Case study: A mid-terrace house in Mirfield with severe mould problems

The problem

This property suffered from very severe condensation and mould in the upstairs rooms. The bedrooms and hallway were severely affected by black mould which represented a health hazard to the occupants.

Our assessment

This was quite an old property, and in common with a great many modern buildings the windows had been replaced for draught proof units, but without trickle vents. The house was quite unusual in that there was only one external door. The majority of houses obviously have doors to the front and rear - and this aids those movement of air. In this case humidity created in the kitchen was rising through the house and condensing on the colder surfaces upstairs

Our solution

The kitchen window was fitted with a trickle vent, which was closed ! so we opened it and suggested to the tenant it should be permanently left open.

We swapped the existing poor quality extract fan in the bathroom for a humidity controlled unit with always-on trickle function.

We installed a whole house ventilation system. This brings in fresh, dry, air from the loft and feeds it into the house in a controlled way.

We also replaced the external grille for the bathroom fan, and cleaned off the mould where possible. However when mould is as severe as this obviously redecoration is required. But the lower levels of humidity will stop the mould from growing back and rapidly reduce the number of mould spores being released into the air.


See our page on solutions for condensation problems for further information.

cavity wall insulation
Severe mould in the master bedroom ...
restricting ventilation encourages mould
... around the window on the landing
mould across a ceiling
... and along the ceiling in the landing
original extract fan
Original extract fan in the bathroom
installing whole house ventilation
The view from within the loft. A hole is created in the ceiling of the landing ready to connected to the whole house ventilation unit.
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Covid 19 ventilation guidance

UK government advises:

"Good ventilation can help reduce the risk of spreading coronavirus"
"Where possible consider ways to maintain and increase the supply of fresh air"

Too much humidity and not enough ventilation
= damp, condensation & mould

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