Dehumidifiers may reduce energy costs as well as solve damp issues

I had this same trouble with one of our properties and was quite confused when our damp-proofing engineer suggested we install a fan in the ceiling below the loft not to extract air but to blow air gently into the house from the dry loft area thereby increasing the air pressure slightly and preventing drawing wet air into the house.
We were amazed when we found that this has worked and all the damp problems have disappeared. Google Remcon for details.

My experience says an even better solution is to install a forced air ventilation system (Envirovent supply and fit them). The very small, continuous, inflow of air from outside forces the air to circulate and stops condensation and mould problems.

Worked brilliantly in my 1970s inadequately insulated flat. Electricity cost minimal.

Reply to the comment left by "Alistair Nicholls" at "08/11/2013 - 12:29":

I have also used Envorivent, very effective but not a quick or cheap fix. However, de-humidifiers are very cheap and if tenants can be persuaded that they could actually reduce their bills they might even go out and buy one for themselves! Now wouldn't that be nice?

With all the news about another 9% rise in energy prices I thought this might be a good time to mention this and see what other landlords think. My personal experience is that whenever I suggested or even supplied a de-humidifier in the past tenants have expressed concerns about the costs of running them.

What I'm ideally looking for is some credible independent research to prove they can actually reduce costs.
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A few figures for you:

My small De'Longhi DEM10 dehumidifier, which cost £130 to buy, has a power consumption of 190W, so it uses 0.19kWh when run for an hour.

The electricity in my rental properties costs £0.108 per kWh incl. VAT, so the dehumidifier costs 2 pence an hour to run. If it is left to run for two hours a day for four months each winter, the total annual cost is £5.

Another point worth making is that if a property has high internal humidity - which is *not* "damp" - this can also spoil a tenant's clothes when stored in a wardrobe on an external wall. The moisture tends to condense in cool spots with poor air circulation, hence the growth of mould in the upper corners of bathrooms unless you have an extractor fan, so wardrobes can be prime locations for mould spores to grow.

On the other hand, unless I have made a mistake in calculation, the difference in energy required to heat a room at 50% or 90% relative humidity is also quite minimal. And by that I mean much less that 0.19 kWh difference to raise the temperature by 1 degree.

So seems to me that if there are any cost savings they'll be pretty small.

This has been an excellent set of suggestions borne out of real experience in countering damp and mould. One tenant of mine kept a set of motorcycle leathers spread out under his bed and these were constantly growing mould. The solution there was to install an airbrick in the wall to allow circulation - somewhat cheaper that a 24/7 running Envirovent, which is the other successful solution I've tried.
In a crowded HMO, I've installed an Envirovent fan in the ceiling at the top of the stairwell, feeding cool loft air, and this provides a gentle positive pressure as Alan Herbert advised. It's worked well for three years. Each time a resident opens a room door, the dry cool air enters - no complaints of damp.

Mark,

I have to say that I take issue with the idea that a dehumidifier can solve a condensation problem in a property. At best you are masking the effects and wasting electricity.

Firstly damp and condensation are different and have different causes, difficult to see how a tenant can cause damp when it is the ingress of water from outside the property or released from internal water systems.

All occupied properties have water vapour inside them and this is generated by living in general. The vapour will start to condense on any surface colder than the air temperature inside the home. The greater the difference the faster the water will condense.

Condensation is a real problem and has negative health effects just like damp. Two usual causes though, insufficient effective heating or lack of ventilation. Both usually problems caused by the landlord and suffered by the tenants.

However a lot of tenants do not ventilate properly out of laziness or ignorance so I guess they have brought it on themselves. However it does impact on the landlord as he will have to redecorate more often. Most councils and housing associations have good leaflets on combatting condensation so it's in a landlords interest to get some and provide them to residents where it is a problem.

Second cause is energy poverty, simply the heating works fine but the tenant can't afford to run it sufficiently to keep condesation under control. This is a real problem because there isn't a really simple solution.

If your property is badly insulated or the heating is very expensive to run then look to yourself, however there are 100% grants to provide insulation, new boilers and heating systems that are based on the resident claiming a range of state benefits for eligibility.

If I was a landlord who could get his property improved using someone else's money I wouldn't be long deciding. However it seems to be the case that a lot of landlords resist improving their properties even in the face of offers of free work.

Anyone got any ideas why this would be ?

Reply to the comment left by "John Daley" at "08/11/2013 - 14:52":

Hi John

Having read your post twice I don't see what you have to "take issue" with based on your response.

You obviously agree that condensation is often caused by tenants own habits and living in the property. Are you are suggesting that condensation does not lead to mould? I ask because it obviously does. Leave pretty much anything wet and either mould or rust will appear.

You also go on to say that ventilation is a primary cause of mould. I agree, if people create extra condensation by drying their clothes on radiators and then never open a window there's going to be a problem. Persuade those same people to use a de-humidifier and the problem has a far greater chance of going away wouldn't you agree? OK, the cause of the problems remains but at least a solution is found and surely that's the point is it not?
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I owned care homes for 24 years and had a damp problem in one particular cellar. There were 2 cellars in this property and I had a fan fitted in one (which had no natural air flow) and put an air vent in the next which had access to the outside. I turned on the fan in 1987 and it was still running in 2005 when I sold out. Minimal cost and problem solved. It's all about air movement. Heat is good but not essential.
Tony

Reply to the comment left by "John Daley" at "08/11/2013 - 14:52":

YOU STATE: 'Two usual causes though, insufficient effective heating or lack of ventilation. Both usually problems caused by the landlord and suffered by the tenants.'
YOU ARE WRONG TO BLAME THE LL AS
1) INSUFFICIENT HEATING IS MORE LIKELY DOWN TO TENANT ECONOMISING OR USING CALOR GAS!
2) DITTO VENTILATION (TENANTS OFTEN TURN OFF FANS, SHUT TRICKLE VENTS AND DONT OPEN WINDOWS)!
FURTHERMORE THE MAIN FACTOR IS MOISTURE GENERATION AND TENANT 'LIFESTYLE' CAN BE VERY SIGNIFICANT.
THE FOURTH FACTOR IS INSULATION AND THAT IS THE ONLY FACTOR WHICH THE LL IS RESPONSIBLE FOR (BUT THE LL HAS NO OBLIGATION TO IMPROVE INSULATION).
MARK IS CORRECT ABOUT DEHUMIDIFIERS...THEY DO HELP PROVIDED THE TENANT DOESNT DISCONNECT AND REMEMBERS TO EMPTY.