Can roof insulation cause damp?

It’s common this time of year, across Autumn and Winter when people begin to notice ‘damp patches’ in their homes, which are often mistaken for roof leaks. More often than not the damp isn’t caused by a leak at all, however caused by incorrectly fitted roof insulation.

How do I know if roof insulation is causing damp?

You can often tell if there is condensation and damp in a loft space if there are noticeable patches of damp, moisture inside of the windows, as well as black spots on the walls of the property. This damp, if not treated can spread to items being stored away in a loft space such as fabrics. In extreme cases, the damp and mold present can lead to significant health risks, as well as damage to the roof timber battens, which can begin to rot away.

How can roof insulation cause damp?

It’s important to remember that a roof needs plenty of ventilation. With a restricted airflow, like most things when the heating is switched back on, a roof can begin to sweat. This is because of condensation and excess moisture builds up when warm, humid air inside the property comes into contact with a cold surface, such as the exterior walls and windows of the property. This warm air is unable to hold the moisture it’s carrying and releases tiny droplets of water against the surface.

This restricted air flow is usually the result of too much insulation without a gap, which can cause the roof to sweat and create condensation resulting in damp and moisture in the home, often mistaken for a roof leak.

How to treat damp and condensation inside a loft space

If you believe a client may be damp and condensation inside a loft space, the issue should be treated as soon as it is noticed.

Rule out any other factors

To first treat the damp inside the roof space, you must ensure that you check for any else that could be causing damp inside that roof space, such as a broken or slipped roof tile, a crack in the leadwork or even a leak or blockage in the guttering or drainage of the roof.

Assess the ventilation in the roof space

You should always ensure any items such as storage boxes are kept away from ventilation points as well as ensuring all items are kept at least 5-10cm away from the walls of the loft.

Assess the current wall insulation to ensure it has not been damaged by things such as birds, insects or rodents as well as other factors. If damaged, ensure the insulation is replaced with a breathable loft insulation, with at least a 50mm gap to allow airflow, and a vapour barrier to protect against condensation.

When installing loft insulation, always ensure you leave a minimum of 250mm gap near the eaves. Keeping this area free and clear ensures that airflow can freely pass up the entire roof elevation and therefore help reduce sweating in the loft space.

Add ventilation

When you have assessed the roof and loft, and concluded that the damp is being caused by the insulation, you may wish to add ventilation to improve air flow, through the following options:

  • Roof Tile Vents – There are a wide range of roof tile vent to suit every roof tile or slate, specifically designed to blend into a roof, yet give a loft space sufficient ventilation without allowing any moisture to enter the loft space below, ensuring it is left  clean and dry.
  • Vented Fascia, Soffit, Ridge and Eaves Support Trays – Installing ventilation at the roofline is a very common application for new builds and roof renovations. Installing over facia vents, vented soffit boards or continuous rafter trays all help airflow pass up the bottom section of your roof elevation. At the top of the roof, refixing ridge tiles using a dry ridge kit will allow airflow to escape out the top of an elevation therefore creating a cool and well ventilated loft space.
How can we help?

If you have a client struggling with damp in their home due to insufficient roof ventilation, we can provide the materials to help!

Here at Bromsgrove Roofing Supplies ltd, we can provide a free no obligation quotation for all roofing materials you need, even a wide range of low pitch roof tiles to match any roofing project! Contact us today to see how we can help you.

Tel: 01527 864944


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