How Much Hotter Is An Attic Than Outside

Intake vents located at the lowest part of the roof under the eaves allow cool.

How much hotter is an attic than outside.

A good sign is when you open your attic in the winter and you don t see any frost on the nails poking through. Watson s hunch is there isn t enough attic ventilation. Here is statistics over the same period of the temperature rh and dewpoint of my unconditioned attic. 105 in the hot summer in the south if outside temp 85 90 35 40 in the dead of winter in the south if outside temp 20 30.

The frost is frozen condensation from the warm air meeting the cold air and not ventilating if that. Since attics are often under insulated poorly sealed and poorly ventilated the temperature environment can be drastically different in an attic than in the rest of the home. In summer if the attic is hotter than the outside temps it increases the temp in the home and makes the air conditioning work harder. Under side of roof deck is not much warmer than the attic air temperature.

At night outside temperatures have dropped to 70 f but after leaving windows open all night the indoor temperature is still at about 79 f. Warner is right that the attic should be close to the outside temp. Attic ventilation works on the principle that heated air naturally rises primarily utilizing two types of vents. Also depends on your humidity roofing etc.

Ideal attic temperatures shouldn t be more than 10 to 20 degrees hotter than outside temperatures. All the heat stored in the insulation filters into the house rather than venting to the outside. If your attic soars above 100 degrees and reaches the 150 mark its time to consult. Your insulating and heating cooling the house not the attic.

This is most notable in the case of attics.