It’s best not to install a radiant barrier directly under insulation because it requires an air gap on at least one side to work properly. Instead, you should install the radiant barrier over your existing insulation to create an air space to reflect the radiant heat.

Three signs that you need crawl space insulation are drafts, high energy bills, and mold. Drafts can start in crawl spaces and cause hot or cold air to spread to the rest of your home through holes in the floors and walls. And even if your entire home is well-insulated, you can still feel an unchecked draft from your crawl space and in your utility bill. Uninsulated crawl spaces can let in air and moisture, and because they’re built directly on the ground and difficult to dry out, they are hotspots for mold and mildew.

If you feel your energy bills are too high or your HVAC system is working harder than necessary to maintain the correct temperature in your home, you may have an under-insulated home. If you’re unsure, consider having your system’s efficiency assessed by a local independent energy auditor.

Insulating an unheated garage can still be worth it. For instance, insulating an attached garage can help with heat loss from your house in general, and it can also make it easier to store electronics in your garage without worrying about them being exposed to extreme temperatures.

If you use your detached garage as a workspace, insulation can still make a difference. Plus, you can use space heaters and a window unit AC to help condition the space while you work without installing heating.