Ottawa gets pretty hot in the summer, so this time of year the same thought crosses my mind about every four hours or so: I’m hungry. Should I cook outdoors to keep the heat out of the apartment?

For those of you who have an outdoor kitchen or even a balcony barbecue, the answer might be obvious. But for me, cooking outdoors involves carting a lot of equipment onto the balcony in multiple trips before I can even get started. Every time I open the balcony door to bring more stuff out (or back in when I’m finished cooking) a blast of hot air rushes in from outside. This made me wonder whether cooking outside is really worth it.

Feeling the heat

To figure out whether it’s better to cook indoors or out, we have to compare the amount of heat generated by cooking to the amount of heat that flows into the apartment from opening or closing the balcony door.

Heat generated by cooking

First, the heat generated by cooking. A typical burner on an electric stove is 1 kW – 3 kW, and I’d guesstimate that cooking a quick meal involves running the burner at about half power for half an hour. That works out to about 900 kJ of energy for a typical meal.

Heat transferred by opening and closing the balcony door

Next, the heat that flows into the apartment by opening and closing the balcony door. We can estimate this based on

\(m\)

  • the amount of air exchanged between inside and outside each time the door is opened (in kg)
  • maybe around 1.2 kg, assuming about one cubic meter of air exchanged per opening and using the density of air at room temperature

\(\Delta T\)

  • the temperature difference between the inside and outside air (in degrees C)
  • probably around 5 C on a warm day

\(C\)

  • the heat capacity of air
  • about 1 kJ per kg per degree C

These are related to the amount of heat entering the apartment \(Q\) through a classic formula from high-school chemistry,

\[Q = mC \Delta T.\]

Substituting in the values above, we get

\[Q = 1.2 \times 1 \times 5\] \[Q = 6 \text{ kJ}.\]

The answer

From the rough calculations above, we get 900 kJ of heat in the apartment from cooking a meal on the stove, and only 6 kJ each time I open the balcony door to bring equipment in or out. That means as long as I make less than 150 trips back and forth from the balcony, cooking outdoors will keep the apartment cooler. I might not be a perfectly organized cook, but even I can manage to cart the equipment I need outside and back in under 150 trips!

I don’t know what my meal plan is for this week, but with the forecast predicting hot weather until the start of winter in a few weeks’ time, I do know one thing: I’ll be cooking outdoors.