garagewinterizing
My garage has a vent grill similar to this one. The vent is near the roof on the outside wall where I have my garage doors. I do have 1/2 of the walls insulated and I was planning to start finishing the insulation on the garage.
Do I need to do anything on the winter to prevent cold air to the garage? Or is it ok to leave as is?
The easiest way to insulate concrete block is to glue foam insulation board directly to the block. These boards come in 4 ft X 8 ft sheets and different R values. The other method is to build a wood or steel stud wall along the block to hold blanket style insulation along with electrical wiring etc. This method is a lot more work, but gives you a base to install sheetrock later on.
Depending on whether or not you want the attic area insulated or not, blanket or blown in insulation can be installed into the ceiling. ( this assumes you have a sheathed ceiling). Otherwise, you can install blanket insulation between the rafters. Depending on budget, sprayed in foam insulation is fantastic. You may also want to look at some venting to help exhaust hot air during the summer months. I may add a few comments later, but here's a start.
Definitely close off the ceiling rather than plugging the vents, IMHO.
The "fanfold" insulation [typically 1/4" X 4ft X 50 ft - R1 possibly some thicker versions available, on a quick look around - thicker would of course be higher R-value, as well] intended for use under siding (and sometimes roofing) might be another option, in larger sheets (less joints to seal.) More than just vapor barrier...and it might support more serious insulation (just not too much) above it.
I presume that you recognize and accept that until you do drywall over it, this (or vapor barrier, or XPS sheets, etc...even exposed fiberglass, to an extent) is a fire hazard. In a similar situation, I'm putting my effort towards getting the drywall on the ceiling so I can insulate the heck out of the ceiling - a 5000W heater does not go very far, otherwise. Specifically, 5KW * 3413 btu/kWh = 17065 btu/hr (input) - .vs. 720 sqft (30x24) of R1 (1 Hr x sq-ft x degree F/BTU) ceiling would only net you 23.7 degrees (F) (17065/720) above outside ambient if that were the ONLY place heat was lost (floor, walls, doors all infinitely insulating, and zero air exchange - obviously an incorrect assumption - just illustrating the point.)
If the walls are 8 ft high, amounting to 864 sq ft, plus the 720 sq ft of ceiling, and we assume that all are insulated to R11 (optimistic for many garage doors and all regular doors & windows - but low for most modern walls and ceilings) the same 5KW could heat to 118 F above outside ambient (but I'm still ignoring the floor and air exchange...)
Best Answer
In most cases, vents are there precisely to be open in the winter (and all other seasons) and plugging them up may result in various problems depending on which of various roles they serve, including but not limited to combustion air supply for fuel-burning appliances, keeping the roof from forming ice dams, preventing mold and mildew, etc.
As such, even without further details about what this particular one is doing, I would tend to think that it was put there precisely because there is supposed to be a vent there, usually to meet building code, and it should not be plugged.