Aug 31, 2016, 3:00 pm EST | 4 min read
Getting a smart thermostat to control the heating and cooling in your house can potentially save you money depending on how you use it, but a thermostat isn’t going to save you money all by itself. Your home also needs good airflow and insulation, and the attic is the biggest piece of the puzzle.
Make Sure It Has Proper Ventilation
It might not make much sense, but in order for your house to stay cool during the summer and warm during the winter, the attic needs to have the proper ventilation, so that hot air can easily escape.
Your attic should have some kind of ventilation with both intake vents and exhaust vents–there are different kinds of vents for both. On most houses, you’ll usually have soffit vents (a.k.a. eave vents) for intake. Exhaust vents usually consist of ridge vents, gable vents, or general fan-operated vents (like the one pictured above). This ensures that hot air can escape during the summer and cold air can get in during the winter.
Wait, why would you want cold air coming into the attic during winter? Because if the attic is too warm, the water from melted snow will run off, and when it reaches the edge of the roof where it’s much colder, it will freeze and form an ice dam. From there, melted snow will puddle up behind the ice dam and possibly leak through the shingles, causing damage to your roof.
However, a cold attic doesn’t mean your living space has to be cold. This is why insulation was invented, and it brings us to the next point of order.
Is There Enough Insulation?
Your attic most likely has some form of insulation, but the question is whether or not you have enough of it–or if it’s even good insulation in the first place. The heat from your house can easily radiate into your attic, which is why insulation is pretty much a necessity.
Make sure that your attic is completely covered in insulation and that there are no bare spots where you can see the floor of the attic (i.e. the drywall ceiling of the room below). If you see a lot of bare spots, it could mean that your attic doesn’t have enough insulation and you might need to add more, or it could also mean insulation is piling up somewhere and you may need to spread it out more.
If you go up into your attic and see that you have insulation all around, you might think you’re good to go, but be sure to inspect it to see if it’s actually still good. Over time, insulation can get damaged or simply become old. Any insulation that’s compressed, moldy, or has water stains on it will need to be replaced. Plus, if you have an older house, your insulation might consist of vermiculite, which could contain asbestos and would need to be professionally discarded and replaced with safer insulation.
There are two types of attic insulation that you’ll see in most homes: loose fill (a.k.a. blown-in) insulation and batt (a.k.a. blanket or roll-out) insulation. Batt insulation is great to use if you plan to DIY, but blow-in insulation requires a special machine to blow it around your attic, which usually requires a professional.
Inspect the Baffles
Attic baffles are pieces of plastic or foam that prevent insulation from blocking soffit vents, as well as create a distinct path for air to get into the attic from the outside. Sometimes they can become damaged or just fall off, allowing insulation to break through and cover up vents. Worse yet, some houses don’t even have baffles in the first place.
Without proper baffles, air can’t flow through the attic, meaning hot air can’t escape during the summer and cold air can’t get in during the winter, which can cause all sorts of problems year round.
Make Sure Bathroom Fans Ventilate Properly
If you have a half-bathroom with just a sink and toilet, ventilating the bathroom fan straight into the attic isn’t really a problem, but bathrooms with tubs and showers where it can get really humid should be ventilated straight to the outside, and not into the attic. If you were to vent it straight into the attic, all that humid air would fill up the attic and cause mold to grow, especially around the spot where the vent hole is.
Instead, it’s a good idea to bypass the attic and vent it straight outside. You can get insulated flexible ducts to reroute the ventilation if needed–the insulation prevents condensation from forming, which could then cause mold growth.
Check for Roof Leaks
It’s likely that you rarely take a visit into your attic–maybe a couple times per year, which is why you really don’t want leaks in your roof. By the time you do discover them, there’s probably mold growing from the moisture and possible damage that could require fixing.
This is why it’s always a good idea to check your rook for leaks whenever you do go into the attic, even if that’s not the main reason you’re heading up there–it’s always best to catch a leak early so that it doesn’t cause more damage later on.
Furthermore, check your roof for damaged or missing shingles, which are the main causes for most roof leaks. If you don’t feel comfortable getting onto your roof, call a capable friend who can do it for you, or hire a professional.
In the end, if you want your house to be in tip-top shape and have the energy efficiency necessary to save money on your heating and cooling, then the attic is one of the most important factors to focus on. Many homeowners often forget about the attic, since it’s one of the most least-visited places in your entire house, but it’s also one of the most important.
Keep this area of the home in good condition so your home stays healthy.
The attic area of the home serves an important function to the home’s ability to keep warm or cool. Not all attics are large spaces, some are mere crawl spaces, others are large enough to be living spaces. Regardless of your attic’s size, it’s important that this area is working properly and helping your home stay comfortable and healthy. Crawling into the attic space can be somewhat tricky. There is usually no flooring and there may be many wires and loose insulation. If you haven’t been in your attic, or aren’t sure about it’s condition, you may want to hire an attic or insulation specialist who can safely inspect the area. Use these tips as a guide to understand the basics of attic maintenance.
1. Keep it well insulated
For homeowners looking to make their home more energy efficient, you’ll want to start with the attic. Properly insulating the attic, sealing leaks, and ensuring that the attic isn’t damp is a great way to increase energy savings in your home. Your roof can also be affected by the condition of your attic. In fact, the best way to prolong the life of your roof is by having a well-insulated attic area. The insulation in the attic reduces the amount of moisture build-up in the attic space, which could negatively impact the roof with excess mold or mildew.
2. Know your insulation types
There are several types of attic insulation like blanket rolls, loose-fill (or blown-in) insulation, and sprayed foam polyurethane. Loose-fill or blown-in insulation requires a professional to install, but is great for filling in small holes and crevices. Sprayed foam polyurethane is best for attics being converted into a bedroom or loft. Fiberglass in insulation can get into your skin and cause irritation. When handling insulation or other chemicals, make sure to always protect yourself by wearing a facemask and gloves.
3. Be aware of leaks
Unfortunately for some homeowners, noticing leaks or damage inside the attic doesn’t always happen until an exterior issue shows up. For example, an ice dam that builds up on the exterior of a gutter can cause water to back up and drip into the attic area. Eventually mold and mildew may become present on interior walls but this happens slowly over time.
4. Prevent Mold
Rain or winter storms that cause roof leaks can lead to trapped moisture in your roof. This can lead to mold damage and trigger harsh allergens. Keep these irritants from seeping into the air in your home by inspecting your roof for missing or damaged shingles. If needed, hire a professional to replace damaged pieces immediately.
5. Get rid of pests
If rats, mice or bats find way into your attic, it is important to know how to get rid of them. Spring traps work best for getting rid of most small pests, but for larger animals like raccoons or bats, call a professional to remove.
Will Housh December 18, 2018
Proper attic ventilation is important to the protection of your home and your comfort throughout the cold months. Attic ventilation in winter protects your roof structures from damaging moisture. Improve your attic ventilation to keep your home in good condition and maintain good indoor air quality this winter.
Why Is Attic Ventilation Important?
Proper attic ventilation protects against many troublesome home problems, making your house more comfortable indoors. It protects your roof against damaging moisture problems, including:
- Moisture variations that can warp roof decking
- Mold growth
- Wood rot
- Popped shingles
- Ice dams
In the winter, heat in your home rises – to the attic. With it comes moisture. When attics are not well ventilated, moisture collects in this area of the home. This moisture can seep into the structure of your home, affecting roofing materials as well as framing and contents of your attic.
Adequate attic ventilation allows cool, dry air from outside to come into the attic, while warm, moist air inside the attic can escape. Good attic ventilation helps keep temperatures even, preventing hot and cold spots that cause damaging ice dams where water can back up and freeze beneath your shingles.
Proper attic ventilation in winter prevents mold and mildew growth, safeguarding your family against these harmful contaminants. Eliminating moisture problems through attic ventilation works to improve indoor air quality. It also prevents the warm, damp, and dark environment that pests love, keeping rodents and insects from nesting in your attic.
Attic Ventilation Solutions
For good attic insulation, one square foot of ventilation is recommended per every 300 cubic feet of space within the attic. A 1:1 ratio of intake and exhaust vents is needed to ensure proper airflow through your attic. Roof vents allow for natural attic ventilation, but mechanical solutions are also available.
Intake vents allow air to move into the attic. There are three main types of intake vents for attic ventilation in winter:
- Gable vents: Gable vents are installed at the roof peak’s highest point in the gable. They can be painted and a number of styles are available to blend with your home’s exteriors. Depending on wind direction, gable vents can serve both intake and exhaust purposes.
- Under-eave vents: An under-eave vent is a continuous, perforated vent that is installed under the home’s eave. These vents can be easily covered by attic insulation, so make sure insulation is not installed over the vent.
- Rafter vents: Rafter vents work with under-eave vents to provide clear airways to the under-eave vent. They are installed along the attic’s rafters, located at the point where ceiling and attic floor meet.
Exhaust vents allow warm, moist air to move out of the attic space. Types of exhaust vents include:
- Ridge vents: These vents run along the roof’s ridge. They are easily disguised by shingles, integrating nicely with the roof line.
- Turbine vents: Turbine vents have a distinctive look, and contain a small fan that turns with the breeze. This sucks warm, moist air out of your attic, expelling it outdoors. Turbine vents are installed on or close to the roof’s ridge.
Attic Ventilation Fans
Attic ventilation fans offer mechanical ventilation, using a fan to draw in cool, outside air and force out warm, moist air. Air is drawn in through the attic fan and air is expelled through the roof vent system to keep your attic cooler and drier, preventing ice and moisture issues throughout the winter. Attic fans do require electricity to operate, which makes this attic ventilation solution more costly to operate than relying on natural attic ventilation through vents.
Attic Ventilation To-Do List
In addition to the attic ventilation solutions above, there are more steps you can take to prevent moisture issues in your attic and help maintain proper attic ventilation throughout the winter:
- Seal penetrations in the attic to stop free air flow. Seal nail penetrations and around electrical, HVAC, and chimney penetrations.
- If your roof vents have been damaged, replace them as well as crushed ridge vents to aid in proper ventilation.
- Do not cover your attic vents for the winter. Doing so in attempts to keep cold air out disrupts attic ventilation, leading to moisture issues.
- Make sure the space between the top of insulation and the roof deck’s underside is clear at the eaves. This allows air to move through the rafter space for good ventilation.
Winter Attic Ventilation Help on HVAC.com
HVAC.com is here to help with your attic ventilation issues this winter! Review our informative resources to learn about attic ventilation systems and solutions. For customized attic ventilation solutions for your home, work with a trusted, local HVAC contractor.
Use our HVAC Contractor Directory to find an HVAC contractor nearby. Search your ZIP code and see a complete listing of local pros in your area who can improve attic ventilation for your comfort and protection this winter.
Your roof ventilation probably isn’t something you think about very often, but it plays an important role in many aspects of day-to-day life in your home. Having the right amount of ventilation in your attic can have a positive effect on the lifespan of your roof system, the comfort and well-being of your family, your future costs for home repairs and how much you pay for heating and cooling.
How Attic Ventilation Works
Effective ventilation in an unfinished attic usually includes intake vents down low along the soffits, and exhaust vents up high at the peak or roof ridge. This allows for a continuous flow of air through the space. Cooler outdoor air gets drawn in through the soffit vents, and warm, humid air that migrates to the highest point exits through the vents along the roof ridge.
Why Adequate Roof Ventilation is Important
Proper ventilation in your attic helps address excess heat and moisture that can otherwise wreak havoc on your home. Heat and moisture buildup in an attic cause predictable but different problems in hot and cold climates; areas with hot summers and cold winters can suffer the effects of both.
- When it’s hot outside, the sun beating down on the roof can increase the temperature in the attic. Exposure to this excessive heat can warp the roof sheathing and distort and prematurely age the shingles. If the attic floor isn’t evenly and adequately insulated, that heat can radiate down into the finished living areas and make it more difficult and costly to keep the living space comfortable.
- In locales where the temperature drops below freezing during the winter, warm air escaping into the attic from the heated living space below rises to the underside of the roof deck. As the roof deck warms, the bottom layer of accumulated snow on the rooftop begins to melt, causing water to trickle down the roof. Once the runoff reaches the cold outer edge, it refreezes into ice. When this happens repeatedly, an ice dam forms along the eaves, blocking the escape of further runoff. Once the water has nowhere to go, it can back up under the shingles. A properly installed self-adhered underlayment is a final defense against ice damming. This tear-resistant, waterproofing product seals tight around nails. It helps prevent water overflow from entering exterior walls or the attic where it can saturate the floor insulation, ruin the drywall underneath or get into the interior walls.
- Humidity, generated from your living area or from outside, that enters a cool attic condenses into a liquid when it meets colder surfaces. Over time, that moisture can cause deterioration of the roof system and interior structural elements or ruin the attic insulation. In a warm attic, the moisture can allow mold and mildew to flourish and put added strain on the home’s cooling equipment.
Spotting the Signs of Improper Ventilation
An inadequate attic ventilation system can cause a variety of problems that manifest themselves in different ways.
Here are some subtle and some not-so-subtle things to watch out for:
- An unexplained uptick in your household heating and cooling bills, which can happen if your attic insulation gets wet and loses its effectiveness
- More frequent HVAC repairs as heating and cooling equipment that’s under a heavier workload can become more prone to breakdowns or even premature failure
- A noticeable buildup of ice along your roof edge during the winter months
- A wavy or rippled appearance to your home’s roofline and shingles that’s caused by warping of moisture-damaged decking underneath.
- Rust and corrosion on metal materials in the attic, such as nail heads, electrical boxes, light fixtures, and HVAC system components
- Dampness, water stains or frost on the attic side of your roof sheathing, or any evidence of deterioration and decay of the roof’s structural supports
- An increase in discomforting allergy symptoms or respiratory illnesses among your family members, which may be related to the spread of fungi spores through your indoor air supply from mold growth in your attic.
If you decide to check for these signs on your roof or in your attic, be sure to keep safety in mind. Instead of climbing up on the roof, walk around the outside of your home and look up from ground level using a pair of binoculars. If you head up to the attic, make sure the space is well-lit, that you have a sturdy walking path and are wearing appropriate protective gear.
What to Do About a Poorly Ventilated Attic
If you identify or have concerns about any of the above warning signs, it’s wise to have your attic inspected by a certified roofing contractor who can assess whether there’s enough ventilation — building codes typically require one sq. ft. of net free-vent area (NFVA) per 300 sq. ft. of space in an unfinished attic. If more is needed, they can advise you on what options exist to improve ventilation and make sure it’s effective. They’ll take various factors into account to do this, such as:
- The local climate in your area
- Your roof’s architecture
- The age of your shingles
- The condition of the decking and other roof components
- Whether your attic floor is sealed and well-insulated
If your roof is getting close to the end of its lifespan, or the decking or other components are damaged or deteriorated, repairs or a replacement may be recommended along with the following steps to properly ventilate your attic:
- Installing continuous soffit vents along the outer edge of the eaves
- Adding a ridge vent
- Insulating along the top plates to meet or exceed the R-value already in the walls
- Sealing the attic floor to make it airtight, and making sure there’s the recommended R-value of properly-installed insulation in place and that it doesn’t block the soffit vents
- Allowing one to two inches of air space between the installed insulation and roof sheathing
Owens Corning’s vent calculator can provide a general guide on the amount of roof ventilation your home needs. For a detailed assessment and expert advice, contact an independent roofing contractor in the Owens Corning Roofing Contractor Network in your area.
Here’s how to install soffit vents step by step to improve the airflow in your attic.
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If you’re looking to install new ventilation in your house, you might want to consider a soffit vent.
Should I Add Soffit Vents?
If your home is fitted solely with small gable-end vents or a ventilator high in the roof, you might want to consider adding soffit vents to increase airflow. These vents allow outside air to enter the attic at the lowest point of the roof—along the underside of the eave. They’re most effective when used in conjunction with a continuous ridge vent.
Soffit vents come in several sizes and styles, including small round discs and rectangular grilles. We opted for aluminum strip vents that measure 3 in. wide x 8 ft. long. This style vent provides a quick way to ventilate every rafter bay. Strips vents come in white, brown and silver; you’ll pay less than $3 for an 8-ft. length.
How to Install Soffit Vents
Make Two Parallel Lines
Start by using a chalk reel to snap two parallel lines down the center of the soffit. Space the lines 2 in. apart; that will allow the vent to overlap the cutout by ½ in. on each edge.
Cut Parallel Lines
Photo by Merle Henkenius
Next, bore a 3⁄4- or 1-in.-dia. hole through the soffit right between the lines and measure the thickness of the soffit panel (probably 1⁄4 or 3⁄8 in.). Then set your circular saw to that depth and cut along the chalk lines.
Cut the two parallel lines with a portable circular saw. Set the blade depth to barely cut through the thin soffit material.
Connect the Two Cuts
Photo by Merle Henkenius
When you near the end of the soffit, stop short and connect the two cuts with a sharp chisel or sabre saw. Once all cuts are made, use a thin pry bar to remove the 2-in. plywood strip. Pull any nails that remain in the soffit framing with a cat’s paw.
Then inspect the length of the vent cutout. If there’s any insulation clogging the slot, pull it out or shove it back up.
Raise the Vent up to the Soffit
Photo by Merle Henkenius
Next, lay the strip vent down on a flat wood surface, such as a plywood sheet or long 2 x 4, and drill 1⁄8-in.-dia. screw holes through both flanges. Space the holes 12 to 14 in. apart. With the help of an assistant, raise the vent up to the soffit and center it over the cutout slot.
Attach the Vent to the Soffit
Photo by Merle Henkenius
Use a cordless drill/driver to secure the vent to the soffit with ½-in.-long No. 4 sheet-metal screws. Continue installing additional strip vents until you reach the far end. Trim the last vent to length using aviation snips.
Remove Any Insulation From the New Vent
Photo by Merle Henkenius
The soffit vents are now installed, but you still need to make sure there’s no insulation blocking the new vents. If the attic is insulated with fiberglass batts, just pull back any that are blocking the flow of air. If there’s blown-in insulation, like ours, rake back the fluffy stuff with a 3- or 4-ft.-long 1 x 6, or use a garden rake or hoe.
Install the Ventilation Baffle
Photo by Merle Henkenius
Finally, to ensure that the airway to the vent remains open, staple a ventilation baffle to the plywood sheathing in each rafter bay. The molded polystyrene baffles, available at home centers and lumberyards for about $1 each, form channels that hold insulation at bay and direct incoming air upward.
Can You Have Too Much Ventilation in Your Attic?
For most of us, the attic is a place to store clothes, luggage and old family photos, but for energy researchers it’s a hot topic of discussion. In the last several decades, building codes have called for increased attic insulation.
Most experts contend that a well-ventilated attic keeps the house more comfortable in summer and guards against moist, heated air building up in winter. There are also dissenting voices who say that the benefits of ventilation are overrated.
Who’s right? Obviously more research is needed, but here’s what we do know:
- Don’t avoid ventilating your attic for fear you’re letting cold air into the house. Your actual living space is sealed and insulated at the attic floor—the attic is outside this envelope.
- If there are asphalt shingles on your roof, the attic must be ventilated to comply with the terms of the manufacturer’s warranty.
- One reason for the lack of agreement over attic ventilation is the tremendous variation in climate across North America. Rarely will you find a building practice that works everywhere.
For instance, attic ventilation is used widely in cold climates to evacuate the warm, moist air that escapes from the living space below. If this air lingers, it can condense on the underside of the roof sheathing and rot it. A healthy airflow also helps with ice dams, which begin to form when warm air in the attic melts the snow from beneath and creates runoff that refreezes on the colder eave. Great, but neither of these problems is experienced in warmer climates.
There are four especially common signs of problems with attic insulation. If you notice one or more of these occurring, you probably need to take action:
Problem 1: Ice Dams
Icicles may look pretty, but they could also be a sign that something is seriously wrong with your roof. These dams form when snow covers the roof and rising heat melts only some of it, causing liquid water to flow down the roof. However, once it’s away from the heat, the ice freezes again. The result is a heavy buildup of ice along the edges of the roof.
If left untreated, ice dams can rip off shingles , crunch gutters , and drop the edges of your roof onto the things below them like your car. Carefully removing the ice will help, but the only permanent fix is repairing your insulation.
Problem 2: Odd Temperatures
This test is a little more complicated. First off, you’ll need to open all of the inside doors for awhile and let the temperature of your home even out. Make sure the vents are open, too. Once you’ve done that, take a walk around and check for rooms that seem significantly warmer or colder than other areas. While you’re at it, feel the ceiling and see if it seems strangely hot or cold in any area.
If any rooms have odd temperature changes, there’s a good chance that the insulation in that area is poor and will need to be replaced. Note that ceilings aren’t the only areas where insulation can be poor. You may also be losing heat through the walls or even through poorly-insulated windows. Be sure to check all areas of your home.
Problem 3: Drafty Rooms
Wind doesn’t just happen on its own. If there’s a draft, it’s coming from somewhere , usually because of cracks and uneven air pressure. Not all drafty rooms are especially obvious, though. The most common problems with drafts in the ceiling are because of light bulbs, so follow this easy process with each ceiling lamp to check for air leaks.
Turn off of any smoke-producing items (typically stoves) several hours before you start. Then, shut every normal exit to the home including doors, windows, fireplaces, and anything else your home may have. Next, turn the house’s vents on. Most homes have at least one in the kitchen, by the stove, as well as one in each bathroom. Finally, light an incense stick or a candle and move it close to the light fixture. If the smoke gets sucked up, there’s an air leak there.
Problem 4: High Energy Bills
This problem is the easiest to notice, because you’re paying for it every few weeks. If your utility bills look high to you, they probably are . High energy bills tend to be a sign that your HVAC system is working harder to compensate for energy loss somewhere in the house. Small leaks tend to cause small increases in your bills, while larger leaks could quickly start costing you hundreds of dollars.
Homeselfe offers a free program for walking through your home and uncovering points where you might be losing energy. Conduct your own home energy audit to discover what’s really going on with your attic insulation . Don’t pay higher energy bills when you don’t have to. Instead, learn to identify problems and find out the best way of dealing with each issue.
Laying an attic blanket across the joists increases the R-value of the insulation in the attic significantly.
Statistics show that 85 percent of a house’s heat loss is straight up through the attic space. Houses built before the energy crunch in the early ’70s, might just have a little bit of fiberglass insulation in the attic or empty cavities between the joists. Either way, the house is probably wasting energy – and the homeowners’ money.
The amount of insulation a material provides is measured by its R-value. The higher the number in the R-value, the more effective the insulation is. Houses built before the 1970s probably have an R-value of 11 or less, but today’s standards call for R-values as high as 38 or more, depending on the house’s location.
Some houses may have gray material between the ceiling joists. If it’s an old house, that could be mineral wool. A newer house is likely to have blown-in cellulose. Either way, it can be left in place and insulation added over it.
When working with insulation, wear gloves, eye protection and a good particle mask, especially when using fiberglass.
In some ways, rigid foam insulation is easier to work with, but fiberglass is usually easier to get up into the attic.
Don’t worry if the fiberglass batt insulation at the home center seems to be too thin. It will expand to as much as 6 inches thick.
To cut a batt to size, lay it on a piece of plywood. Then put a short length of 2×4 at the point where you want to cut, put your foot on the 2×4 and lean on it to compress the fiberglass. Once it’s compressed, it’s easy to cut with a utility knife.
If you already have six inches of insulation and you want to get to the recommended R-38, add an “attic blanket.” It’s also made of fiberglass, but it has no paper backing. To install it, just lay it across the joists. Keep adding layers until you get to R-38.
Look for the new no-itch poly-wrap insulation. It is much easier to work with and it’s safer, so it’s worth the extra cost.
- How Does a Soffit Fan Work?
- How to Improve Air Circulation in a House
- Attic Insulating Tips
- How to Use & Maintain an Attic Fan
- How to Keep Your Central Air Bill Low
Ideal attic temperatures and humidity settings aren’t always easy to maintain. Freezing and excessively hot outdoor temperatures, rain and high exterior humidity levels make it difficult for your attic fan and heating and cooling systems to keep up with desirable attic temperatures and humidity levels. Nonetheless, it helps to shoot for recommended levels so you don’t compromise the effectiveness of your ventilation system.
Cold Outdoor Temperatures Affect Attics
Cold outdoor temperatures, especially below freezing, can wear on your furnace or heating system, making it difficult to maintain ideal attic temperatures. However, heating-system manufacturers must meet codes that enable your heating system to maintain a steady attic temperature of at least 68 degrees. Proper precaution in an uninsulated attic, such as the Department of Energy’s recommended R30 to R49 insulation for warm climates, R30 to R60 for moderate climates and R49 to R60 for cold climates, makes it easier to maintain moderate attic temperatures. Shoot for 68 degrees, but don’t worry if it’s a few degrees below that.
Quelch the Heat Wave
Hot summer weather poses the opposite problem for maintaining recommended attic temperatures. Ideal attic temperatures shouldn’t be more than 10 to 20 degrees hotter than outside temperatures. If your attic soars above 100 degrees and reaches the 150 mark, its time to consult professionals to ensure your attic is properly vented. High attic temperatures put a huge strain on your air conditioning system. You may need to install an attic fan, if you don’t already have one, or hire maintenance technicians to evaluate the proficiency of your current fan.
Cold as Ice
Humidity settings are another issue that can make or break the performance of your heating and cooling systems and your attic ventilation. The normal indoor humidity range in winter should be 15 to 50 percent. For example, if the indoor temperature is 70 degrees and the outdoor temperature is 20 degrees, then the recommended humidity level is 45 percent. As a general rule, the lower the outdoor temperature, the lower the recommended humidity setting. You want to avoid ice buildup or condensation that could lead to structural problems in your attic.
Elevated Humidity Levels
In warmer weather, an air conditioner cools indoor temperatures and helps remove humidity from your home. If your humidity level consistently rises above 70 percent, consider installing a dehumidifier. You might also install a humidistat that automatically turns your attic fan on to vent out humidity once the level exceeds 70 percent. An attic that stays overly humid for days or weeks on end can eventually lead to leaks. Condensation accumulates and leads to structural problems, such as dry rot and deterioration in wooden beams or floors and damage to your existing insulation. High humidity levels also result in the development and growth of mold and mildew.
- Bob Vila: Planning Guide: Attic Conversion
- House Chek: Attic Ventilation and Air Conditioning Costs
- Jet Fan: Frequently Asked Questions About Attic Fans
- Michigan State University Extension: Moisture Problems in the Home
- Energy Star: Recommended Levels of Insulation
As curriculum developer and educator, Kristine Tucker has enjoyed the plethora of English assignments she’s read (and graded!) over the years. Her experiences as vice-president of an energy consulting firm have given her the opportunity to explore business writing and HR. Tucker has a BA and holds Ohio teaching credentials.
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Get insight into the complicated relationship between ridge vents, gable vents, and attic floors.
No short-circuiting here. Even with the gable vents open, air continues to enter the soffit vents and to move upward due to the stack effect. While some of it exits through the gable vents and some exits through the ridge vent, these outlets are not in competition with each other.
As built, the attic of our 22-year-old house was ventilated with gable vents and soffit vents. We replaced the roof recently and when we did we added a ridge vent. According to the guy who writes the home-improvement column in the local paper, if you add a ridge vent, you should close off the gable vents. If not, the air pathway through the attic will be short-circuited, flowing only from the gable vents to the ridge vent and not ventilating the lower part of the attic. The roofer says closing the gable vents isn’t necessary. Who is right?
SUZYPQ from the Breaktime forum
Bruce Harley, technical director of Conservation Services Group in Westborough, Mass., responds:
Everyone has an opinion about this stuff, and most folks overthink it. Here’s what you need to know — t he newspaper guy is wrong; your roofer is right. There is no need to block the gable vents unless they are prone to collecting windblown rain and snow. (This would not be related to adding the ridge vent; that would have already been true before the roof work.)
Although unvented roof assemblies work if they are built properly, attic venting is a good thing for most houses, and having too much venting will not harm the structure. Airflow promotes drying, whether the water comes from inside (condensation in the winter) or outside (roofing or flashing leaks).
For any attic venting to work properly, and for the house to work properly, you must thoroughly air-seal and insulate the attic floor. If there are air leaks between the attic and the living space, attic vents become outlets for conditioned air driven by the stack effect. If you don’t seal the leaks in the attic floor, the heat loss can melt snow (causing ice dams) and create condensation and moisture problems.
Air leaks can even increase the risk of combustion backdrafting, especially for a fireplace with an exterior chimney.
Once leaks are sealed and insulation is installed, the attic is an isolated space. The main force that now drives venting is solar radiation on the roof. That heats up attic air. Adding exhaust vents high on the roof can help to accentuate the inflow of air through the soffit vents. It doesn’t matter if these exhaust vents are ridge vents, gable vents, roof vents, or some combination.
If windblown rain or snow is frequently entering the gable vents, close them. Don’t worry about an airtight seal; just nail a board over the opening from the inside.
To summarize: Seal air leaks in your attic floor so that roof venting doesn’t suck conditioned air into the attic and cause moisture problems. Adding a ridge vent is a fine idea, and don’t worry about it competing with the gable vents. If the gable vents aren’t letting in rain or snow, leave them alone.
Roof ventilation is a complex topic, particularly for cathedral ceilings where there is no attic between the living space and the roof. Improperly designed roof assemblies can lead to a variety of problems, including moisture accumulation and decay. Although unconditioned attics like this one are the simplest assemblies to ventilate, complex roof shapes make the job more difficult.
More about attic venting:
Attic Ventilation Strategies — Simple mistakes can undo the best of intentions for venting a roof. Here are some things to keep in mind.
Venting the Roof — With today’s construction methods, the minimum code requirements may not be enough.
A Crash Course in Roof Venting — Building scientist Joseph Lstiburek explains when to vent your roof, when not to, and how to execute each approach successfully.
Ice Dams — Ice dams are not a roofing problem; they’re an air-sealing problem.
Site-Built Approach to Roof Ventilation — When rafter bays will be filled with dense-packed cellulose, you’re going to need rigid vent baffles.
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