Does Underfloor Insulation Cause Dampness?

Installing insulation in your home, including under the floors, can help make your home more energy efficient and lead to savings on your energy bills. However, many people fear that underfloor insulation will lead to issues with moisture build up, dampness and mould.

Is underfloor insulation to blame for dampness? Read on to find out if underfloor insulation is the culprit and how to prevent moisture issues in your home.

Does Insulation Cause Dampness?

Not exactly. The real cause of dampness is usually because there is not enough ventilation or air flow in a space. When insulation is installed in an area that doesn’t have adequate ventilation, it may make moisture problems worse.

Installing insulation can help prevent air draughts from coming through the floors into the home. While this will help you keep your home at a comfortable temperature, the lack of air flow can lead to moisture problems if there isn’t adequate ventilation.

If you have moisture issues in the wall cavities, under floor area or ceiling area, the issue of ventilation should be addressed first. Once you deal with the causes of dampness, you can enjoy the benefits of underfloor insulation without any of the nasty problems.

What Are The Causes Of Condensation?

There are many causes of moisture in a home including:

Rising Damp

Rising damp is moisture in the ground that rises into porous materials of the home. Porous materials are any materials that have tiny spaces inside their structure which water or air can pass through.

During the building phase, waterproof materials should be used as a barrier between the ground and the home to stop rising damp.

Penetrating Damp

Penetrating damp refers to sources of water, such as rain, that get into the home through gaps. For example, broken roof tiles, missing bricks and damaged gutter systems can all allow moisture into the home.

Penetrating damp can usually be dealt with by fixing the broken areas and improving drainage systems around the home.

Poor Drainage

Moisture may become an issue if the home itself or surrounding landscape has poor drainage. For example, a garden bed with poor drainage that slopes towards the house. 

Landscaping or redesigning the affected areas may help reduce moisture issues.

Moisture From Human Activity

Some of the activities we do at home can cause moisture build up. For example, showering, cooking or drying clothes inside. This moisture occurs when the hot, humid air from our activities comes in contact with a cool surface.

Issues from this type of moisture can be combated by turning on exhaust fans or opening windows when doing the activity.

Thermal Bridges

Thermal bridges are areas in your home that allow heat to travel through them, bypassing your insulation. Thermal bridges may cause cold spots to form and allow for moisture to build up. 

Thermal bridges may also be formed if insulation is installed in some areas, while other areas are not insulated. This increases the risk of damp and mould build up.

How To Improve Subfloor Ventilation?

Without proper ventilation, any moisture in the subfloor space will have nowhere to go. That’s why it’s crucial that there is enough air flow throughout the space to help control moisture issues.

Ways to improve subfloor ventilation include:

  • Passive Ventilation involves simple air vents being placed along the outer edge of the underfloor space. Air will naturally flow in and out of the space, as long as the vents are not obstructed or blocked.
  • Exhaust Fans may be used if there is need for greater ventilation in the area.
  • Redesigning The Underfloor Area may help improve ventilation. Many older homes have had their vents sealed up or were poorly designed in the first place. Issues should be fixed to help manage moisture levels.

Is It Worth Installing Underfloor Insulation?

According to the Your Home government website, floors are responsible for 10% to 20% of a home’s heat loss and gain. Although floors are often overlooked, they actually make a significant difference to your home’s energy efficiency.

Reasons to invest in underfloor insulation include:

  • More comfort year round. Underfloor insulation will help your home regulate temperatures better, meaning less heat loss in winter and less heat gain in summer.
  • More efficient heating and cooling. Air conditioners and heaters don’t have to work as hard to keep you comfortable if your home has insulation.
  • Energy savings. Underfloor insulation helps you rely less on artificial heating and cooling, meaning less electricity used and lower power bills.
  • Short payback period. The energy savings from underfloor insulation will usually pay off the investment in 3 to 5 years.

What’s The Best Underfloor Insulation To Use?

The most common types of underfloor insulation are bulk insulation (for example, Knauf Earthwool insulation batts) and rigid foam board. 

Bulk insulation is appropriate for raised homes with crawl space under the floor. Batts should fit snugly between timber joists and secured in place to prevent them from sagging over time.

If you cannot access the floor space from underneath, you may be able to install rigid foam board insulation under the flooring surface by removing the flooring first and laying the rigid board down.

Should I Get Underfloor Insulation?

If you are considering installing underfloor insulation but are worried about moisture issues, you should have your home professionally assessed. A professional will help you identify and remedy any ventilation or design issues that may cause moisture problems. 

They will also be able to advise you of the best materials and techniques to use for underfloor insulation so that you can experience the benefits and avoid moisture issues.

Malika Lugar

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