The attic is usually one of the parts of a house that have more treatments and repairs for the roof, moisture, mold, and dust that is generated, especially when is used as a warehouse and not as a room. In addition to being in direct contact with the outside, it is necessary that it is well insulated. That is why we bring you a small guide on how to insulate an attic.

How to check attic insulation?

The first thing to evaluate before you install new insulation is that there is no moisture, fungus, or mold, that the structure is sound, and that there are no leaks.


Ventilation is the main thing in an attic, all structures breathe through installed pipes that carry gases out of the structure. The same case for a penthouse. If not, it results in mold, rusty nails, rotting wood, dirt, and condensation in the crawl space.

The most effective way to improve ventilation is with a soffit and ridge. This design allows air to be drawn from the lowest point (soffit) and expelled from the highest point (ridge) of the attic.


floor insulation

A drafty floor at the entrance to the attic may indicate the need for more insulation.

The temperature change in an attic is a clue to assessing missing insulation. Insulation also expires and needs to be replaced from time to time.

A quick way to determine if you need more insulation is to look throughout the attic. If the insulation is right at or below the floor joists, you should add more.


A leaky roof is evidenced by water stains, rot, or mold in the attic, especially in the sheathing. However, leaks don’t always come from a hole in the roof or damaged shingles. If they don’t come from shingles they can come from around pipes, radon systems, and even chimneys, as the tar, which acts as insulation, expires or wears away, causing attic leaks.

Leaks are a problem that initially does not have major consequences but in the long run, they do. You should repair the damage immediately and permanently.


If there are nests, birds, leaves, acorns, and droppings, it is a problem when insulating an attic. It means that they have easy access to the attic through the soffit. You should calmly observe and identify entry points to avoid them in the future.

Exhaust ducts and ventilation stacks

house ventilation

Earlier I mentioned that structures breathe through pipes, these should always terminate outside the structure, above the roof, the terrace, or the wall. Sometimes the latter is not done and these pipes end up inside the attic. If this happens, condensation occurs in the roof seams and insulation, causing mold and mildew.

Make sure that all pipes finish outside the structure and not inside, and check that they are not cracked, expired, or damaged.

Some inspections it is possible to do by following these tips:

  • Perform an inspection on a rainy day, which makes it easier to detect active leaks.
  • Check the attic in natural light to identify possible water leaks.
  • Always wear safety goggles, a dust mask, a hard hat, or a safety helmet.
  • Measure any temperature changes with an inexpensive thermal camera.
  • Use a tape measure to check insulation levels.
  • Always walk on the rafters and not on the backfill, you don’t know what condition the roof is in and if it can fall.
  • Make a report with photos during the inspection, focusing on potential problem areas that you can refer to later.

How to check for mold in attic insulation?

There are many ways but you need to have your five senses active:

1. Look for colored spots

When there is mold it is evident by the stains it presents, so look for discolored spots in the area and usually stand out as pink, orange, green, white, or gray with black, depending on the type of mold, some are usually more harmful than others are. They also spread faster than others did. The most worrisome is the black and green ones because it is a problem associated with home interiors.

When the mold is black, it can be responsible for lung diseases, which usually occur near the ventilation.

2. Moisture

This is very common if you have suffered accidents or water damage, storms or snow, and not repaired in time, this generates mold and can spread quickly because it does not need light, only water, and oxygen, remember that mold is a fungus.

Fungi spend inactive time when the space is not conducive to their development, so the ideal is to fix the water leak permanently.

3. Look for shapes and patterns

White and green mold stains appear as splashes or irregular spots on walls and wood. Black mold forms perfect circles or crescent shapes as it spreads. The latter is a concern and must remove safely and permanently.

4. Smell

Have you ever heard people say: it smells musty? That is because molds smell and they are often not pleasant smells. Many people, for example, smell like urine. Unfortunately, attics have a peculiar odor, either because of enclosed air or because of inadequate ventilation, lack of cleanliness, and the presence of mold.

However, the odor is an unmistakable characteristic that there is a fungus in the attic. Based on this characteristic, you can start looking for patterns, colors, etc.

5. Health problems

Allergies, itchy skin, eyes, and nose, snoring, continuous flu, continuous coughing, or sudden and prolonged respiratory problems may be due to household air and fungus in the attic.

The attic is a favorable place to reproduce and spread many microorganisms, to know how to insulate the attic you should be aware of these small details because you can lose the investment by not eliminating permanently the mold present in the attic.

What is the best way to insulate an attic?

floor insulate

There are functional and inexpensive materials as well as functional and expensive ones that will make you think about it, but whatever you decide to do, keep in mind the benefits it brings.

Loose fill

Are usually placed with special machinery, until the desired depth and density are achieved. It can usually by hand but is not well coated, nor well finished. Generally used for attics:

  • With irregular or non-standard rafters.
  • Many obstructions and penetrations to work around.
  • Where existing insulation needs to be covered, as it fills gaps and joints well.
  • With low headroom for maneuvering during installation

Insulation material options include:


It is lighter than cellulose or mineral wool, and it settles more than other materials so you will have to do several layers before finishing it. It is made of sand melted and spun into fibers or recycled glass. The R-value per inch is 2.2-2.7.


This is the most commonly used material but can rot if it comes in contact with moisture. It is recycled paper treated to resist insects and fire. R-value per inch 3.2-3.8.

Mineral wool

It is fire-resistant but is not as easy to “blow” so it takes more work to install. It is made from rock fibers or recycled blast furnace slag. Its R-value per inch is 3.0-3.3.


The flexible material is usually packaged in rolls and comes in established thicknesses, widths, usually 16, and 24 inches so that they can be installed in a house. They come with a paper or foil liner that acts as a barrier. Several layers are added to achieve the desired level of insulation. They are generally used in attics:

  • That has standard joist spacing, especially those without insulation.
  • With few obstructions or penetrations around which to work.
  • That has sufficient room to maneuver during installation.

Some common choices of insulation material to insulate an attic are:


The most economical and common of the materials, however, the materials can irritate the lungs or skin and is not as efficient at blocking airflow as other materials. It is made of: Recycled glass or sand melted and spun into fibers.

Cellulose insulation

It is fire efficient and does not irritate the lungs or skin, but its manufacture is limited, it is recycled paper.

Mineral wool

It is naturally fire-resistant but is an expensive product. It consists of rock fibers or slag recycled in furnaces.


Efficiently blocks air and sound transmission but is an expensive material.

How do you prevent heat loss in an attic?

Insulation baffles info

Good insulation prevents energy loss and lowers your electric bill, so it is a good long-term investment.

1. Add new insulation to the attic

Good insulation can help you save up to 15% on electricity costs. If your home was built before the 1970s, you should add a new layer of insulation. To check this, just look to see that the insulation is flush with or below the floor joists. 

The second method is to look at the “R rating” of your current insulation, measure the depth of the insulation with a tape measure, and then perform calculations based on a table created by EnergyStar. The “R rating” of your insulation tells you how effective it is. Most homes that are 10 years older have R-11 or R-15 insulation, which pales in insulation capacity compared to today’s R-30 insulation.

Keep in mind that even if your check passes the test, that does not mean it is necessarily good.

2. How to insulate attic ducts

If heating, ventilation, and air conditioning ducts run through the attic, they are likely to leak hot or cold air, as some of it leaks out before it reaches the house. To solve this problem is for professionals to install a special type of insulation that completely covers the ductwork and prevents the transfer of heat or cold air.

3. Inspect the vents

These may obstruct dirt, animal debris, or rust in the case of passive fans. This leads to mold and moisture, which causes rot and insulation deterioration. In addition, poorly configured vents can make it difficult for fresh air to enter the attic.

4. Air Leaks

The attic can cause a large loss of energy and unnecessary wear and tear on heating, ventilation, and air conditioning equipment because it requires more electricity to maintain the desired temperature in your home.

If you begin to notice that your heating or air conditioning is turning on more frequently, or taking longer to reach the desired temperature, you may have an air leak somewhere in your home.

Check window sills and door frames, point the light up and down the joints and ask someone on the other side to look for light gaps.

5. Seal the attic entrance

It is common to forget this detail; depending on the configuration of the house, it could be an air leakage gap. You can seal it tightly with a special attic door cover; it helps to close any air gaps that escape from your house and attic.

Can I insulate my loft myself?

Yes, installing attic insulation is not difficult; it depends on the material you have chosen. If it is loose material, you will need a special machine to help you do it and a pair of skilled hands. This is partly because these machines require some skill to operate. Also, insulation professionals know how to cover tiny spaces, which is one of the biggest benefits of these types of insulation.

Warning: a professional should always do any attic work involving mold or asbestos. These harmful substances must be removed in a certain way to keep you and your family safe.

How much does it cost to insulate your attic?

The price will depend on the material you choose, however, the total amount per project is between $1500 to $4000.

For example, cellulose and fiberglass insulation cost $0.33 and $0.35 per square foot, or $160 to $175 per 500 square feet. However, if you use wool, panels, or cotton the price is around 5-7 dollars per square foot and you need between 1200 and 1500 dollars per 500 square feet.

Now that you know how to insulate an attic, you can do it yourself or seek specialized help depending on the material you use to insulate it. Remember that it must be optimal so that no air leaks occur.

How to insulate an attic? Best options was last modified: January 16th, 2023 by Vanessa Gallanti
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