Moisture Principles
Water vapor is invisible, has no smell, is sporty and active – so it moves freely around in air, can also pass through wood and bricks and some stone. It likes to rise, defying gravity.

Liquid water is heavier and slower – air cannot carry it and it can only pass though bigger gaps in materials, generally moving downhill with gravity.
Air can carry water vapor, and changing the temperature of the air changes how much water vapor can be carried. Dew point is the temperature at which water vapor turns to liquid and is forced out of the air. Air often cools against cold surfaces like windows and outside walls, which can cause the damp conditions that mould loves.

Sources of Moisture and the Moisture Balance
We produce more moisture at home than will escape by itself – so damp is to be expected unless we actively manage moisture in our homes.
People are usually the biggest source of moisture in the home – breathing 2.5 litres per day per person. Showers = 1 litre per shower. Cooking = 2.5 litres per meal. Fridges and freezers = 0.5 litres a day each. Drying a load of washing on radiators = 1.5 litres per load. Each day all this moisture needs to get out of the house to avoid the house becoming damp.

Tips for Managing Moisture:

• Create Less:
  • Put lids on pans
  • Wait to open the dishwasher until it has cooled down
  • Dry washing outside or in a ventilated room
  • Use a squeegee to dry the shower walls after use, so that the water goes down the drain rather than slowly drying into the air
  • Use the fasted spin on the washing machine – this gets rid of masses of damp

• Controlling the Moisture:
  • Shut the kitchen and bathroom doors to trap moisture in the room
  • If you need to dry washing indoors, if possible use one room with some heat on with a window open or extractor fan
  • Bring furniture away from walls a little to allow air to circulate, vent wardrobes and built in cupboards

• Removing Moisture
  • Use extractor fans – check that fans are venting to the outside, not just the loft
  • Open windows to allow the moist air to escape, in the bathroom after a shower and the bedroom once you get up
  • Heat the bathroom a bit to reduce the amount of water on the walls – they will dry quicker

Some of the tips above will cost, but in the long term it is worth it….damp homes are bad for our health, bad for the building and its contents, and are more expensive to heat and be comfortable in.

Remember – we produce more moisture at home than will escape by itself – so damp is to be expected unless we actively manage moisture in our homes.

Monitoring Moisture
Moisture is normally measured as relative humidity – a percentage of the potential moisture that the air can carry. 100% means the air is saturated (dew point) and can carry no more, 50% means the air has capacity to carry more water vapor, etc. This can be misleading because the amount of moisture air can carry depends on its temperature. So, cold air at 100% humidity will contain less water molecules than warmer air also measuring 100% humidity.
However, if we know the temperature of the air and its relative humidity, we can find the actual amount of water (actual humidity) in the air. Actual humidity is measured in grams per cubic meter of air. 7 grams per cubic meter is ideal for humans. As homeowners we are interested in two things…how much ‘actual’ water is in the air, and at what temperature will the air reach saturation (100% relative humidity, ie the dew point) where excess water vapor is released as liquid water (like dew).

Moisture Meters
Using a moisture meter helps raise our awareness and motivates us to both produce less and ventilate better.

Room monitor units (‘hygrometers’) are widely available for under £20; they measure relative humidity and temperature. Some monitors record data over a period, historic data can be downloaded or viewed on an app; this is helpful to monitor for trends.

A conversion chart can show actual humidity and the dew point of the air in a room. A room at 20 degrees with relative humidity of 55% has 9.5g of moisture in every cubic meter, and dew point is 10.5 degrees centigrade. So, if the air cools to 10.5 degrees it will reach 100% relative humidity and liquid moisture will start to form on cooler surfaces.

As an example, a bathroom or kitchen whilst in use may reach 25 degrees and 75% humidity, and therefore has 17.5 g of moisture in it. The walls and windows are often cooler than the dew point of 20 degrees, and are wet. Some moisture escapes into the rest of the house and finds the dew point in a cooler, unused room – often against an outside wall behind furniture. It is both these conditions which mold loves. See the Appendix below

Moisture and Walls
Damp walls are a challenge, which again can be managed to a certain extent. Damp walls occur for two main reasons:

1. Moisture from the air within the house penetrating the walls and causing damp
2. Moisture from maintenance issues, such as blocked drains and gutters

Moisture from Within the House
Older houses built with breathable materials allow moisture vapor to pass through the walls and leave the house. Modern houses on the other hand aim to stop moisture getting into the walls, so moisture must be managed by ventilation. The big challenge for older houses is that many of the retrofit materials commonly used to ‘improve’ houses are non-breathable – this includes cement, many rigid insulation boards and many modern paints. Our houses are generally warmer and consequently the air inside our houses often has more moisture in it. Last month we discovered that 7 grams of moisture per cubic metre of air was ideal, but it is common to find 9-14 grams/m3, increasing moisture vapor travelling through the walls. This additional moisture makes it more likely that the moisture vapor within the wall might reach dew point and therefore turn to liquid. This is exasperated when a house is heated intermittently, or if some rooms are left unheated. Advice is simple:

1. Keep moisture levels low in the house by reducing the moisture being created, using a moisture meter and by ventilating well
2. Avoid over-heating some areas (this encourages high moisture levels in those areas, which then spreads through the house)
3. Heat the home evenly if possible

Moisture from Outside
Walls also become damp if they are in poor condition. For example:

1. Broken or blocked gutters cause water to spill down the wall surface or splash from the ground onto the wall.
2. Blocked down pipes and soak-aways do similar but also saturate the ground around the base of the wall.
3. Often the ground level is higher than when the house was built, covering air vents or reaching the level of floor joists.
4. Cement is rigid and waterproof which makes it prone to cracking, especially when it has been used in old buildings over lime mortar and render.
5. Poor maintenance of the window frames also provides an ingress point for moisture.
6. If there are leaks in pipes within the house, or as they pass through walls. Tiny holes can be almost imperceptible but in winter can create growing damp areas over time.

Good maintenance can prevent or fix the problems above.

Damp walls are cold – liquid water is a very good absorber and conductor of heat, so cold houses may well be transformed simply from drying out. Decisions to insulate are best made after the house is dry. In addition, many of us might find it more comfortable to be in a dry room at 17 degrees centigrade compared with a room at 20 degrees where the walls are damp.

Summary

• Monitor and reduce moisture creation within your home
• Use ventilation to encourage the moisture to escape from the house more easily
• Care for your walls by:
  • Heating your home evenly
  • Protecting the outside of your house through good maintenance
  • Careful choice of materials

Appendix
Actual moisture and dew point table
If room temperature and relative humidity are known, the table below shows actual moisture amounts in grams per cubic meter and in the grey rows the dew point temperature for this quantity of moisture.

This month we went to catch up with Margaret Rattray.

She contacted us a year or so ago 
because one of her storage heaters wasn’t working, and to cut a long story short she now has 2 new storage heaters, 3 new panel heaters and 6 solar panels, all paid for by the government…but more of the funding later.


Old storage heaters have a reputation for letting all their heat out in the morning, well before the heat is needed in the evening. Margaret is delighted that her new heaters are not only far easier to control but are also infinitely more efficient and therefore also cheaper to run. ‘They even look much nicer’, she says. How long did the work take? Heaters, wiring, solar panels – it was all over in about two weeks, and Margaret couldn’t speak more highly of all the workmen who came to install the different parts.


Having started the conversation with heaters, getting solar panels installed as well was a big and unexpected bonus. Margaret doesn’t have a battery, so she does her best to use her solar generated electricity in real time, ie using appliances when the sun is shining or at very least it’s a bright day. For example, it pays to look at the weather forecast and put the washing machine on when it is bright and / or sunny.


Asked if she had any surprises from our initial visit, Meg said that the best surprise was that all this work would be done for nothing. She isn’t on any benefits (just a state pension) and though there are some criteria (householder and the house itself), it is always worth asking the question, as you may too be pleasantly surprised!

If you would like help with the big steps or the little ones, Anna and Tom at Warm Connections would be delighted to chat. Remember, our advice is completely free and there is no catch.
07759 404980, advice@warmconnections.net

This month’s article comes out of paper written by Historic Scotland, which challenges the assumption that 20-21 degrees centigrade is the recommended temperature for a house. These numbers have snuck into our understanding of healthy living recently and can sound like a decree from on high……. But are they???

Many people live in houses which, even if they wanted to live at 20 degrees, could not possibly afford to. Many have also lived in a cooler house all their life and like it that way. Here are some thoughts about how to be comfortable in a house kept at a cooler 16 degrees centigrade. Firstly the lower temperature significantly reduces heat loss from the house, and so reduces costs. Secondly this may be a good temperature if you are active in the house. Lastly, having the house at this temperature may require some behaviour changes, for example:

• Wear an extra layer or two
• Use localised heaters – particularly if you are not moving much, using a heater to heat the area where you are. Directional heaters are designed for this as are radiant heaters which heat things rather than the air
• Be more active if you are able (even moving around a room to turn things on and off rather than always using remote controls)
• High back chairs, with ‘wings’ are designed to ‘wrap you up’ and shield you from draughts
• Pre-warm your bed with a hot water bottle or electric blanket
• Use a duvet with a high tog rating (12 or higher)

As well as these practical things that you can do to stay comfortable whilst your house is a bit cooler, don’t forget there are also things you can do so that your house loses less heat – many of these are very easy, inexpensive and make a significant difference – see our blog article on our website entitled ‘If my House was Human’. There are also things you can do to reduce the price you pay for fuel, which we will discuss this next month.
Remember, our advice is completely free and there is no catch.

Please get in touch with Anna and Tom: 07759 404980, advice@warmconnections.net