Resources & Sources

Here you will find all the resources and sources to back up all the facts on Weathershield Insulation.

Insulation Content

Cellulose insulation is manufactured from recycled paper and cardboard and treated with additives to provide fire resistance and other properties.  Paper stock is 100% recycled material (mostly post-consumer, some post-industrial).  The end insulation product is at about 85% recycled content.  Fiberglass insulation is manufactured from sand with some recycled glass mixed in, which is melted and spun into fibres. With Fiberglass, recycle content varies with manufacturer – claims range from 25% (JM) to 35% (CT) to 53% (OC)

Fibre Structure

Since paper is made from trees and plant materials, the fibre structure is based on cellulose fibre, hence the name of this type of insulation product. This structure is known to be based on a make-up or sub-structure of many tubular strands, which themselves can trap air, thus lending the idea of cellulose fibres being hollow. So in addition to trapping air between fibres, the added trapped air inside the fibres allows for greater insulating ability compared to fiberglass, where fibres are solid (limited insulating air entrapment). Paper is known to be a poor conductor of heat (which is what you want in an insulation product) – and glass is known to be a good conductor of heat (which is what you don’t want).

Cellulose Reference Source:

Fiberglass Reference Source:


Cellulose insulation appears grey due to the contribution of printing inks etc. when recycled paper products are shredded and processed into insulation.  This occurs naturally and no additives are used to mask this. Fiberglass products are colored differently depending on the manufacturer. Dyes or other additives are used.

Reference source: none required

Canadian National Standard for Product
Thermal Resistance

This is determined as required by the national standard of the product.

  • Cellulose Reference source: as indicated by coverage information of manufacturer.
  • Fiberglass Reference source: as indicated by coverage information of manufacturer.
Thickness Needed for R-40
Reference source: not required (simple calculation).
Installation Density

This is determined as required by the national standard of the product.

Cellulose Reference source: as indicated by coverage information of manufacturer.
Fiberglass Reference source: as indicated by coverage information of manufacturer.

Resistance to Air Infiltration

Two identical structures were built and equally insulated, one with fiberglass and the other with cellulose. The cellulose structure was found to be as much as 38% tighter, allowing less heat loss due to air infiltration.

Reference source: University of Colorado 1990, Boonyartikarn, S. and Spiezle, S., “Fiber Glass vs. Cellulose Installed Performance”

Susceptibility to Convective Air Movement

Studies by the Oak Ridge National Laboratory in the US proved that cellulose is not subject to the convective effects that degrade the actual R-value of other loose-fill insulation materials at low attic temperatures.

Reference source: CIMA source

Resistance to “Wind Washing”

This refers to the effect of high winds on loose-fill insulation in attics – material displacement and effect on R-value.  Denser (heavier) insulations like cellulose are far less affected.

Reference source:

Fire Resistance

Anyone able to apply a propane torch on a relatively high setting to each of these insulation products will quickly see the difference:

  • The cellulose product will char and smolder and flame, but once the torch is removed, the flame will go out and smoldering will soon stop as well. The insulation, although charred, will remain in place – this behavior protects the building structure longer and provides more escape time for occupants (and more time for fire fighters to mitigate damage) in the event of a fire.
  • Although it will not burn, fiberglass will quickly melt away, exposing the building structure to flames in the event of a fire. The molten glass may also contribute to fire damage.

The NRCC (National Research Council Canada) reported that cellulose insulation increases the fire resistance of insulated building assemblies by 22-55%.  In contrast, fiberglass insulation decreased the fire resistance of assemblies that were identical in every way except for the insulation.  Full-scale testing in the US suggest cellulose-insulated wall sections complete with steel electrical boxes, are 77% more fire-resistant than uninsulated cavities.

Several studies have confirmed cellulose insulation will retain its fire retardant properties over time.  The S703 national standard for Cellulose requires that material pass fire resistance permanency tests where product is “aged” by temperature and humidity cycling.

Reference source:
-NRCC July 1994 – Results of Fire Resistance Tests on Small-Scale Insulated and Non-Insulated Gypsum Board Protected Wall Assemblies
-CIMA source – Omega Point Laboratories / Large-scale ASTM E119 tests
-Fire retardant permanence – several references on file (CIMA source)


Acoustical Value

Depending on application and needs, acoustical value can be similar.  However, density lends a great deal to stopping sound.

Reference source: CIMA: Cellulose vs. FIberglass Insulation Sound Proofing Demonstration


Relative Toxicity
  • Cellulose insulation is a blended product, mixing together constituents that have been characterized and are known to have relatively low toxicity. Cellulose insulation is considered a nuisance dust hazard for installers.
  • Fiberglass is a unique manufactured fibre that has been linked to severe health implications.

Reference source: CIMA and other sources


Embodied Energy to Manufacture
  • Cellulose insulation is manufactured using electricity-driven processing equipment, resulting in low embodied energy and contributing very little to air pollution.
  • Fiberglass is produced using gas-fired furnaces which,  results in much higher embodied energy.  Production emits CO2 and other greenhouse gases into the air.

Reference source: CIMA sources:  various

Thermal Performance in Extreme Cold

Studies in the US showed that the R-value of fiberglass insulation dropped from R-18 @ 7°C to R-11 @ -28°C.  Over a similar temperature range, R-19 cellulose showed an actual increase in R-value of about 10%.

Reference source: CIMA source (Oak Ridge National Laboratories)

Thermal Performance in Extreme Heat

In addition to being affected by cold, fiberglass is affected by heat.  Glass conducts heat and can lose significant R-value in a hot attic.  Cellulose is only slightly affected.

Reference source:

Moisture Resistance (High Humidity)
  • Cellulose fibre is hygroscopic – it absorbs moisture.  However, it can draw or wick moisture from sheathing and framing lumber and dissipate it to drier areas.  Stored moisture is in the fibres themselves, not in the air spaces between fibres, so R-value isn’t heavily affected.  Once dry, R-value is regained fully.
  • Fiberglass fibres themselves don’t absorb moisture, but moisture can be stored in the spaces between fibres, thus affecting R-value.  If the moisture freezes in the insulation, it can fracture the glass fibres, permanently damaging the insulation.

Reference source: CIMA source

Moisture Resistance (Running Water)

Both products perform poorly when heavily wetted and do not dry out readily.  At this point, however, there is likely structural damage to the building that should take precedence and be addressed.

Reference source: none required

Mould/Fungi Resistance

Cellulose insulation is treated to be mould/fungi resistant, and is required to be so by the national standard and is tested accordingly.  Although fiberglass manufacturers will claim their products do not support mould/fungi growth, countless discoveries are made to the contrary.

Reference source:

Insect/vermin resistance

There is no standard test method to determine whether or not any product is rodent or insect resistant. The reputation of Weathershield™ and WallBAR™ as vermin resistant is largely based on word of mouth and lack of negative feedback from numerous customers who use these products in conditions where vermin exposure is high. Such cannot be said for fiberglass or foam products.

Reference source:


Ease of Installation
Reference source: under development
Additional general sources:  Why Cellulose is Better than Fiberglass Insulation  The Big Burn: The Truth About Cellulose Insulation  Nu-Wool – Cellulose vs Fiberglass