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Pros & Cons of Fibreglass Batt Insulation & Spray Foam Insulation

August 20, 2018

When you are installing insulation, it is important to know that there are different types that can be used throughout the house. Technically speaking, there are some pros and cons between each type, but these minor variances can be mostly overcome with the right approach. This begins with knowing what insulation does, and what factors can affect its performance.

Essentially, insulation is designed to prevent “heat transfer” – in other words, the end result is to make sure that heat either stays inside or outside depending on the season. Undesirable “heat transfer” (in winter and summer) is a major contributor to energy inefficiency, and stopping that dynamic is the aim of insulation. You can read more about the different types of heat transfer here. When a “building envelope" is insulated with fibreglass batt insulation or spray foam insulation it provides interior comfort, reduced energy use, and savings on utilities.

Choosing between fibreglass batt insulation or spray foam insulation: the pros & cons

Fiberglass batt insulation is by far the most common type of home insulation in North America. It’s considerably cheaper than spray foam insulation,– though this does not mean fibreglass is inferior. Because of its many attributes, spray foam insulation is gaining popularity, and is becoming well-known in the insulation community. However, when also considering the multiple factors involved in installation, we begin to see that the two products have similarities in how they perform when everything is done right – it’s more a matter of whether or not you have the right installer.  If you’re deciding between fibreglass batt insulation or spray foam insulation, then comparing the two can be valuable in decision-making.

Product and installation cost

Fiberglass batt insulation is available in standard sizes (pre-cut), making for easy installation into wall studs, attic rafters, and ceiling joists. Irregular-sized spaces can be insulated with custom-cut batts. Both product and installation are affordable, and less expensive than spray foam options. To make sure you achieve maximum performance, you should also consider air sealing. This can be accomplished with a single component foam, ‘flash and batt’ approach, strategic use of polyethylene sheets and caulking, or fluid applied air sealing. If the construction is new, there are more options available to increase its effectiveness.

Spray foam insulation is a more complex installation than fibreglass batts, thus making it more expensive. The product requires professional handling, and the install requires highly specialized equipment. It is a premium-priced product that achieves air sealing at the time of installation – without any extra steps.

Thermal protection - R-Value

When compared with other insulation products, spray foam insulation offers the highest R-Value per installed inch. Because spray foam will completely seal and insulate the “building envelope”,, allowing for the ultimate in thermal protection (and R-Value). Spray foam can be closed-cell or open-cell. Open-cell is usually R-3.5 to R-3.6 per inch, and closed-cell is usually around R6 per inch.

Both fibreglass batts and loosefill fiberglass offer satisfactory R-Values when professionally installed. However, there may be a loss of thermal protection over the lifetime of loosefill fiberglass if it is not professionally installed (i.e. due to settling of the product). This might affect energy efficiency over the long term, and can require “topping up”.  These types of issue may be mitigated by  working with a professional. Additionally, a professional will  help ensure that precautions such as air sealing are performed beforehand. Fibreglass batts and loosefill can provide up to R-4.3 per inch.

Airtight seal and air barrier

One of the key attributes of spray foam insulation is the capacity to seal a space airtight. Spray foam creates an air barrier and insulation barrier at one time. It prevents heat transfer; reduces the likelihood of mold; and increases the energy efficiency for your home.

With fibreglass batts, creating an airtight seal requires additional work. Since the batts do not naturally provide an air seal, it’s necessary to install a separate air barrier to do the job.  A DIY approach to fibreglass may be tempting, but a professional installer has the ability to make fibreglass perform comparably with spray foam at the end of the day. Fibreglass also does not feed mold growth.

Seasonal energy efficiency

Spray foam insulation offers very high energy-efficiency results because of its R-value and air sealing combo. With better R-Values and better airtightness, the results are evident – lower heating and cooling costs; more balanced HVAC performance (furnace/air conditioner); and enhanced indoor comfort season to season.

With fiberglass batt insulation, installing a high-density product can provide much better energy efficiency when space is limited. With the right installation technique, fibreglass batts also do their part in keeping your home cool during the summer and warm during the winter.

Moisture/vapour barrier

Once installed, spray foam insulation performs as a vapour barrier;however, whether or not spray foam can act as a vapour barrier is according to the type of spray foam being used. Of course, spray foam on a massive scale should never be considered a DIY project, so a professional will know what the best approach for you to take is, and what is needed to meet the legal requirements.

Because of the type of product, fibreglass batts do not themselves create a vapour barrier. A proper installation must include a separate vapour barrier. In the attic cavity, where moisture accumulation can be prevalent, this is a major concern for inexperienced installers. When you hire someone to install any installation, you should always make sure that they know every detail of how the product should be installed. Never be afraid to ask either – just make sure to ask these questions before you hire them.

Thermal Barriers

Whatever the installation option (fibreglass batt insulation or spray foam insulation), the issue of thermal barrier protection is an important consideration for every install. With spray foam, this requires a special application of thermal barrier material to be applied over the exposed insulation. Once installed, you can expect the same level of safety in terms of fire that you would with other types of insulation.

Fibreglass is either naturally fire resistant or treated with a fire-retardant – this depends on what type is being used. Fibreglass, like spray foam, can be used for multiple applications in both new and retrofit construction. Whether it’s being blown into an attic, or tightly placed into wall cavities, properly installed fiberglass insulation provides you with a safe and comfortable home.

Choosing the right insulation product for the job

At Great Northern Insulation, our resident experts recommend the product and installation that best suits the project. In a choice of fibreglass batt insulation or spray foam insulation, GNI will consider various criteria, each relative to the situation. From R-Values, to air movement, to air moisture, to whether it’s new or retrofit, everything is assessed. The aim, of course, is to deliver the very best dollar value in the short term, and the very best savings for the long term.

Insulating a home is about enhancing indoor comfort, conserving energy, and saving on seasonal utilities. What’s important is to do it professionally. And while some homeowners might opt for a do-it-yourself approach to insulation, we feel you should really weigh the pros and cons of that scenario, even if it saves a few dollars preparing for the installation – it’s either during or after installing the insulation where savings add up and matter most. Spray foam insulation, for example, is full of risks for the DIY installer. At the same time, the performance of fibreglass batts can be optimized by a professional.

With every home insulation project, the experts at Great Northern Insulation manage the work from end to end. GNI has been in business almost 40 years, supplying the best quality products on the market, and providing superior workmanship regardless of project size. With top installers in the industry, every part of the home is covered – from the attic, to the basement, to the exterior walls. The result is an energy-efficient home.

Many people turn to spray foam as being the leader in insulation because of its inherent performance. In fact, there are many cases where we will recommend it. However, it’s not the only insulation that we pride ourselves in mastering. In some cases, we may well recommend a combination install, which includes both spray foam insulation and fibreglass batt insulation. It’s a cost effective option with excellent outcomes overall. If you choose to opt strictly for fibreglass, we have proven techniques that make sure you get the most out it. Whichever path you choose, rest assured that we have the knowledge to make it work for you.

Find out more by calling GNI at 1-800-265-1914 or filling out a contact form below.


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