Damp Proofing Question

Humidity extractor fan or internal wall insulation

I've recently bought a small semi det old cottage for rental. It has an uninsulated North facing stair case solid external wall. I have fitted gas central heating. The layout is pretty open plan living area upstairs bed and bath downstairs. I have bad condensation mould problems in various places but worse on flank wall particularly at top of stairs. i've fitted vents everywhere but have no control over tenants heating properly. I don't know what else to do. Should i insulate internally n. facing stair wall to warm it up or would some kind of extractor fan to keep down humidity work.
I don't really understand the difference between P.P.V. and heat recovery which would be best? I just seem to keep spending and nothing works.....some investment!

I've now put in aPPv extraction system and am waiting to see if this is the solution. Many thanks for answers

2 Answers

Best Answer

If the wall is cold and you install, for example, a humidity extractor fan then you are only really treating the symptoms - not treating the problem. And of course you have condensate forming on these walls. Insulation is the better option but a surprising amount of room space is lost with internal insulation (if the correct thicknesses are applied). A better option is EWI.

External Wall Insulation (EWI) is basically a direct fix, thermally insulated, protective, decorative exterior cladding system which consists of expanded polystyrene, mineral wool polyurethane foam, together with a reinforced cement based, mineral or synthetic finish. We use expanded polystyrene sheets, a reinforced polymer basecoat and then a flexible acrylic topcoat.

Approximately 35% of heat loss is through poorly insulated walls - and 45% for solid walls. The insulated layer, with low thermal conductivity and therefore low thermal transmittance prevents transference from both sides of the substrate it is directly affixed to. Insulation (the process of lowering thermal transmittance to prevent heat loss) is entirely dependent on product thicknesses, and this importantly includes the existing substrate in any equation. U values can be calculated by taking measurements of the wall type and thickness. But generally a solid brick wall will require between 75 and 100mm; and a cavity wall only as much as 20 or 50mm to provide an energy efficient U value (in the ranges of 0.30 – 0.40 W/m2K).

Answered 15th Feb 2012


Member since 13 Jun 2010

Sounds like you need a heat recovery unit fitted in the property,
If you call a local damp proofer they will be able to advise and quote on these.
The whole house units are designed to go in the loft space but if there is no loft space you can get single room units.
Hope this helps

Answered 16th Jan 2012

Bowe Electrical Services

Member since 28 Nov 2011

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