We often see the window ledge or the brick work around the window (reveals), is a 'cold bridge' and the temperature is significantly influenced by outdoor temperatures. Despite the indoor temperature being around 18°c, the ledge or reveal could be 14°c or lower on a typical winter day.We see this problem a lot in rooms that have an ensuite bathroom or in kitchens. If a room is typically 18°c and 60% humidity, then there is rarely a problem if the wall is 14°c. However, if the room increases to 20°c and 78% humidity, which you typically see during showers or cooking, then the moisture will condense on the colder surface.Ifthe moisture is left on the wall for a few days, then this creates the ideal environment for mould. This is a common problem and so either wiping away the moisture or ventilating to remove the moisture is a good thing to do. Use our tool to see how long it would take to reduce a room from 78% humidity to 55% by purging the room.

This is typically a combination of a cold wall and moisture levels. Where two walls meet is often colder than the rest of the surface, and moisture in the room will condense on any surface that is cold enough or ‘at the dewpoint’.This dewpoint temperature can vary.  Take for instance a room kept at 18°c, and 65% humidity, outside is a winter day at 5°c and the walls are poorly insulated.  The temperature at the wall is 13°c.  The humidity near the cold spot of the wall will be around 80% which is typically ideal for mould to grow. Let’s say that the humidity in the room keeps climbing from 65% to 70% because there is no ventilation. The humidity at the wall could reach 94% which is very near condensation and it won’t take much of a shift in moisture or temperature of the wall for it to become damp.This problem exists in warm homes too. Take a home that is 24°c, with relative humidity at 55% and the wall temperature is 19°c.  On the face of it this should be okay.  However, there is no ventilation and the humidity climbs to 62%.  More moisture is being added and not being removed and the humidity near the wall becomes 83% (mould risk).  All it takes is a short burst of additional moisture in the room (ensuite shower with door open) to take the moisture levels up to the point there is condensation on the wall (damp).To stop condensation, you need to get a good understanding of what the wall temperature is compared to the outside, the humidity in the room and the temperature of the room.  Once you know this and the day to day activity, you can work out when to start ventilating or heating the room to prevent condensation.  Use our tool to get you started on understanding the relationship. If you do get condensation, try and spot it early and dry the wall. Contact us if you need to know more.

Probes are good at recording that a wall is wet but it can't tell you the cause.In a number of cases, people have taken the probe reading and suggested there is a leak from above or a damp proof course is needed when it was wetness due to condensation.If the moisture in the air is constantly condensing on the walls, then this will be picked up by the probe as wet.  The next course of action is to find out whether the air moisture is the culprit.  If it isn’t then it must be something else like a leak or penetrating/rising damp.  In most cases we see that it is condensation.We measure the wall and the room environment to see whether the wetness can be explained by condensation due to the moisture levels in the room. See one of the example homes to see what you would changeWe calculate the heating and ventilation needed to reduce the risk of condensation on the wall and recommend the settings are applied for a couple of days and check the readings to see if there is a significant change. If there is no change, then it is recommended a specialist is contacted. In most cases it is wetness caused by condensation.

These types of bathroom/showers are common especially in new build flats and HMOs converted from Victorian buildings .Unfortunately there is no clear cut answer as it depends on many parts including: #1 when the fan is on (just before, during and after a shower), #2 the ducting to the outside (blocked or too long for the suction power of the fan), #3 the temperature that is maintained indoors ( can it overcome the moisture and maintain a low relative humidity) #4 and the temperature and humidity outside (is the moisture low enough to bring the inside moisture down).There are part F building regulations for the amount of moisture a fan in a bathroom or kitchen should extract in litres per second. and you can test your fan with an anemometer to see if it complies. However, often we find the readings don't reflect reality. We find that it is important to measure how quickly moisture is actually removed from the room when people are living in the home.We calculate is the amount of moisture that is typically created, whether extracting it to outside will help, how the current rate of extraction compares to what you would expect from a fan with no blockages, and what temperature is needed to keep the humidity low.Sometimes our data shows that a simple fan with an overrun is okay, other times a humidistat fan is required that will keep going until a set humidity is reached, other times a constant mechanical ventilation and heating is required.When we supply our data to contractors, we find it helps them to supply the right solution for the environment.

Even on a cold, damp day outside, the amount of moisture outside is typically lower than inside and so opening windows to reduce humidity inside will help.However, in some locations in the UK, the moisture levels could be close to indoor, and opening a window has limited affect or may actually increase the indoor humidity. Locations near rivers, valleys and coastline often have high moisture levels. In these locations, even with good ventilation habits, the solution is sometimes to increase the temperature of the home.  Dehumidifiers aren’t so great as they are just removing the moisture that outside is bringing in.For the rest of the country where opening a window does help, we have found that people are prepared to purge their home for no longer than 10 minutes as they are worried about letting the heat out. With heating costs set to rise, poor ventilation is going to be more of a problem.  For example:If a room is at 18°c and 70% humidity, then to get it to near 55% humidity when outside is about 7°c on a damp day, it would need all windows to be open for about 20 to 25 minutes.This length of time maybe too long for many people as they worry about losing heat or believe it is a security risk as they are on a ground floor flat or in a bungalow. In these cases, alternative continuous ventilation and heating may be needed to keep humidity low whilst maintaining comfort.We measure exactly whether opening a window will make a difference, how long it needs to be open, what humidity level you can get to in 10 minutes and what temperature it needs to be inside to keep humidity to around 55-60%. Use our tool to get an idea of ventilation times

There are two parts to this; temperature for the health of people, and temperature to prevent condensation and mould in the building.There are various studies and guidelines for minimum temperature for people of different ages, with chronic diseases, during the day and during the night. Night is typically 16°c and during the day is 18-21°c. There is no maximum for summer but we have seen overnight temperatures in bedrooms in new builds of 28°c with ‘feels like' temperatures nearer 30°c which puts young and old people at risk.The ideal temperature for buildings to reduce the risk of condensation, damp and mould on surfaces is a bit more complicated. You need to consider the insulation quality, the outdoor temperature and the quality of the ventilation to keep moisture down.If a home has a lot of moisture due to day-to-day activity or in a moisture laden outdoor area, then the indoor temperature may need to be increased if ventilation is limited. When we have applied the physics, we see that temperatures between 18°c to 21°c combined with some ventilation is okay. 16°c is achievable (but not advisable all day), with good ventilation and good insulation.If there is poor ventilation in a humid home, then temperatures at or above 21°c are needed to keep the condensation risk down. However these high temperatures are simply hiding a high moisture problem and it will only need a surface to be 2°c lower for there to be a mould risk.Ventilation, insulation and temperature go hand in hand.  We can tell you what temperature ranges and ventilation levels are right for the home and the people living in it.