Hi all
Sorry for another MVHR newbie post I've been reading up a bit but I can tell that u all understand this better than me!

So I've been thinking about MVHR for a while. We've been renovating a 60s bungalow (concrete block, insulated cavities) and extending the basement to create a house (300cu m) for a while and I'm yet to fit out new bathroom and utility downstairs, both of which will need MV.

We also suffer high humidity (typically 60+% if not using dehumidifier) with mild damp issues and are allergy sufferers. We're in Plymouth, so could just be the marine climate?

I was planning to see if things got better once we've expanded into 2 floors (kids will have affection each then, and we'll have a kitchen extract at least!)...

..but then a friend of mine said he'd got a Toshiba MVHR unit ( vn-m150he) from work and it'll be available cheap...
So it's partly the usual questions ie:
- is it worth bothering as an extract system when we probably can't get fully airtight (we have pv which'll offset the cost/carbon footprint during daylight hours), and bearing in mind that it's probably too small a unit for our house (exchanging half its volume per hour)
- does anyone know anything about these units eg whether they're any good etc

I'm just after a steer as to whether it's worth looking into more. If so I will need to figure out where to mount it and duct routes etc (it won't fit through loft hatch but may slide between rafters if I strip and relay some roof.

Many thanks in advance for any thoughts...
John

Posted By: smokeyjon..but then a friend of mine said he'd got a Toshiba MVHR unit ( vn-m150he) from work and it'll be available cheap...
So it's partly the usual questions ie:
- is it worth bothering as an extract system when we probably can't get fully airtight (we have pv which'll offset the cost/carbon footprint during daylight hours), and bearing in mind that it's probably too small a unit for our house (exchanging half its volume per hour)
- does anyone know anything about these units eg whether they're any good etc

Can't help very much but:

- how airtight do you think your house is? Are there draughts everywhere, or average, or it feels 'tight'? The better it is, the more use an MVHR is, versus continuous mechanical extraction etc
- too small is generally not good, since it will make more noise when its working hard. But 150 m³/hr with a volume of 300 m³ is better than the building regs minimum of 0.44 ACH so it is a possibility
- Toshiba doesn't even appear as a brand in the SAP Appendix Q database, so it's not exactly a mainstream option in this country at least.

It depends on how cheap it is, but it might be better to consider spending a bit more on something more mainstream. Definitely check out maintenance and guarantees if you still want to go ahead.

Posted By: smokeyjonwe're fitting axwoodburner withnno option for dedicated air supply

Forget any ideas of airtightness then! By the time you've made the big hole in the wall for airflow that will be required, you'll have draughts a plenty.

I guess my question was also whether MVHR is an all or nothing thing or whether there can be merit in persuing a half hearted approach over a couple of new regular extractor fans!!

Regular extract fans aren't designed to be run continuously. You'll do better to look at something called Mechanical Extract Ventilation (MEV) or Decentralised Mechanical Extract Ventilation (DMEV or D-MEV). There's also something called Positive Input Ventilation (PIV), which is very popular in places like Sweden but has for some reason been deprecated here.