The 5 Negatives About Fibre Insulation

The 5 Negatives About Fibre Insulation

There’s no doubt that fibreglass is an incredibly cheap way to add a decent thermal blanket to the loft floor. It can be purchased from almost any local DIY store or builders merchants and can be quick to lay down. It’s these qualities that have made it one of the first choices for government back insulation schemes or schemes under the energy company obligation. 

When we say fibreglass we actually mean any fibre based material that is spun into a blanket layer of microfibres. We visit and survey thousands of homes with loft spaces crammed full of fibre-based insulation. On one hand, it’s good to see homeowners treat insulating seriously but on the other hand, the issues with this form of insulation, particularly on the loft floor, are often glaringly obvious.

Rolls of fibreglass insulation partially installed in a loft space.

We’ve spent the last 3 years researching, listening to our customers and taking on board our own observations, in the process, compiling a range of problems that we’ve discovered with fibre-based insulation. These include:

1.Will require replacing or topping up

When fibre-based insulation is installed, you will usually notice a thick layer covering the floor of your loft. This is exactly how its meant to be and it will be providing a good thermal barrier against heat loss.

Fast forward three or four years and you will soon begin to notice that the once thick and fluffy layer has gradually shrunk and may have torn in areas to expose cold spots where heat loss can occur.

Fundamentally, you should look to top up or replace fibre insulation periodically to maintain its performance

2.Holds dust and dirt, creating potential health hazards

The home can be a dusty environment, hence the reason we hoover the floor and polish surfaces. What we never do is go into the loft and hoover, dust or polish because it’s a case of out of sight, out of mind.

The issue with this is that fibre-based insulation, composed with thousands of fibrous strands, attracts and filters dust deep into its layers. You may have visited your loft space to grab the Christmas decorations, leaving with a dry and tingly cough. This will be the dust particles.

There’s no way to avoid dust entering your fibre insulation. You can’t even run a hoover over it because it will break down the insulation and effect its integrity.

Open Cell Spray Foam insulation installed in a loft space creating that extra loft space.

3.Takes away valuable storage space 

For those of us who are older than 35 years old, when we think back to our younger years, self storage facilities were few and far between! Why the boom in the self storage market? It correlates directly back to the surge in the installation of fibre-based loft insulation.

It is still possible to store items in your loft when you have fibre insulation but that’s on the basis you are prepared to compromise it’s performance by making space for a storage area. If that’s the case then there’s little point having it in the first place!
The fact is, once you’ve insulated on the loft floor, you should try to avoid storing items which might flatten or break the thermal layer.

4.The perfect hibernation bed for pests and rodents!

There’s nothing better than climbing under the duvet on a chilly winters night. Imagine you’re a mouse, rat, bat or insect? You don’t have the luxury of a woolly blanket or fluffy duvet. With fibre insulation, you do! There are many small areas where pests and rodents can enter the loft space.

Whether through the eaves, a broken tile or vents in the loft space, when there’s a warm bed available, a pest or rodent will make it their mission to make the loft a home. The health hazards come through urination and excrement that these fluffy creatures leave embedded in your insulation.

If your loft space is susceptible to the influx of pests or rodents, the first step is to remove all fibre insulation to take away the warm habitat. To insulate effectively, it’s time to create a warm roof system using ThermoFoam!

5.Promotes two climates within the home

The idea of fibre-based insulation on the loft floor is to keep the heat from the home to the zones where its most needed. Despite not being an airtight product, it will, at the very least, slow heat loss whilst in good condition with the correct thickness.

The trouble comes when cold air enters the loft space in the winter or hot air enters the roof through solar gain during summer months. We’ve all experienced the rush of cold air when we climb up into the loft to get our Christmas decorations, equally, we barely last two minutes in the loft during the summer before we are sweaty and dehydrated!

That’s a result of the two climates insulating at loft floor level promotes. With ThermoFoam between the roof rafters, you can enjoy one single ambient climate, year round!


It’s always hard to criticise other products but we have great belief in better solutions that create peace of mind for the long term. It’s about investing in your comfort and not choosing the cheap option for the sake of doing your bit to insulate your home. With a better product comes a better thermal performance, therefore, it’s always worth weighing up the pro’s and con’s before investing in any type of insulation.

With the above said, we respect that people will have a certain budget they can afford to spend, therefore, installing any form of insulation will at the very least help to control your energy costs.

Actionable Next Steps

  • Replace your insulation at least every 3 years.
  • Board out your loft space to reclaim much needed space.
  • Install ThermoFoam for a warm and healthy home.

Are you interested in getting spray foam insulation in your home? Contact us to today to find out more!