The benefits of insulation are undeniable, and the rule of thumb is that the more insulation there is, the more you will benefit. However, there is definitely a point at which installing more insulation will not be worth the cost.
There is also a point after this at which installing more insulation can start to cause problems, particularly in your attic, where you are less restricted in terms of how thick you can build up the layers.
Attic insulation should not touch the roof. If it does, there is no channel for air to flow between the insulation and the roof. This airflow is vital for maintaining proper thermal balance in a house and preventing a buildup of moisture. The reason the insulation is touching the roof should be addressed.
Ventilation Affected When Insulation Touches Roof
The space between the roof and insulation may not seem important, but it’s not simply “empty” space; it is the ventilation space. Filling it impedes ventilation, leading to a buildup of heat and moisture.
An attic has to be ventilated. This is achieved with ventilation openings that lead directly outside. Typically, there are openings in the upper part of the attic (ridge vents) and the lower part of the attic (soffit vents).
Hot air naturally rises and escapes to the outside through the ridge vents. However, it cannot do so effectively if the air is not replaced because the vacuum effect will prevent further heat loss. This is where the soffit vents come in.
The loss of air through ridge vents creates an area with pressure lower than the pressure outside of the attic. Air moves naturally down pressure gradients, and so air is drawn back into the attic.
The “new” air that enters the attic through the soffit vents is going to be cooler than the air that is pulled out through the ridge vents.
If the ventilation area is blocked off by insulation that is built all the way up to the roof, then there is limited to no airflow between the two sets of vents. The heat that builds up in the attic is trapped here by the vacuum effect.
Effects on the Areas Below the Insulation
Even with insulation, this buildup of heat can start to affect the temperature in the rest of the house, particularly the room underneath the attic.
The rise in temperature may make the upstairs rooms more comfortable in the winter, but in summer, you are not going to b enjoying it.
You’ll have to run your AC harder and longer, which wastes energy and money. Long-term, it can even cause premature wearing and breakdown of the AC system.
Even in winter, there will be negative repercussions. If you have heat building up on the top floor, you will not be benefiting from the stack effect, which usually helps to balance the temperature at different levels in your home. So, the upstairs will be extra warm, but the lower floors will be extra cold.
Furthermore, the airflow through your house is impeded, leading to stagnant air, which lowers the indoor air quality.
Effects on the Roof
There are also implications above the insulation layers.
If your area experiences snow at any point in the year, a roof that is kept at temperatures above 32 ℉ can lead to ice dams.
Ice dams form when a warm roof melts snow that lands on it. When this melted snow runs down the roof and reaches a part that is below 32 ℉, the water will freeze and begin to form an ice dam.
An ice dam can prevent melted snow from draining from your roof, which can cause water to build up and enter your home.
The built-up ice, snow, and water put a strain on the roof, causing damage.
Ice dams are a “maybe” problem for some people, depending on where you live. However, insulation that touches the roof and impedes ventilation causes other moisture issues, which are not dependent on the climate.
Why Moisture Builds Up
If you’ve ever had a cool glass of water on a hot day, you have definitely witnessed condensation in action.
When the cold temperature of the water comes in contact with the hot, moist air on the outside of the glass, it causes the water vapor in the air to condense and form droplets on your glass. This is because when air loses heat, it can no longer hold as much water.
The same process occurs in the home between the roof and insulation but on a much larger scale and in a much more destructive way.
When insulation is in contact with the roof, there is still a layer of air between the roof and the insulation. However, this air is going to be hot since the insulation is barring cool air from circulating in this space.
The roof itself is likely to be colder, especially during colder months, since it is in contact with the outside.
This means that when the warm attic air comes into contact with the cold roof, the moisture in the warm air will condense and form water on the roof’s surface, just like it does with the glass of water’s surface.
What This Means to the House
The condensed water will build up on the roof and may drip down onto the insulation and into the attic (if the insulation does not stop it fully).
Wet insulation is less effective, and some can start to degrade and/or grow mold.
The worst problem, however, comes when the wooden parts of the roof become wet with condensation.
Although the shingles of the roof are meant to withstand all sorts of weather, the inner wooden components are not as protected. When they get wet, they are likely to lose structural integrity.
In the worst-case scenario, a damp roof can sag and even cave in.
Because the attic is not often checked on, it is likely that this problem will not be identified until it is well on its way to being too late.
Not only will the repairs to your roof be expensive, but a caving-in roof is an acute danger to those living in the house.
Even if this doesn’t happen, the warm, moist conditions in between the roof and the insulation would be ideal for mold growth, which can spread to the rest of your home.
Mold in the home is not only ugly but can also lead to breathing difficulties, especially for those who have asthma or allergies.
Another issue is the weight exerted on the ceiling boards beneath the insulation.
If your insulation is touching your roof, it is most likely layered in really thickly. For many insulation types, this is going to result in a weight that the ceiling boards will not be able to handle, especially over longer periods of time.
Why Is the Insulation Touching the Roof?
If your insulation is piled so high that it is touching the roof, you must reassess the situation and address why this is the case.
Perhaps you or the previous owner simply installed too much insulation. Maybe it was a matter of not knowing how much insulation you should have, or perhaps you just thought that more was better.
There is a point where more insulation won’t be that much more effective than the recommended amount.
The weight of excessive insulation can also cause an increased rate of settling or even compression of the bottom layers, which reduces the R-value, defeating what you were trying to achieve with the extra insulation anyway.
If this is why the insulation is touching the roof, you will need to remove some of it. You can call a professional to help you scale down to the correct thickness.
Another problem may lie in the R-value of the insulation material you have chosen. If the R-value-per-inch is low for a type of insulation, it will have to be much thicker to achieve the desired R-value to optimize energy savings.
If you had to reach a high R-value like R60 for your attic, it might be difficult to do so with low R-value insulation unless you install insulation up to the roof.
In this case, it would be best to get insulation that has a higher inherent R-value so that you can install less but achieve the same R-value.
Try Installing Baffles
If you cannot avoid installing insulation that touches your roof (for example, if you have a low roof), there is a good way to reduce harm to your home and roof.
Installing baffles is a fairly simple way to restore ventilation in your attic.
Baffles do not take up much space, but they act as a route for air to flow from the soffit to the ridge vents, circulating just below the roof.
If instead of having insulation between and over ceiling joists on the floor of the attic, you may have batts, boards, or spray foam in between the rafters. While these will look like they are touching the roof, there may be baffles hidden under them, which is an acceptable practice.
If there are no baffles, then this is problematic, impeding ventilation.