Energy prices are going up around the world, with utility rates even outstripping the U.S. inflation rate. Even worse, the U.S. Energy Information Administration projects utility costs to be a whopping 10% higher than they were in 2024. With energy increasingly costing a pretty penny, more people than ever are learning new ways to reduce their energy costs at home. You may have heard of getting energy-efficient windows or even adding climbing vines to your home to lower the energy bill, but you’ve probably never thought of your roof shape. Luckily, Italians found the perfect roof proportions for their homes centuries ago.

You might be wondering how your roof can affect your energy bills. For starters, a roof with inadequate insulation will let heat escape in winter and seep in during summer — forcing your HVAC system to work overtime. This constant strain on your heating and cooling systems can lead to skyrocketing energy bills. However, different roofing styles can help reduce heat loss during cold weather, allowing your heating systems to enjoy some necessary rest. In particular, a clever observation of the movement of heat and air in the attic spaces of old structures in Naples, Italy, led to the discovery of the perfect roof for maximizing heat.

Hot air naturally rises into your attic space, which is the space between the highest floor of your house and the roof. This hot air accumulation usually poses a temperature-control problem, but it can also be an advantage. Trapped air can serve as a natural insulator, but its efficiency is ultimately determined by the shape of its container — in this case, the roof. If the peak of the roof is less than about three feet from the ceiling of the floor below, then the heat from the trapped air will dissipate in an orderly manner. However, if the peak height is past this threshold, heat flow can become turbulent and chaotic — causing greater energy loss. 

In a 2025 paper published in International Communications in Heat and Mass Transfer, research found that if a roof’s peak is shorter than three feet, then the base should be three to four times wider to ensure maximum insulation and heat efficiency. However, if a peak is taller than three feet, then you should aim for an equilateral triangle with the base having the same length as your peak for the best results. While the builders of centuries-old homes in Italy probably didn’t know about thermodynamics, researchers assume that the simple trial and error of realizing that certain neighbor’s homes were warmer than others in the winter led to the discovery of these mathematical roof principles.

There are a lot of considerations when determining the best roof for your home, especially in terms of energy efficiency. The first is roofing material. The ideal choice should reflect heat in the summer, yet keep heat in the winter — a balance that can be difficult to find. Cool roof shingles can be a great option as they reflect more sunlight than regular materials. However, you can also apply cool roof coating to existing roof materials. These special reflective paints or membranes are applied directly to the roof’s surface, deflecting sunlight instead of absorbing it. 

Most cool roof coatings are white because the color of your roof also matters. Dark-colored roofs absorb and trap heat, making your home warmer in summer and increasing cooling costs. Light-colored roofs reflect sunlight instead, keeping your home cool and reducing the strain on your HVAC system. Also, your roof and insulation choices should be tailored to your local climate. In hotter areas, prioritize reflective roofing materials and proper ventilation to keep heat out, while colder regions should focus on thick insulation and airtight sealing to retain warmth and keep moisture out.

Properly sized extended eaves or porch overhangs can also make a surprising difference. These roof features can block high summer sun while allowing lower winter sunlight to warm the house — a nifty heating and cooling trick that can keep those energy bills lower. And of course, attic insulation is a common option to similarly increase your roof’s energy efficiency.