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Green Homes Grant: what to know about loft insulation

September 22, 2020

As part of the Government’s Green Homes Grant, you may be able to install or top up your home’s loft insulation. Here’s why it’s important and what you need to know.

cold loft insulation laid on floor - green homes grant -

Image: Cold loft insulation is laid on the loft floor to stop heat loss from the home. Photo: Adobe Stock

You may think of your loft as just somewhere to keep the Christmas decorations 11 months out of the year or you may have had a loft conversion to turn it into a functional room. Whatever your situation, it’s important for your home’s energy efficiency to have a well-insulated loft. Here’s what you need to know about loft insulation.

Read more: The Green Homes Grant 

Does my home have enough loft insulation?

If you poke your head up into your loft, you may see insulation and think you’re all set. While there are very few homes with no loft insulation at all, according to statistics from 2012, there are around 11 million UK homes that are under insulated. The recommended depths for loft insulation are 27cm for glass wool, 25cm for rock wool and 22cm for cellulose. Where you are looking to use your loft for storage, you’ll still need to lay insulation under the boards, leaving adequate ventilation and ensuring your insulation isn’t being compressed.

If you do rectify an under insulated loft, this could results in savings of as much as 20% on your heating bills – representing a saving of £225 per year for the average detached home according to The National Insulation Association.

The requirements for both a warm loft and a loft conversion – otherwise known as room-in-a-roof insulation – is different, as you are seeking to not only keep heat from escaping from your home, but also creating a warm loft that’s inhabitable. This will mean treating rafters and party walls, but this is still covered by the Green Homes Grant.

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Choosing a material 

According to stone wool insulation specialist Rockwool, up to 25% of all heat can be lost through a roof.

Any form of insulation should have excellent thermal properties to help reduce heat loss; however, your choice of material will have an effect on the overall result. Mineral wool, such as Rockwool, for example, may be slightly more expensive, but it has a better R-Value than fibreglass, is thermoregulatory (meaning you home will stay cool in summer and warm in winter) and doesn’t come with the added health concerns when installing that fibreglass does.


When properly insulating a loft, you’ll make the space cooler as it stops leeching heat from your home. However, this may create condensation and damp problems, so you will also need to put adequate ventilation in place.

rockwool stone wool loft insulation - green homes grant -

Image: Stone wool insulation from Rockwall. Photo: Adobe Stock

Insulation stops heat escaping from living spaces so will make the loft space cooler. This has the potential to create condensation and damp problems, so when installing loft insulation always make sure there is adequate ventilation. Choosing insulation that has moisture resistant properties will also help in reducing the risk of mould, for example.


While you may not imagine that loft insulation will help to soundproof your home, the right insulation can make a good difference to reducing the sound of street noise, airplanes and even wind and rain, despite the fact that thermal insulation is largely different to acoustic insulation.

Read more: Green Homes Grant scheme extended until 2021

For installing a ground source heat pump where pipes are laid in narrow trenches, you’ll require a large amount of land. A typical 8kW output heat pump would require 200 metres of trench, across several loops, meaning an overall area of 400 square metres required. There are also options to lay pipes vertically, much deeper into the ground, however this requires specialist equipment to drill boreholes which can be an expensive process.

roof insulation installation - green homes grant -

Image: Room in a roof insulation. Photo: Adobe Stock

Fire safety

While fibreglass and mineral wool are naturally flame retardant, the likes of cellulose insulation has to be heavily treated with flame retardants. This can lead to the eventual breakdown of these materials, compromising its fireproof nature.

Non-combustible insulation can help to slow down the spread of fire and don’t give off any significant toxic smoke.

Green Homes Grant

Loft insulation is available as a primary measure under the Green Homes Grant. This means that if your home requires it, the Government will issue a voucher to the value of three-quarters of the cost of work to be completed. You can apply and get quotes from approved registered installers from the Simple Energy Advice website.


Are you considering applying for the Green Homes Grant? Let us know! Tweet us @goodhomesmag or post a comment on our Facebook page

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