We have a HRV and got a summer kit with it we have found it fantastic our house is 7 years old and we had started to get mould and a lot of condensation since putting it last year it is a lot drier and warmer just like when we first moved in.

We've had DVS for 3 years in our house, and we have hardly any condensation and the house is noticably drier than our friends and families that don't have it.

DVS isn't a heat transfer system - if anything it is taking the warmer air from your ceiling space and pushing that out into the house - meaning that the cooler moist air already in the house if getting pushed out via windows etc.

Our power bill is minimal less than $200 during winter for 2 adults.

If you are looking for a heating option then you are better off looking at a heat pump or fire depending on where you live.

That sounds about right, but the MM system is designed to keep the air moving - even on cold chch winter days, think it operates between -10 and +25 degrees from memory? But the air in the roof space will always be warmer than the outside....brrrr! Having said that, the air in the roof in winter will generally be cooler than that in the house overnight, hence the ability to add heated ducts, so not forcing cold air into the house while you are sleeping. Anyway, it seems to be working really well - and we are so happy with it (spent a year saving up to get it installed so was really really hoping it would work!).

Hope that makes sense - rambling a bit as haven't slept in 3 nights

Hi, just thought I would put my 2 cents in

We had a Moisture Master installed in our house in chch - a 120sqm bungalow  - after looking at MM, DVS and HRV. It cost $2800 for a duct into every room, and seems to be working well (place is tenanted out). MM just seemed to be a better product than the other two when I researched them, they also have the option of adding heating into the ducting at a later date if required (another $800) and this would mean the air being moved around from the roof space would be heated. The MM guy said not to bother with the systems that include a heat transfer system built in - it would be cheaper and easier to pop down to Bunnings/Mega mitre10 and buy one of their DIY jobbies instead - which I was a bit suprised at, as he also sold heat transfer systems (why tell a client that your product isn't any good!? But at least that showed honesty).

Our primary reason for getting a system installed was to dry the house out, not a particulary damp house, but got terrible condensation on the windows in winter, which left the house really chilly. By drying it out, the heating has become way more effective - we have electric heating at one end, and a gas fire at the other (flued). The system has paid off in terms of reduced heating costs and less maintainence due to the reduced moisture. And if the tenants want, we will get the ducting heated when they ask, but so far they haven't needed it.