Installing any kind of loft and roof insulation is no small task, which means it requires a lot of planning to be sure of successfully getting the job done. As part of that planning process, there are a few key questions you need to ask yourself before you even think about starting work. You may well come up with your own as you assess the project in question, but here are the absolute essentials to think about!

1. Is it a flat or a pitched roof?

Thankfully, the answer to this first question is generally not very taxing to work out. One of the reasons it’s so important is because each of these types of roofs requires different types of insulation in order to achieve maximum efficiency. What’s more, they require generally different methods of insulation, too (which we’ll go into in more detail in just a second!). 

2. 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. Most importantly though, a thorough health check of the roof guarantees the safety of the people working on it. For this reason alone, it’s quite a good rule of thumb to follow before beginning any sort of work on a roof, insulation or otherwise!

r&j man insulation

3. When’s the roof being replaced?

As you might expect from such a vital part of the property, roofs have quite a long serviceable lifespan, generally estimated to be a few decades at least. However, if during the health check you find that the roof in question probably needs replacing anyway, it’s often best to delay the insulation job until the new one is installed. In the majority of cases, though, a roof that’s in good condition can be retroactively fitted with insulation, so it’s not something to be overly concerned about.

4. 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. As far as homeowners are concerned, essentially it’s the difference between whether they want to use the loft space as a living area or not. If it’s earmarked 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.

Rafter level

You probably don’t need us to tell you that the rafters are the sloping timbers which make up the roof. Most homeowners at the moment are opting for warm roof insulation at rafter level, where the insulation itself is installed between and over the rafters, keeping the roof timbers warm. This can either involve rigid insulation board, or foam insulation carefully sprayed between the rafters. This is the option that requires that bit more investment, but does guarantee that the roof space will be warmer, allowing it to be used as a functional living space.

Ceiling level

If the insulation is installed at ceiling level on the other hand, and there’s no concern about keeping the loft space warm, then mostly it comes down to a choice of which insulation to use. You can opt between rigid board (which is the sturdier but more expensive option) and mineral wool (which is cheaper but not as tough). If you’re boarding the floor so it can be used for storage, you’ll need something that can reliably take the weight, so rigid material is the best choice. If you’re only boarding a small area on the other hand, you’ll often find that mineral wool is more than enough to get the job done, and as a bonus it’s quicker and easier to install.

r&j ceiling insulation

5. What kind of insulation will you use?

For both types of roof, 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 insulations. 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. To maximise its effectiveness, you’ll also need warm ventilation immediately below the roof tiles.

Flat roof

There are a few options with 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). This is the option most heavily favoured across Britain, as it’s effective in damp and cold conditions - which let’s be honest, covers most of the UK!

Cold deck or cold roof - here, the insulation is installed below the roof deck and its associated joists. However, it does require a gap for proper ventilation, otherwise condensation can start to form and cause issues with damp and rot. As with warm roof insulation, the weather membrane (the protective element) will be the uppermost layer, guarding against rain.

Inverted roof - this involves placing a layer of insulation above the weather membrane, lengthening its operational lifespan by protecting it from the heat and cold. Here, instead of the weather membrane going on top, the uppermost layer is made of gravel or something similar.

Of course, each individual project is going to come with its own demands and specific requirements, but by asking these five questions you can be sure that you’ve at least got the basics covered. Plus, here at R&J Builders Hardware you can ensure you’re properly equipped for the job, too. As well as our extensive range of materials for roof insulation, our stock also includes breathable roofing membranes that often come in very handy! You can browse them right here on our website, or give us a call on 01254 52525 if you’d like to place an order, and we’ll be happy to see how we can help.