How to Effectively Insulate and Ventilate a Finished Attic

September 20, 2018

Because attic insulation and attic ventilation must work together to ensure performance, it’s important to properly insulate and ventilate a finished attic. By any definition, the attic space must be properly sealed, properly insulated, and properly ventilated. However, your attic acts differently when it’s finished and becomes a conditioned space like the rest of your home. For this reason, it requires a different approach than when it’s unfinished. This article examines how to effectively insulate and ventilate your finished attic.

It’s recommended to properly insulate and ventilate a finished attic

Your attic is a space that requires special attention when striving for optimum energy efficiency, and it’s often overlooked. For professional contractors, the attic is traditionally considered a separate “envelope”. This is because it’s unconditioned, so it’s the floor of the attic that is insulated. This essentially separates your attic from the rest of your home and its conditioned air.

A finished attic becomes part of the entire building envelope when it becomes open to the rest of the home. A well-insulated attic results in less energy use, reduced energy bills, and enhanced indoor comfort – both for your entire home and anybody spending time in the attic.

In a space like the attic, optimum energy efficiency is achieved when insulation and ventilation work together. It’s therefore not enough just to fill the attic with insulation material. You also need to change the way the ventilation is thought of in your attic. Doing it properly means sealing up the space to prevent air leakage and ventilating for air circulation. Also important in the attic is preventing undesirable moisture and condensation from accumulating.

The importance of a well ventilated attic when the space is finished

In an unfinished attic, outside air is taken in through soffit vents – the under part of your roof. From there, air the air circulates throughout the attic and leaves through a turbine vent, ridge vent, gable vent, or other form of vent. This helps prevent condensation and ice damming by keeping the attic temperature closer to that of the outdoors than your living room. (When you aren’t using your attic, you just need to worry about keeping yourself warm where you actually live!)

When your attic finished, things start to change. There are a couple different scenarios to consider. The first is to keep the ventilation flowing through the soffit to the ventilation at the top of your roof. This can be done by building an attic kneewall with the space that you are not planning to use and guiding the outdoor air behind baffles. This gives a similar effect to an unfinished attic.

The second option is to apply spray foam is to the underside of the attic. This creates a continuous insulative barrier and effective air sealing. It also gives you more space in your finished attic. This also helps to prevent ice damming. It is important to ensure that proper ventilation from the soffit vents is allowable in this case as well. If this is not done, it is known as a hot roof. This method requires special attention from a spray foam certified professional such as Great Northern Insulation. Always confirm with your local building inspector that a hot roof is appropriate/approved in your jurisdiction. In either case, you should make sure to properly ventilate your finished attic with your air system.

What is the best insulation for your attic?

Properly installed attic insulation has several objectives: blocking air leakage; preventing moisture collection; reducing energy usage; and lowering seasonal energy bills. Without proper insulation, rooms are drafty; indoor temperatures fluctuate; and utility bills are high. Deciding on how best to insulate is an important consideration, and hiring a professional contractor can be valuable in the decision process.

In the attic, fiberglass “batt” insulation is a good option. These are the fluffy “batts” (sometimes pink) that are both affordable and effective. They provide satisfactory R-Values over the long term but must be properly installed to ensure performance. While the “batts” do provide a good thermal barrier, it’s still necessary to install both an air barrier and vapor barrier to complete the insulation “system”.

Another option for the attic is blown-in insulation. Available in cellulose or fiberglass, both options are environmentally sustainable options. Both cellulose and fiberglass are fire resistant - cellulose is treated to prevent fire from spreading and fiberglass is fire resistance simply because of its glass content. Blown-in insulation will require an air barrier and vapor barrier.

Last but not least is spray foam. This product is sprayed into the attic and provides a complete envelope of insulation throughout. It acts as an insulating barrier, air barrier, and vapor barrier at one time. Spray foam insulation requires professional application, mainly because the product needs special handling and the installation itself requires experience and expertise.

How much insulation is required in the attic?

Industry statistics show that most residential attics are actually under-insulated. Here, a professional attic inspection can be very valuable in evaluating current conditions, and in recommending what type of retrofit would be required. Naturally, the amount of insulation required depends on which product is being installed and the scope of the retrofit. Oftentimes, a good “top up” is all that would be required.

What R-Value is recommended for the attic?

Regardless of the product installed, insulation performance in the attic is assessed by a measurement referred to as R-Value. The higher the R-Value, the better the thermal performance. Since every home is different (and with different physical challenges), a professional installer can best advise on R-Value requirements. This is done after a comprehensive inspection, which might include a blower door test.

Can you put insulation on top of insulation?

If existing insulation is in good shape, and without signs of deterioration, new insulation can certainly be installed over existing insulation. If there is deterioration, the cause and extent must be determined and necessary repairs must be made. Wet insulation in particular is a problem, as this can be a sign of leak in your roof. In addition, this could quickly lead to mold growth, let alone rotting wooden roof rafters.

Once again, a proper attic inspection will determine if there are any issues with the existing insulation, and what remedies might be required. In some cases, we may recommend that the existing insulation be completely removed. This would allow for the new insulation (plus air barrier and vapor barrier) to be installed from scratch, thus ensuring the maximum in insulation performance.

Worried about the cost of the upgrading?

Great Northern Insulation can offer you financing when you insulate and ventilate a finished attic. On approved credit, you can choose to be payment-free for the first 12 months and then make monthly payments. You can pay the balance at any time. You can even get approval online with no obligation to use the total amount.

If you are a Union Gas customer, the Home Reno Rebate Program can help offset the cost of upgrades. Rebates are available for various "energy smart” upgrades. With major upgrades, you can qualify for up to $5,000 in grants. Here, Great Northern Insulation can recommend the right type of upgrade.

The City of Toronto offers homeowners the Home Energy Loan Program. The program is designed for those who will be replacing an old furnace or upgrading insulation in various parts of the home. HELP provides low-interest loans, amortized over the year, and paid in installments on the Property Tax Bill.

Canada Mortgage and Housing Corporation (CMHC) offers borrowers up to 25% savings on premiums. Borrowers must finance through CMHC and either buy, build, or renovate. The program allows energy efficiency upgrades to be more affordable. Here again, GNI can be valuable in offering upgrade options.

In Ontario, count on Great Northern Insulation for energy efficiency upgrades

If you’re planning to insulate and ventilate a finished attic, you can rely on Great Northern Insulation for the highest quality products and the highest quality installation. Start things off with a FREE in home energy assessment. Call 1.800.265.1914 or fill out a form below.