Back in June, we installed one of our Patented Tranzheat Ventilation Systems at John & Jenni's place in Palmerston North. They had a positive pressure ventilation system but it wasn't working and the home was suffering from bad condensation.
The principal behind a positive pressure system is that the house is pressurised and air will escape through cracks around windows and doors. But the thing about modern homes is they are built to be quite air tight. A modern home has all of its cracks and gaps sealed during construction. So, their positive pressure system didn't work because it fundamentally can't work in a modern home.
The morning after we finished the install, an ecstatic Jenni called to say her condensation was gone already. Before our system was installed the indoor humidity was a whopping 84% - and that was with their positive pressure system running.
For this install John and Jenni chose a combination of round ceiling diffusers, and rectangular wall diffusers (used on a bulk head in two of the bedrooms). Exhaust air went out through the roof using a Branz appraised flashing. Fresh air in comes through a grille under the eaves.