Damp Specialists

Our customer had a substantial mould issue in their penthouse 4 bedroom apartment in Buckinghamshire.

It is a substantial and well appointed property which had been fitted with up market glazing some considerable time previously. Critically no trickle vents had been installed and in this case it was almost impossible to retro fit them. As a result of this it has not had proper airflow for a long time either. The ventilation requirements for a property of this scale under building regulations part F are substantial.

Building regulations Part F as follows:

https://assets.publishing.service.gov.uk/media/61deba42d3bf7f054fcc243d/ADF1.pdf

The regulations make it clear that the dwelling must be considered as a whole, and thats because you have to ventilate all of it or pockets of damp air form in the parts that aren’t ventilated and this causes a lot of problems.

To give a general guideline, this customers property is dealt with at 1.24, Table 1.3 under the 4 bedroom section. The minimum “whole dwelling” ventilation rate should be 37 litres per second. Thats just numbers until you visualise the volumes in play. When you visualise a litre is a  large bottle of cooking oil and you need constantly to be moving 37 of those through the house each second and therefore 37 x 60 x 60 x 24‎ = 3,196,800 bottles in a 24 hour period you start to see how far off the situation is.

Yes you read that correctly, almost 3.2 million litres of new cold air needs to blow through the house each day to comply with the regulations and ensure the house is properly ventilated.

With current energy prices this approach really belongs in a bygone era. Who in their right mind really wants to blow cold air into their house and blow out the warm air that they’ve just paid to heat?

Definitely not me. But if you don’t do the ventilation then the humidity levels rise and before you know it you’ll be running in black mould all over the place.

The customer had been struggling with this for some time before speaking to me, they had received quotes for PIV, and they agreed with me that this is a nonsense approach because it pushes in cold air from the loft and relies on it pushing out the warm air through gaps here and there. The customer considered that after they’d spent what they had on high end windows and doors the place was “tight as a ducks arse” and therefore this approach was nonsense.

It didn’t take much to conclude that the right approach was MVHR. This was made easier because being a top floor we had access to the loft space.

MVHR is often misunderstood as “air recycling”.

It isn’t air recycling, it’s heat recycling. What MVHR does is pump out all of the old air from the house that you don’t want and pump new air in and it does this 24/7.

The installation was a huge success story because the climate in the house dramatically changed within 48 hours. The other positive that was not predicted was that the customers two children reported much better sleep.

Installation of a rigid ducted system with attenuators so that it runs silently:

The whole thing was subsequent covered in insulation.

The MVHR unit itself:

From an energy perspective the unit runs at about 200 watts an hour if going at full speed but it’s designed to run at 30% so that’s about 60 watts an hour or

60 x 24‎ = 1,440 watts a day.

Approximate cost therefore is about £0.50 a day to run it, but you’re not throwing out 3.2 million litres of air you’ve paid to heat so on balance it looks like a win.