When the house was built, I opted to insulate my attached garage. It paid off during the winter. With no climate control, the space stayed well above freezing. But during the summer it is kicking my butt. I don't like leaving the doors open since it invites insects and debris in to work their way into the house. I have come out in the morning to find the garage still holding 90+ degrees when the outside temps are down around 70.
There are windows on the one end of the garage (it is a side entry garage, so the windows are on the "front" of the house/garage elevation). I also have a pull down attic access and have played around with leaving that open to allow heat to rise up through natural convection. I have tried only opening the windows (and attic access) after the sun goes down to try to flow the cooler air through. I have tried leaving them all open all of the time.
My 2 main concerns with the heat in the garage are:
1- Heat load against the house. Although the walls between the garage are well insulated, it is clearly counterproductive to have a hot box attached to an air conditioned house.
2- I have our spare fridge/freezer in the garage and store other dry goods out there. Keeping these items at 85-100 degrees all summer is not a good idea.
My secondary concern is that I do occasionally get to work on a project in the garage. Right now, I grab tools and run outside where it is cooler (day or night).
And yes, this is a small issue. But I have seen you all offer some very good input to other trivial topics so I thought I would see what you think.