Last week, I introduced you to roof overhangs. Remember, a roof overhang is simply an extension of the eave or “edge” of the roof. The overhang can extend beyond the exterior walls of the house many inches, or a few feet.
In part 1 of the mini lesson, we talked about how many homeowners and house designers pay too little attention to roof overhangs because they think of them as purely aesthetic. But overhangs have several important functions: they can protect exterior doors, windows, and exterior walls from rain and snow; they can shade windows from hot summertime sun rays; and they can help keep basements and crawl spaces dry by directing rainwater away from the main structure of the house.
We learned that all sides of the house will benefit from 16-18 inch overhangs because those overhangs will protect the house from the elements. And that the south side of the house will see the most impact from deeper overhangs for shading. Remember, the roof overhangs for shading are usually 24 inches minimally, but more often 36 inches or more.
I’ve been using the word wide to describe the overhang sizes because that’s what the articles I read used, but I think the correct dimension is deep. Deep is measured from front to back. Wide is technically a side to side measurement. The depth of overhangs is mainly what determines how much shading they will give (although width matters too). But I digress…
This week, we’ll go over whether you need deep roof overhangs for shading on the north, east and west sides of your house. Plus I’ll tell you what you can do to protect your house from the sun’s heat and rain if you either don’t want overhangs, or can’t have them because of building code. Yep, building codes in some areas don’t allow overhangs.
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Alright, let’s continue last week’s mini lesson by talking about where we should put overhangs for shading.
Ok, so, for sure on the south side of the house, but what about the north? What’s your guess?
In the northern hemisphere, like here in North America, north facing windows don’t get much direct sun, so roof overhangs for shading are not necessary on the north side of your house. But to reiterate, you will want to add 16-18 inch overhangs to protect your house from the elements.
EAST AND WEST OVERHANGS
On the east and west, sunlight hits windows when the sun is rising or setting — when the sun is low in the sky. It’s challenging to control this nearly horizontal sunlight.
It’s especially hard to add overhangs that are deep enough to shade west-facing windows from the intense afternoon sun. So since controlling that sun and heat on the west is difficult, minimizing or eliminating west facing windows in hot regions is essential. My house will have no west facing windows.
For any west facing windows you do have, consider adding vertical fins which shade the side of the window from horizontal sunlight. Alternatively you can add exterior shutters, shades or sun screens that cover the entire glass area.
Another approach to shading west facing windows, is to design a covered porch on the west side of your house.
East facing windows let in morning sun. The heat from morning sun isn’t as harsh as late afternoon sun is, but you still might want some shading on the east to eliminate glare. If you live in a very hot climate where even morning sun causes overheating, you can minimize or eliminate eastern windows, or add vertical fins or exterior sun screens. For most of us, the sun’s glare from the east, not the heat, is the main issue and interior shades, shutters, drapes or blinds can help.
There are a few circumstances where roof overhangs are not possible. For example, building code in hurricane-prone areas will usually either not allow overhangs, or limit the size of overhangs.
If you live in an area prone to high winds and you can have roof overhangs, let a structural engineer take a look at your plans to make sure the overhang design will resist wind uplift. In most cases, you don’t want to go too deep with overhangs since the larger the roof overhang, the more easily wind can lift and damage the roof. In addition, hurricane clips are often used to attach the roof to the main structure of the house so the roof is more resistant to winds. Hurricane clips are steel clips that help hold the roof in place and they are far stronger than standard nails.
Where else are roof overhangs not allowed? I’ve also read that building code in areas at risk for wildfires don’t allow overhangs. I’m not exactly sure why, but I bet it has something to do with the overhangs making it easier for fires to spread.
Although there are many advantages to overhangs, deep overhangs can reduce incoming light and can minimally obstruct views out the window. For those reasons, you probably don’t want deep overhangs on smallish windows that don’t let in much light. But with small windows, you probably don’t need deep overhangs anyway.
The other common reason people want to avoid roof overhangs is aesthetic. Overhangs can have a dramatic impact on the home’s appearance.
If you like very clean, contemporary profiles, you may not think overhangs on your house. And I get it. I love a sleek, contemporary lines too, and if roof overhangs weren’t so important for protecting my house from the rain and heat, I probably wouldn’t have any overhangs. But the benefits of roof overhangs are just too great to ignore. So, for me and my house, function won out over form— we’re choosing practically over style.
And I’ve learned that overhangs can work with just about any style of house and you can get a contemporary look even WITH overhangs. And, of course overhangs can work on traditional, transitional, Mediterranean and other types of houses too.
If you’re dead set on a flat roof, or a pitched roof with no overhangs, or you can’t have overhangs for one reason or another, here is a list of some things beyond overhangs that you can do to protect your home from rain and sun. They would work even better in conjunction with overhangs, but they should definitely be considered if you’re won’t have overhangs.
1. Recess your windows and doors in thicker walls. In other words, push your windows and door a few inches toward the interior of the house instead of positioning them toward the exterior surface of the house. This may require you using 2x6 walls instead of standard 2x4 walls.
2. Add a rain screen under exterior cladding. Ok, pop quiz. Do you remember what a rainscreen is? We talked about them in episode 145.
Well, A rainscreen is not an actual, tangible screen. It’s a space— an air gap under the exterior cladding. When wind driven rain, and other water or moisture, get behind your brick, stone, stucco or siding, the rainscreen provides a drainage and ventilation space. It’s a space that lets any water and moisture that gets behind the exterior cladding, drip down and/or evaporate. The rainscreen is added protection from rot. If you’ve never heard of a rain screen, take a listen to episode 145.
3. Add covered porches, balconies, or pergolas to help protect exterior walls and windows from the sun and rain.
4. Have permeant or retractable awnings installed. Sometimes awnings are easier to add for style or structural reasons than overhangs. And retractable awnings can be brought in during high winds and storms. When they’re retracted, these awnings have a very minimalistic profile for those who want an ultra sleek exterior
5. Add gutters, roof drains or scuppers. Remember last week's pro term? This is especially important if you aren’t using overhangs. Scuppers or roof drains are the solutions for draining and diverting rainwater when you want a flat roof. Gutters, roof drains and scuppers will help move water away from walls and your foundation when overhangs aren’t being used.
6. For 2 story houses, you can cantilever the second floor windows and walls 16 inches or more. That will help to shield walls beneath the cantilever from rain and sun.
7. Pay extra for windows with the appropriate solar heat gain coefficient for your area. If you live in a hot, sunny climate and don’t want deep overhangs for shading, go for windows with a very low solar heat gain coefficient—request at least Energy Star standards for your area.
The Solar Heat Gain Coefficient represents the percent of the sun's heat that can pass through the window. The number ranges from 0 to 1. The lower the number, the more heat will be blocked. Be aware of the difference between the glazing-only SHGC and the whole-window SHGC. The whole-window SHGC is what we’re looking for. It takes into account the glazing on the window panes and the window frame material itself.
I tried to find out whether overhangs or high performance windows with a low solar heat gain coefficient made the most difference in making a house more comfortable and energy efficient. I came to no solid conclusion. Some resources sited studies that said overhangs provide better protection from heat, other sites said high performance windows were more effective.
Here’s the bottom line. It’s ideal to have both overhangs and good windows. But if you live where summers are hot and you don’t want, or can’t have overhangs, you really need windows with a low SHGC to keep your house from overheating. Otherwise, you’ll be living in a brand new beautiful house that’s uncomfortably hot in the summer.
A final word: Do not expect interior shading devices such as blinds or shades to reduce heat like exterior devices will. Once the sun comes through the window, heat has entered the house too, and at that point all you can do is manage that heat with air conditioning or fans. The most effective way to guard against solar heat gain is the stop the heat before it enters your house.
Before we go, let’s do a couple of quiz questions so you can review and test yourself on some of the key points of the lesson.
1. True or False. Although there is no true standard size for overhangs, overhangs for protection from the elements should ideally be 16-18 inches and overhangs for shading should be 24 inches minimally, but preferably 36 inches or more.
That’s true. There is a software tool that can be used to help you determine the best size for roof overhangs in you area, but as general rule, shoot for overhangs no smaller than 16 inches deep.
2. Roof overhangs are most effective for shading on…
A. North facing windowsB. South facing windows
C. East facing windows
D. West facing windows
The answer is B, south facing windows. 16-18 inch overhangs are a good ideas on all sides of the house for protecting the homes exterior walls from rain. But for shading, deeper overhangs, measuring 36 inches or more, are most effective on south facing windows.
North facing windows don’t need shading. Can you remember what I said about shading east and west facing windows?
East and west facing windows are best shaded with vertical fins or exterior screens or shutters because overhangs don’t do a great job blocking the horizontal light that comes into east and west facing windows. The hot afternoon sun that comes into west facing windows is particularly problematic, especially in warmer climates, so elimination most or all of those west facing windows is ideal.
That’s all I have for you this week. I hope you learned as much as I did.
Please remember that the purpose of this podcast is simply to educate and inform. It is not a substitute for professional advice. The information that you hear is based the only on the opinions, research and experiences of my guests and myself. That information might be incomplete and it’s subject to change, so it may not apply to your project. In addition, building codes and requirements vary from region to region, so always consult a professional about specific recommendations for your home.
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