- breathing (asleep) 0.3 kg
- breathing (awake) 0.85 kg
- cooking 3 kg
- personal washing 1.0 kg
- washing and drying clothes 5.5 kg
- Heating - especially paraffin and flueless gas heaters. For every litre of paraffin burnt over one litre of moisture vaporises into air. Every carbon fuel produces some amount of water from combustion.
-
(1 kg of water equates to about 1 litre) ∙∙
Moisture can also be drawn from the structure of the building into the internal air; from below the floor or through the walls/ceilings. Problems with the structure of the building can mean that its moisture content is unnecessary high. This can either be due to the method of original construction or as a result of structure failures. Older houses may not have a damp proof course (DPC) which prevents soil moisture from rising up into the living areas, lack of a DPC can occur in walls or under solid floors. Buildings may also lack or have insufficient air bricks to allow adequate under floor ventilation.
The effect of moisture generation is made worse by keeping the moist air in the house - it is theoretically possible to avoid condensation by adequate ventilation. Usually in certain areas of a house (such as bathrooms and kitchens) the warm air contains a lot of moisture, if that air then spreads to cooler parts of the house, it will condense on any colder surface. Up until the middle/late part of the twentieth century, most houses had high natural ventilation as the level of home insulation was low. Conservation then became popular and natural ventilation was greatly reduced by the introduction of double glazing, draught excluders, fitted carpets (which prevent air movement up through suspended wooden floors) and the removal of open fire places with the introduction of central heating. ∙∙∙
Houses have become more effectively sealed, keeping any moisture produced within the house and providing better conditions for condensation to occur. Ventilation is only effective if consistent throughout the whole envelope of the house. Condensation is encouraged by poor air circulation where stagnant air pockets form (behind furniture and in cupboards) and the first evidence is often the appearance of mould growth. Modern life styles mean that many houses remain unoccupied and unheated throughout the greater part of the day, allowing the fabric of the building to cool down. The moisture producing activities are then concentrated into relatively short periods (morning and evening) when the structure is relatively cold while the building is still warming up.
Solving Condensation Problem
First of all, you need to ensure that the amount of moisture in the air is not excessive. You can do this by checking the structure of the building.
- Check that the walls are not suffering from rising damp.
- Ensure that there is damp-proof course, that it is not bridged or damaged. A new damp course can either be installed by removing a brick at a time and inserting a physical DPC or a chemical DPC can be injected into existing walls.
- Check that any wall cavities are clear of rumble, debris can accumulate over the years and to remove it normally requires removal of a brick at each corner and racking the cavity clean. Where the dampness is restricted to one area and no other reason can be identified, it is a relatively easy task to check/clean inside the cavity.
- Consider applying a surface finish to outside walls to prevent rain penetrating them. Either a clear waterproofing finish which can be brushed on or a paint/textured finish which will cause most of the rain to run down.
- Check the roof to make sure that it is sound and directing rain into the guttering, not into the structure of the building.
- Check the guttering and down pipes, make sure that they are carrying the water away and that there are no damaged/blocked guttering or drainpipes causing the external wall to become soaking wet.
- Check solid floors to ensure that damp is not coming up through it, if it is, you may need to introduce or replace a damp proof membrane underneath it or fit a more suitable floor covering.
- Check that there are no leaking water pipes or tanks within the house.
Once you are happy with the structure of the building, look at your life style within the building:
- After a bath or shower, try to ventilate the room to the outside, not to the rest of the house - just opening a window and closing the door will help.
- While drying clothes indoors, ventilate the room.
- When people come in with wet coats, hang them outside the living area to dry. A good reason for a porch.
- Try to increase the change of air in the premises - increase ventilation. Add forced ventilation/extraction to areas which produce a lot of moisture (kitchen, bathroom). Extractor fans are available with an air-moisture switch so that they operate automatically while the moisture in the air is above a set amount. Other units (more expensive/complicated) are available which remove the moist air but reuse the thermal energy which would otherwise be wasted.
- Consider changing the fuel you use, electric is the driest, paraffin probably the wettest.
- Consider using a dehumidifier - domestic types are now available and can remove a surprising amount of water from the air.
Gaining a Better Understanding of Condensation
Once the structure of the building is at a high enough standard that it will not contribute to any condensation issues it is then equally important to make sue that the people living in the house have a good understanding of what condensation is, why it occurs and what they can do to prevent it. My employers produce a booklet for their tenants to give them an overall better understanding of condensation. This is turn saves them money because the number of condensation cases are reduced. I have shown an example of a similar booklet to the right. If people were made more aware of the severity of the problems that condensation can lead to such as replacement of plaster boards and redecorations then they might be more careful to avoid actions that will create it.
Above is an example of mould growth due to condensation. The mould was in the bathroom where there was no window and an old electrical vent that turned on with the light.
Above I have shown an example where a stagnant air pocket has formed and because of this mould growth has become to occur.
Example from Work
Below I have explained a case that I have dealt with that I fell is a very good example of condensation problems in the home because it involved condensation problems in different areas of the house but for different reasons.
This survey was carried out because our tenant was baffled by the sudden appearance of the mould growth, shown below, in his bedroom. He had recently had work done on the soffits adjacent to the mould growth but our contractor who did it denied any responsibility He had asked another contractor for an opinion and was told his only course of action was to install a positive pressure fan in the loft, at a cost of £750. He also had mould growth in his bathroom but that had been there for some time.
Inside I could clearly see that severe mould growth was occurring in the main bedroom; mainly in the left hand corner at the junction of the walls and ceiling. The clothes inside a chest of drawers, which was also in this corner, were damp and there was further mould growth behind the bed.
In the main bathroom, the mounting plate holding the extractor fan had mould growth. In the loft, directly above the mould that was growing in the corner of the main bedroom and also, for a short distance along the wall, the glass quilt insulation had been disturbed leaving the plasterboards above the bedroom unprotected. This probably occurred during the recent repairs to the roof.
The problem in the bedroom was due to a lack of insulation in the left hand corner of the loft and along a section of the front wall. This was most probably a result of the roofing repair tradesman moving the loft insulation and not replacing it.
The bathroom fan had been replaced at some time in the past with a smaller fan that was originally there. In order to accommodate the reduced size, a plywood plate had been constructed in which to mount it. This plate was effectively at the same temperature as the outside and consequently condensation was occurring on it each time the bathroom was used.
The loft insulation generally was below par and was increased in line with current standards. Special care was taken over the corner of the bedroom, both to ensure coverage of the living areas and also to retain ventilation from the soffit vents.
Solution
In the end we replaced the bathroom fan with an envirovent which is a special vent made specifically with condensation problems. This fan should be controlled via a humidistat that is set to operate when the Relative Humidity exceeds 65%. We also replaced the insulation over the affected corner of the main bedroom by installing quilt insulation to a depth of 200mm. In addition this depth of insulation was installed over the entire loft area.
Conclusion
Condensation is an increasingly serious problem in dwelling houses and offices. Accompanying condensation there is an increase in the presence of mould growth. Making people more aware of this problem and the remedies to it would help make this less of a prominent problem. The introduction of the homebuyers pack will bring any problems with condensation to the potential buyer’s knowledge and they can therefore make appropriate preparations to deal with any problems. It is important to be able to identify any potential problems and to have the correct knowledge of how to remedy them. This is why it is important to have someone that is qualified or has a good knowledge of the subject if the resident does not have the appropriate knowledge.
WORDS - 2103
References
Condensation in Buildings - , - Applied Science Publishers
Condensation and Dampness Pack - - IHS BRE
Condensation Problems: New and Existing Buildings: a Guide for Practitioners - - The Institution
∙ Condensation and Dampness Pack - - IHS BRE
∙∙ Condensation Problems: New and Existing Buildings: a Guide for Practitioners
∙∙∙ Condensation in Buildings
