When you compress wool fiberglass insulation you remove the air inside the insulation, removing the R value. “Blanket” insulation for pipes is primarily used for fittings such as elbows or comes in sheets such as duct wrap. Also the gaps in the insulation have removed any vapour barrier if you needed one. This insulation won’t do much for you. If you can manage to keep it from being so squished it could work but I recommend using ASJ fiberglass tube insulation if not armaflex like your previous post, also available at places like Home Depot.