If you have condensation or mould, then you need to understand the obvious:  Moist air is condensating on cold surfaces.  Its as simple as that.

To solve the problem, stop moist air getting to cold surfaces.

So, in my view, get the moist air out!

When we bought our house in 2012, the problems we had were:-

  • Kitchen extractor wasn’t connected
  • Bathroom had no fan, with shower or bath, the walls RAN with water that never dried
  • Bedroom windows were soaked daily, needing wiping/drying off
  • Mould appearing in corners
  • Mould behind new furniture (!)
  • In guest room, moisture/mould running off one of the walls.  Previous owner bodged and hid this up well.  Paint was falling off….

You have to remember, old houses were designed to “leak air” – fire places were open fires, windows single glazed, doors had gaps, so air moved around naturally.  Modern double glazing, sealing chimneys, sealing draughty doors, and central heating means the air doesn’t move as much as it used to.

So you need to analyse the whole picture and deal with it, PIV is only part of the solution.

Our tips:-

Stop air getting excess moisture

  • Don’t dry clothes over radiators, as the wetness can only escape into the air.  If you must dry clothes inside, buy a SPIN DRYER to get more moisture out of the clothes in liquid form
  • Use a kitchen hob extractor fan that vents externally.  Boiling pans turns water to steam which stays in the air.  This will condensate and turn back to water when hitting something cold.  Venting this externally with a hob extractor (not just filter) will remove it
  • Vent chimneys in bedrooms – so the normal chimney movement will suck moist air exhaled from overnight breathing out through the chimney
  • Put a decent bathroom extractor in. We have the one on the right, a large 550m3/h extractor venting externally.  (Don’t get a naff 100 or 200m3/h one, get one that works!  We’ve gone from water running off the walls, to the mirror not even steaming up….)

Reduce Cold Spots

  • Ensure upstairs ceilings are fully insulated in loft.  Gaps will cause cold spots and cause small condensating spots
  • If edges get mouldy, consider good coving.  Our roof/ceiling design meant the edges could not be covered in insulation.  So the coving covered this dead spot and negated the risk (and looks better lol!)

Allow & encourage air flow

  • Use a PIV system!
  • Use window vents if appropriate, especially where you are drying clothes
  • Where possible, have furniture “on legs” and slightly away from the walls.  (FYI – Before we installed PIV a new wardrobe had new mould behind…..  After installing PIV and moving it, the mould was dead, and after decorating and moving it, no issues since…. Shows the PIV worked for us)

FYI – the bathroom extractor fan shown on the right is superb.  We have it on a separate switch that only comes on when we shower or bath (not with the light) – and you can see steam being sucked out.  Our bathroom is painted – and not a sign of mould!  Considering the walls RAN with water before the fan, it is worth considering.  It was fan #3 for us, we tried smaller ones but this one is the only one that really is up to the job.

7 thoughts on “Other Condensation Control”

  1. Hi Ryan,
    Just reading your blog about the Nuaire Drimaster Heat, very impressed!
    I would like to fit one and like the idea of having the heater on a separate switch.
    Was this easy to do? as I would like to fit it myself.
    Any help would be appreciated

    1. I am no expert, so ignore everything I say. But yes, easy. The heater is electrically separate from the PIV system. So just wire it up how you like (in line with regs of course)

      I have a fused spur with 2 “wires” from it – one to PIV one to a 2nd fused switch and the heater power is from that. So switch 1 turns and isolates both PIV and heater; and switch 2 just the heater.

      However, as far as I know, you should get the electrics installed or checked by a certified person. Please check this with an expert.

  2. Could you please let me know which extractor fan you have? The comment says the ‘one on the right’ but there isn’t one.

    1. Hi Becky – do you have some form of ad-blocker?
      The fan we have is http://amzn.to/2gcWzlZ – which is a 150mm fan with timer. The suction/flow of the 150 is MASSIVE compared to the standard fans. We tried normal bathroom fan, and even the 100mm little brother of this one, but the 150 is the way to go. (We actually have it going to a 100 (4″) vent in the shower as that has the shower light, just got a 100-150 converter – and then 150 tubing in loft to external vent. This makes a HUGE difference – the shower doors don’t steam up when we have a long hot bath with this fan on.
      If you want to get bathroom clear, cheaper (or not) or smaller fans just don’t cut it – I’ve got 2 barely used lol – these are 550m3 per hour…..
      Good luck

  3. Can you suggest a Piv system or extractor for a lounge where there is no loft. I have an old cottage with a dark corner that just accumulates condensation

    1. I can’t recommend as I am not an expert, but the same company do a system designed for flats and no loft space that just needs ducting to an external wall. e.g. https://amzn.to/2zqEYTp – but you need to do more research. Good luck!

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