Heat Recovery Systems

I am currently looking seriously at a new house that has a "vent axia" mechanical heat recovery system. I don't really know much about these systems except that as I understand it they recycle warm air and mix it with incoming cold air to reduce heating bills. I am a bit wary about this, as I wonder if these new technologies can give trouble over time/ lead to "sick building" problems as the house has no wall vents or chimney. I am also unclear if they cool the house in summer or you just open your windows - this is important as the house is close to the M50 and there is plenty of noise.

I also wonder if it is possible to do an attic conversion on these houses as presumably they have a lot of ducting in the attic area and any new room would need to be linked in (expensively) to the existing system

Any help would be appreciated. Not sure what way to jump

We built our own house 8 years ago and installed a similar heat recovery system. I would view it as a positive aspect in the house you are considering purchasing. We have had no problems with ours, it has needed no servicing except that I change two air filters in it about once every six months - a fairly simple task. Two negative aspects of it is that there is a constant very low whirring noise from it which may be heard in a quiet house and which some people might find annoying, though in your case near the M50 I don't think this will be an issue. The other problem may be the position of vents in the room, if I am directly under a vent bringing air into a room I can feel a definite draft, therefore they need to be positioned away from where beds, seating or dining areas might be. I am no expert but will try to answer some of your queries.

I have heard of no link to sick building problems. I believe it leads to a healthy atmosphere as there is constant 'fresh' air coming into the house leading to the moisture content in the air becoming lower naturally.

We very rarely open a window in the house in winter or summer. The system does seem to have a cooling effect in hot weather.

The pipes in our attic are placed so that they will not interfere with the attic being converted in the future. I presume this would be the case in all well designed systems where there is a possibility of the attic being converted. However, you would definitely need to check this. I don't think you would have to connect any new room into the new system, you could use vents instead, however like with all vents you would get heat loss. I'm not sure if having the heat recovery system elsewhere in the house would make this more significant than normal. It might not be as expensive as you think to link new attic rooms into the system as you will have existing piping close by.

I don't think you should place too much importance on the heat recovery system. It wouldn't be a deal-breaker for me one way or the other, I would view it as a bonus if it was in the house that I wanted.

Thank you for this is very comprehensive response! I suppose I was not aware of the low whirring noise. The show house has this but i noticed on the display in the hot press that it was on boost so assumed i was not present at normal settings. Residents in the estate have told me that there is no noise from the system. Anyone else know whether these systems have a low whirring noise in a quiet house when at normal settings ? Maybe they have eliminated this over the last 8 years?

The HRV system will add to the comfort level of the house. It will reduce your heating costs a little. The house should of course be well insulated and fairly air tight. Some HRV suppliers have changed their supply valves with the result that the air coming into a room is spread across the room. They have a concave plate. This is in contrast to the old valves which directed air in a 'cone' away from a point in the ceiling.