Overcoming Damp and Mould Issues in Homes

Damp and mould issues in houses are generally caused by an excess of moisture.

Some common causes are:

1. Poor Ventilation: Lack of airflow can trap humidity inside, especially in kitchens and bathrooms.

2. Condensation: Warm, moist air meeting cold surfaces can lead to condensation, often on windows and walls.

3. Water Leaks: Leaks from roofs, plumbing, or appliances can introduce moisture into the home.

4. Rising Damp: Ground moisture can rise through walls and floors, especially in older buildings.

5. High Humidity Levels: Areas with high humidity or poor insulation can exacerbate damp issues.

Prevention:

1. Improve Ventilation: Use exhaust fans in kitchens and bathrooms, open windows, and consider air bricks or vents.

2. Control Humidity: Use dehumidifiers and keep humidity levels below 60%. Regularly monitor humidity with a hygrometer.

3. Fix Leaks Promptly: Regularly inspect and repair any leaks in roofs, pipes, and appliances.

4. Insulate Properly: Insulate walls and roofs to reduce condensation. Double-glazing windows can also help.

5. Use Damp-Proofing Treatments: In areas prone to rising damp, consider applying damp-proof paint or membranes.

Building Regulations Part F provides guidance for the amount of ventilation required in homes based on different types of ventilation systems:

1. Background Ventilation and Intermittent Extract Fans 

Extract fans are located in bathrooms, toilets, kitchen and utility rooms.

Minimum extract ventilation rates for intermittent extract systems are:

· Kitchen: 30 l/s adjacent to the hob or 60 l/s elsewhere

· Utility room: 30l/s

· Bathroom (including shower room or ensuite): 15l/s

· Sanitary accommodation: 6 l/s

2. Minimum extract ventilation rates for continuous extract systems are:

· Kitchen: 13l/s

· Utility room: 8l/s

· Bathroom (including shower room or ensuite): 8l/s

· Sanitary accommodation: 6l/s

3. Mechanical Extract Ventilation with Heat Recovery

MVHR provides fresh, filtered air, energy efficiency and a comfortable climate all-year round.  They recover heat which would other wise be exhausted reducing heating demand.

MVHR systems should always provide the minimum whole building ventilation rate as well as the minimum extract rates required in the wet rooms. The Extract and supply rates must be balanced. 

The Domestic Ventilation Compliance Guide describes the whole house ventilation rate for homes as follows: 1 bed homes: 13 l/s, 2 bed homes: 17 l/s, 3 bed homes: 21 l/s, 4 bed homes: 25l/s, 5 bed homes: 29l/s but a minimum ventilation rate of 0.3l/s per m2 of floor area (including all floors) must also be maintained. 

These figures assume that only one bedroom has double occupancy, and if there is a higher occupancy then you need to add 4l/s per occupant. There are also minimum extract rates of 13l/s in the kitchen, 8l/s in bathrooms, shower rooms and utility rooms, and 6l/s in a WC.