Preventing condensation in kitchen cabinets

[Jonesy]

I wondered, given the number of kitchen projects on the forum, if anyone had any experience on the best way to solve condensation problems in kitchen cabinets?

I made a drawer-line type sink base unit for a relative, it was made from 18mm WBP plywood, mounted against a double thickness but solid brick wall. They seem to have been getting some condensation occurring on the backs of the cupbaord due to contact with the cold wall. Over the last 12 months this has caused paintwork at the back of cupboard to dis-colour slightly so I'd like to get this resolved to prevent further deterioration.

Removing the units and re-installing with a space or insulation behind the unit would be very difficult . I was considering either trying to insulate the backs, from inside the cupboard, perhaps using some polystyrene tiles bonded to the backs or perhaps cutting ventilation holes in the base and sides to increase air circulation but I was concerned that increasing the air circulation may be counter-productive and potentially increase the amount of condensation occurring.

The kitchen is already well ventilated as it has an open flue gas boiler with wall vents for this.

Anyone else had this issue, any advice on how to resolve it?

Thanks,

Jonesy

 

[ondablade]

Hi Jonesy. Can't say I've seen the problem, but I can add a bit on mechanisms. At the most basic level the air in the area has a certain moisture content - expressed as % RH (relative humidity) at a given temperature. Cool the air, and with its reducing ability to hold moisture the %RH increases. Cool it enough and it'll reach the dew point (saturation), and the water will start to come out as condensation.

What's a bit odd about your situation is that in a house that's heated over the winter it's not normal to reach the dew point/experience condensation (like you can in a cold workshop) - except very locally in on surfaces that drop to temperatures much lower than that of the room air like aluminium window frames, glass panes and the like. A double leaf cavity wall normally doesn't get cold enough for this to happen unless there is insufficient heating. If it was a regular issue people would experience mould and mildew problems everywhere.

If condensation is occurring then the timber of the kitchen units is going to take a hell of a beating too - not only may it move a lot, it may also develop mould etc.

I guess what I'm heading towards is the thought that there probably shouldn't be a problem unless (?) (1) there's not enough heat around/the wall is unusually cold/poorly insulated, and/or air is not circulating through the space concerned; or (2) there's a source of moisture in the area. (maybe a leaking pipe, or a faulty damp proof course, or a badly constructed cavity, or water getting down the back of the units and getting trapped in an enclosed space)

You can't reasonably be expected to build a kitchen that will routinely tolerate condensation (i.e. damp), so my instincts would be to either look for a way stop the water ingress, and/or insist that the place is kept properly warm.

If the room is reasonably warm and well ventilated through the winter (ie. at the sort of reduced RH levels you get when you warm up incoming outside air) then even if there is a limited amount of moisture getting in from somewhere it should be mopped up by the air in the room and not be a problem - provided it freely circulates into the problem area. (which might entail arranging for some sort of ventilation - but it doesn't take all that much)

The problem with moisture barriers and the like is likely to be that if there a very cold area and/or water ingress all they will do is mask the problem - and create a problem area behind the barrier.

One view anyway....

 

[Jonesy]

I think it's a local temperature issue at the back of the cupboard - it's a Victorian property with solid walls rather than cavity, so whilst the room is heated I expect this area could get quite cold, particularly given that the unit is filled with drawers which restricts air circulation in the cupboard.

Initially I'd thought it could be a plumbing leak or condensation on the pipework but I've checked these several times and lagged the pipes but there's still an issue from time to time and seems dependent on the temperature/weather which makes me think it's condensation. The unit is mounted on plastic feet and there's no evidence of moisture or damp in the kick-board space.

I think I'll try installing some vents at the top and bottom of the cupboard, see if a bit more air circulation will help.

 

[Tusses]

you need air flow behind the cupboard.

It will get condensation still, when cooking / boiling kettles etc, but it will have the chance to dry out again afterwards.

If there is little air circulation behind the cupboard, then heat also will not reach there and will make the temperature difference worse.

Basically, anywhere you have condensation, you need ventilation/air movement.

 

[Rob Platt]

If there is no air movement behind your cupboard how is the saturated air getting in. Why would the condensation be behind your cupboard when the opportunity to condense on other cold surfaces might be so much easier.
Have you looked at the possibility of rising or penetrating damp as the cause of the problem/
All the best
Rob

 

[ondablade]

I'd not picked up that it was a solid wall that's likely to be cold J, and also possibly wicking water through from outside.

The ideal solution is probably as the guys say both ventilation and the cutting off of the moisture source, but if the rate of water ingress is low, then ventilation with properly warmed air (hence lower %RH) may well be enough to mop it up. If there's a lot of moisture getting in, then perhaps not.

If it turns out that ventilation alone can't cope, then it probably is a matter of some sort of moisture barrier. My instincts in that regard would be to try to cut the water off at source by e.g. sealing the external surface of the wall so that the masonry doesn't get soaked with water.

If the wall is allowed to remain wet, then the chances are the moisture will simply migrate to an area that's not protected by the barrier. Not to mention that as above the area between the internal barrier and the wet wall will likely continue to fester.....