You need the gap. Baseboard heaters work by heating the air around it, causing it to rise. This rising air is replaced by the cool air being displaced. By having a gap under the heater, the cool air has a place to go and be heated. This causes a draft that allows the full room to be heated, not just the area around the baseboards. In essence, the gap allows the heater to be more efficient.
If you insist on covering it, use a sheet of decorative metal that is at least partially open to allow airflow through it. Even that will reduce efficiency, but it wont be as bad as blocking it.
I am referring to the small 90° gap between the flooring and the metal where you can see bits of exposed concrete. Are you saying that gap shouldn’t be sealed?
My misunderstanding. I thought you meant from the heater to the floor.
To fix the gap you were talking about, you could do some acrylic caulking. You could do high heat silicone if you were worried about the heat, but the acrylic should be fine. Check the tube for the allowed heat range. The silicone will do vetter against the expansion and contraction, but you’d never be able to paint it. The acrylic would be paintable. But had a high chance of cracking.
My approach would be to get a tube of silicone caulk that handles a decent range of temps and a length of hose that fits over the tip of the tube to reach under if the caulk won’t reach on its own.
DO NOT PUT SPRAY FOAM ON YOUR BASEBOARD RADIATORS MAN!!! They need service occasionally and you are setting yourself up for an absolute nightmare if you get a leak!!!
Who said on??? I said in the crack behind the wall. That is why spray foam has a long tube for application. If someone has to go into the wall for service spray foam isn’t going to be a problem.
You’re absolutely begging for moisture problems if you put spray foam in there. It should be open exactly like it is, albeit cut closer to the wall. That really won’t stop bugs anyway, you’re much better off treating the perimeter and plugging exterior access holes.
