Locations of heat loss at your house Many old homes have holes around the fenestrations (doors and windows), these holes are large enough to allow gusts of air into the house and needs to be sealed up. Heat loss mostly occurs at the point of air leakage around the doors and windows where there is poor insulation. Also, traditional windows have single panes which contributes further to heat loss. Walls of the old house are mostly devoid of thick masonry or adobe walls that are commonly seen in modern structures. These walls are helpful as they absorb solar energy during the day and helps in keeping the interior cool. Apart from windows, uninsulated attic also contributes to the depletion of heat from the houses. Cramped crawlspaces and basements especially common in old houses contribute to the heat loss.