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How to Install Loft Insulation

Installing loft insulation

Installing loft insulation is one of the most cost-effective ways of reducing heat loss and your heating bills. However, for the insulation to be effective, it needs to be installed correctly.

There are many different ways to insulate a loft, each varying not only in cost and effectiveness, but also the degree of difficulty when it comes to installation. For this reason, the majority of loft insulation materials are best installed by professionals, though if you are on a limited budget and considering installing loft insulation yourself, blanket insulation is a more realistic DIY option.

Here we’ll guide you through some of your loft insulation options, including which are best left to insulation professionals, and how to install insulation in a loft space, if you opt to do it yourself.

Should I DIY Install My Insulation?

Opting to insulate a loft yourself is a decision that should not be taken lightly. Poorly installed insulation can not only be ineffective but can also cause other issues such as condensation and damp.

Since not every type of insulation is suitable for DIY installation, you should carefully consider whether to tackle the job yourself. The type of insulating material you are working with as well as your own DIY skills are factors that you will need to take into account.

If budget is the main factor for wanting to lay loft insulation yourself, then it can be a good option, after all some insulation is almost always better than none at all. It can be trickier if your loft space is much more difficult to access, has an irregular shape, or suffers problems with condensation.

With a range of insulation grants available for eligible households, you may not have to resort to installing the loft insulation yourself. Having the work carried out by qualified insulation installers will ensure a professional job and give you peace of mind that your home is properly insulated.

Which Loft Insulation Material Can You Install Yourself?

The most straightforward and cost-effective way to insulate a loft is with blanket insulation and it is this type of insulation that is most suitable for a DIY installation. Blanket insulation typically comes in rolls and batts and are usually made of fibreglass, mineral fibre, or sheep’s wool.

This type of insulation is usually used to insulate the joists, but for it to be effective you need to ensure to install the insulation flush to the joists to ensure that there are no gaps which will affect the effectiveness of the insulation. The difficulties would be even more pronounced if you chose to use rigid insulation boards to insulate your loft.

If your loft has inaccessible loft spaces then blanket insulation can be less effective and you might have to consider alternative insulating materials such as blown fibre insulation, spray foam, and loose-fill insulation, which really require installation by a professional using specialist equipment.

How to Insulate A Loft Space

Here’s a step by step approach on how to install blanket insulation in your loft…

1. Preparation

Having a good inspection of your loft space is key before buying your insulation. Inspect the whole loft area including the joists to ensure there are no issues with rot or cracking or general concerns about condensation.

If you notice any areas of concern, do not blindly crack on with installing the insulation, but instead call in some expert help to remedy the problem. If everything in the loft appears in good order, you can get on with the task of clearing out the loft in readiness for the installation.

You should remove all items from the loft and have a thorough clean up to remove any dust or debris. Cover up any areas, such as light fittings, that could be covered in dust during the installation, but ensure they still have sufficient airflow to prevent overheating. To be able to move safely around the loft, you’ll need loft boards or crawling boards which you can move along as you go. This will prevent you from putting your foot through the loft floor.

Take a look to see if you have any existing loft insulation and examine the condition of it. If it is still in good condition, you might consider topping up with a second layer to at least the recommended levels of 270mm. If the existing insulation is in a poor state, it should be removed.

2. Measure up the loft floor area

Once your loft space is clear, you’ll be able to measure out the area and determine how much insulation you need. Measure the width and the length with a tape measure and multiply the two values to give an indication of the size of the loft in metres squared. Taking into account the ceiling joists means that you can probably deduct around 10% from this value.

Check the coverage of each of the insulation rolls and then this will give you an indication of how much new insulation you will need and the number of rolls required to insulate the entire loft area.

3. Choose your insulation

Building Regulations state that levels of insulation for a loft in a new-build property should be at least 270mm thick, and this is a good guide to follow when insulating your home retrospectively. As well as different thicknesses, loft insulation rolls are available in different widths. You should choose a width that is closest to the space within the joist that you are looking to fill, as this will reduce the amount of cutting to size that is required.

You will have to choose between the different types of blanket insulation depending on your preferences. Mineral wool, rock wool, fibreglass, and sheep’s wool are all good blanket insulation options from a thermal insulation perspective, but do have slightly difficult properties, for example some being more resistant to moisture or water ingress. 

4. Cut the insulation roll to size

You may be fortunate that the loft insulation roll perfectly fits the space between your ceiling joists, but where it doesn’t, you’ll need to cut the loft roll to size. Most blanket insulation types need to be handled with care, so safety goggles, a face mask and gloves should be used as a minimum.

You should lay the insulation on a solid surface where it can easily be cut. Measure and mark out the insulation with a permanent marker so you can clearly see where it needs to be cut. Mineral wool insulation rolls can be cut with a serrated bread knife or electric knife, whereas other types such as sheep’s wool or fibreglass can be cut with a sharp utility knife.

5. Lay the loft floor insulation

After cutting your insulation to size you can start to lay it between your joists. If you are laying completely new insulation without an existing insulation presence, you should lay a base layer with a depth of at least 100mm and then add a second layer to take the thickness to the recommended 270mm. Try not to compress the rolls when installing them.

Do not leave gaps between the insulation as this makes it less effective. However, you should leave a gap between insulation and any areas of heat including chimneys, flues and recessed light fittings.

For safety reasons, you should avoid laying insulation over any electric cables, with cables being clipped to the roof joist out of the way or laid over the insulation once it is in place. When using a new roll, ensure the edge is placed tightly to the other roll to avoid gaps.

6. Don’t overlook additional insulation areas

Insulating your loft doesn’t just end with insulating between the joists. The loft hatch is one area that is often overlooked, but this can be sorted by stapling insulating material to the inside of the door hatch and adding draught-proof strips outside of the loft around the hatch edges.

Insulating your loft, will inevitably keep your house warmer, but will make the space above the insulation colder. This could put your pipes and water tank in the loft space more prone to freezing during very cold weather. For this reason, if you have a cold water tank, you should insulate the tank with an appropriate sized jacket as well as insulating the pipes before laying any insulation.

Avoiding Damp Issues

Loft spaces can often experience issues with condensation and damp. When warm air rises, it condenses in the cooler loft space. You can avoid problems with damp by installing a vapour barrier underneath the insulation.

It is important to ensure that airflow is not restricted when installing insulation. All key ventilation points such as air vents such be kept clear of insulating material or items that are being stored in the loft space. 

Warm Roof (Loft) Insulation

All the advice we have given so far related to cold roof insulation i.e. a loft space that essentially stays largely cold and is really only suitable as storage space. For lofts that you intend to use as a living space, such as a bedroom or office, you’ll need to create a warm roof space.

A warm loft is created by insulating the space between or beneath the roof timbers. Insulating beneath the roof rafter is generally easier, but does take up headspace in the room.

Insulating between the rafters: If you opt for this method, you’ll need to leave a gap of 40-60mm between the insulation and the roof’s membrane to avoid the risk of condensation.

Insulating beneath the rafters: This is usually the easier option because there is no need to leave a ventilation gap. You can insulate the roof beneath the rafters using either foil insulation or rigid insulation boards. 

Need Insulation Advice? 

If DIY installation is beyond your capabilities, or the type of insulation material you need for your loft requires professional installation, ECO Grants is here to help. We can help you find out if there are any free grants available for boosting your home’s insulation and arrange the installation. 

Typically, government grants are available for loft insulation for low income households and those with low Energy Performance Certificate (EPC) ratings. As the schemes, such as the Great British Insulation Scheme and ECO4, aim to help as many households as possible, loft insulation is the most cost-effective and therefore the most likely insulation method that will be recommended.

Our professional installers can typically insulate your loft within a day, especially if using easy-to-instal blanket insulation. Alternatively, you could opt to insulate your loft space with polyurethane foam insulation which is highly effective at minimising heat loss and draughts and boosting energy efficiency to reduce energy bills.

As around 25% of heat is lost through the loft and roof space in an uninsulated home, having it insulated can bring noticeable difference to bills. The Energy Saving Trust suggests that adding 270mm of  loft insulation to a previously uninsulated detached property could bring energy bill savings of £445 per year. With those savings experienced over the lifetime of your insulation, this will add up to a significant difference to a household’s energy bills.  

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