How Important is Insulation in the Attic?

Posted by Ecostar Insulation on April 17, 2018

On the EcoStar Insulation blog, we talk a LOT about how it is important to insulate the attic, and what the benefits are to you and your home, such as increased indoor comfort and better energy savings and efficiency. Installing new insulation can help seal air leakage, reduce or help prevent problems like mold growth, and can help act as a sound barrier.

But that doesn’t truly answer why it’s important to insulate the attic from a structural, building science approach. If you’re considering installing new attic insulation and you’re wondering about the why behind the benefits, read on for more information about what part vapour retardants, ventilation, caulking, and hazardous materials play in keeping your home running as an efficient system.

Why is it so important to insulate your attic?

The Attic System

Your attic is made up of a number of different materials and systems that need to work together effectively to deliver the benefits of good insulation. Today we’re taking you through four of those different materials that make up good (or bad) insulation installations. They’re best used in combination with the right type of insulation for your home - for more information on that topic, read last week’s article Which Type of Insulation is Best for Your Home?

Vapour Retardants

 A vapour retarder, also known as a vapour barrier, is a material that impedes the flow of moisture through your walls, protecting your building envelope from the damage that water and condensation can cause to your insulation or wooden structure. When it comes to why it’s important to insulate the attic, preventing moisture infiltration is one of the most important parts of an effective system. There are three types of vapour barriers that we commonly see:

Polyethylene Sheeting

As you might have guessed from the name, this is a petroleum derived plastic that is installed on the interior of the building. A thickness of .15mm is usually the best for construction purposes and since it’s usually available in wide sheets, it minimizes the opportunity for seams and joints that can become weak over time.

Vapour Retardant Paint

This specially formulated paint is designed to reduce the flow of moisture through interior walls and ceilings, and acts as both a primer and finish in one. It’s most successfully applied to materials like drywall and plaster.

Spray Foam

One of the biggest benefits of choosing spray foam as your insulation material is that closed cell foam acts as a vapour retardant as well as insulator, and works excellently in areas that sheeting cannot be installed.

Attic Baffles and Air Flow

Preventing unwanted air leakage is one of the reasons it’s important to insulate the attic - you don’t want your conditioned air leaking into the attic. But an attic should always have some air flow and circulation to ensure moisture and condensation don’t build up.

Soffits and gable vents are one way fresh air is drawn into the attic, but they can also allow gusts of wind to move loose fill insulation around. Baffles act like a screen to separate your insulation and moving air, keeping it in place so that it doesn’t cover soffits or fall out of the eaves. 

There are several types of baffles commonly used:

  • expanded polystyrene
  • extruded polystyrene
  • cardboard

Sheathing Tape and Caulking

These two materials help to keep vapour barriers, baffles, and other things in their place. It’s important to insulate the attic right the first time, and both sheathing tape and caulking will help keep your insulation where it belongs and protected from the elements and pests.

Sheathing tape is a strong, permanent, all weather polypropylene film designed to seal the joints of weather barrier materials. At every step it’s important to choose the right material for the job - all sheathing tape is not created equally and some types are not recommended for use with polyethylene. Read the packaging carefully and choose the right materials.

Caulking is used to create a tight seal around vapour retarders and to seal joints. It comes in different varieties depending on the task - carefully check the can before using:

  • Acoustical sealant
  • Urethane foam sealant
  • Expanding foam sealant
  • Latex foam sealant
  • Butyl rubber sealant

Hazardous Materials

If you’re replacing old insulation, the age of your home should always be carefully considered. If your home was built before 1980, it’s essential to have a professional assessment of your attic to identify any hazardous materials present in your insulation or building structure. The most common types of hazardous materials found in attics are:


Once touted as a miracle fibre, asbestos is now banned because of its link to lung cancer, asbestosis, and other forms of lung disease.


This popular mineral was used in insulation and can be contaminated with asbestos fibres.

While neither asbestos or vermiculite is harmful if it’s sealed behind walls and floorboards, it is dangerous and a health hazard when disturbed during renovation or demolition. If there is asbestos or vermiculite insulation in your attic, you WILL need a professional asbestos remediation team to ensure that any harmful materials are safely removed.

Insulating your Attic Right

These different materials and tools are important to consider when insulating your attic. They are the reason why your insulation works: they prevent moisture, they help reduce the bad air flow and increase the good kind, and help seal your attic and insulation from unwanted intrusions. If you have any more questions about why it’s important to insulate the attic, just get in touch! We’d be happy to explain any of these materials and why they may - or may not - be working right in your home.

Request Your Quote Now. Call Us 1.866.789.1536 or 647.799.3106


Please, enter a valid value

Please, enter a valid value