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Hi Team, I thought I’d pitch in on the old positive-pressure issue. Below I will mention a specific brand-name product. Hopefully that’s within the rules of the hub….

Lois is right. Until recently, there were no PPVs available in NZ that included humidistats. Most of the available PPVs are controlled on roof temperature alone, and could therefore actually increase humidity in the home.

A local supplier SIMX has recently started marketing a product called Smartvent Evolve. This system includes three humidistats – mounted in the roof, suffit, and interior. It has a setting which specifically targets dew point. This is interesting, since many homeowners are concerned primarily about condensation on glass.
According to the manufacturer, the system only operates when the air source will reduce humidity. Once dew point on the windows is above the outside temp, the system shuts down.

It appears therefore that the design addresses the two main criticisms with PPVs – unnecessarily increased heat load, and wetter houses.

It will be interesting if the any of the other manufacturers/ high-pressure-sales-people follow the lead on this and release comparable products.

Today one of my clients decided that they want to install one of these new-fangled systems (against my reservations…). Once it’s installed I’ll pass on their feedback.