Fibreglass is far more durable and stronger than felt. It has no seams, so it is less prone to fail and let water in, and it is reasonably simple for an expert to fix if it is broken. Because roof felt is not routinely recycled, this is also more environmentally beneficial. The disadvantage of fiberglass roofing is its high cost. However, if you can afford it, it would be worth the investment. Felt comes in various grades with different strengths. Low-grade felt is used for covering small areas such as backyards or garages where weight isn't a concern. Medium-grade felt has greater strength but is also heavier, which makes it less suitable for use on smaller roofs. High-grade felt is even stronger and lighter than medium-grade felt, which makes it ideal for use on larger structures. Felt's main advantage over fiberglass is that it is much cheaper. The quality of felt is very subjective - some people might say that low-grade fiberglass feels similar to felt, while others claim that they can tell the difference even when applied side by side. Another advantage of felt is that it doesn't emit gases when it burns. This is important because felt tends to burn fast when exposed to heat or flames, which could cause a fire at someone's home or office building. Fiberglass does produce gasses when it burns, which could be dangerous if there's enough of it around.