You should not use spray foam insulation in several specific areas. Avoid applying it in spaces exposed to high temperatures, such as near electrical boxes or recessed lighting, unless the foam is specifically rated for such use. Applying foam near electrical boxes can damage the wiring, and using it too close to lightboxes or recessed lights creates a potential fire hazard. Additionally, do not use spray foam in areas prone to shifting or movement, as this can lead to cracks and gaps in the insulation. Finally, open-cell foam is unsuitable for use below ground or in areas exposed to moisture because it can absorb water, which compromises its insulating effectiveness.

It’s technically possible to install loose-fill cellulose insulation without a blower, but it’s much more time-consuming, tedious, and dangerous. You’ll need to wear the proper protective coverings to handle the cellulose after it’s been doused in boric acid; use a shovel when you can to transport the material from the bag into the wall cavity.

That said, if you purchase cellulose materials at a home improvement store, ask if they rent out blowers for free or at a discounted rate. In many cases, if you buy the material from the store, they’ll rent out the blower at no extra cost.

Insulating ductwork improves your HVAC system's energy efficiency by protecting the air from external conditions and preventing energy loss as it travels through the ducts. This means your system doesn't have to work as hard to heat or cool your home, leading to lower energy bills and a reduced carbon footprint. Additionally, insulated ducts help maintain a more consistent and stable indoor temperature, enhancing comfort. Proper insulation also improves indoor air quality by reducing the entry of allergens and pollutants and helps prevent problems like condensation and mold formation within the ductwork.

One of the disadvantages of soffit vents is they can bleed warm air from the attic during winter, resulting in slightly higher energy bills and a colder house. There are ways to mitigate this effect—mostly just closing the vent in the fall. What’s most important is your attic is ventilated to some degree in the winter.