How To Prevent Condensation In Your Home

Condensation in the home can be a serious problem. It can cause damage to buildings as well as mold-related health issues. Here’s how to prevent condensation in your home.

Contents of This Article

    What Causes Condensation in the Home

    Condensation is the collection of water droplets that result when warm, moist air collides with cold surfaces. A common example is the foggy bathroom mirror after a hot shower.

    Moisture can be a year-round problem depending on the climate, but it’s especially common in winter. When heating systems kick on, the warm air hits cold windows, walls, and ceilings and makes your home seem to sweat.

    Wood stoves and propane heaters, in particular, can lead to serious condensation issues if there’s a lack of adequate ventilation.

    word burning stove can cause condensation in the home

    Why Condensation in the Home is a Problem

    Excess moisture in the home can lead to serious problems. Condensation can stain walls and ceilings and cause timber rot around windows. In extreme situations, condensation can even affect the structural integrity of your home.

    What’s worse is that condensation allows mold and mildew to develop which causes all kinds of issues. Mold and mildew can damage clothing, furniture, and belongings. It makes everything smell funky. And, worst of all, it can lead to serious respiratory issues.

    Condensation in the home is no joke, and it’s important to take every step you can to eliminate it.

    The Importance of Vapor Barriers

    Vapor barriers — sometimes called house wraps — prevent moisture intrusion into the external walls of your home. House wraps keep out the weather but also breathe, allowing moisture that’s inside your home to escape to the outside.

    Vapor Barrier/House Wrap

    Vapor barrier use is climate-dependent, and not all areas need or require them. Check your local building codes to see if you need — and will benefit from — having a vapor barrier on your home.

    Vapor Barriers for Tiny Houses and Shed Conversions

    Tiny house builders typically include house wrap as a part of their standard construction. Since most tiny houses are portable and can move easily between climates, the vapor barrier helps protect the building regardless of its location.

    For those converting a shed into a home or office, be aware that sheds do not normally include a vapor barrier. Most builders offer them as an optional upgrade, however, so if you need one, make sure it’s part of your contract.

    Double-Paned Windows

    Double-paned windows are made with two pieces of glass with a space of air or gas between them. These windows slow the transfer of hot and cold air between your house and the outdoors. With their more stable temperature, double-paned windows are less prone to condensation than single-paned windows.

    If your home does not already have double-paned windows, upgrading will serve you well. If cost is prohibitive, change out one or two windows over time. Start with the windows most susceptible to condensation build-up.

    Using double-paned windows will reduce condensation as well as lower your heating and cooling bills.

    Windows for Shed Conversions

    Be aware that standard sheds are built with single-paned windows. With the growing popularity of converting sheds to workshops, offices, and homes, most builders now offer upgrades to double-paned windows. Check with your dealer to see what options are available to you.

    The additional up-front cost for double-paned windows is more than worth it for the increased comfort and lower energy bills you will experience for years to come. An added bonus is that double-paned windows will also help minimize condensation issues in your shed conversion home for years to come.

    Ventilation Is Vital for Preventing Condensation

    Every home should have a ridge vent that runs the length of the roof as shown in the illustration below. Fresh air flows in from the soffit vents along the side of the building up through the roof’s ridge vent. We encourage homeowners to know the difference between a ridge cap and a ridge vent. A Ridge vent will have at least 1″ wide holes in the roof deck for ventilation. A ridge cap will fit over the ridge vent to prevent water intrusion.

    roof ventilation diagram on how to prevent condensation

    Airflow between the roof and insulating material is the key to keeping condensation at bay and inhibiting the growth of mold and mildew.

    Ventilation for Shed Conversions

    If you are converting a shed for habitable use as an office, home, or Accessory Dwelling Unit (ADU), take special care when ordering your building. Shed manufacturers normally do not include soffit and ridge vents because storage sheds typically aren’t insulated.

    If you’ll be insulating your shed, ask the shed dealer and/or builder to add soffit and ridge vents as applicable for ventilation purposes. Otherwise you will be plagued by condensation issues.

    Proper Insulation Controls Condensation

    Proper insulation is essential for controlling condensation. You’ll want to insulate to the R rating recommended for your particular region and climate both for comfort and moisture control.

    It’s vital to provide adequate ventilation for any type of installed insulation other than spray foam. Foam Insulating Baffles are made for this purpose.

    Foam Insulating Baffles

    Foam Insulating Baffles are constructed a bit like egg cartons and provide a ventilation barrier between the roof and insulation material. The baffles are inexpensive, easy to install, and maximize airflow which minimizes condensation issues.

    foam insulating baffle can be used to prevent condensation in the home
    Foam Insulating Baffle

    How to Install Foam Insulating Baffles

    1. Determine the size baffles you need by measuring the space between the rafters in your attic (or loft/roof space in a shed conversion). The baffles are commonly 4′ in length and sold in packs of 10 to fit rafters that are either 16″ or 24″ inches apart on center. The total number of baffles required is calculated by multiplying the number of baffles needed to fill each rafter from base to peak by the total number of rafters.
    2. If you are finishing the entire attic space (or entire roof space in a shed conversion), place the baffle directly adjacent to the soffit vent. This will allow airflow into the tray of the baffle, offering the best circulation. Once in place, staple the baffle through the side flanges directly to the roof deck with a staple gun.
    3. Continue installing baffles, moving up the rafter bay towards the peak of the roof. Overlap each baffle. Repeat the process on each rafter bay. Note that if your attic includes knee walls along the lower sections of the space, you only need to install baffles to the point where the drywall will attach to the roof rafters.
    4. If necessary, seal your baffles. For example, if the baffles extend all the way to the soffit vents, use spray foam where the vent and baffle meet to prevent air loss through the joints. Depending on your roof’s construction, you may also need foam blocking to fill larger spaces. Caulk the outside of each baffle where it meets the roof deck as well as along the overlapping seams between baffles.
    5. Once the baffles are all in place, install insulation in each rafter bay following the manufacturer’s instructions.
    diagram showing installation of roof baffles
    Foam Insulation Baffles Between Rafters

    Choosing Your Insulation

    Before deciding which insulation is best for your needs and budget, you’ll first want to do a little research and measuring. The research will tell you what R-value insulation your building requires. The measuring will tell you how much and what size insulation is best. A little effort up front will pay off in greater comfort and less condensation in the long run.

    R-Value

    First and foremost, you’ll want to determine the proper R-value for your building and location. The R-value is an industry-standard measurement of how resistant insulation is to heat passing through it.

    Different climates will require different R-values for the best insulation efficiency. EnergyStar.gov provides a handy map and corresponding chart to help you determine the ideal R-value insulation for your needs.

    Measurements

    In addition to figuring out the R-value, you’ll want to calculate how much insulation you’ll need. Then you’ll want to measure your wall and rafter wood depth. The greater the depth, the thicker your insulation will need to be. The goal is to be able to secure your insulation without compressing it. This is because compressed insulation is not effective insulation.

    Ill-fitting insulation will not only reduce comfort but also increase condensation issues.

    Insulation Types with Pros and Cons of Each

    There are a number of insulation options to consider for your home or shed conversion, and each choice can affect future comfort as well as condensation issues. The following information will help you select the best insulation for your needs and budget.

    Rolled Insulation

    Rolled insulation – also known as batt and roll or blanket insulation – is the most familiar type of insulation. It is made up of a thick layer of fibers backed with paper and sold as a roll. Fiberglass is the most commonly used fiber in rolled insulation, but plastics and natural fibers such as wool and cotton are used in some brands.

    roll of fiberglass insulation

    Pros of Rolled Insulation

    There are many advantages to using rolled fiberglass insulation:

    • Readily available at building supply retailers
    • Comes in a variety of sizes and R-values
    • Costs less than other insulation options
    • Easy to install
    • Moisture and fire resistant

    Installing rolled insulation is as simple as unrolling it, placing it against the wall or roof between the studs, and stapling the paper flanges to the studs. Use a utility knife to cut the insulation as needed to fit smaller bays or to make room for obstacles such as electrical boxes.

    installed rolled insulation
    Installed Rolled Insulation

    Note that the paper facing on rolled insulation serves as a vapor barrier. It should not be removed. This barrier plays an integral part in keeping condensation at bay.

    Cons of Rolled Insulation

    Although rolled insulation is the most common and widely-used, it does have some drawbacks:

    • Overall lower R-value than other forms of insulation
    • Is easy to install incorrectly
    • Can cause skin and and respiratory irritations during installation
    • Can cause mold and mildew if it becomes wet

    It’s important to take precautions when working with fiberglass insulation. Always wear protective clothing (long sleeves) and wear gloves, a dust mask, and safety goggles when installing fiberglass insulation.

    When installing rolled insulation, be sure all spaces are filled completely. Do not compress it to fit smaller spaces. Instead, take the time to cut it to the proper size. Proper coverage is the key to maximizing the efficiency of rolled fiberglass insulation.

    Rolled Insulation and Water Leaks

    A definite of rolled fiberglass insulation is that it will not immediately soak up water if it gets wet. This means no instant damage will be done to your home’s structure if, say, you have a roof leak or a broken pipe in a wall. If the problem goes unfixed, however, issues can develop. Excess moisture can cause structural damage to the building as well as decrease the effectiveness of the affected insulation.

    For minor moisture issues, use a dehumidifier and/or fans to dry your fiberglass insulation in place. If this is not sufficient to dry the insulation, carefully remove the individual insulation bats, then lay them out to dry indoors or put them in the sun if feasible. Continue to use fans and/or a dehumidifier to dry out the wall or roof area surrounding the leak.

    Once the insulation and the affected wall/roof areas are completely dry and the leak repaired, re-install your insulation. Then, keep an eye on the area for the next few weeks. If you notice mold or smell mildew, take action and replace the contaminated insulation immediately.

    Spray Foam Insulation

    Spray foam insulation is a chemical-based mixture of polyurethane that conforms to the space where it’s applied. It’s becoming an increasingly popular form of insulation.

    man applying spray foam insulation that helps prevent condensation

    Pros of Spray Foam Insulation

    There are a number of reasons spray foam insulation is becoming so popular:

    • Expands upon application, filling in all spaces, gaps, and cracks
    • Creates an air- and water-tight seal
    • Retains R-value over time
    • Adds structural support

    Spray foam insulation has a lot going for it. It seals spaces completely, providing incomparable insulating coverage no matter the size or shape of the space. Once hardened, spray foam insulation doesn’t absorb water, thereby deterring mold and mildew issues. And given that it can even improve the structural integrity of your home, what’s not to love?

    Cons of Spray Foam Insulation

    Even though spray foam insulation has a lot going for it, there are still a few cons to consider:

    • It’s expensive
    • It is fire-resistant but not fireproof
    • The chemical fumes during installation can be deadly – professional installation is highly recommended
    • The foam may shrink over time, reducing its effectiveness

    Unfortunately, the high cost of spray foam insulation puts it out of reach of many people. And prices can vary widely between housing markets and between suppliers within an area.

    Be sure to get multiple quotes before deciding on a spray foam insulation company. Check references and examine contract clauses, too, especially as it pertains to potential shrinkage over time. Taking these steps will ensure you get the most out of your investment.

    Most importantly, don’t treat spray foam insulating as a DIY project unless you truly know what you’re doing. The fumes given off by the foam during installation are toxic and can cause severe respiratory issues and even death as noted on the Environmental Protection Agency’s website.

    Bottom line, it’s best to hire a professional to install spray foam insulation. They will have all the proper safety equipment, including protective suits and respirators, to make the job safe. Plus they will have the experience to make sure your insulation is sprayed in efficiently and effectively.

    Spray Foam Insulation and Water Leaks

    Spray foam insulation repels water and provides a moisture barrier. This means water cannot usually penetrate the surface so, in case of leaks in the home, your insulation will not be damaged.

    However, water trapped between the spray foam insulation and the wall or roof can be a problem. If you experience leaks, be sure the entire area is dry before sealing the space back up. Otherwise, mold, mildew, and wood rot may result.

    Mineral Wool and Rockwool Insulation

    Mineral Wool is similar to fiberglass insulation. The difference is that the primary materials used in making mineral wool are rocks and metal slag rather than glass.

    detail of rockwool insulation

    Rockwool is the trademarked name of a proprietary insulation material manufactured by Rockwool International.

    The Rockwool brand of insulation is made up primarily of basalt rock and recycled slag from steel-making. These materials are super-heated to a liquid state then spun, much like how cotton candy is spun, to make fibers. The fibers are then compressed to make large mats which are cut to standard roll-insulation sizes.

    Other mineral wool insulation manufacturers may use different base materials, but the process is the same.

    The brand name Rockwool has come to be associated with all types of mineral wool insulation. From here on in this article, the name Rockwool will be used for ease of communication, but the information provided refers to all brands of mineral wool insulation.

    Pros of Rockwool Insulation

    Rockwool has become increasingly popular for good reason:

    • Quick and easy to install – flexible edge compensates for normal frame variability, cuts easily
    • Non-combustible, fire-resistant up to 2150 degrees Fahrenheit
    • Water-resistant
    • Does not promote growth of fungi or mildew
    • Excellent sound absorbency
    • Made from natural and recycled materials – user friendly, no fiberglass in product
    • GREENGUARD certified; chemically inert – CFC and HCFC free product and process
    • Does not sag, retains optimum performance over the years

    Aside from its superb insulating and fire-resistant properties, Rockwool is especially valued for its sound-dampening ability. This feature is particularly useful in urban homes, industrial buildings, and multi-unit dwellings such as condominiums or apartment buildings.

    Cons of Rockwool Insulation

    The drawbacks of Rockwool are, honestly, few:

    • More expensive than rolled fiberglass insulation
    • Rockwool dust is hazardous to inhale – gloves, mask, and safety glasses should be worn during installation

    In most cases, the choice of Rockwool over fiberglass insulation comes down to budget.

    Rockwool Insulation and Water Leaks

    Because of its base organic materials, Rockwool does not develop or promote mold and mildew. It does not readily absorb moisture, so will not be ruined due to a leaking roof or wall pipe.

    As always, however, the entire area surrounding any water leak should be thoroughly dried before the space is sealed off again. Rockwool insulation can be removed temporarily to allow the affected area to dry out completely. The insulation can then be put back in place as it was without concern of mold or mildew development.

    Rigid Foam Board Insulation

    Rigid foam board insulation – also called rigid insulation sheathing – is just what the name says: sheets of rigid plastic. The sheets are made of different types of plastic as shown in the image below. The sheets are most commonly sold as 4’x8′ or 4’x10′ panels that are 1′ or 2′ thick.

    image of different types of foam board insulation

    Stores typically carry extruded polystyrene foam board, otherwise known as XPS. These XPS sheets are pink or blue depending on the brand and are 1 – 2 inches thick. XPS panels are usually not faced with any other material, and the R-value is about a 5.

    Polyiso, or ISO, is a thermoset closed-cell foam board manufactured with a lamination process that increases strength and rigidity compared to XPS boards. Polyiso is sold with foil or coated glass facing material in thicknesses ranging from .5 inch to 4.5 inches. The greater the thickness, the greater the R-value.

    Expanded polystyrene, commonly referred to as EPS, is a closed-cell insulation that is 2% plastic and 98% trapped air. the thickest of the rigid foam board insulations.

    Pros of Foam Board Insulation

    Foam board insulation, as a whole, provides a number of benefits:

    • Inexpensive
    • Easy to install
    • No fume or dust hazards
    • Water resistant

    Cons of Foam Board Insulation

    Despite the benefits, however, there are a number of cons to consider before investing in foam board insulation:

    • Cost can add up quickly if multiple layers are needed to increase R-value
    • Panels are often treated with toxic fire-retardants
    • Untreated foam boards are flammable and produce toxins when burning
    • Leaves gaps that reduce effectiveness if not properly caulked or taped
    • Difficult to fit into awkward spaces and around obstacles
    • XPS and ISO deteriorate over time, reducing R-value and leaving gaps where moisture problems can develop

    Foam Board Insulation and Water Leaks

    Foam board insulation is water-resistant and not prone to mold or mildew. However, both XPS and ISO boards can be negatively affected by extended exposure. Repairing leaks quickly and drying out the affected area thoroughly before replacing the insulation is the best recourse. Be sure to examine your foam board insulation and any sealants used with it for degradation after any water leaks and repairs. If there are any signs of damage to the foam board, replace it with new material.

    How To Prevent Condensation in the Home Without a Major Renovation

    Unfortunately, when a house has already been constructed with inadequate ventilation or been poorly insulated, it can be a huge job and major expense to deal with the root cause of any condensation problems.

    The good news, though, is there are a number of other ways to deal with condensation in the home that don’t involve major renovations.

    Consider Your Heat Source

    Did you know that propane produces four cubic feet of water vapor for every cubic foot of gas burned? Which explains why condensation can be such a huge problem for homes heated via propane, especially if they are smaller shed conversion homes.

    Whether you’re burning propane, natural gas, or wood, it’s absolutely vital to ventilate this moisture to the outdoors through a well-maintained and properly insulated pipe or chimney.

    Understanding exactly how your heat source impacts the humidity in your home can help you take steps to offset condensation issues.

    Maintain a Set Temperature Inside the Home

    Condensation is typically an issue during the winter months when warm air from your heat source hits the cold surfaces in your home. Maintaining a constant indoor temperature naturally stabilizes the differences between air and surface temperatures, minimizing condensation. So pick a comfortable temperature and avoid raising and lowering the thermostat if you are noticing condensation.

    If you’re using a wood stove, keep it heating at a steady pace by using a consistent type of wood — ideally hardwood such as maple, oak, or ash — that’s all cut to relatively the same size. Feeding the fire at regular intervals will help you maintain a more constant temperature in your home.

    Open Some Windows

    In this article, we’ve explored how inadequate ventilation is a major contributor to condensation in the home. Therefore, it stands to reason that improving ventilation will help reduce condensation. Obviously opening a window won’t be comfortable when the temperature plummets, but take advantage of moderate days to let fresh air circulate through your home.

    Use Fans

    Using fans, especially in attic and loft spaces, is another easy way to keep air circulating in your home to minimize condensation. Directing warm, rising air downward helps normalize the temperature throughout the home. Keeping the air moving inhibits the formation of moisture droplets on surfaces. Invest in a few small, high-powered but energy-efficient fans, and then keep them running 24/7 for best results.

    Invest In a Dehumidifier

    Whether you live in an area that’s humid year-round or only struggle with condensation during a particular season, buying a humidifier is a wise investment.

    A dehumidifier – DeHu as they are called for short – draws moisture from the air, collecting it in a drain pan within the unit that is emptied periodically.

    The size dehumidifier you’ll need depends on the size of the room or rooms where condensation is a problem. The AUX Portable-N available in our Homestead Store is a unit we use ourselves and highly recommend. Not only does it dehumidify, but it’s also an air conditioner and air purifier.

    AUX Portable-N dehumidifier prevents condensation

    How to Prevent Condensation in Your Home a Few More Ways

    Here are a few more ways to minimize condensation in the home:

    • Keep hot showers and baths short
    • Install and use a bathroom fan that vents to the outside
    • Keep the bathroom door closed while bathing and showering
    • Use lids on pots while cooking to contain steam vapor
    • Do not hang wet clothes indoors to dry
    • Keep interior doors open as much as possible for air circulation throughout the home

    The Best Way to Prevent Condensation in Your Home

    The best way to deal with condensation in your home is to never let it start. This means using all the best building practices including house wrap, ventilating soffits and ridge vents, properly-installed insulation, and double-paned windows.

    The next best way to prevent condensation in your home is to be proactive if you’re finding excess moisture in your home. Consider your heat source, which could be a huge part of the problem. Keep the temperature in your home constant. Use whatever ventilation and air circulation techniques possible to keep fresh air moving through your home. This may include opening windows, running fans, or using a dehumidifier.

    Condensation isn’t just unsightly, it’s problematic for buildings, belongings, and health. We hope you’ll use the information in this article to help prevent condensation from developing in your home.


    This article was co-authored and edited by Cheri Jones, a freelance writer for hire. Learn more about her services at CheriAnnJones.com