Condensation problem in the house?

It's usually a lifestyle thing. If the tenant does not open the windows from time to time and dries washing on radiators,boils veg on the stove with out running the kitchen extractor, runs baths by putting in the hot water first rather than mixing with cold etc.

Often difficult to persuade the tenant that they are the cause of the problem though.

Bob

I'd start with a visit to the property so you have some idea whats going on. I'd have said no to damp specialists, most are no more than scammers, but it sounds like you've gotten away without the usual bs.

You cant really force the tenants to heat the house more, and a dehumidifier is fine as a long term solution.

ps a fair few victorian houses have cavity walls, yet its widely believed that none do, even by people in various areas of the building trade.

NT

Hi

pardon my ignorance if I'm off the mark but do gas fires themselves not produce a lot of water vapour?

Allan

The water vapour from most gas fires doesn't matter, as it goes up the chimney. Flueless ones are a problem.

SteveW

I was thinking if there were extracts in the bathroom with perhaps a humidistat, and a true extract in the kitchen. Without those it doesn't surprise me in an otherwise well "sealed" house.

I agree totally with Bob on both counts.

I seem to have solved it myself in a rented-out two-up-two-down by fitting the bathroom with a humidistat-controlled extractor fan and advising the tenants to keep the bathroom door open so that it has a chance to work over the whole property - seems to have done the trick.

Other than that, providing a dehumidifier seems a reasonable propositition, except that if they are eco-warriors as you say, they'll probably baulk at switching the thing on... :(

David

yes off course I was thinking of those portable heater things.

Its all right bunging the property up with insulation all that does is cause condensation, from bath, shower and cooking. The answer is extractors in the kitchen and bathroom with a window open while cooking and after showering or bath. Portable gas fires are one of the biggest condensation makers.

Flat out lack of ventilation...

Dehumidifiers are one solution.

- They are expensive to run, 250W (compressor) to even 800W (dessicant)

- They are not cheap to buy =A3130 for a DD8L to =A3320 for Mitsubishi

- You really need two re hall & main living area

- They are barstool noisy if you want to run at night

Better solution is a programmed ventilation.

- Airflow Quietair QT100T

- Cheap to run at 10Watt, 6 min every 24hr to 23min every 4hrs

- Cheap to buy at =A365

- Awkward to fit re dust creation needing dust sheets taped to wall

I have not used that exact model, and there are other similar products available, but the idea is sound - you create enforced ventilation to keep humidity below about 68% which is when mould begins to get excited.

Do the open flue(s) have a rain cap? You get about 72" of rainfall or something silly down an open flue annually. Quite a few gas fires when not in use can provide limited ventilation depending on the cold draw of the chimney, so moisture can build up. Put on the other gas fire and it will draw air down the other chimney often bringing mould laden air with it.

A puzzle is how can the baseline level of ventilation be low yet you have two gas fires - unless they are balanced flue? Balanced flue draw in their own air for combustion via the inset tube, exhausting products of combustion through the outer tube. A seriously defective fitment can result in leakage into the room or cavity but this is solid wall.

Has the occupier bunged up every vent? If the problem is draughts the "Black Hole" labyrinth ducted things supposedly work. They tend to require a 125mm core drill, most enforced extractors use a 107mm core drill. 780W drill is usually sufficient unless you have pig hard bricks in which case hire - and also hire a very good dust cleaner because core drills produce "brick flour" on an epic scale.

I think heat recovery fans of the "1-piece in a wall" will be a disaster outside a lab because if there is any reduction in flow from back pressure or prevailing wind the actual heat recovered will plummet. Extracting heated air is not really a problem - in moderation

- because it is the fabric which takes time to heat, it takes very little to reheat the amount of air removed. Just a case of dishonest lobbyists and garbage research. The central heat recovery units will work ok - if adequately lined - although their price seems somewhat ridiculous as with most "Govmint says you must have and we collect the lolly".

Check that the chimney is clear. It could be that they are acting as flueless ones. Have the tenants been experiencing headaches?

If it's an older property, I suspect the walls are solid masonry. They act like 'storage heaters' and respond better to permanent low levels of heating rather than short bursts. Old properties can take several days to heat up.

If the tenants are reluctant to turn the central heating on, they may be relying on the gas fires for a few hours which only manages to heat up the air in the room and a few millimetres of the wall causing the dew point to appear in the plaster!

If you've got a functioning central heating system, then take the fires out. Stick a programmable roomstat in with a minimum setting of, say, 16-degrees. If they must have a fire in the living room, try a solid fuel one. It's easy to sell it on ecological grounds - it uses timber which only releases the carbon already captured. That, and the flue would ventilate the room.

Sorry about the delay in getting back to you, had to go visit the in- laws after a bit of an emergency although all is now well. Thanks for all the suggestions - I'm afraid we've got to go out again now so I haven't time to reply to each one or really take it all in yet but I really do appreciate the help and we'll go over everything later. Cheers all.

We did the calcs comparing the 2 options here a while back, and found the dh option to be significantly cheaper overall. Dont forget the dh only runs a fraction of the time, doesnt chuck heat outdoors, and is a lot more effective at dropping rh.

NT

Have you got a link to those calculations?

It depends. If the damp source is primarily in one area, eg bathroom, kitchen etc, putting the dh there is quite effective.

NT

Regrettably I didnt find it. I'd redo them if I could remember the real life run times of the fan in a situation where I've used both, but I cant.

NT

Mike