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Can Loft Insulation Cause Damp? The Definitive Answer

can loft insulation cause damp

If you have been thinking about insulating your loft, or adding to the insulation that is already there, you may be worried that you will cause damp, rather than cure it.

There are lots of stories in the press recently regarding damp associated with wall cavity insulation, so it is easy to understand why you might fear that loft insulation could cause the same issue.

But can insulation in the loft really cause damp, and, if so, what is the best way to avoid it? We have the answers, and we’re here to share them in the following article…

What Causes Condensation In Lofts?

In recent years, the government has been promoting schemes to encourage people to insulate their lofts. In almost all cases, these schemes have offered a thick layer of mineral wool insulation that is placed between the floor joists on the floor of the loft space.

This may be what is behind any damp issues in lofts that you might experience.

By insulating the floor of the loft, you are insulating the rooms below, but not the loft itself. This means that the heat from the house is not penetrating the loft space through the ceiling, and being lost through the roof (a good thing), but the loft room is perpetually col,d and at risk of becoming damp (a bad thing).

This is especially the case if there are gaps in the insulation that allow some warm moisture laden air from below to make its way into the loft area. This warm air rapidly cools in the cold loft, and hey presto – condensation!

Equally, warm air from outside during the Summer can enter the loft, but not make its way into the house, leading to overheated loft spaces, and fluctuations in temperature from day to night, that can literally leave the loft walls and roof dripping with condensation.

can loft insulation cause damp

Making sure that the insulation you have added to the floor of your loft is covering it fully and offering a good barrier will help to minimise the issue of warm air coming through from lower floors, but unfortunately, the nature of batts is that there are often gaps – especially around electrical outlets, such as downlights

What Else Exacerbates The Issue Of Damp In The Loft?

The makeup of your roof can also contribute to this problem. Older style homes (the ones that are targeted for additional insulation), often have bitumen felting as part of the roof structure, and this material does not breathe like other more modern materials.

This means that the warm air that enters the loft from downstairs cannot make its way out through the roof, and it hangs around, getting cold and condensing.

Making sure that the insulation you have added to the floor of your loft is covering it fully and offering a good barrier will help to minimise the issue of warm air coming through from lower floors, but unfortunately, the nature of batts is that there are often gaps – especially around electrical outlets, such as downlights.

This can cause all kinds of problems inside your loft, including:

● Mould growth that can be an irritant to people suffering from asthma
● Rotting timber and structural issues caused by bowing wood and loss of structural integrity.
● Dripping water that can cause the insulation to become wet and ineffective
● Destruction of property stored in the loft, due to damp, mould and generally becoming wet.

If your choice is to have floor insulation, there are a number of other measures you can take to prevent damp in your loft...

can loft insulation cause damp

As your home become warmer, the humidity levels will rise, and the chances of damp in the loft will increase. Opening windows, installing vents and extractors downstairs will help this issue, but leave the home feeling cooler. It seems like a lose lose situation

Damp In Loft Solution No.1: Adequate Airflow

One way to ensure that condensation is not an issue in your loft is to make sure there is adequate airflow. If your attic or loft is not used for anything more than storage, you can afford to have a few gaps where air can circulate.

This means openings under the eaves, and other purpose built gaps in the fabric of the building that are designed to prevent a build-up of moisture.

You could also consider adding Velux type windows to your roof to allow you to release any build up of warm air.

The problem with adding airflow either to your loft or to the rooms below is that you are losing the entire purpose of insulating your home in the first place – that is, making your home warmer.

As your home become warmer, the humidity levels will rise, and the chances of damp in the loft will increase. Opening windows, installing vents and extractors downstairs will help this issue, but leave the home feeling cooler. It seems like a lose lose situation.

Damp In Loft Solution No.2: Use An Extractor Fan

You can also choose to add an extractor fan to your loft room. This is very similar to the type you would use in your bathroom – although with the loft often being a larger space, you may need 2 or more extractors to properly do the job.

These fans would also need to be running regularly to be worthwhile, but they can provide a short-term solution to the problem.

can loft insulation cause damp

Spray foam is also never affected by becoming wet. Where other insulation types will become ineffective if they become damp, spray foam will carry on doing the job, just as intended

Damp And Moisture Dilemmas: The Spray Foam Solution

If damp in your loft is caused by the room itself not being adequately insulated, the answer may be to use a product that allows easy insulation of the roof and even the walls of the loft as opposed to the floor.

Spray foam insulation is the perfect choice for this type of job, and is especially useful if you wish to use your loft room as a playroom, study or bedroom. In particular, if the loft is to have a bathroom, ensuring damp is dealt with is essential.

Spray foam insulation is a mix of chemicals that when forced together under pressure, expand up to several times their original size to fill all gaps. Once hardened, this foam is very stable and long lasting, and can provide a total barrier to warm air leaving the house.

Spray foam insulation is usually applied between the rafters of the underside of the roof, and will seal it tight from the outside, making it both a usable room, but also one that is warm and comfortable. The act of insulating the roof will also ensure the rest of the house is well insulated as well.

Damp issues are almost always eliminated by using spray foam insulation. This is because it cures the issues highlighted above. Warm air from outside cannot penetrate the roof and enter the loft, therefore reducing temperature differences between the house and the loft space.

Equally, warm air from downstairs can make its way into the the loft, dissipating the warmth in the home, but not causing damp, as the difference in temperature between the loft and the rest of the house is negligible.

Spray foam is also never affected by becoming wet. Where other insulation types will become ineffective if they become damp, spray foam will carry on doing the job, just as intended.

Open Cell vs Closed Cell Spray Foam: Which Is Best?

In homes where condensation has been a problem, it is usually recommended that open cell foam is used, rather than a closed cell equivalent. Open cell spray foam contains air bubbles that trap the air as it leaves the home, but it does still allow the air to leave at a slow rate.

Closed cell , meanwhile, forms a complete barrier and will trap air inside the loft, leading to impaired ventilation. By choosing the former, you still have some airflow, and the heat levels in the room will not build up.

While insulating your loft is always a great idea, you need to consider the construction of your loft space (does it have open eaves or other methods of establishing airflow) and is it going to be a usable room.

If you think that damp might be an issue, and you want to make sure you avoid it, spray foam insulation really is the only option that will give you a warm home, and one that is free from damp and its associated issues. Simply call our team of team of spray foam experts on 0800 1700 636, or click the button below, to get the ball rolling today!