How Much Hotter Is An Attic Than Outside

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.

How much hotter is an attic than outside.

Warner is right that the attic should be close to the outside temp. 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. 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.

Here is statistics over the same period of the temperature rh and dewpoint of my unconditioned attic. All the heat stored in the insulation filters into the house rather than venting to the outside. Note the average condition 80 5f and less than 47 37 rh this attic makes it into ashrae 55 s comfort zone. The frost is frozen condensation from the warm air meeting the cold air and not ventilating if that.

During the summer this leads to the hot air from the attic seeking out the cooler conditioned floors below. This is most notable in the case of attics. Ideal attic temperatures shouldn t be more than 10 to 20 degrees hotter than outside temperatures. Attic ventilation works on the principle that heated air naturally rises primarily utilizing two types of vents.

Watson s hunch is there isn t enough attic ventilation. If your attic soars above 100 degrees and reaches the 150 mark its time to consult. Also depends on your humidity roofing etc. Now if the ridge vent is only partial or if the attic air temperature is excessive 20 degrees higher than the outside air fans may prove beneficial pick the right fan.

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.