Damp Surveys - Trade secrets - Bathroom ventilation 1

Misdiagnosed rising damp is mainly caused by insufficient bathroom ventilation.
Here I introduce a simple technique for testing ventilation as part of a ventilation assessment. Builders, homeowners and all surveyors should undertake a ventilation assessment after making changes and before recommending more expensive destructive measures.
Trade secrets - this is a simple how to video on bathroom ventilation introducing simple anemometer.
See surveyors.tips. Damp surveyors (with no conflicts of interests, i.e. independent of rising damp proofing contractors), are likely to undertake a ventilation assessment during the survey, especially during the "condensation season". Condensation accounts for about 80% of the damp issues in properties.
Here we demonstrate the a simple cheap method of testing whether the wind speed going out of vent matches the wind speed measured on the other side of the vent.
In the order of 30% of extractors fans in damp properties are not running efficiently. Sometimes it because of dirty, blockage, damp or backdraft shutter issues. Sometimes it's because the ducting or piping is leaking.
With the greatest respect to most builders, laziness can be a factor. The only way you'll know if the ventilation work is to test it.
Top tip..... if you don't have an anemometer, put toilet paper up to the bottom 1/4 of your fan, the toilet paper should be held up, a similar test can be used on kitchen extractor fan, using A4 paper on all panels at the same time.
Do visit dampsurveys.com for more guidance, including our DIY damp assessment guide.
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[@matthewwakeham2206]

Piv's do work for some damp scenarios but you still need proper extraction in kitchens and bathrooms. I'm in the process of learning the pros and cons of piv. They are not fit and forget and to my mind the controls are too basic. You need to assess and adjust the ventilation for each room. Winter will be the real trial and other issues need addressing. I bought and installed it because it was the quickest and easiest way to reduce the humidity especially at night when a dehumidifier is too noisy.

[@dampsurveys769]

Matthew, thank you for your insightful comment. You've highlighted an important aspect of PIV (Positive Input Ventilation) systems: while they can be beneficial in lowering indoor vapour levels in some scenarios, they are often seen as a standalone solution when in fact, they should be part of a broader moisture management strategy.
Extractor Fans: It's crucial to have and actively use good-quality extractor fans in both the kitchen and bathroom. If these are functioning efficiently, the necessity for a PIV system could be reduced or eliminated.
Positioning and Airflow: Improper positioning of PIV units can lead to issues such as air short-circuiting, where fresh air exits through nearby trickle vents with minimal impact on indoor vapour, or even worse, vapour being reintroduced into the property if the unit is placed near a bathroom extractor outlet.
Environmental Conditions: PIV systems were originally designed to take advantage of solar heat gains in loft spaces, presupposing that the air introduced would be both dry and warm. Unfortunately, in flats or during rainy conditions, these benefits are negligible, as external vapour levels can approach those indoors, precisely when ventilation needs are highest.
Costs: Installation, ongoing maintenance, and the necessity to offset the heat lost due to the continuous introduction of new air can make PIV systems a costly option for ventilation.
Comfort: The continuous influx of cold air, especially if heated electrically, can be both uncomfortable and costly, reducing occupant satisfaction with the system.
Targeted Solutions: A more effective approach often involves directly addressing the sources of moisture with robust extractor fans and dehumidifiers. Monitoring internal vapour levels relative to the dew point and external temperatures allows for tailored adjustments in ventilation and humidity control.
On the positive side, PIV systems do offer the advantage of filtering incoming air, which can significantly reduce the ingress of allergens like pollen during late spring, potentially easing symptoms of hay fever.
By considering these factors, you can ensure a comprehensive approach to indoor air quality that addresses specific needs while optimising comfort and cost.

[@mileshorn4601]

Hi,
I really find all your videos very interesting and engaging. I agree with almost everything state, however...
Would you say any extract fan will only work well if there is free air available to extract?
So, if the bathroom door is shut and there are no gaps around the door, then regardless of the fan power/speed, it won't extract..?

[@dampsurveys769]

Thank you for your comment. You are absolutely right. As part of my survey, I will ensure there's at least a 10mm gap at the base of the bathroom door. This approach achieves several important things:
It allows sufficient airflow for the extractor to work properly, preventing the 'sealed room' issue you mentioned.
It enables air filled with internal vapour to be drawn from the rest of the house and replaced by air with external levels of vapour.
It's worth noting that in the UK, our humid climate means external air typically has a dew point just below the outside temperature. This external air has a lower moisture content than the warm, humid air inside the bathroom.
This method effectively manages humidity while maintaining the door's integrity and appearance. It's a simple yet efficient solution that works well in most residential settings.

[@dampsurveys769]

Thanks Logan and Music for your comments.