How much Insulation do I need in my loft?

Posted: 2nd March 2023 | Author: Adam Brown | Category: Insulation

How much Insulation do I need in my loft?

The recent cost of living crisis has sent energy bills soaring. So to keep bills in check, many of us are trying to find ways to reduce our energy consumption.

One of the most effective things you can do is improve the insulation in your home, especially in the loft. This is where the majority of heat is lost in most homes, so it really is worth doing. It’s also a good idea to do it now, before the next winter arrives and temperatures fall.

But how much loft insulation do you need? Read on, as we’ve put together a helpful guide covering everything you need to know about loft insulation.

What is loft insulation?

Loft insulation is a barrier of material, usually placed between the joists of your roof. Its main purpose is to trap heat, preventing it from escaping. This helps to make your home warm and also prevents it becoming overheated in summer - as it traps heat both ways.

There are a few different kinds of loft insulation out there. These include the following:

• Mineral wool - This is made from either glass wool (melted wool) or rock wool (melted stone), which is spun into a yarn. It usually comes in the form of loft insulation rolls, which are rolled out into the spaces between loft joists. It’s affordable, good at conducting heat and recyclable, although it can irritate the skin during installation.
• Sheep’s wool insulation - This insulation material appears similar to mineral wool, but it’s 100% natural. It’s better for storing heat, and easier to install. However, it does tend to be more expensive.
• Spray foam - An insulation material that should only be installed by a professional, spray foam is a chemical product (although some are eco-friendly). It’s made through a chemical reaction, which expands to fill gaps and create a dry, hard, airtight seal. It offers good heat insulation and is quick to install, but can be more expensive due to professional installation costs.
• PIR insulation board - Lastly, there are PIR insulation boards, also known as sheet loft insulation. These are thick boards made from polyisocyanurate foam, which offers excellent thermal performance. The beauty of this product is that it’s easy to fit, as it can be cut to size and slotted in where needed.

How does loft insulation work?

Before installing your insulation, it’s useful to know a little more about how it works. The first thing to know is that the heat in your home rises. So, when you put your heating on, or the sun shines through the window and warms up the room, that heat will inevitably end up near the top of your home. Without insulation, this heat can escape through the roof.

Insulation acts as a barrier to keep this heat inside. It traps heat in the rooms below, keeping your home warmer for longer. This means you don’t need to use as much heat, which means lower energy bills.

So, how does insulation work in summer? The process is similar, with the insulation acting as a barrier between your home and the open air outside. You’ll find that your loft gets very hot in the summer, as the sun shines on the roof. This heat can transfer to the rooms below (even without the effect of heat rising) and make them uncomfortably warm.

Your loft insulation keeps that heat contained in the roof space, so that rooms below stay cooler for longer.

How much loft insulation should I have?

Now we come to the important part - how much loft insulation should you be using? To work out how much you’ll need, the first step is to measure your loft space. Measure the area of the loft, the space between joists and the height of the joists too. If you already have some insulation installed, take a note of the thickness.

Building regulations require a depth of 270mm (for mineral or glass wool), but we recommend 400mm. You can use this as your starting point. If you want a greater level of insulation and you have the budget to match, you can add a thicker layer as desired.

Then, you’ll need to check how much insulation is in a roll, or the size of the board if you’re using PIR insulation boards. This will help you work out how many rolls or boards you’ll need to buy.

You can also use our handy loft insulation calculator to estimate the amount of insulation you’ll need.

Can loft insulation be too thick?

Is there such a thing as too much insulation? Generally speaking, the more insulation you install, the more efficient it’ll be.

However, there are a couple of critical things to remember. The first is to ensure you have adequate ventilation in your loft, or you could end up with damp problems. If installing it yourself, you should avoid squashing insulation down too much, or pushing it right into the eaves. You’ll need to leave an air gap around the edge of the loft to allow air to circulate. It’s all about getting the balance right.

You should also bear in mind that very thick insulation could start to impinge on the amount of storage space available in the loft.

The Author: Adam Brown

With a background as a Mechanical Engineer, I started Nationwide Supplies alongside my brother with a vision to modernise what seemed a stuck-in-its-ways industry in the builders merchant sector.  Since 2011 it has been my goal to source quality products at the correct prices to be able to offer a saving to customers along with high quality customer service which offers quick delivery and superior technical knowledge in the industry.  

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