You are:

Does Night Ventilation Protect Against Summer Overheating?

After a hot day you open up the windows at night to let the cooler air in. It is one of the most intuitive things you do. But how much effect does this have on the indoor temperature, really?

Summer heat waves are a health risk, for the elderly, young and people needing care most at risk. Our research team from the VIVA park in Wopfing, Austria wanted to find out which effect night-time ventilation in the summer has on the room temperature of different building types.

Does it make a difference to let cooler night-time air into an uninsulated brick house versus an insulated one? In each house the research team opened the windows three times a day for 1.5 hours (once in the morning and twice in the late evening) to entirely replace the inside air. The average temperature of each house was sent for evaluation every five minutes.

It was shown that the max. room temperature in the insulated houses was already during a short heat period of 4 days more than 2°C lower than that of the uninsulated house of the same design.
This effect is due to the insulation of the outer walls. Opening the windows at night only brought a short-term drop in the internal temperature in both houses.

The best methods for achieving a pleasant room temperature in a sustainable and environmentally friendly way are the most solid construction possible and efficient thermal insulation. Solid insulated walls serve as a heat shield, support the cooling effect and ensure more constant room temperatures.