Cellar advice

[dandrew]

Many thanks for all the comments offered as potential solutions. As far as I can ascertain, the best line of attack seems to be:

1) Increase ventilation
2) Dehumidify OR increase air cirulation
3) Wait and see what happens ( any idea how long, weeks or months ?)
4) Lime the walls if necessary to deal with salts accumulation
5) If no improvement consider lining or tanking

Matt has hit the nail on the head though - cellars were never intended to be used a living space, but have become adopted as such to deal with modern living habits.

 

[NT]

Second the rate of water transport through the walls depends on interior RH, and a dehumidifier can reliably and controlledly be set to whatever RH you choose. A damp operated fan can not. Thus the dh does no more salt damage than the fan. Both will cause salt deposits, and there are ways to deal with this. One is to lime the walls, the lime acts as a sacrificial layer.

Always pick a humidistatic dehumidifier.

That is also sensible, although are humidistatic fans that much more unreliable than humidistatic dehumidifiers? I would have thought the components were reasonably similar. At this point though we have reached the ragged edge of my knowledge.

There is a real difference. A dehumidifier need only concern itself with the RH in the room. If too high, on it comes and down the RH goes. An extractor fan is a different animal, because it can only reduce RH some of the time, and there are 4 factors that all need to be considered to determine when it can and cant, and so should be on or off. They are interior RH, exterior RH, interior temp, exterior temp. The humidistat measures only 1 of the 4 factors, thus it is simply incapable of controlling itself properly. It will not run when it should, and will run when in fact its bringing damp in not throwing it out.

Compared to a fan with no control its some better, but compared to a dehumidifier its a rough performer. This is exactly why they have limited effectiveness.

I am, I suppose, erring on the side of caution having seen heavy-handed contractors install DHs that suck the sweat from your body in cellars in an effort to dry them, then call us in to comment on their ineptitude.

Yes dehumidifiers can do damage if misused, just like any tool. The more powerful and effective the tool, the more damage misuse can do.

There is less scope for damage with fans, don't require you to regularly lift litres of water from your cellar, and don't become a feature of the room. However, that all said, I see different situations than regular domestic environments and it seems there may reasonable arguments for routine DH use.

A dh is bigger, but I've not found that a problem in practice. Usually for permament use a very narrow drain hose is attached, but of course some rooms have nowhere to drain to. The plus side is the water produced is of as high purity as distilled, and is great for use in irons, batteries, medical uses, washing windows, and so on. In rooms with no sink it gives you a small supply of water on hand, which can be handy for spot cleaning etc.

That will actually bring damp into the cellar some of the time. When the cellar is cool and outdoors is hot and a little damp, the fan will run and warm air with more water vapour will be brought in.

That assumes you bring the air in directly from outside and not through the building. I'm not sure if that would generate a big effect or not.

Air from the main building would be higher water content than outdoor air, since households always produce and expel moisture. If you want to dry the place with a fan you'd want to use outdoor air really. If OTOH you just need to get at least some ventilation, and thats all thats needed, pulling in air from the main house would bring some warmth with it. There is the risk of it causing condensation, but sometimes it would be ok. Any fan based approach would throw a fair bit of heat away though.


NT

 

[NT]

dandrew
>Many thanks for all the comments offered as potential solutions. As far as I can ascertain, the best line of attack seems to be:
>
>1) Increase ventilation

helps initial drying. OK long term if you want a cellar at outdoor temperature, but not so useful when you want it warm and liveable.

>2) Dehumidify OR increase air cirulation

dehumidify yes,

>3) Wait and see what happens ( any idea how long, weeks or months ?)

a century? One of the plus sides of a dehumidifier is the job is done in days at most. Just plug in and come back.

>4) Lime the walls if necessary to deal with salts accumulation

you need to do this before salts accumulate though. The salting will damage the lime coat and not the bricks, which is pretty much a non-problem. When due for a repaint, just scrape and paint. A dehumidifier can quickly reduce a rooms RH to normal level, unlike other methods, so will produce the most salting. Lime is a simple way to avoid this causing damage.


>5) If no improvement consider lining or tanking

there are better optoins than tanking. A dehumidifier is bound to work really, unless its a small unit in a mansion. Note if cellar temp is very low eg 12C or less and you wont be heating it, you need an absorption wheel type. If its not that cold the cheaper more common refrigeration ones are more energy efficient and all round better.


>Matt has hit the nail on the head though - cellars were never intended to be used a living space

yes

>, but have become adopted as such to deal with modern living habits.

yes as they were in Victorian times, it wasnt unusual for people to live in them, but they werent really fit for it.


NT

 

[NT]

One more thing, wood warps when its RH changes anything more than slowly, so if youve got significant woodwork down there it may be best to go slowly.


NT