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Good Room Temperature & Humidity – Tested

Room Temperature - Humidity

What is Room Temperature?

You might hear people talking about ‘Room Temperature’ informally as though it is a specific temperature. However, realistically it varies according to many factors (too many to list all). At the end of the day it is a combination of the climate (including the effect of outdoor conditions) and what you do to control that temperature, both heating and cooling.

What Should Room Temperature be?

Most people in the UK tend to find the sweet spot for room temperature is in the range of 18-22 °C give or take a few degrees. This will vary from person to person as people have different perceptions and tolerances to heat and cold. Plus, how this room temperature feels to people can vary depending on things such as relative humidity in the room, ventilation / air flow and of course what they are wearing seasonally!

Room Temperature and Relative Humidity
Room Temperature and Relative Humidity

The other things that varies in an individual property is what room you are in around the house. For example, some people like bedrooms to be colder for sleeping and living rooms warmer. In this particular article, we are going to focus on bathroom temperature and humidity, following our articles on bathroom condensation, baths vs shower and black mould in bathrooms. In particular how temperature and relative humidity varies in different locations in a bathroom.

Something that helps control humidity, condensation and mould in bathrooms is ‘mechanical ventilation’ through the use of bathroom extractor fans or even air brick vents.

Why is Room Temperature Important?

In the work we do around leak detection, work on condensation problems, damp (including damp on walls) and mould problems, temperature and humidity are both important factors.

In particular, we are interested in understanding the links to humidity and water leaks / water damage and also climatic conditions that can lead to mould, condensation and damp problems. We explain this further on our dew point calculator page (or if you are looking for something simpler – dew point charts) and our article explaining infrared thermometers.

On top of that, we do a lot of work in bathrooms, shower rooms and ensuite bathrooms, so we thought we do an experiment to understand how the conditions vary in different locations in a bathroom (more on this later), and understanding how that affects other things too.

Leak in Ceiling
Leak in Ceiling from Toilet Above

Does Room Temperature Vary?

In our recent article about black mould, we looked at how (even in the same house) the temperature and relative humidity vary in a house. In that article we showed these charts:

Black Mould - Temperature
Black Mould Test – Temperature
Black Mould - Humidity
Black Mould Test – Humidity

As you can see, there are significant variances in room temperature and relative humidity both in different rooms, time of day and according to what activity is taking place in those rooms. We discussed that last point in more detail in our article about bathroom condensation and our article on humidity in houses, in which we did some tests. So on to our new test…

Room Temperature and Humidity – Our Test

This test took place in the UK in February, when the outside temperature was around 5 to 10°C during the daytime. The property had central heating on during the day with the thermostat set to 19°C.

In this test we placed five different hygrometers, which measure room temperature and relative humidity. We placed them in different fixed locations and different heights to see if these made a difference. This information might explain why certain locations get higher levels of condensation or mould, such as condensation on windows, mould on walls or damp on ceilings.

The five locations we monitored (for 24 hours) were:

  1. A central location in the bathroom, at waist height.
  2. A central location in the bathroom, at floor height
  3. A central location in the bathroom, at head height
  4. Next to the radiator (towel rail) in the bathroom
  5. Next to the window in the bathroom (east facing)

So let’s look at the results, from noon one day to the next…

Temperature in Bathroom

The chart below shows the air temperature across the five location over the 24 hours:

Bathroom Temperature
Bathroom Temperature

As you can see, there are quite a lot of variances, both by placement and by time of day. You can also see how certain events impact on the room temperature readings too. For example, at two points in the day when people took a bath (at about 6pm and another at 10pm). Plus how sunshine shining on the window in the morning had a dramatic effect!

It is interesting to see the following observations:

  • The coldest area generally was the window (apart from in the morning sun)
  • On that, the sun shining on the window had a dramatic effect!
  • At some points of the day it was about 3 degrees colder than the room temperature
  • The sun shining on it made it 4 to 5 degrees warmer
  • Unsurprisingly, next to the radiator was generally the warmest!
  • It was generally cooler at floor level (we all remember heat rises)
  • That said, when the heating was on the differential was less
  • This is, in part, because the radiators ‘radiate’! and circulate heat
  • You can see how having a bath increased temperature quite suddenly

The table below shows the average room temperature by location in the bathroom:

Room Temperature - Average
Room Temperature – Average

So, as you can see, the window was on average, just under 1 degree colder and the radiator about half a degree warmer. Although, as we said above, that varied a lot during the day.

The results of this test are interesting but what about humidity?…

Humidity in Bathroom

Before we look at the humidity stats, remember that ‘Relative Humidity‘ is the amount of water moisture / vapour in the air, expressed as a percentage, relative to what that air is capable of holding at a given temperature. As we said in that linked article, the temperature makes a difference, as warmer air is generally capable of holding more moisture.

All other things being equal, as temperature rises, relative humidity falls. So let’s look at the relative humidity trends and differences by location:

Bathroom Relative Humidity
Bathroom Relative Humidity

As you can clearly see above, the variances in humidity is very dramatic in comparison to room temperature. As expected, there is generally an inverse relationship between temperature and humidity. That said, the lines are often close to each other, irrespective of location. The slight difference is the floor level but the main, dramatic, difference is (as expected the window).

Apart from the fact that it is colder, there is a bit of a ‘chicken and egg’ situation as remember we are looking at air temperature. In actual fact, like other parts of the room, air temperature will be different to surface temperature (which we know is important for dew point). This is explored in our article about cold spots in houses.

This is especially the case for the window, which is much cooler even though it is double glazed. Condensation settled on the window, especially when having a bath which in turn contributed to higher humidity in that area, because of the presence of moisture.

We might look at this a bit more for a separate test article. We’ve already looked at it as part of our article on condensation on pipes and condensation in lofts.

Importantly, during the period of our test, the window was closed, we will look at how opening affects these stats another time. We’re sure it will be interesting to see that.

Room Temperature, Humidity and Height Variances

So overall, the test proved to be interesting and showed how, even in the same room, location and external factors (of which there can be many) can have an impact on room temperature and humidity. These in turn can have an influence, along with other factors, on condensation, damp and mould etc.

If you have a problem with damp, condensation, mould or humidity in your property, get in touch with us to discuss our survey services we offer in these areas, as well as treatments.

On the subject of testing humidity, you may want to read our article about silica gel which explains what it is, how it works and an experiment we did to test it, that also produced some very informative results that might surprise you regarding how effective they are.

On the subject of tests, we also did some on a Water Testing Kit. logo logo

What is an ideal room temperature?

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Ideal room temperature will vary according to your own preferences and where you live in the world, different people are comfortable at different levels of temperature (and humidity for that matter). That said, most people tend to like room temperatures in the region of 20 degrees Celsius (plus or minus a few degrees). This may vary from season to season too.

What is ideal humidity in a UK house?

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For a number of reasons, the ideal and manageable humidity in your house in the UK is most commonly between 40% and 60% relative humidity. This will clearly vary according to other climatic conditions and the construction, age and design of your property but below 40% is perhaps too dry in normal months (excluding summer) and above 60% can lead to secondary issues like mould, especially above 70%.