How to Insulate Eaves of Roof: Your Complete Guide

Can I insulate Roof Eaves

Many houses in the UK have sloped ropes to prevent water retention on the roofs.Yet, that useful outside slope translates into an awkwardly shaped angle at the edges of attics from inside your house, making it more difficult to insulate than a typical loft.

Despite the difficulties, insulating the eaves of your roof prevents heat from leaving your property in the colder months and entering it in the warmer months. In this post, we’ll discuss how to insulate the eaves of your roof, the materials you can use, the tools you will need, and a detailed step-by-step guide. 

Eave Insulation: Understanding the Different Types of Insulation

Before you begin the insulation process, you must decide on the most suitable insulation material. Each material has its pros and cons and not every insulation material can be installed without professional assistance.

There are four main types of insulation materials that you can choose from to insulate the roof eaves. These include:

Fibreglass Batts

Fibreglass batts are the most affordable and the most readily available eave-insulating materials. They are made from woven glass fibres that can be easily installed without professional assistance. 

They’re also lightweight, easy to handle, and require minimal tools for installation. Most importantly, they have a good R-value (good thermal resistance) for the price.

However, that thermal resistance is acquired when the batts are installed at full height, which isn’t easy to utilise if you’re installing them in tight spaces like eaves. 

Rockwool Batts

Rockwool batts are fairly similar to fibreglass batts when it comes to use and consistency. However, since they’re made from volcanic rock fibres, they are more expensive and less readily available.

Additionally, they’re heavier, which makes them more cumbersome to carry and handle. Yet, they provide better fire resistance compared to fibreglass. 

Loose-Fill Cellulose

Loose-fill cellulose is made from recycled paper and natural fibres, making it a more environmentally friendly option compared to fibreglass and rockwool. It’s also excellent for filling irregular spaces like roof eaves. It also has a better R-value compared to fibreglass. 

However, loose-fill cellulose requires special blowing equipment for installation, which makes it more expensive and complex compared to batts. It also settles over time, which requires constant ventilation and periodic topping up. 

As such, while doable, it’s not ideal as a DIY project.

Spray Foam

The foam is made from expanding polyurethane which is applied directly to the surfaces you want to insulate.As such, it provides the best air-sealing and insulation capabilities, as you’ll end up with virtually no leaks. It also has the best R-value among all options and provides soundproofing benefits as well.

However, it’s less environmentally friendly, hard to remove and/or repair, expensive, and requires special equipment which calls for professional installation. It’s not an option that can be installed without a professional installer.

Insulating the Eaves of Your Roof

Since loose-fill cellulose and spray foam are often used by professionals and dedicated insulation companies, we’ll focus more on the insulation types that you can do yourself; fibreglass and rockwool batts. 

First things first, here are the tools you’ll need:

  • Your chosen insulation material: In our case, it’s either glass fibre or rockwool.
  • A utility knife: For cutting the batts to size.
  • A tape measure: For accurate measurements of joist cavities and batts.
  • Spray foam: For sealing any air gaps around pipes, wires, and other objects present within the insulation space.
  • Gloves: To protect your hands from itchy fibres.
  • Goggles: To shield your eyes from dust and debris.
  • Long-sleeved shirt and pants: For added protection from fibres.
  • A ladder: For reaching higher areas in your eaves or attic.
  • A flashlight: To illuminate tight spaces and corners.
  • A marker: To mark your measurements whenever needed. 

These are the essential tools that you must have before insulating your roof eaves on your own. The following tools are not as essential, but they’ll make the process a lot easier. 

  • Knee pads: To make kneeling on the attic floor or joists more comfortable.
  • A dust mask: If you’re sensitive to dust or working in a dusty environment.
  • A staple gun and staples: For securing batts in vertical applications (walls) before drywall installation.
  • Friction clips: An alternative to staples for holding batts in place.

Now that we have the tools, it’s time to start the insulation process itself. To do so, follow these steps:

Step #1: Cleaning and Inspection

Your insulation’s ability to prevent heat transmission will be adversely affected if cracks or leaks are present anywhere in the attic. If you’re in a rainy area, leaky roofs are extra dangerous because they can result in mould growth, which can force you to change your entire insulation again.

As such, your first step would be to clean the attic as thoroughly as possible. This will help you identify any imperfections, cracks, or leaks that can compromise the integrity of your insulation. If any of those are present, you should address them before beginning the insulation process.

Step #2: Ensure Proper Ventilation

Ensuring proper ventilation is paramount before beginning the insulation process. Without it, warm air from inside your home can rise and condense within the eaves space, especially as it comes into contact with colder roof elements. This leads to mould and mildew growth, wood rot, and paint peeling. 

This ventilation can be in the form of vents and attic fans (in addition to the rigid wood baffles or rafter vents present within the eaves space for air circulation). If those baffles aren’t present, you have to install them or have someone do it for you. 

Step #3: Prepare You Insulating Material

Use the tape measure to figure out the length of the insulating material that you need. Once you acquire that material (fibreglass or rockwool batts), inspect them for any damage or tears. You’ll then need to measure:

  • The ground space you need to cover.
  • The ceiling space you need to cover, all the way down to the edge of your eaves.
  • The space between the rafter vents.

Once you double-check all the measurements, use your utility knife to cut your insulation batts according to said measurements, but make sure to add an extra quarter inch (0.6 cm) in each increment you cut.

This extra length provides a snug fit of your insulation material and prevents air leaks. Keep in mind that you need a snug fit, not a compressed fit. So don’t go beyond that quarter inch.

Tip: Make sure you try fitting the first few increments you cut into their respective spaces between rafter vents. That way, you’ll figure out early on if your cutting isn’t accurate enough. 

Step #4: Installing the Insulation Material 

Once you make sure that you’ve gotten the hang of accurate cutting, it’s time to place the increments in place. You need to adequately cover the ceiling, ground, and walls (if your attic doesn’t end in a sharp triangle angle). Your marker should help you visualise the increments before they are put. 

For freedom of movement, you should leave the ground insulation for last. Start by snuggling the batt increments you cut in between the rafter shafts. Typically, you don’t need fixation, assuming that the increments fit well. Still, you can fit the batts in place using a staple gun. 

At one point, you won’t be able to reach the ceiling without a ladder. Having someone hold the ladder for you at this point can be useful. If that’s not available, consider having a few batts around the ladder in case you fall by accident. 

Once you finish the ceiling insulation, proceed to follow the same steps with the wall insulation as well if applicable. Finalise by adding the ground insulation. 

Note: If the depth in between the rafter shafts is too much, or if you live in an especially cold area, you may add a second layer of insulation material. However, that means you’ll need to purchase double the amount you’d have originally used. 

Step #5: Apply the Spray Foam

Step 5 is to be applied when you’re met with a penetrating object within your work area during step 4, like wires, roof vents, and pipes.

Since it’s difficult to cut your insulating material to fit exactly around such structures, we should use other means of selecting sealing at these particular spots. In this scenario, a spray foam will seal any gaps, providing air tightness which improves insulation and energy efficiency. 

Step #6: Filling in the Gaps

Your previously cut increments won’t cover every inch of your attic space. It’s especially common for the eave gaps to require custom cutting of your insulation batt. 

You should have a few extra metres for this occasion. Try to cut the required shapes to fill in these remaining gaps, and make sure not to over-condensate the insulating materials. 

Exclusively Insulating the Floor of Your Attic

It is possible to add the insulating material on the floor of your attic but not the ceiling and walls. Despite providing less insulation than fully insulating all surfaces, it’s a much easier DIY project.

However, this type of insulation often requires an additional layer or two of the insulating batts on the ground. That’s because the bottom layer will leave a small, triangle-shaped non-covered area at the junction between the floor and the eaves.

To compensate for that area, an additional one or two layers of insulation materials are needed to provide the best possible thermal insulation. 

Insulating Roof Eaves Conclusions

With careful planning and some skills, you can insulate the eaves of your roof using fibreglass or rockwool batts. They don’t require special equipment to handle, and they can be installed without professional help.

However, if you prefer not to do it as a DIY project, or if you want to have the best possible insulation you can get, you need to have them installed by dedicated insulation contractors.

Find out the best insulation contractors around you through Insulation Advisor. Just enter your postcode, and you’ll get a free quote. 

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