation. Interstitial condensation is the one that forms between the layers of your roof. It occurs when cold air and hot air meet and the humidity condenses into droplets. These droplets, when accumulating, can damage the materials that make up your roof. However, adequate insulation avoids heat transmission through the roof and mitigates the risk of condensation between its different layers of materials.
  • Extends the life of shingles. On a adequately insulated roof, your shingles are not exposed to ice dikes and undergo less temperature variations. Therefore, they are likely to remain in good condition longer.
  • Warns damage to gutters. Without insulation, the platform of your roof is exposed to greater temperature differences and may expand and contract faster. Over time, these expansion and contraction movements can deflect the gutters and weaken the gutter fasteners.

In addition to contributing to the good condition of your roof, adequate insulation of the attic can also make your home more comfortable and have other advantages for you:

  • Facilitates heating and air conditioning. In a adequately insulated house, the hot air in the house escapes less during the winter and the heat of the sun penetrates less into the attic during the summer. Heat resistance keeps the house air at a comfortable temperature for you at a lower cost.
  • Increases the life of the HVAC system. Elements of the heating, ventilation and air conditioning system can last longer if they are less in demand. On the contrary, HVAC systems which operate continuously to compensate for heat losses by it more often fail and last less.
  • Stabilizes the temperature. Insulation of the attic keeps air conditioning inside the house instead of letting it escape through the ceilings. The rooms of the house therefore remain at a more homogeneous temperature, from floor to ceiling. This makes your home more comfortable, especially if you have a cathedral ceiling.
  • Isolates noise. Insulation of the roof can also reduce the level of noise from outside. This additional benefit is interesting if you live on the edge of a noisy street, near a construction site or other source of noise. However, if sound insulation is your main objective, wall insulation is generally more effective.

Types of insulation for the attic

You wonder what type of insulation is ideal for your attic? Here is an overview of the main choices available to homeowners:

  • Insulating in bulk. This type of insulation is in the form of fine particles that are blown in the attic. The bulk insulation may consist of fiberglass, mineral wool or cellulose. It is a wise choice for spaces under the roof that have many small holes.
  • Insulating in mats or rolls. This type of insulation resembling a thick cover is found in mats or rolls. It can be composed of natural fiber, plastic fiber, mineral wool or fiberglass, the latter choice being the most common for attics. The mats are offered in a format adapted to the typical spacing between farms and rafters. The insulation in mats or rolls can also be fitted with a vapor barrier membrane on one side, which prevents condensation and facilitates the fixing of the insulation.

Each type of insulation and each product in particular is offered in different R values. The R value indicates the degree of thermal resistance of a material, therefore its ability to prevent heat from passing through it, inch of thickness. The higher the R value of a material, the better its insulating capacity. Although better results can be obtained with any type of insulation simply by installing a thicker layer, the energy department recommends a thermal resistance of at least R30 for insulation of a roof. In colder regions, this requirement may be even higher.

Rigid foam panels, like those made of polyisocyanurate, often offer the highest value R per inch. However, these materials are generally used for insulation of commercial buildings and not houses. That said, some rigid foam panels, such as IKO Enerfoil®, can be used for residential applications when the thinness and yield of the insulation are crucial. For example, an access hatch to the attic cannot accommodate thick insulation, but contributes greatly to the loss of heat, which justifies the use of a rigid panel. Likewise, a cathedral ceiling often does not allow the use of thicker insulation.

Hot roof or cold roof

We sometimes hear the terms “hot roof” or “cold roof” when we are interested in the different ways of isolating a roof. These terms do not refer to a particular type of insulation or material, but rather to where the insulation is installed. To obtain a cold roof, the insulation is installed on the attic floor. It therefore remains cold during the winter since it is exposed to external conditions. This type of insulation is only suitable for unmanaged attics which will remain as follows.

For insulation of the “hot roof” type, the insulation is installed directly on the inside of the roof, therefore on the ceiling of the attic. With this type of insulation, your attic stays warm during the winter since the heat of the heating system can reach it. If you are considering fitting out your attic, this is the type of insulation you need. Otherwise, it will be very difficult to heat it in winter and keep it cool in summer.

The latter type of insulation, however, has repercussions on the performance of shingles. Indeed, a warm roof does not allow air circulation between the shingles and the insulation. With such a configuration, the shingles become warmer than on a cold roof. This increased heat is more likely to cause shingles, which will age prematurely. In addition, hot flattening is more subject to the formation of ice dikes, condensation and mold.

How to isolate an attic

Always use the services of an expert to install the insulation under your roof. An isolation specialist will take many essential precautions, for which owners may not have the necessary knowledge or equipment. In addition, errors that owners may make in trying to isolate their roofs by themselves, such as blocking vents or using an inadequate installation technique, can lead to very costly repairs.

Here is what you can expect when a professional comes to isolate your attic:

  • Inspection of the current insulation. With an expert, you should inspect the current insulation in your attic (if it is already isolated) and assess its condition. This is an important step, since it makes it possible to detect any damaged roof or chevron problem, to be repaired by a roofer before installing the new insulation. Otherwise, leakage from the roof could damage the new insulator. Your contractor will also be able to assess the quality of the current insulation and ensure that the new materials used will be an improvement. During the inspection, it will determine the dimensions of the space available under the roof, since certain insulating materials may be too thick to be installed there.
  • Choice of new insulator. Then you should review the different choices available to you. Your insulation expert may recommend certain options depending on the space available, your budget and the desired R value. If you do not know precisely what type of insulation and which R value best suit your climate, consult your building code to find out the requirements and recommendations that apply to your province or territory. You can consult the Canadian Building Codes and Standards and other codes in effect. Residents of the United States can refer to their climate zone according to the IECC. When you have made your choice and accepted a bid, work can begin.
  • Port of protective equipment. During the works, the insulation professionals will wear protective equipment. The exact composition of this equipment depends on the type of insulation to install, but in general, they wear a combination that covers their entire skin, in addition to protective glasses and a mask.
  • Application of insulation according to manufacturer’s instructions. Your contractor should follow the manufacturer’s instructions to install the selected products to the letter. However, these guidelines vary widely depending on the product. For example, the outside temperature may affect certain types of insulation during installation. If this is the case, the work should be postponed until the right conditions arise. Otherwise, in the case of a roller insulator, it may be necessary to take additional measures in order not to block any electrical device or vent. As for the duration of the work, it will also depend on the type of insulation installed. Your entrepreneur should be able to provide you with an estimate according to your specific needs.
  • Examination of the gutters. A few days after the end of the work of insulation of the roofs, it is advisable to ask your roofer to examine your gutters. Now that the front-to-roof platform and border are protected from air conditioning in the house, a rapid change in temperature may have inflated or contracted the materials. Your roofer may need to adjust your gutters so that they continue to perform their water discharge function well. If the gutters have deformed, it may be necessary to replace them.

Insulation under a low slope roof

Low slope roofs can be difficult to isolate. On the edge of the attic, where the slope of the roof joins the floor, there is often not enough room for a sufficient thickness of insulation. This is particularly true if the roof has soffite vents with deflectors allowing air circulation. In this case, Natural Resources Canada suggests that the space available for the insulation may be as small as 10 cm.

It is then necessary to use a superior quality insulator, which will provide a high R value despite its small thickness. Rigid foam panels are generally suitable. Insulating in mats or rolls may also be suitable and is easier to install in small spaces than the blown insulation. Seasoned entrepreneurs can still install this type of insulation, provided they can get it with an adequate R value.

In order to save when insulating a low slope roof, it is possible to install a very thin and high quality insulation at the edge of the attic (and in other critical areas), then to install a different, thicker and more economical insulation in the rest of the attic. It is best to chat with your contractor to determine if this is suitable for your home.

Insulation of a roof without attic

Houses with a cathedral ceiling or that do not have an attic have less space available to install insulating materials. This can affect the longevity of the roofing system, as there is often insufficient space to allow adequate air circulation under the roof. Manufacturers who design cathedral ceilings should provide enough space for insulation and air circulation, but this is not always the case. The problem is accentuated if typically thick insulating materials are used, such as insulation in mats or rolls.

In addition, the ceilings are pierced with several holes intended for plumbing or electrical devices, which can be difficult to seal properly. Your entrepreneur may offer you several options, including:

  • Install rigid foam panels on the ceiling. This material is thin and generally with an impressive R value.
  • Install a high quality blown insulation in the ceiling. This material fills the gaps around plumbing elements and electrical devices very well.

You have your roof replaced? Take the opportunity to renew your insulation

A roof repair is a good opportunity to modernize the insulation of your attic. If your roof has leaked, the insulation may have been affected. Your insulation is all the more likely to be damaged if your flattening is affected by rot, since this means that humidity has been present in the roof for a long time. That said, some types of insulation, such as closed-cell insulation, are not sensitive to moisture. All other types of insulation should be replaced if they have been wet, as they will no longer perform their function.

In addition, when repairing the roof, your roofer may need to add roof vents to maximize the life of the shingles. If so, he may need to remove part of the insulation in place. However, if the attic floor is isolated, a new vent can be made in the roof platform without moving or removing the insulation.

Before installing a flat roof, it is strongly recommended to determine whether better insulation would be advantageous. Once the flat roof is installed, it will have to be removed if you ever want to improve the insulation.

You are ready to enjoy the benefits of a well-insulated attic? Communicate with your roofer to find out what choices are available to you, using the IKO entrepreneur locator

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