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Does my home exacerbate my child’s asthma?

IMG_0149A home is regarded as one’s sanctuary, a place to feel safe and above all a place to bring up children in a healthy environment. But what would you do if your home was making your child unwell.

Well many homes I see in London are potentially unhealthy and in some cases create the conditions to trigger respiratory conditions such as asthma.

Please don’t think that this is solely associated with older Victorian homes. New build homes with their multiple bathrooms, hermetically sealed double glazing and ultra-strict air-tightness specifications are becoming a real issue.

If you’re going to buy a property then you might like to consider these 5 housing health hazards.

1. Lower ground floor (basement) flats tend to be colder, more prone to condensation, have less direct sunlight and are closer to the pollution from road traffic. The basement is a pollution and moisture sump and will be the unhealthiest position in the building. That’s why they’re less valuable than those higher up the building. Did you know that developers will increase the price of an identical property by around £5,000 per floor as you go up the building.

2. Homes near busy roads are less valuable for a reason. They’re closer to dirtier/polluted air.

3. Homes with multiple bathrooms are very popular (partly due to the demand from the buy-to-let market). However, having multiple bathrooms in small two bed flats with double glazing greatly increases the humidity inside the home. Dust mites just love warm moist homes and can multiply rapidly in these types of conditions.

4. Single aspect properties (homes with windows on only one elevation, mainly new build flats) are difficult to ventilate. This makes it difficult to fully ventilate the interior thus allowing moist stagnant air to linger. This allows bacteria and condensation mould to colonise these areas which may be enough to trigger or exacerbate asthma.

5. Small bedrooms with solid brick heat loss walls with a northerly orientation and double glazing are extremely prone to condensation. Never put a young child in this type of room.

Brick matching is vital when extending your home

Bricks old and newWhen planning an extension to the house, make sure the correct bricks are used for the main walls. Getting the right bricks for the extension will be more expensive, but the additional cost will be more than off-set by the added value to your home.

An extension I’ve been involved with recently has been made all the more authentic by ensuring that the bricks used are the same as those used in the house.

There are several reasons why brick matching is important.

  1. The new extension blends in with the existing,
  2. The old and new brick courses line up since the brick dimensions are the same,
  3. The chipped edges  of the bricks give a softer more irregular appearance and add to the visual effect,
  4. Since the extension looks more appealing, the extension actually adds value to the property. The added value should pay for the bricks!!

The bricks in the main photo were matched by Match-It and are the same bricks as the original. The original bricks are darker because of the build up of dirt over the years. It is anticipated that the lighter bricks of the extension will weather and darken over time.

Nitrates, rising damp and a defective DPC

Photo showing nitrates in tap water, rainwater and ground water

Photo showing nitrates in (A) Rain water, (B) Tap water and (C) Ground water

I would like to explain the de facto link some rising damp aficionados make between Nitrates found in wall masonry and a defective damp proof course.

This is important because great weight is placed on this piece of science to justify costly remedial work.

The photo opposite shows 3 test tubes marked A, B and C. Each test tube contains a different type of water:

Test tube A = RAINWATER

Test tube B = TAP WATER

Test tube C = GROUND WATER

Each water sample has been tested for Nitrates (NO3) using a simple nitrates tester used for aquarium water.

Test tube A – Rainwater, contains approximately 10ppm (parts per million) of nitrates while test tubes B and C contain approximately 50ppm.

Why does tap water and ground water contain more nitrates than rainwater?

The answer is simple, the tap water and ground water have a greater concentration of nitrates because they have both been contaminated with nitrates from the Nitrogen Cycle. The Nitrogen Cycle takes place in reservoir water and in the ground. The rainwater sample was caught in a bucket and so has not been contaminated with nitrates.

The reason why rising damp aficionados feel it’s important to test for nitrates in wall masonry is simply to establish the link between the nitrates in the wall and the nitrates in the water found in the ground.

The logic is simple; the build up of nitrate salts in the wall is due to nitrate rich water from the ground rising up the wall and depositing the salts at the maximum height of the rise in the wall.

Many unscrupulous rising damp aficionado however attests that the passage of water up the masonry must has occurred as a result of a defective damp proof course (DPC). Forgetting of course that this could have occurred from material merely bridging the DPC.

This allows them to link nitrates in the wall directly to a defective damp proof course. Some have gone one step further and stated that a certain moisture meter reading profile up the wall is proof of a defective DPC, thus avoiding the costly business of testing the wall for nitrates at all!

So to recap…

Nitrates in wall = rising damp = defective DPC = Costly remedial work

I don’t have this binary mindset; my approach is more holistic:

Nitrates in wall = damp ground = find out why ground is damp = rectify cause of damp ground

Relative humidity doesn’t measure humidity

thermo-hygrometerIt is common for people to use the term relative humidity to describe how humid an environment feels.

They may describe a dry environment as having a low relative humidity (RH 40%); while a damp environment as having a high relative humidity (RH 70%). I hope to prove to you that this is not the case at all.

This afternoon I placed one thermo-hygrometer outside and another inside and left them there for an hour to acclimatise. I recorded the air temperature and relative humidity from each instrument and recorded my findings. You can use 2 low cost device as shown above. I bought this one from ETI Ltd.

Readings taken internally

Air temperature = 18.2oC

Relative humidity = 44%

Readings taken externally

Air temperature = 10oC

Relative humidity = 51%

Now the question is, which air is more humid, the inside air at 44% RH or the outside air at 51% RH?

Some people may say that the outside air has more water because it has a higher relative humidity. Let’s work out the actual quantity of water per kg of dry air, for each air sample just to see if there is a link between RH and the actual quantity of water.

Now there are three different ways of finding out the mass of water vapour in an air sample.

1. Using the Psychrometric chart

2. Using the Mixing Ratio formula to calculate the moisture content (g/kg of dry air)

3. Using a web-based calculating tool. (e.g. Vaisala humidity calculator)

I tend to use the Vaisala calculation tool because it’s quick and very accurate. You can check it out yourself.


Based on the recorded thermo-hygrometer readings above for internal and external air, I obtained the following…

Mass of water internally at 44% RH and 18.2oC = 5.72 g/kg of dry air

Mass of water externally at 51% RH and 10oC = 3.88 g/kg of dry air

This is proof that the relative humidity doesn’t tell you anything about the actual humidity of the air. Relative humidity actually changes with a change in the air temperature as well as the mass of water vapour in the air.

For a great tutorial on relative humidity, check out Richard Clements on U-Tube.

Old House Eco Handbook review

Old house eco book croppedSince I religiously record my CO2 emissions on a weekly basis, I can confirm that between 30th September 2012 and 31st March 2013 my home’s CO2 emissions have increased by 27.3% compared with the same period the previous year. This is mainly due to the very harsh winter that hopefully is now at an end.

It’s a fact also that for those with older houses, more and more of our hard earned money is being diverted into heating our homes rather than keeping them in tip-top condition! If this trend continues our homes will start to deteriorate to a point where they’ll be too costly to repair!

However, help is at hand in a brand new publication by Marianne Suhr and Roger Hunt called The Old House Eco Handbook.

This book is a beautifully crafted work packed full of easy to follow and practical advice that explains how older houses can be “tuned-up” to become more energy efficient. There are countless colour photographs that help to explain methods and to captivate the reader’s interest.

Moreover, this book is different to all the other advice you might find because here the wants and needs of the “Old House” are central to the type and method of the enhancements being employed; the protection of the building’s historic and aesthetic value being of paramount importance.

The book is sub-divided into the following chapters:

1. Old houses can be green

2. Old house to eco house

3. The building envelop

4. Roofs and ceilings

5. Windows and doors

6. Walls

7. Floors

8. Paints

9. Energy and water

10. Old house for the future

For those who treasure their old house this book will enable you to save serious money, the financial savings can then be diverted back into maintenance. The carbon footprint of the house will also reduce thus ensuring a double win!

For the very best advice on maintaining your old house, please look no further than The Old House Handbook by the same authors.

Rising salts is a more accurate description of rising damp

Base of wall dampness but not alas Rising Damp

Base of wall dampness but not alas Rising Damp

I have posted several times on matters relating to Rising Damp and I have often expressed my dislike of the term.

I would like to just explain why I don’t like these two words used together.

The term rising damp can be misunderstood by homeowners and thus allow some to exploit this ambiguity for personal gain.

Let me explain…

If you think rising damp is a term used to describe dampness rising up a wall then you would only be half right. This is because rising damp and dampness rising up a wall are not the same and should not be confused. The photo above is dampness rising up a wall but was caused by a leak in an old lead main under the hall floor and is not rising damp.

Possibly a genuine case of rising damp

Possibly a genuine case of rising damp

Rising damp isn’t really about dampness, it’s about salts. I have many photos of dampness rising up a wall, none of which are rising damp! This means that the word “damp” in rising damp isn’t very helpful because it doesn’t allow us to differentiate it from other types of base of wall dampness. It merely mixes them up!

Instead of using the term rising damp, just use the term rising salts. This is because rising salts, in my view, completely explains and differentiates “rising damp” from other types of base of wall dampness. It’s the type and distribution of salts in a wall affected by “rising damp” that’s the key to it’s diagnosis, not the dampness.

So the next time you hear the term “rising damp” just change the “damp” to “salts” and you’ll be completely up to speed. This may lead you to then ask some awkward questions!


Sorry…you can’t understand why someone would deliberatly use the term “rising damp” instead of “rising salts”… oh well let me explain, why don’t you.

I see many homes in my travels and during the course of one year I may see 40 properties with visible base of the wall dampness. However, only about 2 will be “rising salts”.

This dampness is caused by poor surface water drainage and is NOT "rising damp"

This dampness is caused by poor surface water drainage and is NOT “rising damp”

So in my world, if you were to use the term rising salts you would only get 2 opportunities to inject a chemical damp proof course (DPC). However, if you were a little more “commercial” and used the term rising damp, you’d get 40 possible opportunities. This you will agree makes the term “rising damp” a most lucrative proposition.

The 38 walls that don’t have rising salts but do have base of wall dampness would be caused by pipe leaks, high ground and surface water drainage /leaking gutters defects. These can be dealt with in other ways.

Anyway, this is all very theoretical, because no matter what the type of dampness, you must always establish the source and reason for the dampness BEFORE a remedial strategy is proposed. This is in accordance with Part 4 of BS 6576 2005.

How do I optimise ventilation without losing too much warm internal air?

Not opening windows leads to high internal humidity

Not opening windows leads to high internal humidity

Anyone who lives in a small enclosed space such as a 2 bed flat needs to open their windows. However, the temptation is to keep the windows shut, since heating a property is now very expensive.

Opening windows is important for several reasons.

1. It removes household contaminants such as CO2, H2O and body odour.

2. It helps prevent mould growth and reduces dust mites.

3. If windows are opened daily, the cooler fresher air will help keep your home drier.


Take a look at the example below.

Air at 20oC at 50% relative humidity will contain 7.28g of water vapour/kg of dry air;


Air at 10oC and at 50% relative humidity will only contain 3.80g of water vapour/kg of dry air.

This means that by replacing 100% of the internal air you can halve the amount of moisture inside the property. However, the big problem is that while you have halved the moisture content of the air you will have also halved the internal air temperature!

If you can afford to re-heat the new cooler air by switching the central heating on then fine, but what if you can’t!!

How do I ventilate the house without losing too much warm air?

Well, why not give the house a short period of ventilation in the morning and once again in the evening?

If you open the windows for 15 minutes just before you go to work in the morning and again in the evening (at around 8pm) you will hopefully be getting the Ventilation-Heat Loss balance about right.

The peaks in net vapour pressure are the best times to open the windows.

The peaks in net vapour pressure are the best times to open the windows.

Why open the windows in the morning and evening?

Well, having carried out some monitoring of vapour pressure fluctuations in a domestic environment recently, I‘ve found out that by identifying the maximum net vapour pressure levels from 00:00hrs to 12:00hrs and again from 12:00hrs to 24:00hrs, I can determine the best time to open the windows.

The reason why the best time to open the windows is when the net vapour pressure is at a maximum is simple. It’s the time when you can expel the most amount of water vapour in the shortest time, thus limiting the loss of centrally heated internal air.