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Insulating Existing Walls

December 15, 2015

In most cases, the building code requires a defined minimum of insulation in a home's exterior walls and ceilings. Interior walls are not as important, although insulating these walls may contribute to energy savings and certainly soundproofing. Needless to say, insulating any wall is best expedited during initial construction, but it's also possible to install insulation into existing walls (exterior and interior). And the benefits of doing so will make the investment worthwhile.

Improving Energy Efficiency

Insulating existing walls (particularly exterior) will enhance the energy efficiency of a home, and will consequently save on heating and cooling costs throughout the year. As for interior walls, adding insulation does more for soundproofing than energy efficiency - however, "heat transfer" will be reduced, making for more comfort, especially where seasonal temperatures are extreme.

Noticeable Soundproofing

For some homeowners, it's important to soundproof inside the home. Installing insulation in the interior walls can reduce "sound transfer" but success is dependent on the insulation product being used. For those with a home theater or media room, insulating the interior walls could be the ideal option and a practical solution. Here, the benefits will outweigh the project cost.

Multi-Unit Party Walls

Where living units are divided by interior walls (multiplexes or apartments), the so-called "party walls" will require insulation. Soundproofing is definitely beneficial, but averting "heat transfer" is more of an issue for occupants. Probably most important is stopping the spread of fire between the units, and here, fire-rated insulation along with a professional install is recommended.

Insulation Products

Fiberglass "batts" are a popular option for insulating existing walls, and are cost-effective. The installation, the fit, and the placement are critical for product performance. Another fiberglass option is "blown-in" insulation, which requires drilling holes into an existing wall, then patching and finishing. In general, a professional install will ensure the best long-term performance.

Retrofit Drill and Fill

Whatever the approach for insulating existing walls, the aims are common - stopping warm air from escaping in winter, and keeping cool air inside in summer. The objective is creating energy efficiency in the home and reducing energy consumption. "Drill-and-Fill" is an innovative approach for insulating existing walls (good for both interior and exterior walls). Essentially, holes are drilled into an existing wall and "loose fill" insulation is then blown into the wall cavity. The walls are then patched. Where exterior walls feel cold, the retrofit "Drill-and-Fill" option is ideal. The much-improved insulation will reduce heating and cooling costs overall, and will prevent pockets of uneven heat and cool. Finally, indoor comfort will be enhanced. "Drill-and-Fill" is particularly well suited for loose-fill insulation products. It's preferable to have a professional install where the product is blown into a wall with consistency and uniformity. The insulation doesn't disturb the structure of the wall. For exterior walls that are finished and hard to access, "Drill-and-Fill" is the ultimate insulation retrofit. R-Values are significantly upgraded, and the energy savings are substantial. Best of all, "Drill-and-Fill" averts the need for serious renovation.

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935 Keyes Drive
Woodstock, Ontario
Canada N4V 1C3

Phone: 1-800-265-1914

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K2R 1H4

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L2G 0B4

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Best of 2017

From reputation to responsiveness, HomeStars consistently ranks Great Northern Insulation at better than 95% for customer satisfaction. Thanks to everyone for the great ratings! 

HomeStars 2018

Best of 2018

For the second year in a row, HomeStars consistently ranks Great Northern Insulation at better than 95% for customer satisfaction. Thank you again to everyone!

Homestars Best of 2019 Award

Best of 2019

For the third year in a row, HomeStars ranked Great Northern Insulation at better than 95% for customer satisfaction.

Homestars Best of 2020 Award

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For four years now, HomeStars has ranked Great Northern Insulation at better than 95% for customer satisfaction.

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HomeStars has ranked Great Northern Insulation as a company that goes above and beyond in every aspect of business for the year of 2021.

Homestars Best of 2022 Award

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HomeStars has ranked Great Northern Insulation as a company that goes above and beyond in every aspect of business for the year of 2022.


GNI is the Authorized & Trusted Insulation and Air Sealing Installer for Lowe’s

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Energy saving and energy efficiency is easier than one might think. Great Northern Insulation helps to identify performance issues, while taking advantage of improvement opportunities.

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Great Northern Insulation is recognized as Canada's largest full-service insulation contractor. GNI is 100% Canadian owned, proudly serving Ontario customers since 1980.

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- with foam mastersTM

WALLTITE® ECO™ is a high-performance system, professionally installed by certified and approved specialists. Its C.C.M.C. approved (Canadian Construction Materials Centre) - with product quality guaranteed - and with installation by highly trained experts with the technical know-how to do the job right, the first time.

Insulthane Extreme

Insulthane® Extreme

For the ultimate in high performance spray foam insulation, Insulthane® Extreme is the professional choice for residential, commercial, and industrial application. With improved thermal performance over other products, Insulthane® Extreme has an exceptionally low Global Warming Potential (GWP). Considered environmentally friendly, this next generation spray foam insulation is non-ozone depleting, and exceeds specifications of other HFC product alternatives.


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3MTM energy-saving products are designed to keep warm air in, and cold air out, while keeping energy bills down. Products optimize energy efficiency in buildings and homes; improve indoor environment for occupants; and effect the reduction of seasonal energy costs. 3M products are authorized for LEED credits (Leadership in Energy/Environmental Design).


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Mike Holmes and his son Mike Jr. (MJ) convert MJ’s bachelor bungalow into a two-storey home for MJ and his girlfriend Lisa. Choosing the newest materials and build techniques, the father and son team follow Mike’s famous motto – “Make it right.” The show can be watched on HGTV and DIY Network.


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