Case study: A detached bungalow with mould and damp walls

The problem

This bungalow had been recently vacated and the landlord was making the property reading for the new tenants. There was evidence of quite severe mould in the bedrooms as a result of dam walls, and on entering the property the air smelled stale and musty.

Our assessment

Evidently this was a long standing problem in the property and in an attempt to improve matters a bathroom extract fan had been fitted.

Unfortunately there was no easy way to vent the fan to the outside so it had been simply allowed to vent into the loft. Presumably in the belief that the humid air would make its way to the outside.

We quite often see this type of short-cut and in reality the only way to correctly deal with the stale humid air from the bathroom is to vent it to the outside - using insulted ducting to prevent the humid air from condensing in the duct causing drops of water to fall back into the fan.

The windows were all modern draught proof units without vents.

The loft insulation was poor and there was no cavity wall insulation. Colder walls are therefore more likely to attract condensation and form mould.

Our solution

Our assessment was that this property was suffering from a severe lack of ventilation and was poorly insulated.

Unfortunately because of the walls were constructed of random stone it was not possible to insulate the wall cavity. The loft insulation was thin by current standards and we felt that the bungalow would benefit from additional layer of insulation.

To resolve these problems we:

  1. Replaced the bathroom fan for a much better quality unit that varies its speed depending on humidity and has an always-on trickle function.
  2. Vented the fan to the outside correctly with insulated ducting.
  3. Installed a whole-house ventilation system to bring a controlled flow of filtered fresh air from the loft into the house.
  4. Installed trickle vents on five windows. These work in tandem with the ventilation system to provide an imperceptible background movement of air.
  5. Re-deployed the original bathroom fan to the kitchen ceiling (venting it correctly the through wall).
  6. Arranged for an additional layer of insulation to be laid in the loft.

We are very confident that the changes we made will make it warmer and vastly improve the air quality in the bungalow which will lower the humidity and eradicate the mould problem.


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

Mould on bedroom walls
Mould on bedroom walls
Damp walls causes wallpaper to fall away
Damp walls causes wallpaper to fall away
fan vents into loft
.The existing bathroom fan vents straight into the loft
poor loft insulation
Poor loft insulation
fitting window trickle vents
We fitted trickle vents to a number of windows
extract fan in ceiling
... and installed a good quality humidity controlled, multi-speed extract fan with "trickle" mode
extract fan ducting
The extract fan now vents externally (using insulated ducting)
loft insulation
and the loft is insulated
Request a survey & report
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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