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Ventilation System Not Working Mystery

26 January 2017
Ventilation System Not Working Mystery Ventilation System Not Working Mystery Blog

Here at Unovent we had a situation where a ventilation system simply didn't work. That didn't make sense as the Unovent system (or any other ventilation system) is simply a way of moving stale air out of a house and replacing it with fresh air ... just like opening the windows on a nice day. The elimination of moisture in the home is simple physics - given time, it must work.

However, in this rare instance, after a few months our customers - who were very nice and kept lots of good records of temperatures in the roof and house, rainy days, etc, called to say they were disappointed.  Our agent in the area investigated and could not see any reason why it wasn’t working perfectly.  We went to look and couldn't see any problem either. It was a good installation in what we considered the perfect candidate home - 10 years old, Hardiplank with owners who did all the right things (Showerdome, range hood, dryer in garage, etc). We returned three times over two weeks. We crawled under the house, into the roof space, walked around outside, looked for broken pipes, peered into every nook and cranny, scratched the head - it didn't make sense.

One day we read something in a scientific study about home ventilation (this problem had resulted in LOTS of study). Bing!!!  A little light went on!

We went back and climbed up into the ceiling space - switched off the roof space light - it was pitch black. No little shafts of light from the soffit area or anywhere else. We then noticed the faint light among the insulation from the top of the down-lights ... and it all became clear. The ceiling space was totally sealed - there was even plastic sheeting taped over the gable ends and the building paper was sealed to the top plate along both sides. The area looked brand new and was as clean as a lounge.

When the Unovent fans were working, air was being pushed down into the rooms below ... and straight back up through the down-lights. The same damp air was just going around and around with no dry air added to the mix. The owners lit the fire to heat and dry the house - which resulted in even more water vapour being held in the air - ready to condense out on the windows each morning and no doubt being absorbed into the walls and drapes.

We also discovered the little vents on the aluminum joinery had been closed to stop heat escaping - a false economy. Always leave the tiny slot vents open - not much heat escapes.

The solution was easy, open the window vents, open some air gaps into the roof space and fit approved down-light covers. Within two days the home was dry with no more condensation problems.

Installer Lesson - check the ceiling space isn't fully sealed stopping fresh air entering from the outside. This may be a problem with lots of modern homes, particularly those built from 2002 until 2012 when it was then recognised that sealed roof spaces cause dampness and black mould in the roof space.

Ventilation systems properly installed do work. If the result isn’t as expected there is bound to be a reason other than the fan units. It may not be easy to discover but you can be sure if air is entering the room from the fans and moisture reduction is not happening, it will be something else weird with the property.

Here at Unovent we are always happy to provide advice to ensure your home becomes drier and healthier.