No experience of Unovent but I had a Smartvent system installed yesterday for under $3k. I realise this isn't low cost but I get the feeling that ventilation systems are most effective when fitted by an expert. The thing I liked about Smartvent was the installer did the quote and he was able to talk through some realities and options at that stage, so I knew exactly what I was buying. It also made it cheaper because there was no sales person to pay commission to. Other organisations had a sales rep tell me what I wanted to hear and quoted me on a system that they couldn't say for sure would work.