Frequently Asked Home Insulation Questions

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Homeowner FAQs

Home Insulation Questions and Answers

We've put together a list of our most asked questions about insulation in the home. From thermal insulation questions to questions about the insulation in your attic, if you can't find what you're looking for, get in contact today.

What are the benefits of loft insulation?

  1. In cold weather, loft insulation will keep your home warmer, for longer.
  2. It can contribute to saving on your heating bills and making your home more energy-efficient.
  3. During hot weather, it also helps to keep your home cooler.

How much loft insulation do I need?

The Energy Saving Trust recommends a minimum depth of 270mm of Glass Mineral Wool insulation. This is achieved by laying 100mm between the ceiling joists and 170mm cross-laid over the joists. New build homes are built using between 300-400mm insulation. You can use our table below to work out the estimated usage of our Space Insulation products you would need for your project.

You will need to measure the area of your loft to calculate how many rolls of loft insulation you will need to buy, as well as understanding how much loft insulation you already have.

To give an indication of how many rolls you may need, please see the table below:




Average Terraced House 40m2

Average Semi-Detached House 50m2

Average Detached House 60m2

Large Detached House 80m2



M2 per pack

No. of packs

No. of packs

No. of packs

No. of packs

Base Layer

Space Loft Roll 100mm






Top Layer

Space Loft Roll 170mm






Top Layer

Space Loft Roll 200mm






Top Layer

Space Blanket King Size 200mm






Top Layer

Space Blanket 200mm 






How do I find out how much loft insulation I already have?

Simply push a tape measure or ruler down the side of a piece of loft insulation until it hits the plasterboard ceiling to measure the depth.   

Can I use my loft for storage once it's insulated?

When insulating your loft, you will need to use a loft storage solution to use it for storage, whilst maintaining the performance of the insulation installed. This will ensure your loft insulation is not compressed, which would reduce its performance. You must also ensure you leave an air gap of 50mm between the underside of the loft boards and the top of the insulation to prevent condensation. If installed correctly, you will be able to continue to use your loft space for storage.

How long does it take to insulate my loft?

Allow about half a day once you have cleared the loft of its contents. 

What tools will I need to use?

You will need gloves, a face mask, and goggles to protect against dust whilst in the loft. You will also need a crawl board long enough to span three joists, to provide a safe working area. In addition, a retractable knife will be needed to carefully open the packs.

Will I need to cut rolls to size?

If you are laying insulation between the joists, you will need to separate the pack according to your joists widths. Whilst the insulation is still in the pack, cut through the roll at the desired width (indentation marks on the pack will provide a guide). For ease of carrying in to the loft, keep the insulation in the packaging until you are in the loft space.

If over-laying across existing insulation, rolls can be used full width. However, you may need to trim to length.

Do I need space between the loft insulation and the eaves?

Yes, retain a 50mm air gap between the loft insulation and the eaves. This will help prevent condensation.

Should I insulate underneath the water tank in my loft?

No, do not insulate directly below your water tank. The warm air from the room below will help prevent your water tank from freezing in cold weather. Do insulate around and above the tank to prevent warm air from escaping.

Can I insulate over the top of downlights?

It is recommended to use downlight covers to prevent downlights from overheating and causing a fire risk. Once covers are installed, insulation can be laid around the cover and over the top.

Can I insulate over the top of electric cables?

A cable feeding an electric shower SHOULD NOT be covered as this risks overheating. Instead the cable should be laid on top of the insulation.

If electric cables are low-voltage, they can be covered with insulation. This tends to be the case in newer homes where cables are often clipped to the joists. However, if in doubt, ALWAYS ensure cables rest on top of the insulation.

What do the numbers on some of your product names mean?

The numbers on our product names are related to the thermal conductivity of the product. So the lower the number, the better thermal performance that product will give. For example Loft Roll 40 will give a better thermal performance than Loft Roll 44.

What accreditation should I check my installer has?

We would recommend making sure that whoever installs your insulation has been accredited by PAS2030 as well as Trustmark. 

Still can't find what you're looking for?

Contact us today!

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