Would temperature harm my health if my house is 59 degrees fahrenheit / 15 drgrees celsius?
Hopefully a Medical Doctor will give you an authentic answer. I was stationed at Goose Bay, Labrador for 3 years. One heating plant was supposed to provide steam heat for the entire base, but frequently the barracks and dependent family housing would remain at 60 degrees F for several hours at a time. We also took Boy Scouts into the fields where their tents were 45 degrees inside for 24 hours at a time. So long as people wore enough clothes to keep warm, their health seemed unaffected. Breathing air below about 40 degrees can harm your lungs (the Air Force doctors told us), but they said it was safe to let the Boy Scouts remain at camp for 24 hours. They used sleeping bags at night. Several counsellors were over 50 years old and did not seem to suffer any arm.
