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Roof Insulation: A homeowner’s Introduction

Home is where the heart is, but a house without insulation can be an uncomfortable place to live. We all want to be cool in summer, and warm in winter, but we live in a country known for its extreme temperature fluctuations. It can go as high as 45 Degrees Celsius in the day and as low as minus 10  0 degrees at night. With sky-rocketing electricity costs, not to mention continued load shedding, as a homeowner how are you supposed to keep your home at a constant temperature and energy-efficient?

roof insulation

In this article, we’ll be briefly touching on the different types of insulation materials, what they are made from and how each one can benefit your home. More importantly, we will provide you with questions to pose to any insulation company and expert, even a Builders Warehouse Roof Insulation salesperson.

What types of insulation are there?

You can choose to insulate your roof, floors, walls, windows, and doors. The most important thing is the walls since for a typical house the walls will lose around 30 to 40 per cent of the heat. The roof comes in second place, accounting for approximately 25% of heat loss. Then comes windows and doors with 20% and finally, the floor. In this article, we will only look at roof insulation.

What Is Home Roof Insulation?

Insulation is defined as a material used to insulate something, especially a building. Basically, insulation is a material used that reduces heat loss or heat gain by providing a barrier between the inside of your home and the significantly different temperatures outside. Roof insulation is specially designed for homes and offices and is available in many forms. From standard blankets to the chemical miracle of spray foams, it’s a field with many options, and each one has its place in a building.

It’s essential to make sure you brace your home or office building against the elements, hot or cold.

Types of House Insulation Materials

There are three major types of insulation used in homes: foam, fibreglass, and cellulose.

Foam insulation

Foam insulation comes in two different forms, which are spray and injection foam.

  • Spray foam is sprayed in an open cavity, like in new construction, attics, crawl spaces, rim joists, and pole barns, in a liquid state. The spray foam then expands and fills the cavity.
  • Injection foam is pumped into an existing cavity, like walls, which makes it great for insulating existing homes.

Spray foam can be either open-cell or closed-cell foam insulation.

  • Open-cell spray foam is very light and pliable due to its composition. As open-cell foam dries, the gas inside the cells escapes through openings in the cell’s wall resulting in foam that is light and pliable that shifts as it settles.
  • Closed-cell spray foam is a much more dense and heavy composition. It creates a dense surface that is more resistant to weathering and temperature change.

Fibreglass insulation

Fibreglass comes in batts and rolls. It can be placed in unfinished walls, floors, attics, and ceilings. Fibreglass insulation is fitted between studs, joists, and beams.

Cellulose Insulation

Cellulose can be either loose-fill or blown-in. It is best used in enclosed existing walls or open new wall cavities. Cellulose insulation can also be used in unfinished attic floors.

What is the roof insulation made of?

Not all home insulation materials are made up of the same ingredients.

a.      Foam Insulation

Foam insulation is made from a tri-polymer blend dry powder resin. As the resin mixes with a foaming agent and water, it transforms into Foam insulation. Much like injection foam, spray foam insulation has the same shaving cream consistency when it is sprayed.

b.      Fiberglass Insulation

Fibreglass insulation is made of plastic reinforced by tiny glass fibres. This composition gives the plastic additional strength while improving its insulation capacity.

c.       Cellulose Insulation

Cellulose insulation is made up of 75 to 85 per cent recycled paper fibre – usually post-consumer waste newsprint. The other 15 per cent is a fire retardant such as boric acid or ammonium sulphate.

Making An Informed Decision


The first thing you need to know about insulation is what the R-value means. The R-value of any insulation product measures its resistance to heat flow. The higher the R-value it has, the greater the insulation’s effectiveness and power.

As mentioned above, there are several types of insulation available in the marketplace. When it comes to residential applications, cellulose and fibreglass blankets are both standard and common types of insulation. Depending on certain factors such as your budget, geographical location, and R-value desire, other factors to consider include:

  • Resistance to settling
  • Thermal performance
  • Fire safety
  • Permanence
  • Moisture resistance
  • environmental impact
  • Health effects/risks
  • Local building codes
  • Expense
  • Life span

The Roof

Before deciding on the best type of Roof Insulation consider the following:

  • Is it a flat or a pitched roof?
  • What’s the overall condition of the roof?

Before any sort of work begins on the roof, it first needs to be assessed for any leaks, issues with damp or structural problems, and see if it requires any roof repair. This will help identify any problems or obstacles early, so that they don’t take unnecessary time and expense to deal with later.

  • When’s the roof being replaced?
  • Whether to insulate a pitched roof at ceiling level or rafter level

If you’re dealing with a pitched roof, you’ll want to ask yourself this question quite early on. Do you want to use the loft space as a living area or not? if it’s destined for use as a bedroom, home office or other functional room, rafter level insulation is preferable, whereas if it’s just being used for storage – or not being used at all – insulating at ceiling level can help save on unnecessary cost.

  • How easily is the roof space accessible?
  • What kind of insulation will you use?

For both types of roofs, you’ve essentially got a choice between two options: warm or cold insulation.

Pitched roof.

Cold loft insulation – often just referred to by default as loft insulation, this is the cheapest and simplest of roof insulation. It involves the insulation being placed over and between the wooden joists, above the ceiling of the property’s top floor. This keeps the heat safely contained inside the living areas of the property, but don’t forget that it leaves the actual loft space uninsulated, which means it varies through the extremes of heat and cold throughout summer and winter.

Warm loft insulation – if cold loft insulation is unsuitable because the loft space is actively in use (rather than just used for storage or something similar), then you’re left with warm loft insulation. This involves installing the insulation directly under the roof, in the plane of the roof’s pitch.

Flat roof

There are a few options with a flat roof:

Warm deck or warm roof – this involves the insulation being installed above the roof deck (the panel beneath the roofing material, which is generally made of wood).

Cold deck or cold roof – here, the insulation is installed below the roof deck and its associated joints.

Can I insulate my loft myself?

It’s possible (in fact quite simple) to lay roof insulation yourself, as long as:

  • It’s easy to get into your roof space.
  • There are no damp or condensation problems.
  • Your loft joists are regularly spaced.
  • You’re not trying to insulate a flat roof.

For anything more complicated than this, you’ll need to be an experienced DIY-er or bring in a professional installer who knows how to insulate a loft in the most appropriate and effective way.

Flat roofs should always be insulated by a professional, and if the space is damp you’ll need to sort that out before starting any loft insulation work.

As far as insulation material goes you have 2 choices.


Insulation fibres are packaged in bags and blown in place to the desired depth and density using special machinery you can rent from a home centre. You can pour the fill in place and spread it manually, but the process is much more labour-intensive, and the results won’t be nearly as good.

It works best for:

  • Attics with irregular or nonstandard joist spacing.
  • Attics with lots of obstructions and penetrations to work around.
  • Attics where there is existing insulation to be topped since it fills gaps and joints well.
  • Low-clearance attics with limited headroom for manoeuvring during installation
  • DIYers who want to get the job done quickly and are comfortable working with power equipment.

Insulation material options:

  • Fibreglass
  • Cellulose
  • Mineral wool

Rolls or Blankets

This flexible insulation material is most often packaged in rolls that come in various thicknesses and standard widths, usually 40 cm and 60 cm, to fit between joists or studs in a house’s framing.

They work best for:

  • Attics with standard joist spacing, especially those with no insulation.
  • Attics with few obstructions or penetrations to work around.
  • Attics with sufficient headroom for manoeuvring during installation
  • DIYers who don’t mind cutting the material to fit around obstructions.

Insulation material options:

  • Fibreglass
  • Cellulose
  • Mineral wool
  • Cotton

Important Questions to Ask Your Insulation Contractor and Builders Warehouse salesperson.

  • Are you a licensed installer?

Depending on the product, the contractor may need a license. For example, loose-fill fibreglass cellulose or batt insulation requires no specialized licensing while spray foam requires an exclusive license.

  • How long have you been in business?

In general, it takes approximately 10,000 hours to master a trade – that is the equivalent of five years on the job. Eliminate any contractors with less than five years of experience because they haven’t learned the insulation trade.

  • What warranty or guarantee do you provide for your insulation?

Warranties for renovation projects are two-stage documents. One covers the labour performed in the installation process, and the other warranty comes from the product manufacturer.

  • Do you carry liability insurance and worker’s comp insurance?
  • What type of insulation products do you offer?
  • What type of insulation do you recommend, and why?

Any contractor worth his or her salt will be able to extoll the virtues of the different insulation products on the market. An accurate assessment of the pros and cons of each product should be an essential part of the presentation.

  • How long will the work take and how much will it cost?

The time to complete the job and costs are listed in the estimate that you should receive free of charge from the contractor.

  • Will you be making improvements?

Depending on the necessity, air sealing can be required to extract the maximum result from your new attic insulation. Most insulation contractors are capable of making the improvements your home will need – if not, ask who can.

Contact us for all your roof insulation needs.

Every home improvement project succeeds when the right party is hired for the work. Your insulation contractor choice is crucial to the project and getting the most out of home improvement rands.

At Eco-Insulation, we have a consultation ready when you call our office today at +27 (0)860 105 231   to discuss the particulars of your project. To get an estimate, please fill out our online form, and we will respond in 24 hours.

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Cape Town
Western Cape
South Africa

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