Flat Roof Insulation Guide

Flat Roof Insulation Guide
Posted in: Guides, Insulation

Flat Roof Insulation Guide

There are plenty of benefits to insulating your roof, whether it’s a pitched or flat roof. This guide will be taking you through the latter, explaining what flat roof insulation is, why it is important, and how you would go about installing it into your home.


What is Flat Roof Insulation?

To begin with, it’s important to note that a roof is considered to be ‘flat’ if it has a pitch below 10 degrees, and it’s crucial to know whether your roof is flat or pitched as they are insulated differently.


The main reason for flat roof insulation is to help retain heat in the winter months so that each room feels warmer, and to help keep the home cool in the summer months.


There are several options regarding materials to use, with foam becoming increasingly popular, particularly in modern homes.


When looking to install flat roof insulation, there are two main approaches: warm flat roofing and cold flat roofing.


Warm Roof and Cold Roof Insulation: What’s The Difference?

As time goes on, warm flat roof insulation is often recommended ahead of cold flat roof insulation, as the latter is slightly outdated and can lead to issues with damp and condensation, particularly in colder areas such as Scotland.


What is Warm Roof Insulation?

Warm roof insulation is when the insulating layer sits above the timber rafts in the roof. The main result of this is to ensure that the roof and loft area are around the same temperature as the rest of the house.


It is extremely efficient from a thermal standpoint, and it’s cost-effective too. It must be said that it’s not a simple task to install for anyone that isn’t a professional, and they’ll likely need to have scaffolding ready too.


Why Choose Warm Roof Insulation?

The main benefits to warm flat roof insulation include:


-        Energy usage is reduced, and thus you’ll be paying much less on your energy bills in the long run.

-        Your home will also be much more energy efficient, improving your property’s Energy Performance Certificate.

-        It helps reduce condensation as moisture is allowed to escape, which cold roof insulation doesn’t do.

-        Heat can be conserved without the need for roof void ventilation.


Which Materials Should I Use For Warm Roof Insulation?

There are a range of options you can choose with warm flat roof insulation, but the best is probably a type of PIR insulation board, such as Celotex GA4000. The main plus points of these insulation boards are that they are extremely durable, so can last a long time, and they are hugely effective at retaining heat in the winter and allowing the home to stay cool in the summer. 


What is Cold Roof Insulation?

Cold roof insulation differs as it is placed between or underneath the timber rafters in the roof. The purpose is to keep the roof cold, as the name suggests, though this method is slightly outdated when compared to warm roof insulation.


The main drawback is the fact that condensation issues can arise due to the cold temperatures, which in turn can develop into more serious issues like mould and damp.


Why Choose Cold Roof Insulation?

Though there are drawbacks, there can be benefits to going with cold flat roof insulation too, such as:


-        It generally has a much lower installation cost when compared to the warm alternative.

-        Is a better option for outbuildings that don’t require the longer list of benefits that warm roof insulation provides.


Which Materials Should I Use For Cold Roof Insulation?

As the material is placed between the rafters, loft insulation roll is the best option for cold roof insulation, such as Kanuf Earthwool Loft Roll.


The main plus is that loft roll is lightweight and easy to move around, making it easier to install than other options. 

How To Install Flat Roof Insulation

As mentioned earlier, it is best to bring in the help of a professional or a specialist for this job, as insulating a flat roof requires the use of specialist equipment.


The professional will likely take the following steps:


1.     Lay down a board of plywood across the timber joints, which acts as a base.

2.     Add a vapour control layer to help reduce the risk of condensation and moisture.

3.     Add marks onto this vapour control layer to show where fixings will go, and place butyl tape over the marks to help form a seal.

4.     Lay down the insulation board as required.

5.     Add an extra layer of plywood.

6.     Fix the deck together with helical fixings that pierce through each layer.

7.     Install a waterproof membrane to help protect from the elements.


How Long Does Flat Roof Insulation Last?

The good thing about insulation products is that they are built to last, and shouldn’t need to be replaced for decades. Typically, flat roof insulation is expected to last between 25 and 40 years before it will need to be replaced.


Cold roof insulation tends to last a bit longer than warm roof, as the latter is exposed to wear and tear from the elements.


You can also view our guide to roof and loft insulation for more information and advice on the overall process.

4 months ago
156 view(s)