Condensation in Buildings - Part 2 – How to reduce the risk!

There are a few very simple, but nevertheless very effective ways we can reduce the risk of condensation, just by simply being aware of some of the activities we would normally undertake without even thinking

Source: thevideo.biz

In order to understand how to reduce the risk of condensation it is important to first understand how it occurs. If you have not already done so I would recommend reading last week’s article (Link), ‘How condensation occurs’, before going any further. You will then understand that the ‘ingredients’ necessary for condensation to occur are moisture vapour and cold surfaces, which are exacerbated by poor heating and poor ventilation.  The cold surfaces could be present due to thermally inefficient walls and surfaces, particularly in older buildings.  In fact there are a whole host of reasons why the internal surface temperature of the internal fabric of a building may be cold (walls, windows, ceilings etc.,) including poor maintenance of external walls, rising damp, penetrating damp due to leaking rainwater guttering or downpipes, leaking roofs, single glazed windows, poor weather sealing around openings and cold bridges, which are areas of the building fabric which are less thermally efficient than the surrounding construction.

To reduce the risk of condensation occurring there are two things we should consider. Firstly, dealing with the cause of the condensation and secondly, looking at the way we use a building and trying to find ways of reducing the amount of moisture vapour we emit.

In order to rectify the problem, we first need to establish the cause. This is where you may need the advice of a Building Surveyor, who will be able to undertake a thorough inspection and establish which factors or combination of factors are contributing to the condensation. This is important because if you do not deal with ALL of the contributing factors, you may slow down the amount of condensation occurring, however you will not actually solve the problem. For example you may decide to improve the heating system, but if you do not deal with the thermally inefficient walls, then all of that increased heat will just disappear through the walls, and will have a limited effect. So depending on what is established as the cause, it may be necessary to increase the internal surface temperature of the walls by either insulating internally (dry lining) or externally (insulated render system), replacing windows, improving ventilation (possible a mechanical extractor fan) and upgrading the heating system. As you would imagine, this could become very expensive, which highlights why you may need the advice of a professional to ensure that the correct remedial measures are undertaken. All buildings are different and the way we use buildings will also be different, therefore we cannot assume that the cause of condensation and the remedial works required will be the same in every situation.

After dealing with the building we must also consider ways in which we can reduce the amount of moisture vapour we emit in buildings.   There are a few very simple, but nevertheless very effective ways we can achieve this, just by simply being aware of some of the activities we would normally undertake without even thinking.

Source: www.prokil.co.uk

Bathing, washing and cooking are activities that we cannot avoid however all produce large amounts of moisture vapour. We must undertake these activities on a day to day basis, however when showering/bathing, try to not leave the shower or bath taps running more than you need, switch them off as soon as you can.  If you have extractor fans, ensure that they are working, adequately sized and switched on when needed. Although it may be cold outside, when you are leaving the bathroom, open the window to let fresh air in, which will soon clear the moisture vapour and prevent it condensing on the walls and windows.

If you are using a tumble dryer ensure that it is vented to the outside.  I have undertaken a number of previous inspections where I have seen the flexible tumble dryer vents extracting into a room, rather than outside.  This was due to in both cases to lack of thought of the location of the tumble dryer and a general lack of understanding on the part of the occupiers. Also, when drying clothes try to avoid placing them on top of radiators.  This is usually done for convenience, however again produces large amounts of moisture vapour.  Whenever possible washing should be dried outside, or if weather conditions do not permit this then consider using an appropriately vented tumble dryer, or maybe a trip to the launderette.

When cooking use an extractor hood if you have one above your cooker and keep lids on saucepans as much as you can.  Avoid using bottled gas and paraffin heaters these produce large amounts of moisture vapour. 

Finally, but very importantly, try to ensure you have a regular flow of fresh air around your house/buildings.  This effectively dries out any moisture vapour and prevents it reaching concentration levels where condensation may become an issue.  Granted, nobody wants to release all of that lovely heat from a building in the depths of winter, however, opening windows for a short period of time may result in the internal environment becoming temporarily cooler, but it will also significantly help to reduce the risk of condensation.

Hopefully, now that you know how condensation occurs you can start to thing about ways in which you can help to reduce the risk.  In future articles I will discuss other forms of damp in buildings such as rising damp and penetrating damp.

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Information/opinions posted on this site are the personal views of the author and should not be relied upon by any person or any third party without first seeking further professional advice. Also, please scroll down and read the copyright notice at the end of the blog.

Rising Damp – A Salty Problem - An update for 2015

Guest Article - Joe Malone - Principal: Malone Associates Ltd

My academic research into rising damp led me to the conclusion that most text books are wrong in their description of rising damp since they state that it is caused by capillary action.

Following on from my articles written in 2013 I thought it was time to provide a further update on one problem in particular relating to the diagnosis of rising damp. In my update for 2013 I wrote that, ‘you need to confirm that three conditions are present to definitively confirm a case of rising damp.’ These are:

1.  You must have a rising damp moisture profile. That is a profile that is wetter at the wall base but gradually decreases with height to a theoretical maximum height of circa 1.5m.

2.  You must prove that moisture is present at depth in the masonry and it is not enough to take surface readings from the plasterwork. You will need deep wall probes or a calcium carbide (speedy) meter to confirm this on site.

3.  You will need to confirm that nitrates are present in the damp apex of your moisture profile. This will involve doing on site analysis or sending a sample off to the labs. You might have noted that I've ignored chloride salts because these can be present in tap water or building materials. A positive test for nitrates confirms that the moisture has leached up from the soil.

My academic research into rising damp led me to the conclusion that most text books are wrong in their description of rising damp since they state that it is caused by capillary action. Since we know that the major moisture pathway for rising damp is the mortar perps and since we also know that the moisture transfer mechanism in mortar is diffusion then clearly the generally accepted cause by capillary action is incorrect. It is probably worth reprinting my own updated description at this point…

‘Rising damp is an upward migration of groundwater in masonry walls. It will act in combination on the masonry units and their separating mortar joints or it will act primarily on the mortar joints. The moisture transfer mechanism in masonry is capillary action whilst the moisture transfer mechanism within mortar is diffusion. The major moisture pathway for rising damp is the mortar perps so it can be stated that there are dual moisture transfer mechanisms for rising damp, diffusion and capillary action’

The purpose of this article is to right another wrong with regard to the academically accepted principle for salts analysis. If you note again the requirement to prove the third condition, the need to prove that Nitrates are present in the damp apex of your moisture profile. This requirement stems from the fact that Nitrates are present in the soil so if moisture is leached up from the soil then it stands to reason that the moisture contains Nitrates. Personally I have always used the chloride test very little since it has extremely limited value in the course of most damp investigations and it is a test that has always been of zero value for the diagnosis of rising damp, simply because we know that chlorides are present in tap water so a positive test for chlorides does not help us determine the source of moisture.

The Nitrates Anomaly

When testing for Nitrates we do so on the assumption  that Nitrates are not present in tap water and therefore a positive result moves us to conclude that moisture in the masonry has been drawn from the ground. I’m only aware of one salts analysis kit sold by Protimeter and indeed this is the one I use. Interestingly, Protimeter do not make their own salts analysis tablets and these are sourced from a company called Palintest.

Figure 1. Protimeter salts analysis kit.                   Source: surveyexpress.co.uk

However, we know that Nitrates can be present at very low levels. World Health Organisation guidelines stipulate a guideline for 50mg/l or less. So this raises a key question… Do we know that the tablets supplied by Palintest for the Protimeter salts analysis kit are discriminatory enough to only give a positive test result when  Nitrates levels are above and below 50 milligrams per litre? If not, then the source of moisture cannot be determined using this test since a positive result may also be obtained when the source of the wall base damp is a leaking incoming water main containing Nitrates at low levels of 50mg/l or less? If you have used the Protimeter kit you will know that a positive test for Nitrates turns the water cherry red and there is no colour chart to match against your sample to help determine the approximate quantity of Nitrates present. The practice of matching the sample colour obtained against a colour chart is a principle that may be familiar to a lot of freshwater fish enthusiasts since they have to regularly check Nitrate levels in their fish tanks to ensure levels do not become so high as to become dangerous for their fish.

Figure 2. Colour card familiar to freshwater fish keepers. Source: www.cichlid-forum.com

The Protimeter test for Nitrates appears to be less discriminatory than the test used by freshwater fish enthusiasts since it will turn cherry red and give a simple positive result with no clue as to the level of Nitrates present.

Figure 3. A positive nitrates test using Protimeter kit with Palintest tablets

I was uncomfortable with this and decided to contact the technical team at Palintest to ask them how discriminatory the Nitrates test was? They were incredibly helpful in providing the following response…

‘Your question is a good one.  I'm afraid you won't ever be able to be certain that the nitrates don't come from the tap water.  The test doesn't know the source of the water, it'll just react to any nitrates present.

You're also correct that the limit for nitrates is 50mg/l.

What I would recommend is to test the tap water on the site to test the 'baseline' nitrate level.  If your 'real test' is higher than this, you can be sure that some nitrate is coming from the rising damp.  If it’s less or equal to the baseline though, you aren't going to be able to tell.

You could expand your test protocol to include other minerals (sulphate, chloride etc) which would be able to give you some more confidence that the water is from the ground as opposed to the tap but you would need more equipment and would be a bit more complex than your current method.’

Before I even asked the question of Palintest I was already experimenting with a Nitrates test kit manufactured by Salifert. I chose this particular kit since I’d read on most forums that this was generally thought to be the most accurate kit. The kit is supplied with a colour match chart and is significantly cheaper than the Protimeter test kit.

Figure 4. Alternative Nitrates Test Kit  Source: Authors own

In fact I had been doing precisely what was recommended by Palintest… I was and am testing the tap water to establish a baseline Nitrates level according to my Salifert colour chart before I take a sample from the wall. The advice given by Palintest is good but of course ignores the issue relating to the absence of a colour chart in the Protimeter kit. It would seem that I was being advised to use another kit since the Protimeter kit can not discriminate and will simply, ‘just react to Nitrates present.’

In figure 5 you can see where I have obtained a positive test result for Nitrates at a level of around 25mg/l but this was for a tap water sample.

Figure 5. Positive nitrates test result in tap water.   Source: Authors Own

My trials and research with this alternative test method are still ongoing since rising damp is incredibly rare and to date I have only obtained negative results from walls and positive results from tap water.  I will need substantially more time to evaluate the effectiveness of my alternative Nitrates test but what is clear is that an alternative test is needed or some refinement is needed in the Nitrates test kit currently used by most building surveyors or damp investigators.  

Joe Malone - Principal: Malone Associates Ltd

First Published: 16/2/15 at   www.buildingdefectanalysis.co.uk

Please feel free to share this article and other articles on this site with friends, family and colleagues who you think would be interested

Information/opinions posted on this site are the personal views of the author and should not be relied upon by any person or any third party without first seeking further professional advice. Also, please scroll down and read the copyright notice at the end of the blog.