David we have two engel 40 L units one as a frig and one as a freezer where we live the summer temperature can get up to 45 c so when i built the frig engel in i used 1'' high density foam on 3 sides and i fitted plastic vents into the box that the unit sits in The dealer where i bought my units suggested to me that it is better to leave them running if i could ,so that is what i do we have 2x40watt
solar panels and iam not connected to shore panels -my engels havent been turned off in 7 years i have included photos of my
installation in my humble view you definiately need vent holes to let hot air to escape I have attached a picture of my
installation ,unfortunatly you cant see the rows of vents on the left hand side of the engel cheers andy