Cost-effectiveness of MVHR

[Dave Howorth]

There was a question about the cost-effectiveness of MVHR on the navitron forum - the gist of which was that MVHR here costs £2000 to buy and £40/year to run in order to save £80/year in gas, whilst HRV units in Canada cost $300 to buy. So I'm interested by some points in this discussion 

Am I right in thinking that if the heating is gas-powered then the energy-based and carbon-based balance points will be at different temperatures?

Does the 14C figure for SAPQ systems mean that the makers of the best systems have not bothered to qualify their systems for the UK?

Does the claimed cost difference between here and Canada mean that the Canadian units are poor performers, that European manufacturers are expensive, or something else?

I'd be grateful for any insights.

Cheers, Dave

[Mark Siddall]

Dave,
I split this as this really warrents a new thread. (For new readers, the 14C reference is discussed here http://www.aecb.net/forum/index.php?topic=2308.0). I've not time to begin to discuss this now - heading to work. ope others dive in before I'm able to dip in again.

Mark

[Nick Grant]

Dave

$300 sounds unrealistic for proper quality kit although prices could come down a lot with mass production as not inherently expensive. Some cheaper units in UK are certainly more noisy and used to have very inefficient fans but I expect all are getting better with DC fans the norm.

Various corners can be cut to save costs such as smaller heat exchanger with smaller airways which means more fan power and more easily blocked by condensation.

Cost effectiveness calcs are complicated by fact that MVHR is providing useful function of controlled ventilation (as would MEV) and improved comfort (fresh air is not cold).

The interesting metric for me is £/T CO2 saved (say over life time). I have not done that for MVHR.

Nick

[Mark Siddall]

Okay. Back from work.

I agree with Nick about quality of products, but I'd also add a cautionary note. It strikes me that focusing upon the elemental approach - a wall, a roof, a floor, a window, or an MVHR system risks squandering the chance to engage with whole systems engineering - by taking an elemental approach you can 'pessimise' the whole.

The whole systems approach is in many ways inherent to PassivHaus. Obviously there will be a cost limit to what is affordable but this has to be viewed on a project by project basis over a realistic time frame, say 25-30 years, and you have to choose the correct datum - i.e. say an uninsulated building or the regional/national average stock rather than current regulations (if you don't do this you can't compare really apples with apples). If viewed in this way any additional life cycle cost associated purely with MVHR can balanced against the savings made elsewhere.... besides picking up on Nick's theme, can you put a price on comfort and good indoor air quality?

Mark