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How to Insulate a Roof and an Attic

Last modified: 2022-11-29 | Approximate reading time 5 mins

Léa Plourde-Archer

The attic is one of those parts of the house that we tend to forget. Like they say, out of sight, out of mind. Yet the things that go on up there can end up having a concrete effect on numerous elements that affect us on a daily basis. To gain a better understanding of how important attic insulation is, has prepared a brief presentation on the subject:

First, it is important to note that different kinds of attics exist. In some houses, the attic is set up into a livable space, with rooms and windows. For the sake of this article, however, we will be concentrating on attics that are more difficult to access. In most houses, these attics are reached through a trap door in the top floor ceiling.

Others are accessible through an opening on the outside of the house. It can be hard and even impossible to get into the attic. Some have ceilings that are too low (less than one meter in height), whereas others are blocked by architectural elements. If such is the case in your house, you will have to do business with a professional contractor at every step of the process.

How to inspect your attic

Attic home

Source: Canva

An attic should be inspected on a regular basis, in order to detect any worrying signs before they are able to turn into real problems. Pay special attention to the condition of the roof framing. If you notice the smell of mould, try to find the source of this smell. 

Also, check to see if there are any water and air leaks. The insulating product that covers the surfaces should be dry and firmly held in place. If it sags in certain areas, you’ll have to find a way to put them back into place.

Beware: if your insulation material is made with vermiculite, DO NOT TOUCH IT. Vermiculite may contain asbestos. Hire a qualified inspector. For more info, check How to recognize lead and asbestos in your home

Check if your attic has an air barrier and a vapour barrier. Most modern houses are equipped with this type of insulating material. However, such is not the case in older buildings. If you live in an older house, you should get in touch with a contractor to ask for their advice. In some cases, a few layers of vapour-barrier paint on the top-floor ceiling could do the job.

How to improve your attic’s insulation

First of all, it is important to know that if you have noticed any problems with mould, you have to solve this situation before you add any other insulation material. Mould can indicate a serious problem with the roof’s water-tightness, or a humidity problem in certain rooms inside the house. Adding insulation in the attic would then be equivalent to putting a plaster on a fracture.

Seal any and all air leaks. Unfortunately, it is impossible for us to give more precise information on this subject. Each case is very different; therefore we suggest that you call or get in contact with a contractor who will be able to find the best solution to fix your situation.

There are many different reasons to improve your attic’s insulation, the main one being that this will help protect the building in which you live. The effects of these renovations will also be felt on your heating and electricity bills. Therefore, do not neglect this very important part of your house.

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Roof insulation: what to know

Source : canva

Materials used for roof insulation and their prices

There are several options available to insulate your roof. First of all, you can opt for blown-in cellulose which offers an insulation degree of R-3.7 per inch of thickness. The main advantage of cellulose is that it can slip into crevices, which makes it very efficient. There are a number of other advantages, such as the low cost, the resistance to fire, the soundproofing qualities and the way it manages to control humidity. Since it is rather hard to install, it is best to hire a professional to do so. The average price for blown-in cellulose is $1/square foot. 

As with blown-in cellulose, blown-in fibreglass can fill all the space inside the roof. However, its degree of insulation per inch is lower and only reaches 2.85 per inch of thickness. It must, however, be noted that it is better for thermal insulation than batt insulation, whilst also being resistant to fire and humidity.The average price for blown-in fibreglass is $1/square foot.

Lastly, you can also choose batt insulation (fibreglass or rock wool). This material has an insulation factor of R-3.3 per inch of thickness. It is resistant to fire, humidity, mould and parasites. It also provides a good energy performance in addition to having a good price/quality ratio. The average price for batt insulation is $1,20 /square foot.

Note that there are other options for insulation materials, such as hemp, polyurethane and expanded cork.

To learn about the average prices of insulation materials, check out our article The cost of insulation

The importance of proper attic insulation

If the roof allows air and humidity into your house, this will affect the building’s energy performance. It could also have a negative effect on the house’s occupants. In a house that is properly insulated, the attic’s temperature should be temperate (only varying by a few degrees compared to the outside temperature). This means that the warm air (or the cool air coming from air conditioning) is well confined inside the house.

Roof insulation is extremely important as it helps to: 

  • Benefit from a comfortable room temperature inside the house;
  • Reduce your consumption levels for air conditioning and heating;
  • Reduce your electricity bill.

The benefits of proper ventilation on air quality

Source : Canva 

Another crucial aspect to take into consideration is the attic’s ventilation. If you have problems with the house overheating and that your air conditioner works hard during the summer, this might be due to ventilation problems.

What might be the causes of this particular issue?

There are numerous potential sources, but here are a few leads:

  • By looking to insulate the walls and other surfaces in the attic, we sometimes end up blocking the ventilation sources without realizing it.
  • The hatches and blowholes are sometimes blocked by the insulating material.
  • The ventilation can also be affected by dirt and dust build-up.

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