Looking across your attic, if the insulation is level with or below the attic floor joists, you probably need to add more insulation. If you cannot see any of the floor joists because the insulation is well above them, you probably have enough, and adding more insulation may not be cost-effective.
One sign of good insulation is having even temperatures throughout your home. If different rooms have different temperatures – say, you freeze in the kitchen but feel too warm in your living room – that's a clear sign your house is under-insulated.
Another way to check is to look for drafts around windows and doors. If you can feel a draft, that means that warm air is escaping from your home, which means your insulation isn't doing its job properly. Glazing is one of the main heat loss elements in a household and anything less than double glazing is a concern.
Either read the R-value printed on the batts of your existing insulation or use a measuring tape to measure the depth of the insulation (inches). Next, use the table below to calculate the R-value of your insulation by multiplying the measured depth with the number provided below.
It is possible to over-insulate your house so much that it can't breathe. The whole point of home insulation is to tightly seal your home's interior. But if it becomes too tightly sealed with too many layers of insulation, moisture can get trapped inside those layers. That's when mold starts to grow.
For standard 2x4 walls, which are common in older homes, an R-value of R-15 is considered good, while R-21 is excellent. This can be achieved with high-performance fiberglass batts, dense-packed cellulose, or a combination of cavity insulation and continuous insulation.
You will want to bring up your attic up to R-38:
If your attic has 5-6″ of existing insulation, you'll want to install an R-19 to achieve a total of R-38.
To check the level of your wall insulation, consider purchasing an infrared thermometer. The device will detect any poor insulation and alert you of any specific problem area.
Check Behind the Baseboards
Put the wood between the wall and the pry bar to avoid any drywall damage. Then you can easily pry the trim away to get access to the bottom of the wall. If there is existing insulation like fiberglass or cellulose, you will be able to see it in the gap at the bottom of the drywall.
Most forms of insulation can last for decades under ideal conditions. However, various issues inside your home can make retrofitting or replacement necessary much sooner. Some homes have the original insulation for upwards of a century, while others may require upgraded insulation in as little as 15 years.
If your walls feel cold when you touch them, then it is likely that your home is not well insulated. Fortunately, you can easily make your walls warmer by installing extra insulation and completing other home energy upgrades. This will reduce heat loss, lower carbon emissions, and save you money on utility bills.
The DOE Insulation Fact Sheet (DOE/CE-0180) can be ordered from the Energy Efficiency and Renewable Energy Clearinghouse or accessed from the Internet at www.ornl.gov/ roofs+walls. Fiberglass and rock wool batts—2x4 walls can hold R-13 or R-15 batts; 2x6 walls can have R-19 or R-21 products.
Drywall has a relatively low R-value — about 0.45 at ½” thickness. This is similar to building materials such as siding, concrete, dirt, face brick, particleboard, wood and single-pane glass. However, it is significantly less than materials that are commonly used for insulation.
High R-value: Because foam board insulation has a greater R-value than standard fiberglass/batt insulation, it is more effective at insulating and decreasing heat loss.
Removing old insulation is generally recommended if it's damaged, contaminated with mold, or infested with pests. However, if the insulation is in decent shape and just needs a boost, adding a new layer on top can be a cost-effective option.
The optimal R-value for most homes is 30, but you can go as high as 38 if you live in a tropical climate. Anything higher than 38 indicates an over-insulated space. While you might think that too much insulation can't be bad, there are some significant consequences to consider.
Never place insulation close to water heaters, oil burners or anything hot. The backing is especially flammable and will be a major fire hazard for your home.
You can easily detect areas of missing insulation by walking around your house with a thermal imager and looking for temperature differences. For best results, you'll want at least a 20 degree temperature difference.
In order to calculate the R-value of a particular piece of insulation, you divide the thickness of the material by its thermal conductivity. Thermal conductivity measures the rate at which temperatures transmit through an insulating material.
If you're wondering what bad insulation looks like, check to see if it is moldy, wet, or discolored. It may be unevenly dispersed and thin in areas. If you see these problems, take action right away. Poor household insulation can cascade into expensive, uncomfortable, and even dangerous problems.