Roof overhangs are a valuable architectural component, especially for detached dwellings or standalone houses. They are aesthetic and practical, significantly impacting a property’s energy efficiency.
So, how do roof overhangs help you save energy and money?
How Roof Overhangs Can Help You Save Energy and Money
Roof overhangs can help you save energy and money since they keep your house cooler in summer and warmer in winter if designed correctly. Also, roof overhangs can reduce your use of artificial lights and protect your house from inclement weather, including rain and snow.
The net savings will vary based on many factors, such as a house’s location, orientation, size, type, the design of roof overhangs, etc. But most residential properties will enjoy a significant reduction in energy consumption with roof overhangs.
Roof Overhangs: What They Are and Why They’re Important
In architecture, roof overhangs are any structural extension or part protruding beyond the walls and sidings of a property.
The most common type of roof extension is an eave, but eaves are much shorter than roof overhangs. Even shallow overhangs recommended in colder climates are more extensive than most eaves. Plus, an overhang isn’t necessarily an organic extension of the roof.
Broadly, there are three types of roof overhangs:
- Deep roof overhang – the structure extends several feet beyond the walls and sidings
- Envelop roof overhang – the piece almost or entirely envelops the sides facing the sun
- Shallow roof overhang – the component extends a few feet and is smaller than deep overhangs
Here are the typical applications of these three styles:
- A deep overhang is usually ideal for mild and subtropical climates.
- Enveloped overhangs are necessary for tropical environments and sweltering temperatures.
- Shallow overhangs are generally suitable for temperate regions.
The generic relevance is always in play, but the design and style you should select depends on the following, among other factors:
Additionally, features such as the material of roof overhangs are influenced by the property’s architecture and construction.
The Effects of Roof Overhangs on Your Property’s Energy Efficiency
Energy consumption and efficiency in a house depend on many factors, so generalizing will be futile.
To determine a property’s general energy efficiency, let’s assume that the property meets the minimum insulation requirements according to the local building code. These requirements vary from region to region and refer to the respective R values for exterior walls, ceilings, attics, etc.
Keeping Your House Cooler in Summer and Warmer in Winter
The primary purpose of any roof overhang is to shield your house from the sun’s direct rays.
A deep overhang will direct sunlight toward the ground, thus shading the walls and windows facing the equator. An enveloping overhang will shield one or more south-facing sides.
Therefore, roof overhangs will decrease your heating and cooling requirements in the summer and winter, respectively. However, the savings on your heating in the winter may be insignificant in the IECC climate zones 6 and 7.
These cold and snowy climate zones require a shallow overhang to maximize exposure to direct sunlight. So, the roof overhang per se won’t have much influence on your energy needs in the winter. But a shallow overhang as a part of a passive solar design delivers savings.
Integral Components of a Passive Solar Design
The primary financial objective of passive solar designs is reducing cooling and heating costs by using and regulating solar gain.
Here’s how roof overhangs work in a passive solar design:
- A deep or enveloping roof overhang in the tropics reduces solar gain in the summer, so the cooling costs decrease since the interiors don’t get as hot.
- A shallow roof overhang in colder climates increases solar gain in the winter, so the net heating costs go down since the interiors warm up during the day.
In both scenarios, you need appropriate passive solar design concepts to maximize and minimize solar gain, regulate the heating and cooling effects, etc.
Suppose you want to maximize the solar gain with a shallow overhang in the winter. In any such scenario, you may include a Trombe wall with an overhang in your passive solar design.
To minimize the solar gain with a deep or enveloping roof overhang, consider a metal roof overhang optimized with coatings. A metal overhang with sealant will ensure maximum efficacy and efficiency in reflecting sunlight and heat.
Reduced Energy Consumption
Roof overhangs will reduce energy consumption, but that is not solely due to lower cooling and heating costs.
A passive solar design with an appropriate roof overhang might reduce your reliance on:
- Artificial lights
- Humidifier or dehumidifier
Suppose your house has a deep overhang. Using a reflective material for the underside of roof overhangs can reflect artificial interior lights and the exterior fixtures on sidings. An enveloping overhang can do the same with a much larger reflective bottom.
Similarly, shallow roof overhangs can also reduce your dependence on artificial light—the only difference is the time. You will need fewer or no lights during the day with a passive solar design and a shallow overhang allowing sunlight directly into your house.
Mitigating Moisture Problems
All roof overhangs can mitigate moisture problems and prevent water buildup, and they are much more effective at both than standard eaves. With an optimum sloping, you might not even need gutters and downspouts if the overhang is considerably beyond the sidings.
Protecting Sidings and Windows from the Elements
Roof overhangs are sturdy structures.
They can protect the following fixtures of your house from inclement natural elements:
- Rain, snow, and wind: exterior doors and light fixtures, sidings, windows
- Moisture prevention: walls, along with ceilings and floors, to varying extents
- Water damage or pooling: basement, crawlspace, and the ground floor in some cases
Roof Overhangs Should Have a Bespoke Design
Overhangs can be as aesthetic or practical as you want. But you should always customize the design for your property and specific requirements.
A generic approach is unlikely to be effective, even for two houses in the same area, if they have different attributes, such as:
- Architectural design
- Floor layout or plan
- Insulation quality
- Number of levels
Likewise, you also need to check the sun’s angle of incidence as per the location and orientation of a house. While the angle of incidence will vary latitudinally, seasonal variations exist for the exact location and orientation. In addition, measuring the angle of incidence at solar noon would be best.
Solar noon is different from what the clock says. Every meridian has a unique solar noon, and it varies seasonally. So, longitude also comes into the equation.
A well-conceived passive solar design with an appropriate roof overhang can deliver a lifetime of savings and sustainability. Additionally, you might save money on periodic maintenance and repairs due to moisture buildup, rainwater, snow, and winds accompanying thunderstorms.
- Pacific Northwest National Laboratory, United States Department of Energy: IECC Climate Zone Map
- Attainable Home: What Is Passive Solar Home Design – Should You Consider It?
- Attainable Home: Go Green with a Metal Roof – A Step-By-Step Guide
- United States Department of Energy: Passive Solar Home Design
- United States Department of Energy: Energy Efficiency in Log Homes
- United States Department of Energy: Guide to Passive Solar Home Design
- ScienceDirect: Optimum Overhang Dimensions for Energy Saving
- ResearchGate: Applicability of Overhangs for Energy Saving in Existing High-Rise Housing in Different Climates
- ResearchGate: Effect of Louvres, Overhang, and Side Fins Shading Patterns on Energy Consumption in an Office Building
- Houzz: Roof Overhangs Project Lower Energy Costs